feat: init Rust VM

2026-03-14 11:42:39 +08:00
parent 40d00a6c47
commit 198d847151
26 changed files with 3621 additions and 994 deletions
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -41,12 +41,6 @@ version = "0.2.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "683d7910e743518b0e34f1186f92494becacb047c7b6bf616c96772180fef923"

-[[package]]
-name = "allocator-api2"
-version = "0.4.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c880a97d28a3681c0267bd29cff89621202715b065127cd445fa0f0fe0aa2880"
-
 [[package]]
 name = "anes"
 version = "0.1.6"
@@ -196,9 +190,7 @@ dependencies = [

 [[package]]
 name = "boxing"
-version = "0.1.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7a817f12ef805b34fe1565bea00630d84f8f08bf26200b05c41456c77cdada88"
+version = "0.1.3"
 dependencies = [
 "sptr",
 ]
@@ -220,7 +212,7 @@ version = "3.20.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5d20789868f4b01b2f2caec9f5c4e0213b41e3e5702a50157d699ae31ced2fcb"
 dependencies = [
- "allocator-api2 0.2.21",
+ "allocator-api2",
 ]

 [[package]]
@@ -804,7 +796,6 @@ checksum = "5baebc0774151f905a1a2cc41989300b1e6fbb29aff0ceffa1064fdd3088d582"
 name = "fix"
 version = "0.1.0"
 dependencies = [
- "allocator-api2 0.4.0",
 "anyhow",
 "base64",
 "boxing",
@@ -835,10 +826,13 @@ dependencies = [
 "rusqlite",
 "rust-embed",
 "rustyline",
+ "sealed",
 "serde",
 "serde_json",
 "sha1",
 "sha2",
+ "small-map",
+ "smallvec",
 "string-interner",
 "tap",
 "tar",
@@ -980,20 +974,18 @@ dependencies = [
 [[package]]
 name = "gc-arena"
 version = "0.5.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3cd70cf88a32937834aae9614ff2569b5d9467fa0c42c5d7762fd94a8de88266"
+source = "git+https://github.com/kyren/gc-arena?rev=75671ae03f53718357b741ed4027560f14e90836#75671ae03f53718357b741ed4027560f14e90836"
 dependencies = [
- "allocator-api2 0.2.21",
+ "allocator-api2",
 "gc-arena-derive",
- "hashbrown 0.14.5",
- "sptr",
+ "hashbrown 0.16.1",
+ "smallvec",
 ]

 [[package]]
 name = "gc-arena-derive"
 version = "0.5.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c612a69f5557a11046b77a7408d2836fe77077f842171cd211c5ef504bd3cddd"
+source = "git+https://github.com/kyren/gc-arena?rev=75671ae03f53718357b741ed4027560f14e90836#75671ae03f53718357b741ed4027560f14e90836"
 dependencies = [
 "proc-macro2",
 "quote",
@@ -1079,9 +1071,6 @@ name = "hashbrown"
 version = "0.14.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e5274423e17b7c9fc20b6e7e208532f9b19825d82dfd615708b70edd83df41f1"
-dependencies = [
- "allocator-api2 0.2.21",
-]

 [[package]]
 name = "hashbrown"
@@ -1098,7 +1087,7 @@ version = "0.16.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "841d1cc9bed7f9236f321df977030373f4a4163ae1a7dbfe1a51a2c1a51d9100"
 dependencies = [
- "allocator-api2 0.2.21",
+ "allocator-api2",
 "equivalent",
 "foldhash 0.2.0",
 ]
@@ -2024,6 +2013,15 @@ dependencies = [
 "getrandom 0.3.4",
 ]

+[[package]]
+name = "rapidhash"
+version = "4.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b5e48930979c155e2f33aa36ab3119b5ee81332beb6482199a8ecd6029b80b59"
+dependencies = [
+ "rustversion",
+]
+
 [[package]]
 name = "rayon"
 version = "1.11.0"
@@ -2385,6 +2383,17 @@ dependencies = [
 "windows-sys 0.61.2",
 ]

+[[package]]
+name = "sealed"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22f968c5ea23d555e670b449c1c5e7b2fc399fdaec1d304a17cd48e288abc107"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "security-framework"
 version = "3.6.0"
@@ -2524,6 +2533,17 @@ version = "0.4.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0c790de23124f9ab44544d7ac05d60440adc586479ce501c1d6d7da3cd8c9cf5"

+[[package]]
+name = "small-map"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "64c0b79fa0e86d80062670059d27f93911776cdeba2555bf428b455d8738c32f"
+dependencies = [
+ "hashbrown 0.16.1",
+ "rapidhash",
+ "rustc-hash 2.1.1",
+]
+
 [[package]]
 name = "smallvec"
 version = "1.15.1"
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,7 +1,8 @@
 [workspace]
 resolver = "3"
 members = [
-    "fix"
+    "fix",
+    "boxing",
 ]

 [profile.profiling]
--- a/boxing/Cargo.toml
+++ b/boxing/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "boxing"
+version = "0.1.3"
+edition = "2021"
+description = "NaN-boxing primitives (local fork with bool fix)"
+
+[dependencies]
+sptr = "0.3"
--- a/boxing/src/lib.rs
+++ b/boxing/src/lib.rs
@@ -0,0 +1,2 @@
+pub mod nan;
+mod utils;
--- a/boxing/src/nan.rs
+++ b/boxing/src/nan.rs
@@ -0,0 +1,7 @@
+pub mod raw;
+
+pub use raw::RawBox;
+
+const SIGN_MASK: u64 = 0x7FFF_FFFF_FFFF_FFFF;
+const QUIET_NAN: u64 = 0x7FF8_0000_0000_0000;
+const NEG_QUIET_NAN: u64 = 0xFFF8_0000_0000_0000;
--- a/boxing/src/nan/raw.rs
+++ b/boxing/src/nan/raw.rs
@@ -0,0 +1,471 @@
+use super::{NEG_QUIET_NAN, QUIET_NAN, SIGN_MASK};
+use crate::utils::ArrayExt;
+use sptr::Strict;
+use std::fmt;
+use std::mem::ManuallyDrop;
+use std::num::NonZeroU8;
+
+pub trait RawStore: Sized {
+    fn to_val(self, value: &mut Value);
+    fn from_val(value: &Value) -> Self;
+}
+
+impl RawStore for [u8; 6] {
+    #[inline]
+    fn to_val(self, value: &mut Value) {
+        value.set_data(self);
+    }
+
+    #[inline]
+    fn from_val(value: &Value) -> Self {
+        *value.data()
+    }
+}
+
+impl RawStore for bool {
+    #[inline]
+    fn to_val(self, value: &mut Value) {
+        value.set_data([u8::from(self)].truncate_to());
+    }
+
+    #[inline]
+    fn from_val(value: &Value) -> Self {
+        value.data()[0] == 1
+    }
+}
+
+macro_rules! int_store {
+    ($ty:ty) => {
+        impl RawStore for $ty {
+            #[inline]
+            fn to_val(self, value: &mut Value) {
+                let bytes = self.to_ne_bytes();
+                value.set_data(bytes.truncate_to());
+            }
+
+            #[inline]
+            fn from_val(value: &Value) -> Self {
+                <$ty>::from_ne_bytes(value.data().truncate_to())
+            }
+        }
+    };
+}
+
+int_store!(u8);
+int_store!(u16);
+int_store!(u32);
+
+int_store!(i8);
+int_store!(i16);
+int_store!(i32);
+
+fn store_ptr<P: Strict + Copy>(value: &mut Value, ptr: P) {
+    #[cfg(target_pointer_width = "64")]
+    {
+        assert!(
+            ptr.addr() <= 0x0000_FFFF_FFFF_FFFF,
+            "Pointer too large to store in NaN box"
+        );
+
+        let val = (unsafe { value.whole_mut() } as *mut [u8; 8]).cast::<P>();
+
+        let ptr = Strict::map_addr(ptr, |addr| {
+            addr | (usize::from(value.header().into_raw()) << 48)
+        });
+
+        unsafe { val.write(ptr) };
+    }
+
+    #[cfg(target_pointer_width = "32")]
+    {
+        let _ = (value, ptr);
+        unimplemented!("32-bit pointer storage not supported");
+    }
+}
+
+fn load_ptr<P: Strict>(value: &Value) -> P {
+    #[cfg(target_pointer_width = "64")]
+    {
+        let val = (unsafe { value.whole() } as *const [u8; 8]).cast::<P>();
+        let ptr = unsafe { val.read() };
+        Strict::map_addr(ptr, |addr| addr & 0x0000_FFFF_FFFF_FFFF)
+    }
+
+    #[cfg(target_pointer_width = "32")]
+    {
+        let _ = value;
+        unimplemented!("32-bit pointer storage not supported");
+    }
+}
+
+impl<T> RawStore for *const T {
+    fn to_val(self, value: &mut Value) {
+        store_ptr::<*const T>(value, self);
+    }
+
+    fn from_val(value: &Value) -> Self {
+        load_ptr::<*const T>(value)
+    }
+}
+
+impl<T> RawStore for *mut T {
+    fn to_val(self, value: &mut Value) {
+        store_ptr::<*mut T>(value, self);
+    }
+
+    fn from_val(value: &Value) -> Self {
+        load_ptr::<*mut T>(value)
+    }
+}
+
+#[derive(Copy, Clone, PartialEq, Eq)]
+enum TagVal {
+    _P1,
+    _P2,
+    _P3,
+    _P4,
+    _P5,
+    _P6,
+    _P7,
+
+    _N1,
+    _N2,
+    _N3,
+    _N4,
+    _N5,
+    _N6,
+    _N7,
+}
+
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub struct RawTag(TagVal);
+
+impl RawTag {
+    #[inline]
+    #[must_use]
+    pub fn new(neg: bool, val: NonZeroU8) -> RawTag {
+        unsafe { Self::new_unchecked(neg, val.get() & 0x07) }
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn new_checked(neg: bool, val: u8) -> Option<RawTag> {
+        Some(RawTag(match (neg, val) {
+            (false, 1) => TagVal::_P1,
+            (false, 2) => TagVal::_P2,
+            (false, 3) => TagVal::_P3,
+            (false, 4) => TagVal::_P4,
+            (false, 5) => TagVal::_P5,
+            (false, 6) => TagVal::_P6,
+            (false, 7) => TagVal::_P7,
+
+            (true, 1) => TagVal::_N1,
+            (true, 2) => TagVal::_N2,
+            (true, 3) => TagVal::_N3,
+            (true, 4) => TagVal::_N4,
+            (true, 5) => TagVal::_N5,
+            (true, 6) => TagVal::_N6,
+            (true, 7) => TagVal::_N7,
+
+            _ => return None,
+        }))
+    }
+
+    /// # Safety
+    ///
+    /// `val` must be in the range `1..8`
+    #[inline]
+    #[must_use]
+    pub unsafe fn new_unchecked(neg: bool, val: u8) -> RawTag {
+        RawTag(match (neg, val) {
+            (false, 1) => TagVal::_P1,
+            (false, 2) => TagVal::_P2,
+            (false, 3) => TagVal::_P3,
+            (false, 4) => TagVal::_P4,
+            (false, 5) => TagVal::_P5,
+            (false, 6) => TagVal::_P6,
+            (false, 7) => TagVal::_P7,
+
+            (true, 1) => TagVal::_N1,
+            (true, 2) => TagVal::_N2,
+            (true, 3) => TagVal::_N3,
+            (true, 4) => TagVal::_N4,
+            (true, 5) => TagVal::_N5,
+            (true, 6) => TagVal::_N6,
+            (true, 7) => TagVal::_N7,
+
+            _ => unsafe { core::hint::unreachable_unchecked() },
+        })
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn is_neg(self) -> bool {
+        matches!(self.0, |TagVal::_N1| TagVal::_N2
+            | TagVal::_N3
+            | TagVal::_N4
+            | TagVal::_N5
+            | TagVal::_N6
+            | TagVal::_N7)
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn val(self) -> NonZeroU8 {
+        match self.0 {
+            TagVal::_P1 | TagVal::_N1 => NonZeroU8::MIN,
+            TagVal::_P2 | TagVal::_N2 => NonZeroU8::MIN.saturating_add(1),
+            TagVal::_P3 | TagVal::_N3 => NonZeroU8::MIN.saturating_add(2),
+            TagVal::_P4 | TagVal::_N4 => NonZeroU8::MIN.saturating_add(3),
+            TagVal::_P5 | TagVal::_N5 => NonZeroU8::MIN.saturating_add(4),
+            TagVal::_P6 | TagVal::_N6 => NonZeroU8::MIN.saturating_add(5),
+            TagVal::_P7 | TagVal::_N7 => NonZeroU8::MIN.saturating_add(6),
+        }
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn neg_val(self) -> (bool, u8) {
+        match self.0 {
+            TagVal::_P1 => (false, 1),
+            TagVal::_P2 => (false, 2),
+            TagVal::_P3 => (false, 3),
+            TagVal::_P4 => (false, 4),
+            TagVal::_P5 => (false, 5),
+            TagVal::_P6 => (false, 6),
+            TagVal::_P7 => (false, 7),
+            TagVal::_N1 => (true, 1),
+            TagVal::_N2 => (true, 2),
+            TagVal::_N3 => (true, 3),
+            TagVal::_N4 => (true, 4),
+            TagVal::_N5 => (true, 5),
+            TagVal::_N6 => (true, 6),
+            TagVal::_N7 => (true, 7),
+        }
+    }
+}
+
+impl fmt::Debug for RawTag {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("RawTag")
+            .field("neg", &self.is_neg())
+            .field("val", &self.val())
+            .finish()
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq)]
+#[repr(transparent)]
+struct Header(u16);
+
+impl Header {
+    #[inline]
+    fn new(tag: RawTag) -> Header {
+        let (neg, val) = tag.neg_val();
+        Header(0x7FF8 | (u16::from(neg) << 15) | u16::from(val))
+    }
+
+    #[inline]
+    fn tag(self) -> RawTag {
+        unsafe { RawTag::new_unchecked(self.get_sign(), self.get_tag()) }
+    }
+
+    #[inline]
+    fn get_sign(self) -> bool {
+        self.0 & 0x8000 != 0
+    }
+
+    #[inline]
+    fn get_tag(self) -> u8 {
+        (self.0 & 0x0007) as u8
+    }
+
+    #[inline]
+    fn into_raw(self) -> u16 {
+        self.0
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+#[repr(C, align(8))]
+pub struct Value {
+    #[cfg(target_endian = "big")]
+    header: Header,
+    data: [u8; 6],
+    #[cfg(target_endian = "little")]
+    header: Header,
+}
+
+impl Value {
+    #[inline]
+    pub fn new(tag: RawTag, data: [u8; 6]) -> Value {
+        Value {
+            header: Header::new(tag),
+            data,
+        }
+    }
+
+    #[inline]
+    pub fn empty(tag: RawTag) -> Value {
+        Value::new(tag, [0; 6])
+    }
+
+    pub fn store<T: RawStore>(tag: RawTag, val: T) -> Value {
+        let mut v = Value::new(tag, [0; 6]);
+        T::to_val(val, &mut v);
+        v
+    }
+
+    pub fn load<T: RawStore>(self) -> T {
+        T::from_val(&self)
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn tag(&self) -> RawTag {
+        self.header.tag()
+    }
+
+    #[inline]
+    fn header(&self) -> &Header {
+        &self.header
+    }
+
+    #[inline]
+    pub fn set_data(&mut self, val: [u8; 6]) {
+        self.data = val;
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn data(&self) -> &[u8; 6] {
+        &self.data
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn data_mut(&mut self) -> &mut [u8; 6] {
+        &mut self.data
+    }
+
+    #[inline]
+    #[must_use]
+    pub unsafe fn whole(&self) -> &[u8; 8] {
+        let ptr = (self as *const Value).cast::<[u8; 8]>();
+        unsafe { &*ptr }
+    }
+
+    #[inline]
+    #[must_use]
+    pub unsafe fn whole_mut(&mut self) -> &mut [u8; 8] {
+        let ptr = (self as *mut Value).cast::<[u8; 8]>();
+        unsafe { &mut *ptr }
+    }
+}
+
+#[repr(C)]
+pub union RawBox {
+    float: f64,
+    value: ManuallyDrop<Value>,
+    bits: u64,
+    #[cfg(target_pointer_width = "64")]
+    ptr: *const (),
+    #[cfg(target_pointer_width = "32")]
+    ptr: (u32, *const ()),
+}
+
+impl RawBox {
+    #[inline]
+    #[must_use]
+    pub fn from_float(val: f64) -> RawBox {
+        match (val.is_nan(), val.is_sign_positive()) {
+            (true, true) => RawBox {
+                float: f64::from_bits(QUIET_NAN),
+            },
+            (true, false) => RawBox {
+                float: f64::from_bits(NEG_QUIET_NAN),
+            },
+            (false, _) => RawBox { float: val },
+        }
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn from_value(value: Value) -> RawBox {
+        RawBox {
+            value: ManuallyDrop::new(value),
+        }
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn tag(&self) -> Option<RawTag> {
+        if self.is_value() {
+            Some(unsafe { self.value.tag() })
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn is_float(&self) -> bool {
+        (unsafe { !self.float.is_nan() } || unsafe { self.bits & SIGN_MASK == QUIET_NAN })
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn is_value(&self) -> bool {
+        (unsafe { self.float.is_nan() } && unsafe { self.bits & SIGN_MASK != QUIET_NAN })
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn float(&self) -> Option<&f64> {
+        if self.is_float() {
+            Some(unsafe { &self.float })
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn value(&self) -> Option<&Value> {
+        if self.is_value() {
+            Some(unsafe { &self.value })
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    pub fn into_float_unchecked(self) -> f64 {
+        unsafe { self.float }
+    }
+}
+
+impl Clone for RawBox {
+    #[inline]
+    fn clone(&self) -> Self {
+        RawBox {
+            ptr: unsafe { self.ptr },
+        }
+    }
+}
+
+impl fmt::Debug for RawBox {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self.float() {
+            Some(val) => f.debug_tuple("RawBox::Float").field(val).finish(),
+            None => {
+                let val = self.value().expect("RawBox is neither float nor value");
+
+                f.debug_struct("RawBox::Data")
+                    .field("tag", &val.tag())
+                    .field("data", val.data())
+                    .finish()
+            }
+        }
+    }
+}
--- a/boxing/src/utils.rs
+++ b/boxing/src/utils.rs
@@ -0,0 +1,16 @@
+pub trait ArrayExt<const LEN: usize> {
+    type Elem;
+
+    fn truncate_to<const M: usize>(self) -> [Self::Elem; M];
+}
+
+impl<T: Default + Copy, const N: usize> ArrayExt<N> for [T; N] {
+    type Elem = T;
+
+    fn truncate_to<const M: usize>(self) -> [Self::Elem; M] {
+        let copy_len = usize::min(N, M);
+        let mut out = [T::default(); M];
+        out[0..copy_len].copy_from_slice(&self[0..copy_len]);
+        out
+    }
+}
--- a/fix/Cargo.toml
+++ b/fix/Cargo.toml
@@ -6,8 +6,16 @@ edition = "2024"
 [dependencies]
 mimalloc = "0.1"

-tokio = { version = "1.41", features = ["rt-multi-thread", "sync", "net", "io-util"] }
-nix-compat = { git = "https://git.snix.dev/snix/snix.git", version = "0.1.0", features = ["wire", "async"] }
+tokio = { version = "1.41", features = [
+    "rt-multi-thread",
+    "sync",
+    "net",
+    "io-util",
+] }
+nix-compat = { git = "https://git.snix.dev/snix/snix.git", version = "0.1.0", features = [
+    "wire",
+    "async",
+] }

 # REPL
 anyhow = "1.0"
@@ -26,7 +34,11 @@ miette = { version = "7.4", features = ["fancy"] }

 hashbrown = "0.16"
 string-interner = "0.19"
-bumpalo = { version = "3.20", features = ["allocator-api2", "boxed", "collections"] }
+bumpalo = { version = "3.20", features = [
+    "allocator-api2",
+    "boxed",
+    "collections",
+] }

 rust-embed = "8.11"

@@ -42,7 +54,10 @@ hex = "0.4"

 base64 = "0.22"

-reqwest = { version = "0.13", features = ["blocking", "rustls"], default-features = false }
+reqwest = { version = "0.13", features = [
+    "blocking",
+    "rustls",
+], default-features = false }
 tar = "0.4"
 flate2 = "1.0"
 xz2 = "0.1"
@@ -64,9 +79,15 @@ tap = "1.0.1"

 ghost-cell = "0.2"
 colored = "3.1"
-boxing = "0.1"
-gc-arena = { version = "0.5.3", features = ["allocator-api2"] }
-allocator-api2 = "0.4.0"
+boxing = { path = "../boxing" }
+sealed = "0.6"
+small-map = "0.1"
+smallvec = "1.15"
+
+[dependencies.gc-arena]
+git = "https://github.com/kyren/gc-arena"
+rev = "75671ae03f53718357b741ed4027560f14e90836"
+features = ["allocator-api2", "hashbrown", "smallvec"]

 [dev-dependencies]
 criterion = { version = "0.8", features = ["html_reports"] }
--- a/fix/benches/utils.rs
+++ b/fix/benches/utils.rs
@@ -1,18 +1,18 @@
 #![allow(dead_code)]

-use fix::context::Context;
 use fix::error::{Result, Source};
+use fix::runtime::Runtime;
 use fix::value::Value;

 pub fn eval(expr: &str) -> Value {
-    Context::new()
+    Runtime::new()
        .unwrap()
        .eval(Source::new_eval(expr.into()).unwrap())
        .unwrap()
 }

 pub fn eval_result(expr: &str) -> Result<Value> {
-    Context::new()
+    Runtime::new()
        .unwrap()
        .eval(Source::new_eval(expr.into()).unwrap())
 }
--- a/fix/src/bytecode.rs
+++ b/fix/src/bytecode.rs
@@ -1,36 +1,36 @@
 use std::ops::Deref;
-use std::path::Path;

+use gc_arena::Collect;
 use hashbrown::HashMap;
 use num_enum::TryFromPrimitive;
 use rnix::TextRange;
+use string_interner::Symbol as _;

-use crate::ir::{ArgId, Attr, BinOpKind, Ir, Param, RawIrRef, SymId, ThunkId, UnOpKind};
+use crate::ir::{ArgId, Attr, BinOpKind, Ir, Param, RawIrRef, StringId, ThunkId, UnOpKind};

-#[derive(Clone, Hash, Eq, PartialEq)]
-pub(crate) enum Constant {
-    Int(i64),
-    Float(u64),
-}
+pub(crate) struct InstructionPtr(pub usize);

+#[derive(Collect)]
+#[collect(require_static)]
 pub struct Bytecode {
    pub code: Box<[u8]>,
    pub current_dir: String,
 }

 pub(crate) trait BytecodeContext {
-    fn intern_string(&mut self, s: &str) -> u32;
-    fn intern_constant(&mut self, c: Constant) -> u32;
-    fn register_span(&self, range: TextRange) -> u32;
-    fn get_sym(&self, id: SymId) -> &str;
-    fn get_current_dir(&self) -> &Path;
+    fn intern_string(&mut self, s: &str) -> StringId;
+    fn register_span(&mut self, range: TextRange) -> u32;
+    fn get_code(&self) -> &[u8];
+    fn get_code_mut(&mut self) -> &mut Vec<u8>;
 }

 #[repr(u8)]
 #[derive(Clone, Copy, TryFromPrimitive)]
 #[allow(clippy::enum_variant_names)]
 pub enum Op {
-    PushConst,
+    PushSmi,
+    PushBigInt,
+    PushFloat,
    PushString,
    PushNull,
    PushTrue,
@@ -106,58 +106,78 @@ struct ScopeInfo {

 struct BytecodeEmitter<'a, Ctx: BytecodeContext> {
    ctx: &'a mut Ctx,
-    code: Vec<u8>,
    scope_stack: Vec<ScopeInfo>,
 }

-pub(crate) fn compile_bytecode(ir: RawIrRef<'_>, ctx: &mut impl BytecodeContext) -> Bytecode {
-    let current_dir = ctx.get_current_dir().to_string_lossy().to_string();
+pub(crate) fn compile_bytecode(ir: RawIrRef<'_>, ctx: &mut impl BytecodeContext) -> InstructionPtr {
+    let ip = ctx.get_code().len();
    let mut emitter = BytecodeEmitter::new(ctx);
    emitter.emit_toplevel(ir);
-    Bytecode {
-        code: emitter.code.into_boxed_slice(),
-        current_dir,
-    }
+    InstructionPtr(ip)
 }

 impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
    fn new(ctx: &'a mut Ctx) -> Self {
        Self {
            ctx,
-            code: Vec::with_capacity(4096),
            scope_stack: Vec::with_capacity(32),
        }
    }

    #[inline]
    fn emit_op(&mut self, op: Op) {
-        self.code.push(op as u8);
+        self.ctx.get_code_mut().push(op as u8);
    }

    #[inline]
    fn emit_u8(&mut self, val: u8) {
-        self.code.push(val);
+        self.ctx.get_code_mut().push(val);
    }

    #[inline]
    fn emit_u16(&mut self, val: u16) {
-        self.code.extend_from_slice(&val.to_le_bytes());
+        self.ctx
+            .get_code_mut()
+            .extend_from_slice(&val.to_le_bytes());
    }

    #[inline]
    fn emit_u32(&mut self, val: u32) {
-        self.code.extend_from_slice(&val.to_le_bytes());
+        self.ctx
+            .get_code_mut()
+            .extend_from_slice(&val.to_le_bytes());
+    }
+
+    #[inline]
+    fn emit_i32(&mut self, val: i32) {
+        self.ctx
+            .get_code_mut()
+            .extend_from_slice(&val.to_le_bytes());
+    }
+
+    #[inline]
+    fn emit_i64(&mut self, val: i64) {
+        self.ctx
+            .get_code_mut()
+            .extend_from_slice(&val.to_le_bytes());
+    }
+
+    #[inline]
+    fn emit_f64(&mut self, val: f64) {
+        self.ctx
+            .get_code_mut()
+            .extend_from_slice(&val.to_le_bytes());
    }

    #[inline]
    fn emit_i32_placeholder(&mut self) -> usize {
-        let offset = self.code.len();
-        self.code.extend_from_slice(&[0u8; 4]);
+        let offset = self.ctx.get_code_mut().len();
+        self.ctx.get_code_mut().extend_from_slice(&[0u8; 4]);
        offset
    }
    #[inline]
    fn patch_i32(&mut self, offset: usize, val: i32) {
-        self.code[offset..offset + 4].copy_from_slice(&val.to_le_bytes());
+        self.ctx.get_code_mut()[offset..offset + 4].copy_from_slice(&val.to_le_bytes());
    }

    #[inline]
@@ -168,11 +188,18 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {

    #[inline]
    fn patch_jump_target(&mut self, placeholder_offset: usize) {
-        let current_pos = self.code.len();
+        let current_pos = self.ctx.get_code_mut().len();
        let relative_offset = (current_pos as i32) - (placeholder_offset as i32) - 4;
        self.patch_i32(placeholder_offset, relative_offset);
    }

+    #[inline]
+    fn emit_str_id(&mut self, id: StringId) {
+        self.ctx
+            .get_code_mut()
+            .extend_from_slice(&(id.0.to_usize() as u32).to_le_bytes());
+    }
+
    fn current_depth(&self) -> u16 {
        self.scope_stack.last().map_or(0, |s| s.depth)
    }
@@ -390,13 +417,13 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
            let label_idx = self.ctx.intern_string(&label);

            let skip_patch = self.emit_jump_placeholder();
-            let entry_point = self.code.len() as u32;
+            let entry_point = self.ctx.get_code_mut().len() as u32;
            self.emit_expr(inner);
            self.emit_op(Op::Return);
            self.patch_jump_target(skip_patch);
            self.emit_op(Op::MakeThunk);
            self.emit_u32(entry_point);
-            self.emit_u32(label_idx);
+            self.emit_str_id(label_idx);
            let (_, local_idx) = self.resolve_thunk(id);
            self.emit_op(Op::StoreLocal);
            self.emit_u32(local_idx);
@@ -406,14 +433,17 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
    fn emit_expr(&mut self, ir: RawIrRef<'_>) {
        match ir.deref() {
            &Ir::Int(x) => {
-                let idx = self.ctx.intern_constant(Constant::Int(x));
-                self.emit_op(Op::PushConst);
-                self.emit_u32(idx);
+                if x <= i32::MAX as i64 {
+                    self.emit_op(Op::PushSmi);
+                    self.emit_i32(x as i32);
+                } else {
+                    self.emit_op(Op::PushBigInt);
+                    self.emit_i64(x);
+                }
            }
            &Ir::Float(x) => {
-                let idx = self.ctx.intern_constant(Constant::Float(x.to_bits()));
-                self.emit_op(Op::PushConst);
-                self.emit_u32(idx);
+                self.emit_op(Op::PushFloat);
+                self.emit_f64(x);
            }
            &Ir::Bool(true) => self.emit_op(Op::PushTrue),
            &Ir::Bool(false) => self.emit_op(Op::PushFalse),
@@ -421,7 +451,7 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
            Ir::Str(s) => {
                let idx = self.ctx.intern_string(s.deref());
                self.emit_op(Op::PushString);
-                self.emit_u32(idx);
+                self.emit_str_id(idx);
            }
            &Ir::Path(p) => {
                self.emit_expr(p);
@@ -433,20 +463,20 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {

                self.emit_op(Op::JumpIfFalse);
                let else_placeholder = self.emit_i32_placeholder();
-                let after_jif = self.code.len();
+                let after_jif = self.ctx.get_code_mut().len();

                self.emit_expr(consq);

                self.emit_op(Op::Jump);
                let end_placeholder = self.emit_i32_placeholder();
-                let after_jump = self.code.len();
+                let after_jump = self.ctx.get_code_mut().len();

                let else_offset = (after_jump as i32) - (after_jif as i32);
                self.patch_i32(else_placeholder, else_offset);

                self.emit_expr(alter);

-                let end_offset = (self.code.len() as i32) - (after_jump as i32);
+                let end_offset = (self.ctx.get_code_mut().len() as i32) - (after_jump as i32);
                self.patch_i32(end_placeholder, end_offset);
            }
            &Ir::BinOp { lhs, rhs, kind } => {
@@ -510,10 +540,8 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
                self.emit_op(Op::LoadBuiltins);
            }
            &Ir::Builtin(name) => {
-                let sym = self.ctx.get_sym(name).to_string();
-                let idx = self.ctx.intern_string(&sym);
                self.emit_op(Op::LoadBuiltin);
-                self.emit_u32(idx);
+                self.emit_u32(name.0.to_usize() as u32);
            }
            &Ir::ConcatStrings {
                ref parts,
@@ -540,7 +568,7 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
                self.emit_expr(*assertion);
                self.emit_expr(*expr);
                self.emit_op(Op::Assert);
-                self.emit_u32(raw_idx);
+                self.emit_str_id(raw_idx);
                self.emit_u32(span_id);
            }
            &Ir::CurPos(span) => {
@@ -549,16 +577,12 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
                self.emit_u32(span_id);
            }
            &Ir::ReplBinding(name) => {
-                let sym = self.ctx.get_sym(name).to_string();
-                let idx = self.ctx.intern_string(&sym);
                self.emit_op(Op::LoadReplBinding);
-                self.emit_u32(idx);
+                self.emit_str_id(name);
            }
            &Ir::ScopedImportBinding(name) => {
-                let sym = self.ctx.get_sym(name).to_string();
-                let idx = self.ctx.intern_string(&sym);
                self.emit_op(Op::LoadScopedBinding);
-                self.emit_u32(idx);
+                self.emit_str_id(name);
            }
            &Ir::With {
                namespace,
@@ -568,10 +592,8 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
                self.emit_with(namespace, body, thunks);
            }
            &Ir::WithLookup(name) => {
-                let sym = self.ctx.get_sym(name).to_string();
-                let idx = self.ctx.intern_string(&sym);
                self.emit_op(Op::WithLookup);
-                self.emit_u32(idx);
+                self.emit_str_id(name);
            }
        }
    }
@@ -584,20 +606,20 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
                self.emit_op(Op::ForceBool);
                self.emit_op(Op::JumpIfFalse);
                let skip_placeholder = self.emit_i32_placeholder();
-                let after_jif = self.code.len();
+                let after_jif = self.ctx.get_code_mut().len();

                self.emit_expr(rhs);
                self.emit_op(Op::ForceBool);
                self.emit_op(Op::Jump);
                let end_placeholder = self.emit_i32_placeholder();
-                let after_jump = self.code.len();
+                let after_jump = self.ctx.get_code_mut().len();

                let false_offset = (after_jump as i32) - (after_jif as i32);
                self.patch_i32(skip_placeholder, false_offset);

                self.emit_op(Op::PushFalse);

-                let end_offset = (self.code.len() as i32) - (after_jump as i32);
+                let end_offset = (self.ctx.get_code_mut().len() as i32) - (after_jump as i32);
                self.patch_i32(end_placeholder, end_offset);
            }
            Or => {
@@ -605,20 +627,20 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
                self.emit_op(Op::ForceBool);
                self.emit_op(Op::JumpIfTrue);
                let skip_placeholder = self.emit_i32_placeholder();
-                let after_jit = self.code.len();
+                let after_jit = self.ctx.get_code_mut().len();

                self.emit_expr(rhs);
                self.emit_op(Op::ForceBool);
                self.emit_op(Op::Jump);
                let end_placeholder = self.emit_i32_placeholder();
-                let after_jump = self.code.len();
+                let after_jump = self.ctx.get_code_mut().len();

                let true_offset = (after_jump as i32) - (after_jit as i32);
                self.patch_i32(skip_placeholder, true_offset);

                self.emit_op(Op::PushTrue);

-                let end_offset = (self.code.len() as i32) - (after_jump as i32);
+                let end_offset = (self.ctx.get_code_mut().len() as i32) - (after_jump as i32);
                self.patch_i32(end_placeholder, end_offset);
            }
            Impl => {
@@ -626,20 +648,20 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
                self.emit_op(Op::ForceBool);
                self.emit_op(Op::JumpIfFalse);
                let skip_placeholder = self.emit_i32_placeholder();
-                let after_jif = self.code.len();
+                let after_jif = self.ctx.get_code_mut().len();

                self.emit_expr(rhs);
                self.emit_op(Op::ForceBool);
                self.emit_op(Op::Jump);
                let end_placeholder = self.emit_i32_placeholder();
-                let after_jump = self.code.len();
+                let after_jump = self.ctx.get_code_mut().len();

                let true_offset = (after_jump as i32) - (after_jif as i32);
                self.patch_i32(skip_placeholder, true_offset);

                self.emit_op(Op::PushTrue);

-                let end_offset = (self.code.len() as i32) - (after_jump as i32);
+                let end_offset = (self.ctx.get_code_mut().len() as i32) - (after_jump as i32);
                self.patch_i32(end_placeholder, end_offset);
            }
            PipeL => {
@@ -688,7 +710,7 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
        let thunk_ids: Vec<ThunkId> = all_thunks.iter().map(|&(id, _)| id).collect();

        let skip_patch = self.emit_jump_placeholder();
-        let entry_point = self.code.len() as u32;
+        let entry_point = self.ctx.get_code().len() as u32;
        self.push_scope(true, Some(arg), &thunk_ids);
        self.emit_scope_thunks(thunks);
        self.emit_expr(body);
@@ -710,20 +732,14 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
            self.emit_u8(if *ellipsis { 1 } else { 0 });

            for &(sym, _) in required.iter() {
-                let name = self.ctx.get_sym(sym).to_string();
-                let idx = self.ctx.intern_string(&name);
-                self.emit_u32(idx);
+                self.emit_str_id(sym);
            }
            for &(sym, _) in optional.iter() {
-                let name = self.ctx.get_sym(sym).to_string();
-                let idx = self.ctx.intern_string(&name);
-                self.emit_u32(idx);
+                self.emit_str_id(sym);
            }
            for &(sym, span) in required.iter().chain(optional.iter()) {
-                let name = self.ctx.get_sym(sym).to_string();
-                let name_idx = self.ctx.intern_string(&name);
                let span_id = self.ctx.register_span(span);
-                self.emit_u32(name_idx);
+                self.emit_str_id(sym);
                self.emit_u32(span_id);
            }
        } else {
@@ -735,7 +751,7 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {

    fn emit_attrset(
        &mut self,
-        stcs: &crate::ir::HashMap<'_, SymId, (RawIrRef<'_>, TextRange)>,
+        stcs: &crate::ir::HashMap<'_, StringId, (RawIrRef<'_>, TextRange)>,
        dyns: &[(RawIrRef<'_>, RawIrRef<'_>, TextRange)],
    ) {
        if stcs.is_empty() && dyns.is_empty() {
@@ -745,42 +761,35 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {

        if !dyns.is_empty() {
            for (&sym, &(val, _)) in stcs.iter() {
-                let key = self.ctx.get_sym(sym).to_string();
-                let idx = self.ctx.intern_string(&key);
                self.emit_op(Op::PushString);
-                self.emit_u32(idx);
+                self.emit_str_id(sym);
                self.emit_expr(val);
            }
            for (_, &(_, span)) in stcs.iter() {
                let span_id = self.ctx.register_span(span);
-                let idx = self.ctx.intern_constant(Constant::Int(span_id as i64));
-                self.emit_op(Op::PushConst);
-                self.emit_u32(idx);
+                self.emit_op(Op::PushSmi);
+                self.emit_u32(span_id);
            }
            for &(key, val, span) in dyns.iter() {
                self.emit_expr(key);
                self.emit_expr(val);
                let span_id = self.ctx.register_span(span);
-                let idx = self.ctx.intern_constant(Constant::Int(span_id as i64));
-                self.emit_op(Op::PushConst);
-                self.emit_u32(idx);
+                self.emit_op(Op::PushSmi);
+                self.emit_u32(span_id);
            }
            self.emit_op(Op::MakeAttrsDyn);
            self.emit_u32(stcs.len() as u32);
            self.emit_u32(dyns.len() as u32);
        } else {
            for (&sym, &(val, _)) in stcs.iter() {
-                let key = self.ctx.get_sym(sym).to_string();
-                let idx = self.ctx.intern_string(&key);
                self.emit_op(Op::PushString);
-                self.emit_u32(idx);
+                self.emit_str_id(sym);
                self.emit_expr(val);
            }
            for (_, &(_, span)) in stcs.iter() {
                let span_id = self.ctx.register_span(span);
-                let idx = self.ctx.intern_constant(Constant::Int(span_id as i64));
-                self.emit_op(Op::PushConst);
-                self.emit_u32(idx);
+                self.emit_op(Op::PushSmi);
+                self.emit_u32(span_id);
            }
            self.emit_op(Op::MakeAttrs);
            self.emit_u32(stcs.len() as u32);
@@ -796,15 +805,13 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
    ) {
        self.emit_expr(expr);
        for attr in attrpath.iter() {
-            match attr {
+            match *attr {
                Attr::Str(sym, _) => {
-                    let key = self.ctx.get_sym(*sym).to_string();
-                    let idx = self.ctx.intern_string(&key);
                    self.emit_op(Op::PushString);
-                    self.emit_u32(idx);
+                    self.emit_str_id(sym);
                }
                Attr::Dynamic(expr, _) => {
-                    self.emit_expr(*expr);
+                    self.emit_expr(expr);
                }
            }
        }
@@ -826,15 +833,13 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
    fn emit_has_attr(&mut self, lhs: RawIrRef<'_>, rhs: &[Attr<RawIrRef<'_>>]) {
        self.emit_expr(lhs);
        for attr in rhs.iter() {
-            match attr {
+            match *attr {
                Attr::Str(sym, _) => {
-                    let key = self.ctx.get_sym(*sym).to_string();
-                    let idx = self.ctx.intern_string(&key);
                    self.emit_op(Op::PushString);
-                    self.emit_u32(idx);
+                    self.emit_str_id(sym);
                }
                Attr::Dynamic(expr, _) => {
-                    self.emit_expr(*expr);
+                    self.emit_expr(expr);
                }
            }
        }
--- a/fix/src/context.rs
+++ b/fix/src/context.rs
@@ -1,592 +0,0 @@
-use std::cell::UnsafeCell;
-use std::hash::BuildHasher;
-use std::path::Path;
-
-use bumpalo::Bump;
-use ghost_cell::{GhostCell, GhostToken};
-use hashbrown::{DefaultHashBuilder, HashMap, HashSet, HashTable};
-use rnix::TextRange;
-use string_interner::DefaultStringInterner;
-
-use crate::bytecode::{self, Bytecode, BytecodeContext, Constant};
-use crate::disassembler::{Disassembler, DisassemblerContext};
-use crate::downgrade::*;
-use crate::error::{Error, Result, Source};
-use crate::ir::{ArgId, Ir, IrKey, IrRef, RawIrRef, SymId, ThunkId, ir_content_eq};
-use crate::store::{DaemonStore, Store, StoreConfig};
-use crate::value::{Symbol, Value};
-
-fn parse_error_span(error: &rnix::ParseError) -> Option<rnix::TextRange> {
-    use rnix::ParseError::*;
-    match error {
-        Unexpected(range)
-        | UnexpectedExtra(range)
-        | UnexpectedWanted(_, range, _)
-        | UnexpectedDoubleBind(range)
-        | DuplicatedArgs(range, _) => Some(*range),
-        _ => None,
-    }
-}
-
-fn handle_parse_error<'a>(
-    errors: impl IntoIterator<Item = &'a rnix::ParseError>,
-    source: Source,
-) -> Option<Box<Error>> {
-    for err in errors {
-        if let Some(span) = parse_error_span(err) {
-            return Some(
-                Error::parse_error(err.to_string())
-                    .with_source(source)
-                    .with_span(span),
-            );
-        }
-    }
-    None
-}
-
-impl Context {
-    pub fn eval(&mut self, _source: Source) -> Result<Value> {
-        todo!()
-    }
-    pub fn eval_shallow(&mut self, _source: Source) -> Result<Value> {
-        todo!()
-    }
-    pub fn eval_deep(&mut self, _source: Source) -> Result<Value> {
-        todo!()
-    }
-
-    pub fn eval_repl<'a>(&'a mut self, _source: Source, _scope: &'a HashSet<SymId>) -> Result<Value> {
-        todo!()
-    }
-
-    pub fn disassemble(&self, bytecode: &Bytecode) -> String {
-        Disassembler::new(bytecode, self).disassemble()
-    }
-
-    pub fn disassemble_colored(&self, bytecode: &Bytecode) -> String {
-        Disassembler::new(bytecode, self).disassemble_colored()
-    }
-
-    pub fn add_binding<'a>(
-        &'a mut self,
-        name: &str,
-        expr: &str,
-        scope: &'a mut HashSet<SymId>,
-    ) -> Result<Value> {
-        todo!()
-    }
-}
-
-pub struct Context {
-    symbols: DefaultStringInterner,
-    global: HashMap<SymId, Ir<'static, RawIrRef<'static>>>,
-    sources: Vec<Source>,
-    store: DaemonStore,
-    spans: UnsafeCell<Vec<(usize, TextRange)>>,
-    thunk_count: usize,
-    global_strings: Vec<String>,
-    global_string_map: HashMap<String, u32>,
-    global_constants: Vec<Constant>,
-    global_constant_map: HashMap<Constant, u32>,
-    synced_strings: usize,
-    synced_constants: usize,
-}
-
-/// Owns the bump allocator and a read-only reference into it.
-///
-/// # Safety
-/// The `ir` field points into `_bump`'s storage. We use `'static` as a sentinel
-/// lifetime because the struct owns the backing memory. The `as_ref` method
-/// re-binds the lifetime to `&self`, preventing use-after-free.
-struct OwnedIr {
-    _bump: Bump,
-    ir: RawIrRef<'static>,
-}
-
-impl OwnedIr {
-    fn as_ref(&self) -> RawIrRef<'_> {
-        self.ir
-    }
-}
-
-impl Context {
-    pub fn new() -> Result<Self> {
-        let mut symbols = DefaultStringInterner::new();
-        let mut global = HashMap::new();
-        let builtins_sym = symbols.get_or_intern("builtins");
-        global.insert(builtins_sym, Ir::Builtins);
-
-        let free_globals = [
-            "abort",
-            "baseNameOf",
-            "break",
-            "dirOf",
-            "derivation",
-            "derivationStrict",
-            "fetchGit",
-            "fetchMercurial",
-            "fetchTarball",
-            "fetchTree",
-            "fromTOML",
-            "import",
-            "isNull",
-            "map",
-            "placeholder",
-            "removeAttrs",
-            "scopedImport",
-            "throw",
-            "toString",
-        ];
-        let consts = [
-            ("true", Ir::Bool(true)),
-            ("false", Ir::Bool(false)),
-            ("null", Ir::Null),
-        ];
-
-        for name in free_globals {
-            let name = symbols.get_or_intern(name);
-            let value = Ir::Builtin(name);
-            global.insert(name, value);
-        }
-        for (name, value) in consts {
-            let name = symbols.get_or_intern(name);
-            global.insert(name, value);
-        }
-
-        let config = StoreConfig::from_env();
-        let store = DaemonStore::connect(&config.daemon_socket)?;
-
-        Ok(Self {
-            symbols,
-            global,
-            sources: Vec::new(),
-            store,
-            spans: UnsafeCell::new(Vec::new()),
-            thunk_count: 0,
-            global_strings: Vec::new(),
-            global_string_map: HashMap::new(),
-            global_constants: Vec::new(),
-            global_constant_map: HashMap::new(),
-            synced_strings: 0,
-            synced_constants: 0,
-        })
-    }
-
-    fn downgrade_ctx<'ctx, 'id, 'ir>(
-        &'ctx mut self,
-        bump: &'ir Bump,
-        token: GhostToken<'id>,
-        extra_scope: Option<Scope<'ctx>>,
-    ) -> DowngradeCtx<'ctx, 'id, 'ir> {
-        let source = self.get_current_source();
-        DowngradeCtx::new(
-            bump,
-            token,
-            &mut self.symbols,
-            &self.global,
-            extra_scope,
-            &mut self.thunk_count,
-            source,
-        )
-    }
-
-    fn get_current_dir(&self) -> &Path {
-        self.sources
-            .last()
-            .as_ref()
-            .expect("current_source is not set")
-            .get_dir()
-    }
-
-    fn get_current_source(&self) -> Source {
-        self.sources
-            .last()
-            .expect("current_source is not set")
-            .clone()
-    }
-
-    fn downgrade<'ctx>(
-        &'ctx mut self,
-        source: Source,
-        extra_scope: Option<Scope<'ctx>>,
-    ) -> Result<OwnedIr> {
-        tracing::debug!("Parsing Nix expression");
-
-        self.sources.push(source.clone());
-
-        let root = rnix::Root::parse(&source.src);
-        handle_parse_error(root.errors(), source).map_or(Ok(()), Err)?;
-
-        tracing::debug!("Downgrading Nix expression");
-        let expr = root
-            .tree()
-            .expr()
-            .ok_or_else(|| Error::parse_error("unexpected EOF".into()))?;
-        let bump = Bump::new();
-        GhostToken::new(|token| {
-            let ir = self
-                .downgrade_ctx(&bump, token, extra_scope)
-                .downgrade_toplevel(expr)?;
-            let ir = unsafe { std::mem::transmute::<RawIrRef<'_>, RawIrRef<'static>>(ir) };
-            Ok(OwnedIr { _bump: bump, ir })
-        })
-    }
-
-    pub fn compile_bytecode(&mut self, source: Source) -> Result<Bytecode> {
-        let root = self.downgrade(source, None)?;
-        tracing::debug!("Generating bytecode");
-        let bytecode = bytecode::compile_bytecode(root.as_ref(), self);
-        tracing::debug!("Compiled bytecode: {:#04X?}", bytecode.code);
-        Ok(bytecode)
-    }
-
-    pub fn get_store_dir(&self) -> &str {
-        self.store.get_store_dir()
-    }
-}
-
-impl BytecodeContext for Context {
-    fn intern_string(&mut self, s: &str) -> u32 {
-        if let Some(&idx) = self.global_string_map.get(s) {
-            return idx;
-        }
-        let idx = self.global_strings.len() as u32;
-        self.global_strings.push(s.to_string());
-        self.global_string_map.insert(s.to_string(), idx);
-        idx
-    }
-
-    fn intern_constant(&mut self, c: Constant) -> u32 {
-        if let Some(&idx) = self.global_constant_map.get(&c) {
-            return idx;
-        }
-        let idx = self.global_constants.len() as u32;
-        self.global_constants.push(c.clone());
-        self.global_constant_map.insert(c, idx);
-        idx
-    }
-
-    fn register_span(&self, range: TextRange) -> u32 {
-        // FIXME: SAFETY
-        let spans = unsafe { &mut *self.spans.get() };
-        let id = spans.len();
-        let source_id = self
-            .sources
-            .len()
-            .checked_sub(1)
-            .expect("current_source not set");
-        spans.push((source_id, range));
-        id as u32
-    }
-
-    fn get_sym(&self, id: SymId) -> &str {
-        self.symbols.resolve(id).expect("SymId out of bounds")
-    }
-
-    fn get_current_dir(&self) -> &Path {
-        Context::get_current_dir(self)
-    }
-}
-
-impl DisassemblerContext for Context {
-    fn lookup_string(&self, id: u32) -> &str {
-        self.global_strings
-            .get(id as usize)
-            .expect("string not found")
-    }
-    fn lookup_constant(&self, id: u32) -> &Constant {
-        self.global_constants
-            .get(id as usize)
-            .expect("constant not found")
-    }
-}
-
-enum Scope<'ctx> {
-    Global(&'ctx HashMap<SymId, Ir<'static, RawIrRef<'static>>>),
-    Repl(&'ctx HashSet<SymId>),
-    ScopedImport(HashSet<SymId>),
-    Let(HashMap<SymId, ThunkId>),
-    Param(SymId, ArgId),
-}
-
-struct ScopeGuard<'a, 'ctx, 'id, 'ir> {
-    ctx: &'a mut DowngradeCtx<'ctx, 'id, 'ir>,
-}
-
-impl Drop for ScopeGuard<'_, '_, '_, '_> {
-    fn drop(&mut self) {
-        self.ctx.scopes.pop();
-    }
-}
-
-impl<'id, 'ir, 'ctx> ScopeGuard<'_, 'ctx, 'id, 'ir> {
-    fn as_ctx(&mut self) -> &mut DowngradeCtx<'ctx, 'id, 'ir> {
-        self.ctx
-    }
-}
-
-struct ThunkScope<'id, 'ir> {
-    bindings: bumpalo::collections::Vec<'ir, (ThunkId, IrRef<'id, 'ir>)>,
-    cache: HashTable<(IrRef<'id, 'ir>, ThunkId)>,
-    hasher: DefaultHashBuilder,
-}
-
-impl<'id, 'ir> ThunkScope<'id, 'ir> {
-    fn new_in(bump: &'ir Bump) -> Self {
-        Self {
-            bindings: bumpalo::collections::Vec::new_in(bump),
-            cache: HashTable::new(),
-            hasher: DefaultHashBuilder::default(),
-        }
-    }
-
-    fn lookup_cache(&self, key: IrRef<'id, 'ir>, token: &GhostToken<'id>) -> Option<ThunkId> {
-        let hash = self.hasher.hash_one(IrKey(key, token));
-        self.cache
-            .find(hash, |&(ir, _)| ir_content_eq(key, ir, token))
-            .map(|&(_, id)| id)
-    }
-
-    fn add_binding(&mut self, id: ThunkId, ir: IrRef<'id, 'ir>, token: &GhostToken<'id>) {
-        self.bindings.push((id, ir));
-        let hash = self.hasher.hash_one(IrKey(ir, token));
-        self.cache.insert_unique(hash, (ir, id), |&(ir, _)| {
-            self.hasher.hash_one(IrKey(ir, token))
-        });
-    }
-
-    fn extend_bindings(&mut self, iter: impl IntoIterator<Item = (ThunkId, IrRef<'id, 'ir>)>) {
-        self.bindings.extend(iter);
-    }
-}
-
-struct DowngradeCtx<'ctx, 'id, 'ir> {
-    bump: &'ir Bump,
-    token: GhostToken<'id>,
-    symbols: &'ctx mut DefaultStringInterner,
-    source: Source,
-    scopes: Vec<Scope<'ctx>>,
-    with_scope_count: usize,
-    arg_count: usize,
-    thunk_count: &'ctx mut usize,
-    thunk_scopes: Vec<ThunkScope<'id, 'ir>>,
-}
-
-fn should_thunk<'id>(ir: IrRef<'id, '_>, token: &GhostToken<'id>) -> bool {
-    !matches!(
-        ir.borrow(token),
-        Ir::Builtin(_)
-            | Ir::Builtins
-            | Ir::Int(_)
-            | Ir::Float(_)
-            | Ir::Bool(_)
-            | Ir::Null
-            | Ir::Str(_)
-            | Ir::Thunk(_)
-    )
-}
-
-impl<'ctx, 'id, 'ir> DowngradeCtx<'ctx, 'id, 'ir> {
-    fn new(
-        bump: &'ir Bump,
-        token: GhostToken<'id>,
-        symbols: &'ctx mut DefaultStringInterner,
-        global: &'ctx HashMap<SymId, Ir<'static, RawIrRef<'static>>>,
-        extra_scope: Option<Scope<'ctx>>,
-        thunk_count: &'ctx mut usize,
-        source: Source,
-    ) -> Self {
-        Self {
-            bump,
-            token,
-            symbols,
-            source,
-            scopes: std::iter::once(Scope::Global(global))
-                .chain(extra_scope)
-                .collect(),
-            thunk_count,
-            arg_count: 0,
-            with_scope_count: 0,
-            thunk_scopes: vec![ThunkScope::new_in(bump)],
-        }
-    }
-}
-
-impl<'ctx: 'ir, 'id, 'ir> DowngradeContext<'id, 'ir> for DowngradeCtx<'ctx, 'id, 'ir> {
-    fn new_expr(&self, expr: Ir<'ir, IrRef<'id, 'ir>>) -> IrRef<'id, 'ir> {
-        IrRef::new(self.bump.alloc(GhostCell::new(expr)))
-    }
-
-    fn new_arg(&mut self) -> ArgId {
-        self.arg_count += 1;
-        ArgId(self.arg_count - 1)
-    }
-
-    fn maybe_thunk(&mut self, ir: IrRef<'id, 'ir>) -> IrRef<'id, 'ir> {
-        if !should_thunk(ir, &self.token) {
-            return ir;
-        }
-
-        let cached = self
-            .thunk_scopes
-            .last()
-            .expect("no active cache scope")
-            .lookup_cache(ir, &self.token);
-
-        if let Some(id) = cached {
-            return IrRef::alloc(self.bump, Ir::Thunk(id));
-        }
-
-        let id = ThunkId(*self.thunk_count);
-        *self.thunk_count = self.thunk_count.checked_add(1).expect("thunk id overflow");
-        self.thunk_scopes
-            .last_mut()
-            .expect("no active cache scope")
-            .add_binding(id, ir, &self.token);
-        IrRef::alloc(self.bump, Ir::Thunk(id))
-    }
-
-    fn new_sym(&mut self, sym: String) -> SymId {
-        self.symbols.get_or_intern(sym)
-    }
-
-    fn get_sym(&self, id: SymId) -> Symbol<'_> {
-        self.symbols.resolve(id).expect("no symbol found").into()
-    }
-
-    fn lookup(&self, sym: SymId, span: TextRange) -> Result<IrRef<'id, 'ir>> {
-        for scope in self.scopes.iter().rev() {
-            match scope {
-                &Scope::Global(global_scope) => {
-                    if let Some(expr) = global_scope.get(&sym) {
-                        let ir = match expr {
-                            Ir::Builtins => Ir::Builtins,
-                            Ir::Builtin(s) => Ir::Builtin(*s),
-                            Ir::Bool(b) => Ir::Bool(*b),
-                            Ir::Null => Ir::Null,
-                            _ => unreachable!("globals should only contain leaf IR nodes"),
-                        };
-                        return Ok(self.new_expr(ir));
-                    }
-                }
-                &Scope::Repl(repl_bindings) => {
-                    if repl_bindings.contains(&sym) {
-                        return Ok(self.new_expr(Ir::ReplBinding(sym)));
-                    }
-                }
-                Scope::ScopedImport(scoped_bindings) => {
-                    if scoped_bindings.contains(&sym) {
-                        return Ok(self.new_expr(Ir::ScopedImportBinding(sym)));
-                    }
-                }
-                Scope::Let(let_scope) => {
-                    if let Some(&expr) = let_scope.get(&sym) {
-                        return Ok(self.new_expr(Ir::Thunk(expr)));
-                    }
-                }
-                &Scope::Param(param_sym, id) => {
-                    if param_sym == sym {
-                        return Ok(self.new_expr(Ir::Arg(id)));
-                    }
-                }
-            }
-        }
-
-        if self.with_scope_count > 0 {
-            Ok(self.new_expr(Ir::WithLookup(sym)))
-        } else {
-            Err(Error::downgrade_error(
-                format!("'{}' not found", self.get_sym(sym)),
-                self.get_current_source(),
-                span,
-            ))
-        }
-    }
-
-    fn get_current_source(&self) -> Source {
-        self.source.clone()
-    }
-
-    fn with_let_scope<F, R>(&mut self, keys: &[SymId], f: F) -> Result<R>
-    where
-        F: FnOnce(&mut Self) -> Result<(bumpalo::collections::Vec<'ir, IrRef<'id, 'ir>>, R)>,
-    {
-        let base = *self.thunk_count;
-        *self.thunk_count = self
-            .thunk_count
-            .checked_add(keys.len())
-            .expect("thunk id overflow");
-        let iter = keys.iter().enumerate().map(|(offset, &key)| {
-            (
-                key,
-                ThunkId(unsafe { base.checked_add(offset).unwrap_unchecked() }),
-            )
-        });
-        self.scopes.push(Scope::Let(iter.collect()));
-        let (vals, ret) = {
-            let mut guard = ScopeGuard { ctx: self };
-            f(guard.as_ctx())?
-        };
-        assert_eq!(keys.len(), vals.len());
-        let scope = self.thunk_scopes.last_mut().expect("no active thunk scope");
-        scope.extend_bindings((base..base + keys.len()).map(ThunkId).zip(vals));
-        Ok(ret)
-    }
-
-    fn with_param_scope<F, R>(&mut self, param: SymId, arg: ArgId, f: F) -> R
-    where
-        F: FnOnce(&mut Self) -> R,
-    {
-        self.scopes.push(Scope::Param(param, arg));
-        let mut guard = ScopeGuard { ctx: self };
-        f(guard.as_ctx())
-    }
-
-    fn with_with_scope<F, R>(&mut self, f: F) -> R
-    where
-        F: FnOnce(&mut Self) -> R,
-    {
-        self.with_scope_count += 1;
-        let ret = f(self);
-        self.with_scope_count -= 1;
-        ret
-    }
-
-    fn with_thunk_scope<F, R>(
-        &mut self,
-        f: F,
-    ) -> (
-        R,
-        bumpalo::collections::Vec<'ir, (ThunkId, IrRef<'id, 'ir>)>,
-    )
-    where
-        F: FnOnce(&mut Self) -> R,
-    {
-        self.thunk_scopes.push(ThunkScope::new_in(self.bump));
-        let ret = f(self);
-        (
-            ret,
-            self.thunk_scopes
-                .pop()
-                .expect("no thunk scope left???")
-                .bindings,
-        )
-    }
-
-    fn bump(&self) -> &'ir bumpalo::Bump {
-        self.bump
-    }
-}
-
-impl<'id, 'ir, 'ctx: 'ir> DowngradeCtx<'ctx, 'id, 'ir> {
-    fn downgrade_toplevel(mut self, root: rnix::ast::Expr) -> Result<RawIrRef<'ir>> {
-        let body = root.downgrade(&mut self)?;
-        let thunks = self
-            .thunk_scopes
-            .pop()
-            .expect("no thunk scope left???")
-            .bindings;
-        let ir = IrRef::alloc(self.bump, Ir::TopLevel { body, thunks });
-        Ok(ir.freeze(self.token))
-    }
-}
--- a/fix/src/disassembler.rs
+++ b/fix/src/disassembler.rs
@@ -3,11 +3,10 @@ use std::fmt::Write;
 use colored::Colorize;
 use num_enum::TryFromPrimitive;

-use crate::bytecode::{Bytecode, Constant, Op};
+use crate::codegen::{Bytecode, Op};

 pub(crate) trait DisassemblerContext {
    fn lookup_string(&self, id: u32) -> &str;
-    fn lookup_constant(&self, id: u32) -> &Constant;
 }

 pub(crate) struct Disassembler<'a, Ctx> {
@@ -55,6 +54,22 @@ impl<'a, Ctx: DisassemblerContext> Disassembler<'a, Ctx> {
        i32::from_le_bytes(bytes)
    }

+    fn read_i64(&mut self) -> i64 {
+        let bytes = self.code[self.pos..self.pos + 8]
+            .try_into()
+            .expect("no enough bytes");
+        self.pos += 8;
+        i64::from_le_bytes(bytes)
+    }
+
+    fn read_f64(&mut self) -> f64 {
+        let bytes = self.code[self.pos..self.pos + 8]
+            .try_into()
+            .expect("no enough bytes");
+        self.pos += 8;
+        f64::from_le_bytes(bytes)
+    }
+
    pub fn disassemble(&mut self) -> String {
        self.disassemble_impl(false)
    }
@@ -144,14 +159,17 @@ impl<'a, Ctx: DisassemblerContext> Disassembler<'a, Ctx> {
        let op = Op::try_from_primitive(op_byte).expect("invalid op code");

        match op {
-            Op::PushConst => {
-                let idx = self.read_u32();
-                let val = self.ctx.lookup_constant(idx);
-                let val_str = match val {
-                    Constant::Int(i) => format!("Int({})", i),
-                    Constant::Float(f) => format!("Float(bits: {})", f),
-                };
-                ("PushConst", format!("@{} ({})", idx, val_str))
+            Op::PushSmi => {
+                let val = self.read_i32();
+                ("PushSmi", format!("{}", val))
+            }
+            Op::PushBigInt => {
+                let val = self.read_i64();
+                ("PushBigInt", format!("{}", val))
+            }
+            Op::PushFloat => {
+                let val = self.read_f64();
+                ("PushFloat", format!("{}", val))
            }
            Op::PushString => {
                let idx = self.read_u32();
--- a/fix/src/downgrade.rs
+++ b/fix/src/downgrade.rs
@@ -50,16 +50,16 @@ pub trait DowngradeContext<'id: 'ir, 'ir> {
    fn new_arg(&mut self) -> ArgId;
    fn maybe_thunk(&mut self, ir: IrRef<'id, 'ir>) -> IrRef<'id, 'ir>;

-    fn new_sym(&mut self, sym: String) -> SymId;
-    fn get_sym(&self, id: SymId) -> Symbol<'_>;
-    fn lookup(&self, sym: SymId, span: TextRange) -> Result<IrRef<'id, 'ir>>;
+    fn new_sym(&mut self, sym: String) -> StringId;
+    fn get_sym(&self, id: StringId) -> Symbol<'_>;
+    fn lookup(&self, sym: StringId, span: TextRange) -> Result<IrRef<'id, 'ir>>;

    fn get_current_source(&self) -> Source;

-    fn with_param_scope<F, R>(&mut self, param: SymId, arg: ArgId, f: F) -> R
+    fn with_param_scope<F, R>(&mut self, param: StringId, arg: ArgId, f: F) -> R
    where
        F: FnOnce(&mut Self) -> R;
-    fn with_let_scope<F, R>(&mut self, bindings: &[SymId], f: F) -> Result<R>
+    fn with_let_scope<F, R>(&mut self, bindings: &[StringId], f: F) -> Result<R>
    where
        F: FnOnce(&mut Self) -> Result<(Vec<'ir, IrRef<'id, 'ir>>, R)>;
    fn with_with_scope<F, R>(&mut self, f: F) -> R
@@ -456,8 +456,8 @@ impl<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>> Downgrade<'id, 'ir, Ctx> fo

 enum PendingValue<'ir> {
    Expr(ast::Expr),
-    InheritFrom(ast::Expr, SymId, TextRange),
-    InheritScope(SymId, TextRange),
+    InheritFrom(ast::Expr, StringId, TextRange),
+    InheritScope(StringId, TextRange),
    Set(PendingAttrSet<'ir>),
    ExtendedRecAttrSet {
        base: ast::AttrSet,
@@ -466,7 +466,7 @@ enum PendingValue<'ir> {
 }

 struct PendingAttrSet<'ir> {
-    stcs: HashMap<'ir, SymId, (PendingValue<'ir>, TextRange)>,
+    stcs: HashMap<'ir, StringId, (PendingValue<'ir>, TextRange)>,
    dyns: Vec<'ir, (ast::Attr, PendingValue<'ir>, TextRange)>,
 }

@@ -510,7 +510,7 @@ impl<'id: 'ir, 'ir> PendingAttrSet<'ir> {

    fn insert_static(
        &mut self,
-        sym: SymId,
+        sym: StringId,
        span: TextRange,
        path: &[ast::Attr],
        value: ast::Expr,
@@ -846,7 +846,7 @@ fn make_attrpath_value_entry<'ir>(path: Vec<'ir, ast::Attr>, value: ast::Expr) -
 }

 struct FinalizedAttrSet<'id, 'ir> {
-    stcs: HashMap<'ir, SymId, (IrRef<'id, 'ir>, TextRange)>,
+    stcs: HashMap<'ir, StringId, (IrRef<'id, 'ir>, TextRange)>,
    dyns: Vec<'ir, (IrRef<'id, 'ir>, IrRef<'id, 'ir>, TextRange)>,
 }

@@ -930,23 +930,23 @@ fn downgrade_attrpath<'id, 'ir>(

 struct PatternBindings<'id, 'ir> {
    body: IrRef<'id, 'ir>,
-    required: Vec<'ir, (SymId, TextRange)>,
-    optional: Vec<'ir, (SymId, TextRange)>,
+    required: Vec<'ir, (StringId, TextRange)>,
+    optional: Vec<'ir, (StringId, TextRange)>,
 }

 fn downgrade_pattern_bindings<'id, 'ir, Ctx>(
    pat_entries: impl Iterator<Item = ast::PatEntry>,
-    alias: Option<SymId>,
+    alias: Option<StringId>,
    arg: ArgId,
    ctx: &mut Ctx,
-    body_fn: impl FnOnce(&mut Ctx, &[SymId]) -> Result<IrRef<'id, 'ir>>,
+    body_fn: impl FnOnce(&mut Ctx, &[StringId]) -> Result<IrRef<'id, 'ir>>,
 ) -> Result<PatternBindings<'id, 'ir>>
 where
    Ctx: DowngradeContext<'id, 'ir>,
 {
    let arg = ctx.new_expr(Ir::Arg(arg));
    struct Param {
-        sym: SymId,
+        sym: StringId,
        sym_span: TextRange,
        default: Option<ast::Expr>,
        span: TextRange,
@@ -1045,7 +1045,7 @@ fn downgrade_let_bindings<'id, 'ir, Ctx, F>(
 ) -> Result<IrRef<'id, 'ir>>
 where
    Ctx: DowngradeContext<'id, 'ir>,
-    F: FnOnce(&mut Ctx, &[SymId]) -> Result<IrRef<'id, 'ir>>,
+    F: FnOnce(&mut Ctx, &[StringId]) -> Result<IrRef<'id, 'ir>>,
 {
    downgrade_rec_attrs_impl::<_, _, false>(entries, ctx, |ctx, binding_keys, _dyns| {
        body_fn(ctx, binding_keys)
@@ -1081,7 +1081,7 @@ where
    Ctx: DowngradeContext<'id, 'ir>,
    F: FnOnce(
        &mut Ctx,
-        &[SymId],
+        &[StringId],
        &[(IrRef<'id, 'ir>, IrRef<'id, 'ir>, TextRange)],
    ) -> Result<IrRef<'id, 'ir>>,
 {
@@ -1106,7 +1106,7 @@ where
 fn collect_inherit_lookups<'id, 'ir, Ctx: DowngradeContext<'id, 'ir>>(
    entries: &[ast::Entry],
    ctx: &mut Ctx,
-) -> Result<HashMap<'ir, SymId, (IrRef<'id, 'ir>, TextRange)>> {
+) -> Result<HashMap<'ir, StringId, (IrRef<'id, 'ir>, TextRange)>> {
    let mut inherit_lookups = HashMap::new_in(ctx.bump());
    for entry in entries {
        if let ast::Entry::Inherit(inherit) = entry
@@ -1128,7 +1128,7 @@ fn collect_inherit_lookups<'id, 'ir, Ctx: DowngradeContext<'id, 'ir>>(
 fn collect_binding_syms<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>, const ALLOW_DYN: bool>(
    pending: &PendingAttrSet,
    ctx: &mut Ctx,
-) -> Result<HashSet<SymId>> {
+) -> Result<HashSet<StringId>> {
    let mut binding_syms = HashSet::new();

    for (sym, (_, span)) in &pending.stcs {
@@ -1146,7 +1146,7 @@ fn collect_binding_syms<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>, const AL

 fn finalize_pending_set<'id, 'ir, Ctx: DowngradeContext<'id, 'ir>, const ALLOW_DYN: bool>(
    pending: PendingAttrSet,
-    inherit_lookups: &HashMap<SymId, (IrRef<'id, 'ir>, TextRange)>,
+    inherit_lookups: &HashMap<StringId, (IrRef<'id, 'ir>, TextRange)>,
    ctx: &mut Ctx,
 ) -> Result<FinalizedAttrSet<'id, 'ir>> {
    let mut stcs = HashMap::new_in(ctx.bump());
@@ -1176,7 +1176,7 @@ fn finalize_pending_set<'id, 'ir, Ctx: DowngradeContext<'id, 'ir>, const ALLOW_D

 fn finalize_pending_value<'id, 'ir, Ctx: DowngradeContext<'id, 'ir>, const ALLOW_DYN: bool>(
    value: PendingValue,
-    inherit_lookups: &HashMap<SymId, (IrRef<'id, 'ir>, TextRange)>,
+    inherit_lookups: &HashMap<StringId, (IrRef<'id, 'ir>, TextRange)>,
    ctx: &mut Ctx,
 ) -> Result<IrRef<'id, 'ir>> {
    match value {
--- a/fix/src/ir.rs
+++ b/fix/src/ir.rs
@@ -4,6 +4,7 @@ use std::{
 };

 use bumpalo::{Bump, boxed::Box, collections::Vec};
+use gc_arena::Collect;
 use ghost_cell::{GhostCell, GhostToken};
 use rnix::{TextRange, ast};
 use string_interner::symbol::SymbolU32;
@@ -23,6 +24,10 @@ impl<'id, 'ir> IrRef<'id, 'ir> {
        Self(bump.alloc(GhostCell::new(ir)))
    }

+    pub fn borrow<'a>(&'a self, token: &'a GhostToken<'id>) -> &'a Ir<'ir, Self> {
+        self.0.borrow(token)
+    }
+
    /// Freeze a mutable IR reference into a read-only one, consuming the
    /// `GhostToken` to prevent any further mutation.
    ///
@@ -42,13 +47,6 @@ impl<'id, 'ir> IrRef<'id, 'ir> {
    }
 }

-impl<'id, 'ir> Deref for IrRef<'id, 'ir> {
-    type Target = GhostCell<'id, Ir<'ir, IrRef<'id, 'ir>>>;
-    fn deref(&self) -> &Self::Target {
-        self.0
-    }
-}
-
 #[repr(transparent)]
 #[derive(Clone, Copy)]
 pub struct RawIrRef<'ir>(&'ir Ir<'ir, Self>);
@@ -68,7 +66,7 @@ pub enum Ir<'ir, Ref> {
    Null,
    Str(Box<'ir, String>),
    AttrSet {
-        stcs: HashMap<'ir, SymId, (Ref, TextRange)>,
+        stcs: HashMap<'ir, StringId, (Ref, TextRange)>,
        dyns: Vec<'ir, (Ref, Ref, TextRange)>,
    },
    List {
@@ -119,7 +117,7 @@ pub enum Ir<'ir, Ref> {
        body: Ref,
        thunks: Vec<'ir, (ThunkId, Ref)>,
    },
-    WithLookup(SymId),
+    WithLookup(StringId),

    // Function related
    Func {
@@ -137,7 +135,7 @@ pub enum Ir<'ir, Ref> {

    // Builtins
    Builtins,
-    Builtin(SymId),
+    Builtin(StringId),

    // Misc
    TopLevel {
@@ -146,19 +144,26 @@ pub enum Ir<'ir, Ref> {
    },
    Thunk(ThunkId),
    CurPos(TextRange),
-    ReplBinding(SymId),
-    ScopedImportBinding(SymId),
+    ReplBinding(StringId),
+    ScopedImportBinding(StringId),
 }

 #[repr(transparent)]
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub struct ThunkId(pub usize);

-pub type SymId = SymbolU32;
+#[repr(transparent)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord, Collect)]
+#[collect(require_static)]
+pub struct StringId(pub SymbolU32);

 #[repr(transparent)]
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
-pub struct ArgId(pub usize);
+pub struct ArgId(pub u32);
+
+#[repr(transparent)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct SpanId(pub u32);

 /// Represents a key in an attribute path.
 #[allow(unused)]
@@ -169,7 +174,7 @@ pub enum Attr<Ref> {
    Dynamic(Ref, TextRange),
    /// A static attribute key.
    /// Example: `attrs.key`
-    Str(SymId, TextRange),
+    Str(StringId, TextRange),
 }

 /// The kinds of binary operations supported in Nix.
@@ -248,8 +253,8 @@ impl From<ast::UnaryOpKind> for UnOpKind {
 /// Describes the parameters of a function.
 #[derive(Debug)]
 pub struct Param<'ir> {
-    pub required: Vec<'ir, (SymId, TextRange)>,
-    pub optional: Vec<'ir, (SymId, TextRange)>,
+    pub required: Vec<'ir, (StringId, TextRange)>,
+    pub optional: Vec<'ir, (StringId, TextRange)>,
    pub ellipsis: bool,
 }

--- a/fix/src/lib.rs
+++ b/fix/src/lib.rs
@@ -1,11 +1,12 @@
 #![warn(clippy::unwrap_used)]
+#![allow(dead_code)]

-pub mod context;
 pub mod error;
 pub mod logging;
+pub mod runtime;
 pub mod value;

-mod bytecode;
+mod codegen;
 mod derivation;
 mod disassembler;
 mod downgrade;
@@ -13,7 +14,6 @@ mod downgrade;
 mod ir;
 mod nar;
 mod nix_utils;
-mod runtime;
 mod store;
 mod string_context;

--- a/fix/src/main.rs
+++ b/fix/src/main.rs
@@ -3,9 +3,9 @@ use std::process::exit;

 use anyhow::Result;
 use clap::{Args, Parser, Subcommand};
-use hashbrown::HashSet;
-use fix::context::Context;
 use fix::error::Source;
+use fix::runtime::Runtime;
+use hashbrown::HashSet;
 use rustyline::DefaultEditor;
 use rustyline::error::ReadlineError;

@@ -40,7 +40,7 @@ struct ExprSource {
    file: Option<PathBuf>,
 }

-fn run_compile(context: &mut Context, src: ExprSource, silent: bool) -> Result<()> {
+fn run_compile(runtime: &mut Runtime, src: ExprSource, silent: bool) -> Result<()> {
    let src = if let Some(expr) = src.expr {
        Source::new_eval(expr)?
    } else if let Some(file) = src.file {
@@ -48,10 +48,11 @@ fn run_compile(context: &mut Context, src: ExprSource, silent: bool) -> Result<(
    } else {
        unreachable!()
    };
-    match context.compile_bytecode(src) {
+    todo!()
+    /* match runtime.compile_bytecode(src) {
        Ok(compiled) => {
            if !silent {
-                println!("{}", context.disassemble_colored(&compiled));
+                println!("{}", runtime.disassemble_colored(&compiled));
            }
        }
        Err(err) => {
@@ -59,10 +60,10 @@ fn run_compile(context: &mut Context, src: ExprSource, silent: bool) -> Result<(
            exit(1);
        }
    };
-    Ok(())
+    Ok(()) */
 }

-fn run_eval(context: &mut Context, src: ExprSource) -> Result<()> {
+fn run_eval(runtime: &mut Runtime, src: ExprSource) -> Result<()> {
    let src = if let Some(expr) = src.expr {
        Source::new_eval(expr)?
    } else if let Some(file) = src.file {
@@ -70,7 +71,7 @@ fn run_eval(context: &mut Context, src: ExprSource) -> Result<()> {
    } else {
        unreachable!()
    };
-    match context.eval_deep(src) {
+    match runtime.eval_deep(src) {
        Ok(value) => {
            println!("{}", value.display_compat());
        }
@@ -82,7 +83,7 @@ fn run_eval(context: &mut Context, src: ExprSource) -> Result<()> {
    Ok(())
 }

-fn run_repl(context: &mut Context) -> Result<()> {
+fn run_repl(runtime: &mut Runtime) -> Result<()> {
    let mut rl = DefaultEditor::new()?;
    let mut scope = HashSet::new();
    const RE: ere::Regex<3> = ere::compile_regex!("^[ \t]*([a-zA-Z_][a-zA-Z0-9_'-]*)[ \t]*(.*)$");
@@ -101,20 +102,20 @@ fn run_repl(context: &mut Context) -> Result<()> {
                            eprintln!("Error: missing expression after '='");
                            continue;
                        }
-                        match context.add_binding(ident, expr, &mut scope) {
+                        match runtime.add_binding(ident, expr, &mut scope) {
                            Ok(value) => println!("{} = {}", ident, value),
                            Err(err) => eprintln!("{:?}", miette::Report::new(*err)),
                        }
                    } else {
                        let src = Source::new_repl(line)?;
-                        match context.eval_repl(src, &scope) {
+                        match runtime.eval_repl(src, &scope) {
                            Ok(value) => println!("{value}"),
                            Err(err) => eprintln!("{:?}", miette::Report::new(*err)),
                        }
                    }
                } else {
                    let src = Source::new_repl(line)?;
-                    match context.eval_shallow(src) {
+                    match runtime.eval_repl(src, &scope) {
                        Ok(value) => println!("{value}"),
                        Err(err) => eprintln!("{:?}", miette::Report::new(*err)),
                    }
@@ -141,11 +142,11 @@ fn main() -> Result<()> {

    let cli = Cli::parse();

-    let mut context = Context::new()?;
+    let mut runtime = Runtime::new()?;

    match cli.command {
-        Command::Compile { source, silent } => run_compile(&mut context, source, silent),
-        Command::Eval { source } => run_eval(&mut context, source),
-        Command::Repl => run_repl(&mut context),
+        Command::Compile { source, silent } => run_compile(&mut runtime, source, silent),
+        Command::Eval { source } => run_eval(&mut runtime, source),
+        Command::Repl => run_repl(&mut runtime),
    }
 }
--- a/fix/src/runtime.rs
+++ b/fix/src/runtime.rs
@@ -1 +1,531 @@
+use std::hash::BuildHasher;
+
+use bumpalo::Bump;
+use gc_arena::{Arena, Rootable, arena::CollectionPhase};
+use ghost_cell::{GhostCell, GhostToken};
+use hashbrown::{DefaultHashBuilder, HashMap, HashSet, HashTable};
+use rnix::TextRange;
+use string_interner::DefaultStringInterner;
+
+use crate::codegen::{BytecodeContext, InstructionPtr};
+use crate::downgrade::{Downgrade as _, DowngradeContext};
+use crate::error::{Error, Result, Source};
+use crate::ir::{ArgId, Ir, IrKey, IrRef, RawIrRef, StringId, ThunkId, ir_content_eq};
+use crate::runtime::builtins::new_builtins_env;
+use crate::store::{DaemonStore, StoreConfig};
+use crate::value::Symbol;
+
+mod builtins;
+mod stack;
 mod value;
+mod vm;
+use vm::{Action, VM};
+
+pub struct Runtime {
+    bytecode: Vec<u8>,
+    global_env: HashMap<StringId, Ir<'static, RawIrRef<'static>>>,
+    sources: Vec<Source>,
+    store: DaemonStore,
+    spans: Vec<(usize, TextRange)>,
+    thunk_count: usize,
+    strings: DefaultStringInterner,
+    arena: Arena<Rootable![VM<'_>]>,
+}
+
+impl Runtime {
+    const COLLECTOR_GRANULARITY: f64 = 1024.0;
+
+    pub fn new() -> Result<Self> {
+        let mut strings = DefaultStringInterner::new();
+        let global_env = new_builtins_env(&mut strings);
+
+        let config = StoreConfig::from_env();
+        let store = DaemonStore::connect(&config.daemon_socket)?;
+
+        Ok(Self {
+            global_env,
+            store,
+            strings,
+            thunk_count: 0,
+            bytecode: Vec::new(),
+            sources: Vec::new(),
+            spans: Vec::new(),
+            arena: Arena::new(|mc| VM::new(mc)),
+        })
+    }
+
+    pub fn eval(&mut self, source: Source) -> Result<crate::value::Value> {
+        let root = self.downgrade(source, None)?;
+        let ip = crate::codegen::compile_bytecode(root.as_ref(), self);
+        self.run(ip)
+    }
+
+    pub fn eval_shallow(&mut self, _source: Source) -> Result<crate::value::Value> {
+        todo!()
+    }
+
+    pub fn eval_deep(&mut self, source: Source) -> Result<crate::value::Value> {
+        // FIXME: deep
+        let root = self.downgrade(source, None)?;
+        let ip = crate::codegen::compile_bytecode(root.as_ref(), self);
+        self.run(ip)
+    }
+
+    pub fn eval_repl(
+        &mut self,
+        source: Source,
+        scope: &HashSet<StringId>,
+    ) -> Result<crate::value::Value> {
+        // FIXME: shallow
+        let root = self.downgrade(source, Some(Scope::Repl(scope)))?;
+        let ip = crate::codegen::compile_bytecode(root.as_ref(), self);
+        self.run(ip)
+    }
+
+    pub fn add_binding(
+        &mut self,
+        _ident: &str,
+        _expr: &str,
+        _scope: &mut HashSet<StringId>,
+    ) -> Result<crate::value::Value> {
+        todo!()
+    }
+
+    fn downgrade_ctx<'a, 'bump, 'id>(
+        &'a mut self,
+        bump: &'bump Bump,
+        token: GhostToken<'id>,
+        extra_scope: Option<Scope<'a>>,
+    ) -> DowngradeCtx<'a, 'id, 'bump> {
+        let Runtime {
+            global_env,
+            sources,
+            thunk_count,
+            strings,
+            ..
+        } = self;
+        DowngradeCtx {
+            bump,
+            token,
+            strings,
+            source: sources.last().unwrap().clone(),
+            scopes: [Scope::Global(global_env)].into_iter().chain(extra_scope.into_iter()).collect(),
+            with_scope_count: 0,
+            arg_count: 0,
+            thunk_count,
+            thunk_scopes: vec![ThunkScope::new_in(bump)],
+        }
+    }
+
+    fn downgrade<'a>(&'a mut self, source: Source, extra_scope: Option<Scope<'a>>) -> Result<OwnedIr> {
+        tracing::debug!("Parsing Nix expression");
+
+        self.sources.push(source.clone());
+
+        let root = rnix::Root::parse(&source.src);
+        handle_parse_error(root.errors(), source).map_or(Ok(()), Err)?;
+
+        tracing::debug!("Downgrading Nix expression");
+        let expr = root
+            .tree()
+            .expr()
+            .ok_or_else(|| Error::parse_error("unexpected EOF".into()))?;
+        let bump = Bump::new();
+        GhostToken::new(|token| {
+            let ir = self
+                .downgrade_ctx(&bump, token, extra_scope)
+                .downgrade_toplevel(expr)?;
+            let ir = unsafe { std::mem::transmute::<RawIrRef<'_>, RawIrRef<'static>>(ir) };
+            Ok(OwnedIr { _bump: bump, ir })
+        })
+    }
+
+    fn run(&mut self, ip: InstructionPtr) -> Result<crate::value::Value> {
+        let mut pc = ip.0;
+        loop {
+            let Runtime {
+                bytecode,
+                strings,
+                arena,
+                ..
+            } = self;
+            let action =
+                arena.mutate_root(|mc, root| root.run_batch(bytecode, &mut pc, mc, strings));
+            match action {
+                Action::NeedGc => {
+                    if self.arena.collection_phase() == CollectionPhase::Sweeping {
+                        self.arena.collect_debt();
+                    } else if let Some(marked) = self.arena.mark_debt() {
+                        marked.start_sweeping();
+                    }
+                }
+                Action::Done(done) => {
+                    break done;
+                }
+                Action::Continue => (),
+                Action::IoRequest(_) => todo!(),
+            }
+        }
+    }
+}
+
+fn parse_error_span(error: &rnix::ParseError) -> Option<rnix::TextRange> {
+    use rnix::ParseError::*;
+    match error {
+        Unexpected(range)
+        | UnexpectedExtra(range)
+        | UnexpectedWanted(_, range, _)
+        | UnexpectedDoubleBind(range)
+        | DuplicatedArgs(range, _) => Some(*range),
+        _ => None,
+    }
+}
+
+fn handle_parse_error<'a>(
+    errors: impl IntoIterator<Item = &'a rnix::ParseError>,
+    source: Source,
+) -> Option<Box<Error>> {
+    for err in errors {
+        if let Some(span) = parse_error_span(err) {
+            return Some(
+                Error::parse_error(err.to_string())
+                    .with_source(source)
+                    .with_span(span),
+            );
+        }
+    }
+    None
+}
+
+struct DowngradeCtx<'ctx, 'id, 'ir> {
+    bump: &'ir Bump,
+    token: GhostToken<'id>,
+    strings: &'ctx mut DefaultStringInterner,
+    source: Source,
+    scopes: Vec<Scope<'ctx>>,
+    with_scope_count: u32,
+    arg_count: u32,
+    thunk_count: &'ctx mut usize,
+    thunk_scopes: Vec<ThunkScope<'id, 'ir>>,
+}
+
+fn should_thunk<'id>(ir: IrRef<'id, '_>, token: &GhostToken<'id>) -> bool {
+    !matches!(
+        ir.borrow(token),
+        Ir::Builtin(_)
+            | Ir::Builtins
+            | Ir::Int(_)
+            | Ir::Float(_)
+            | Ir::Bool(_)
+            | Ir::Null
+            | Ir::Str(_)
+            | Ir::Thunk(_)
+    )
+}
+
+impl<'ctx, 'id, 'ir> DowngradeCtx<'ctx, 'id, 'ir> {
+    fn new(
+        bump: &'ir Bump,
+        token: GhostToken<'id>,
+        symbols: &'ctx mut DefaultStringInterner,
+        global: &'ctx HashMap<StringId, Ir<'static, RawIrRef<'static>>>,
+        extra_scope: Option<Scope<'ctx>>,
+        thunk_count: &'ctx mut usize,
+        source: Source,
+    ) -> Self {
+        Self {
+            bump,
+            token,
+            strings: symbols,
+            source,
+            scopes: std::iter::once(Scope::Global(global))
+                .chain(extra_scope)
+                .collect(),
+            thunk_count,
+            arg_count: 0,
+            with_scope_count: 0,
+            thunk_scopes: vec![ThunkScope::new_in(bump)],
+        }
+    }
+}
+
+impl<'ctx: 'ir, 'id, 'ir> DowngradeContext<'id, 'ir> for DowngradeCtx<'ctx, 'id, 'ir> {
+    fn new_expr(&self, expr: Ir<'ir, IrRef<'id, 'ir>>) -> IrRef<'id, 'ir> {
+        IrRef::new(self.bump.alloc(GhostCell::new(expr)))
+    }
+
+    fn new_arg(&mut self) -> ArgId {
+        self.arg_count += 1;
+        ArgId(self.arg_count - 1)
+    }
+
+    fn maybe_thunk(&mut self, ir: IrRef<'id, 'ir>) -> IrRef<'id, 'ir> {
+        if !should_thunk(ir, &self.token) {
+            return ir;
+        }
+
+        let cached = self
+            .thunk_scopes
+            .last()
+            .expect("no active cache scope")
+            .lookup_cache(ir, &self.token);
+
+        if let Some(id) = cached {
+            return IrRef::alloc(self.bump, Ir::Thunk(id));
+        }
+
+        let id = ThunkId(*self.thunk_count);
+        *self.thunk_count = self.thunk_count.checked_add(1).expect("thunk id overflow");
+        self.thunk_scopes
+            .last_mut()
+            .expect("no active cache scope")
+            .add_binding(id, ir, &self.token);
+        IrRef::alloc(self.bump, Ir::Thunk(id))
+    }
+
+    fn new_sym(&mut self, sym: String) -> StringId {
+        StringId(self.strings.get_or_intern(sym))
+    }
+
+    fn get_sym(&self, id: StringId) -> Symbol<'_> {
+        self.strings.resolve(id.0).expect("no symbol found").into()
+    }
+
+    fn lookup(&self, sym: StringId, span: TextRange) -> Result<IrRef<'id, 'ir>> {
+        for scope in self.scopes.iter().rev() {
+            match scope {
+                &Scope::Global(global_scope) => {
+                    if let Some(expr) = global_scope.get(&sym) {
+                        let ir = match expr {
+                            Ir::Builtins => Ir::Builtins,
+                            Ir::Builtin(s) => Ir::Builtin(*s),
+                            Ir::Bool(b) => Ir::Bool(*b),
+                            Ir::Null => Ir::Null,
+                            _ => unreachable!("globals should only contain leaf IR nodes"),
+                        };
+                        return Ok(self.new_expr(ir));
+                    }
+                }
+                &Scope::Repl(repl_bindings) => {
+                    if repl_bindings.contains(&sym) {
+                        return Ok(self.new_expr(Ir::ReplBinding(sym)));
+                    }
+                }
+                Scope::ScopedImport(scoped_bindings) => {
+                    if scoped_bindings.contains(&sym) {
+                        return Ok(self.new_expr(Ir::ScopedImportBinding(sym)));
+                    }
+                }
+                Scope::Let(let_scope) => {
+                    if let Some(&expr) = let_scope.get(&sym) {
+                        return Ok(self.new_expr(Ir::Thunk(expr)));
+                    }
+                }
+                &Scope::Param(param_sym, id) => {
+                    if param_sym == sym {
+                        return Ok(self.new_expr(Ir::Arg(id)));
+                    }
+                }
+            }
+        }
+
+        if self.with_scope_count > 0 {
+            Ok(self.new_expr(Ir::WithLookup(sym)))
+        } else {
+            Err(Error::downgrade_error(
+                format!("'{}' not found", self.get_sym(sym)),
+                self.get_current_source(),
+                span,
+            ))
+        }
+    }
+
+    fn get_current_source(&self) -> Source {
+        self.source.clone()
+    }
+
+    fn with_let_scope<F, R>(&mut self, keys: &[StringId], f: F) -> Result<R>
+    where
+        F: FnOnce(&mut Self) -> Result<(bumpalo::collections::Vec<'ir, IrRef<'id, 'ir>>, R)>,
+    {
+        let base = *self.thunk_count;
+        *self.thunk_count = self
+            .thunk_count
+            .checked_add(keys.len())
+            .expect("thunk id overflow");
+        let iter = keys.iter().enumerate().map(|(offset, &key)| {
+            (
+                key,
+                ThunkId(unsafe { base.checked_add(offset).unwrap_unchecked() }),
+            )
+        });
+        self.scopes.push(Scope::Let(iter.collect()));
+        let (vals, ret) = {
+            let mut guard = ScopeGuard { ctx: self };
+            f(guard.as_ctx())?
+        };
+        assert_eq!(keys.len(), vals.len());
+        let scope = self.thunk_scopes.last_mut().expect("no active thunk scope");
+        scope.extend_bindings((base..base + keys.len()).map(ThunkId).zip(vals));
+        Ok(ret)
+    }
+
+    fn with_param_scope<F, R>(&mut self, param: StringId, arg: ArgId, f: F) -> R
+    where
+        F: FnOnce(&mut Self) -> R,
+    {
+        self.scopes.push(Scope::Param(param, arg));
+        let mut guard = ScopeGuard { ctx: self };
+        f(guard.as_ctx())
+    }
+
+    fn with_with_scope<F, R>(&mut self, f: F) -> R
+    where
+        F: FnOnce(&mut Self) -> R,
+    {
+        self.with_scope_count += 1;
+        let ret = f(self);
+        self.with_scope_count -= 1;
+        ret
+    }
+
+    fn with_thunk_scope<F, R>(
+        &mut self,
+        f: F,
+    ) -> (
+        R,
+        bumpalo::collections::Vec<'ir, (ThunkId, IrRef<'id, 'ir>)>,
+    )
+    where
+        F: FnOnce(&mut Self) -> R,
+    {
+        self.thunk_scopes.push(ThunkScope::new_in(self.bump));
+        let ret = f(self);
+        (
+            ret,
+            self.thunk_scopes
+                .pop()
+                .expect("no thunk scope left???")
+                .bindings,
+        )
+    }
+
+    fn bump(&self) -> &'ir bumpalo::Bump {
+        self.bump
+    }
+}
+
+impl<'id, 'ir, 'ctx: 'ir> DowngradeCtx<'ctx, 'id, 'ir> {
+    fn downgrade_toplevel(mut self, root: rnix::ast::Expr) -> Result<RawIrRef<'ir>> {
+        let body = root.downgrade(&mut self)?;
+        let thunks = self
+            .thunk_scopes
+            .pop()
+            .expect("no thunk scope left???")
+            .bindings;
+        let ir = IrRef::alloc(self.bump, Ir::TopLevel { body, thunks });
+        Ok(ir.freeze(self.token))
+    }
+}
+
+struct ThunkScope<'id, 'ir> {
+    bindings: bumpalo::collections::Vec<'ir, (ThunkId, IrRef<'id, 'ir>)>,
+    cache: HashTable<(IrRef<'id, 'ir>, ThunkId)>,
+    hasher: DefaultHashBuilder,
+}
+
+impl<'id, 'ir> ThunkScope<'id, 'ir> {
+    fn new_in(bump: &'ir Bump) -> Self {
+        Self {
+            bindings: bumpalo::collections::Vec::new_in(bump),
+            cache: HashTable::new(),
+            hasher: DefaultHashBuilder::default(),
+        }
+    }
+
+    fn lookup_cache(&self, key: IrRef<'id, 'ir>, token: &GhostToken<'id>) -> Option<ThunkId> {
+        let hash = self.hasher.hash_one(IrKey(key, token));
+        self.cache
+            .find(hash, |&(ir, _)| ir_content_eq(key, ir, token))
+            .map(|&(_, id)| id)
+    }
+
+    fn add_binding(&mut self, id: ThunkId, ir: IrRef<'id, 'ir>, token: &GhostToken<'id>) {
+        self.bindings.push((id, ir));
+        let hash = self.hasher.hash_one(IrKey(ir, token));
+        self.cache.insert_unique(hash, (ir, id), |&(ir, _)| {
+            self.hasher.hash_one(IrKey(ir, token))
+        });
+    }
+
+    fn extend_bindings(&mut self, iter: impl IntoIterator<Item = (ThunkId, IrRef<'id, 'ir>)>) {
+        self.bindings.extend(iter);
+    }
+}
+
+enum Scope<'ctx> {
+    Global(&'ctx HashMap<StringId, Ir<'static, RawIrRef<'static>>>),
+    Repl(&'ctx HashSet<StringId>),
+    ScopedImport(HashSet<StringId>),
+    Let(HashMap<StringId, ThunkId>),
+    Param(StringId, ArgId),
+}
+
+struct ScopeGuard<'a, 'ctx, 'id, 'ir> {
+    ctx: &'a mut DowngradeCtx<'ctx, 'id, 'ir>,
+}
+
+impl Drop for ScopeGuard<'_, '_, '_, '_> {
+    fn drop(&mut self) {
+        self.ctx.scopes.pop();
+    }
+}
+
+impl<'id, 'ir, 'ctx> ScopeGuard<'_, 'ctx, 'id, 'ir> {
+    fn as_ctx(&mut self) -> &mut DowngradeCtx<'ctx, 'id, 'ir> {
+        self.ctx
+    }
+}
+
+struct OwnedIr {
+    _bump: Bump,
+    ir: RawIrRef<'static>,
+}
+
+impl OwnedIr {
+    unsafe fn new(ir: RawIrRef<'_>, bump: Bump) -> Self {
+        Self {
+            _bump: bump,
+            ir: unsafe { std::mem::transmute::<RawIrRef<'_>, RawIrRef<'static>>(ir) }
+        }
+    }
+
+    fn as_ref(&self) -> RawIrRef<'_> {
+        self.ir
+    }
+}
+
+impl BytecodeContext for Runtime {
+    fn intern_string(&mut self, s: &str) -> StringId {
+        StringId(self.strings.get_or_intern(s))
+    }
+
+    fn register_span(&mut self, range: TextRange) -> u32 {
+        let id = self.spans.len();
+        let source_id = self
+            .sources
+            .len()
+            .checked_sub(1)
+            .expect("current_source not set");
+        self.spans.push((source_id, range));
+        id as u32
+    }
+
+    fn get_code(&self) -> &[u8] {
+        &self.bytecode
+    }
+
+    fn get_code_mut(&mut self) -> &mut Vec<u8> {
+        &mut self.bytecode
+    }
+}
--- a/fix/src/runtime/builtins.rs
+++ b/fix/src/runtime/builtins.rs
@@ -0,0 +1,51 @@
+use hashbrown::HashMap;
+use string_interner::DefaultStringInterner;
+
+use crate::ir::{Ir, RawIrRef, StringId};
+
+pub(super) fn new_builtins_env(
+    interner: &mut DefaultStringInterner,
+) -> HashMap<StringId, Ir<'static, RawIrRef<'static>>> {
+    let mut builtins = HashMap::new();
+    let builtins_sym = StringId(interner.get_or_intern("builtins"));
+    builtins.insert(builtins_sym, Ir::Builtins);
+
+    let free_globals = [
+        "abort",
+        "baseNameOf",
+        "break",
+        "dirOf",
+        "derivation",
+        "derivationStrict",
+        "fetchGit",
+        "fetchMercurial",
+        "fetchTarball",
+        "fetchTree",
+        "fromTOML",
+        "import",
+        "isNull",
+        "map",
+        "placeholder",
+        "removeAttrs",
+        "scopedImport",
+        "throw",
+        "toString",
+    ];
+    let consts = [
+        ("true", Ir::Bool(true)),
+        ("false", Ir::Bool(false)),
+        ("null", Ir::Null),
+    ];
+
+    for name in free_globals {
+        let name = StringId(interner.get_or_intern(name));
+        let value = Ir::Builtin(name);
+        builtins.insert(name, value);
+    }
+    for (name, value) in consts {
+        let name = StringId(interner.get_or_intern(name));
+        builtins.insert(name, value);
+    }
+
+    builtins
+}
--- a/fix/src/runtime/stack.rs
+++ b/fix/src/runtime/stack.rs
@@ -0,0 +1,89 @@
+use std::mem::MaybeUninit;
+
+use gc_arena::Collect;
+use smallvec::SmallVec;
+
+// FIXME: Drop???
+pub(super) struct Stack<const N: usize, T> {
+    inner: Box<[MaybeUninit<T>; N]>,
+    len: usize,
+}
+
+unsafe impl<'gc, const N: usize, T: Collect<'gc> + 'gc> Collect<'gc> for Stack<N, T> {
+    const NEEDS_TRACE: bool = true;
+    fn trace<U: gc_arena::collect::Trace<'gc>>(&self, cc: &mut U) {
+        for item in self.inner[..self.len].iter() {
+            unsafe {
+                item.assume_init_ref().trace(cc);
+            }
+        }
+    }
+}
+
+impl<const N: usize, T> Default for Stack<N, T> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<const N: usize, T> Stack<N, T> {
+    pub(super) fn new() -> Self {
+        Self {
+            inner: Box::new([const { MaybeUninit::uninit() }; N]),
+            len: 0,
+        }
+    }
+
+    pub(super) fn push(&mut self, val: T) -> Result<(), T> {
+        if self.len == N {
+            return Err(val);
+        }
+        unsafe {
+            self.inner.get_unchecked_mut(self.len).write(val);
+        }
+        self.len += 1;
+        Ok(())
+    }
+
+    pub(super) fn pop(&mut self) -> Option<T> {
+        if self.len == 0 {
+            return None;
+        }
+        let ret = unsafe {
+            self.inner
+                .get_unchecked_mut(self.len - 1)
+                .assume_init_read()
+        };
+        self.len -= 1;
+        Some(ret)
+    }
+
+    pub(super) fn tos(&self) -> Option<&T> {
+        if self.len == 0 {
+            return None;
+        }
+        Some(unsafe { self.inner.get_unchecked(self.len - 1).assume_init_ref() })
+    }
+
+    pub(super) fn tos_mut(&mut self) -> Option<&mut T> {
+        if self.len == 0 {
+            return None;
+        }
+        Some(unsafe { self.inner.get_unchecked_mut(self.len - 1).assume_init_mut() })
+    }
+
+    pub(super) fn len(&self) -> usize {
+        self.len
+    }
+
+    pub(super) fn pop_n<const M: usize>(&mut self, n: usize) -> SmallVec<[T; M]> {
+        assert!(n <= self.len, "pop_n: not enough items on stack");
+        let mut result = SmallVec::new();
+        let start = self.len - n;
+        for i in start..self.len {
+            result.push(unsafe { self.inner.get_unchecked(i).assume_init_read() });
+        }
+        self.len = start;
+        result
+    }
+}
--- a/fix/src/runtime/value.rs
+++ b/fix/src/runtime/value.rs
@@ -1,68 +1,121 @@
 use std::fmt;
 use std::marker::PhantomData;
+use std::mem::size_of;
+use std::ops::Deref;

 use boxing::nan::raw::{RawBox, RawStore, RawTag, Value as RawValue};
-use gc_arena::{Collect, Gc};
-use hashbrown::HashTable;
+use gc_arena::{Collect, Gc, Mutation, RefLock, collect::Trace};
+use sealed::sealed;
+use smallvec::SmallVec;
+use string_interner::{Symbol, symbol::SymbolU32};

-trait Storable {
+use crate::ir::StringId;
+
+#[sealed]
+pub(crate) trait Storable {
    const TAG: (bool, u8);
 }
-trait InlineStorable: Storable + RawStore {}
-trait GcStorable: Storable {}
+pub(crate) trait InlineStorable: Storable + RawStore {}
+pub(crate) trait GcStorable: Storable {}

-macro_rules! inline_types {
-    ($($type:ty => $id:expr),*$(,)?) => {
+macro_rules! define_value_types {
+    (
+        inline { $($itype:ty => $itag:expr, $iname:literal;)* }
+        gc { $($gtype:ty => $gtag:expr, $gname:literal;)* }
+    ) => {
        $(
-        impl Storable for $type {
-            const TAG: (bool, u8) = (false, $id);
+        #[sealed]
+        impl Storable for $itype {
+            const TAG: (bool, u8) = $itag;
        }
-        impl InlineStorable for $type {}
+        impl InlineStorable for $itype {}
        )*
+        $(
+        #[sealed]
+        impl Storable for $gtype {
+            const TAG: (bool, u8) = $gtag;
+        }
+        impl GcStorable for $gtype {}
+        )*
+
+        const _: () = assert!(size_of::<Value<'static>>() == 8);
+        $(const _: () = assert!(size_of::<$itype>() <= 6);)*
+        $(const _: () = { let (_, val) = $itag; assert!(val >= 1 && val <= 7); };)*
+        $(const _: () = { let (_, val) = $gtag; assert!(val >= 1 && val <= 7); };)*
+
+        const _: () = {
+            let tags: &[(bool, u8)] = &[$($itag),*, $($gtag),*];
+            let mut mask_false: u8 = 0;
+            let mut mask_true: u8 = 0;
+            let mut i = 0;
+            while i < tags.len() {
+                let (neg, val) = tags[i];
+                let bit = 1 << val;
+                if neg {
+                    assert!(mask_true & bit == 0, "duplicate true tag id");
+                    mask_true |= bit;
+                } else {
+                    assert!(mask_false & bit == 0, "duplicate false tag id");
+                    mask_false |= bit;
+                }
+                i += 1;
+            }
        };
+
+        unsafe impl<'gc> Collect<'gc> for Value<'gc> {
+            const NEEDS_TRACE: bool = true;
+            fn trace<T: Trace<'gc>>(&self, cc: &mut T) {
+                let Some(tag) = self.raw.tag() else { return };
+                match tag.neg_val() {
+                    $(<$gtype as Storable>::TAG => unsafe {
+                        self.load_gc::<$gtype>().trace(cc)
+                    },)*
+                    $(<$itype as Storable>::TAG => (),)*
+                    (neg, val) => unreachable!("invalid tag: neg={neg}, val={val}"),
+                }
+            }
+        }
+
+        impl fmt::Debug for Value<'_> {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                match self.tag() {
+                    None => write!(f, "Float({:?})", unsafe {
+                        self.raw.float().unwrap_unchecked()
+                    }),
+                    $(Some(<$itype as Storable>::TAG) => write!(f, "{}({:?})", $iname, unsafe {
+                        self.as_inline::<$itype>().unwrap_unchecked()
+                    }),)*
+                    $(Some(<$gtype as Storable>::TAG) =>
+                        write!(f, "{}({:?})", $gname, unsafe { self.as_gc::<$gtype>().unwrap_unchecked() }),)*
+                    Some((neg, val)) => write!(f, "Unknown(neg={neg}, val={val})"),
+                }
            }
-macro_rules! gc_types {
-    ($($type:ty => $id:expr),*$(,)?) => {
-        $(
-        impl Storable for $type {
-            const TAG: (bool, u8) = (true, $id);
        }
-        impl GcStorable for $type {}
-        )*
    };
 }

-inline_types! {
-    i32 => 1,
-    bool => 2,
-    Null => 3,
-    SmallStringId => 4,
+define_value_types! {
+    inline {
+        i32 => (false, 1), "SmallInt";
+        bool => (false, 2), "Bool";
+        Null => (false, 3), "Null";
+        StringId => (false, 4), "SmallString";
+        PrimOp => (false, 5), "PrimOp";
+    }
+    gc {
+        i64 => (false, 6), "BigInt";
+        NixString => (false, 7), "String";
+        AttrSet<'_> => (true, 1), "AttrSet";
+        List<'_> => (true, 2), "List";
+        Thunk<'_> => (true, 3), "Thunk";
+        Closure<'_> => (true, 4), "Closure";
+        PrimOpApp<'_> => (true, 5), "PrimOpApp";
    }
-gc_types! {
-    i64 => 1,
-    NixString => 2,
-    SmallAttrSet<'_> => 3,
-    AttrSet<'_> => 4,
-    Box<[Value<'_>]> => 5,
 }

 /// # Nix runtime value representation
 ///
-/// NaN-boxed value fitting in 8 bytes. Morally equivalent to:
-/// ```ignore
-/// enum Value<'gc> {
-///     Float(SingleNaNF64),
-///     SmallInt(i32),
-///     BigInt(Gc<'gc, i64>),
-///     Bool(bool),
-///     Null,
-///     SmallString(SmallStringId),
-///     String(Gc<'gc, NixString>),
-///     SmallAttrSet(Gc<'gc, SmallAttrSet<'gc>>),
-///     AttrSet(Gc<'gc, AttrSet<'gc>>),
-///     List(Gc<'gc, Box<[Value<'gc>]>>),
-/// }
-/// ```
+/// NaN-boxed value fitting in 8 bytes.
 #[repr(transparent)]
 pub(crate) struct Value<'gc> {
    raw: RawBox,
@@ -79,90 +132,16 @@ impl Clone for Value<'_> {
    }
 }

-macro_rules! trace_impl {
-    ($self:expr, $cc:expr, $tag:expr; $($type:ty),*$(,)?) => {
-        match $tag.neg_val() {
-            // Positive tags are inline data - skip it.
-            (false, _) => (),
-
-            // Negative tags are Gc pointers - reconstruct and trace it.
-            $(
-            <$type as Storable>::TAG => unsafe { $self.load_gc::<$type>().trace($cc) },
-            )*
-
-            (true, val) => unreachable!("invalid negative tag value: {val}"),
-        }
-    };
-}
-
-unsafe impl<'gc> Collect for Value<'gc> {
-    fn trace(&self, cc: &gc_arena::Collection) {
-        // No tag - raw float
-        let Some(tag) = self.raw.tag() else { return };
-        trace_impl! {
-            self, cc, tag;
-            i64,
-            NixString,
-            SmallAttrSet<'gc>,
-            AttrSet<'gc>,
-            Box<[Value<'gc>]>,
-        }
-    }
-
-    fn needs_trace() -> bool
-    where
-        Self: Sized,
-    {
-        true
-    }
-}
-
-macro_rules! debug_impl {
-    ($self:expr; $($type:ty),*$(,)?) => {
-        match $self.tag() {
-            None => write!(f, "Float({:?})", unsafe {
-                self.raw.float().unwrap_unchecked()
-            }),
-
-            $(
-            Some()
-            )*
-        }
-    };
-}
-
-impl fmt::Debug for Value<'_> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self.tag() {
-            None => write!(f, "Float({:?})", unsafe {
-                self.raw.float().unwrap_unchecked()
-            }),
-            Some(i32::TAG) => write!(f, "SmallInt({:?})", unsafe {
-                self.as_inline::<i32>().unwrap_unchecked()
-            }),
-            Some(bool::TAG) => write!(f, "Bool({:?})", unsafe {
-                self.as_inline::<bool>().unwrap_unchecked()
-            }),
-            Some(Null::TAG) => write!(f, "Null"),
-            Some(SmallStringId::TAG) => {
-                write!(f, "SmallString({:?})", unsafe {
-                    self.as_inline::<SmallStringId>().unwrap_unchecked().0
-                })
-            }
-            Some(i64::TAG) => write!(f, "BigInt(Gc<..>)"),
-            Some(NixString::TAG) => write!(f, "String(Gc<..>)"),
-            Some(SmallAttrSet::TAG) => write!(f, "SmallAttrSet(Gc<..>)"),
-            Some(AttrSet::TAG) => write!(f, "AttrSet(Gc<..>)"),
-            Some(<Box<[Value<'_>]> as Storable>::TAG) => write!(f, "List(Gc<..>)"),
-            Some((neg, val)) => write!(f, "Unknown(neg={neg}, val={val})"),
-        }
+impl Default for Value<'_> {
+    #[inline(always)]
+    fn default() -> Self {
+        Self::new_inline(Null)
    }
 }

 impl<'gc> Value<'gc> {
    #[inline(always)]
    fn mk_tag(neg: bool, val: u8) -> RawTag {
-        debug_assert!((1..=7).contains(&val));
        // Safety: val is asserted to be in 1..=7.
        unsafe { RawTag::new_unchecked(neg, val) }
    }
@@ -175,20 +154,13 @@ impl<'gc> Value<'gc> {
        }
    }

-    /// Store a GC pointer with the given (negative) tag value.
-    #[inline(always)]
-    fn store_gc<T>(tag_val: u8, gc: Gc<'gc, T>) -> Self {
-        let ptr = Gc::as_ptr(gc);
-        Self::from_raw_value(RawValue::store(Self::mk_tag(true, tag_val), ptr))
-    }
-
    /// Load a GC pointer from a value with a negative tag.
    ///
    /// # Safety
    ///
    /// The value must actually store a `Gc<'gc, T>` with the matching type.
    #[inline(always)]
-    unsafe fn load_gc<T>(&self) -> Gc<'gc, T> {
+    unsafe fn load_gc<T: GcStorable>(&self) -> Gc<'gc, T> {
        unsafe {
            let rv = self.raw.value().unwrap_unchecked();
            let ptr: *const T = <*const T as RawStore>::from_val(rv);
@@ -214,13 +186,13 @@ impl<'gc> Value<'gc> {

    #[inline]
    pub(crate) fn new_inline<T: InlineStorable>(val: T) -> Self {
-        Self::from_raw_value(RawValue::store(Self::mk_tag(false, T::TAG.1), val))
+        Self::from_raw_value(RawValue::store(Self::mk_tag(T::TAG.0, T::TAG.1), val))
    }

    #[inline]
    pub(crate) fn new_gc<T: GcStorable>(gc: Gc<'gc, T>) -> Self {
        let ptr = Gc::as_ptr(gc);
-        Self::from_raw_value(RawValue::store(Self::mk_tag(true, T::TAG.1), ptr))
+        Self::from_raw_value(RawValue::store(Self::mk_tag(T::TAG.0, T::TAG.1), ptr))
    }
 }

@@ -268,6 +240,7 @@ impl<'gc> Value<'gc> {
    }
 }

+#[derive(Clone, Copy, Debug)]
 pub(crate) struct Null;
 impl RawStore for Null {
    fn to_val(self, value: &mut RawValue) {
@@ -278,17 +251,15 @@ impl RawStore for Null {
    }
 }

-// TODO: size?
-#[repr(transparent)]
-#[derive(Clone, Copy, PartialEq, Eq, Debug, Collect)]
-#[collect(require_static)]
-pub(crate) struct SmallStringId(u32);
-impl RawStore for SmallStringId {
+impl RawStore for StringId {
    fn to_val(self, value: &mut RawValue) {
-        self.0.to_val(value);
+        (self.0.to_usize() as u32).to_val(value);
    }
    fn from_val(value: &RawValue) -> Self {
-        Self(u32::from_val(value))
+        Self(
+            SymbolU32::try_from_usize(u32::from_val(value) as usize)
+                .expect("failed to read StringId from Value"),
+        )
    }
 }

@@ -320,45 +291,199 @@ impl fmt::Debug for NixString {
    }
 }

-/// Fixed-size attribute set (up to 8 entries).
-#[derive(Collect)]
+#[derive(Collect, Debug)]
 #[collect(no_drop)]
-pub(crate) struct SmallAttrSet<'gc> {
-    // TODO: proper key storage, length tracking, and lookup
-    inner: [Value<'gc>; 8],
-}
-
-/// Hash-table-backed attribute set.
 pub(crate) struct AttrSet<'gc> {
-    inner: HashTable<AttrSetEntry<'gc>>,
+    pub(crate) entries: SmallVec<[(StringId, Value<'gc>); 4]>,
 }

-unsafe impl<'gc> Collect for AttrSet<'gc> {
-    fn trace(&self, cc: &gc_arena::Collection) {
-        for entry in self.inner.iter() {
-            Collect::trace(&entry.key, cc);
-            Collect::trace(&entry.value, cc);
+impl<'gc> AttrSet<'gc> {
+    pub(crate) fn from_sorted(entries: SmallVec<[(StringId, Value<'gc>); 4]>) -> Self {
+        debug_assert!(entries.is_sorted_by_key(|(key, _)| *key));
+        Self { entries }
+    }
+
+    pub(crate) fn lookup(&self, key: StringId) -> Option<Value<'gc>> {
+        self.entries
+            .binary_search_by_key(&key, |(k, _)| *k)
+            .ok()
+            .map(|i| self.entries[i].1.clone())
+    }
+
+    pub(crate) fn has(&self, key: StringId) -> bool {
+        self.entries
+            .binary_search_by_key(&key, |(k, _)| *k)
+            .is_ok()
+    }
+
+    pub(crate) fn merge(&self, other: &Self, mc: &Mutation<'gc>) -> Gc<'gc, Self> {
+        use std::cmp::Ordering::*;
+
+        debug_assert!(self.entries.is_sorted_by_key(|(key, _)| *key));
+        debug_assert!(other.entries.is_sorted_by_key(|(key, _)| *key));
+
+        let mut entries = SmallVec::new();
+        let mut i = 0;
+        let mut j = 0;
+        while i < self.entries.len() && j < other.entries.len() {
+            match self.entries[i].0.cmp(&other.entries[j].0) {
+                Less => {
+                    entries.push(self.entries[i].clone());
+                    i += 1;
+                }
+                Greater => {
+                    entries.push(other.entries[j].clone());
+                    j += 1;
+                }
+                Equal => {
+                    entries.push(other.entries[j].clone());
+                    i += 1;
+                    j += 1;
+                }
+            }
+        }
+        entries.extend(other.entries[j..].iter().cloned());
+        entries.extend(self.entries[i..].iter().cloned());
+
+        debug_assert!(entries.is_sorted_by_key(|(key, _)| *key));
+
+        Gc::new(mc, AttrSet { entries })
    }
 }

-    fn needs_trace() -> bool
-    where
-        Self: Sized,
-    {
-        true
-    }
-}
-
-#[derive(Collect)]
+#[derive(Collect, Debug)]
 #[collect(no_drop)]
-struct AttrSetEntry<'gc> {
-    key: AttrKey<'gc>,
-    value: Value<'gc>,
+pub(crate) struct List<'gc> {
+    pub(crate) inner: SmallVec<[Value<'gc>; 4]>,
 }

-#[derive(Collect)]
+pub(crate) type Thunk<'gc> = RefLock<ThunkState<'gc>>;
+
+#[derive(Collect, Debug)]
 #[collect(no_drop)]
-pub(crate) enum AttrKey<'gc> {
-    Small(SmallStringId),
-    Large(Gc<'gc, str>),
+pub(crate) enum ThunkState<'gc> {
+    Pending {
+        ip: u32,
+        env: Gc<'gc, RefLock<Env<'gc>>>,
+    },
+    Blackhole,
+    Evaluated(Value<'gc>),
+}
+
+#[derive(Collect, Debug)]
+#[collect(no_drop)]
+pub(crate) struct Env<'gc> {
+    pub(crate) locals: SmallVec<[Value<'gc>; 4]>,
+    pub(crate) prev: Option<Gc<'gc, RefLock<Env<'gc>>>>,
+}
+
+impl<'gc> Env<'gc> {
+    pub(crate) fn empty() -> Self {
+        Env {
+            locals: SmallVec::new(),
+            prev: None,
+        }
+    }
+
+    pub(crate) fn with_arg(
+        arg: Value<'gc>,
+        n_locals: u32,
+        prev: Gc<'gc, RefLock<Env<'gc>>>,
+    ) -> Self {
+        let mut locals = smallvec::smallvec![Value::default(); 1 + n_locals as usize];
+        locals[0] = arg;
+        Env {
+            locals,
+            prev: Some(prev),
+        }
+    }
+}
+
+#[derive(Collect, Debug)]
+#[collect(no_drop)]
+pub(crate) struct Closure<'gc> {
+    pub(crate) ip: u32,
+    pub(crate) n_locals: u32,
+    pub(crate) env: Gc<'gc, RefLock<Env<'gc>>>,
+    pub(crate) pattern: Option<Gc<'gc, PatternInfo>>,
+}
+
+#[derive(Collect, Debug)]
+#[collect(require_static)]
+pub(crate) struct PatternInfo {
+    pub(crate) required: SmallVec<[StringId; 4]>,
+    pub(crate) optional: SmallVec<[StringId; 4]>,
+    pub(crate) ellipsis: bool,
+    pub(crate) param_spans: Box<[(StringId, u32)]>,
+}
+
+#[derive(Clone, Copy, Debug, Collect)]
+#[collect(require_static)]
+pub(crate) struct PrimOp {
+    pub(crate) id: u8,
+    pub(crate) arity: u8,
+}
+
+impl RawStore for PrimOp {
+    fn to_val(self, value: &mut RawValue) {
+        value.set_data([0, 0, 0, 0, self.id, self.arity]);
+    }
+    fn from_val(value: &RawValue) -> Self {
+        let [.., id, arity] = *value.data();
+        Self { id, arity }
+    }
+}
+
+#[derive(Collect, Debug)]
+#[collect(no_drop)]
+pub(crate) struct PrimOpApp<'gc> {
+    pub(crate) primop: PrimOp,
+    pub(crate) args: SmallVec<[Value<'gc>; 2]>,
+}
+
+#[repr(transparent)]
+pub(crate) struct StrictValue<'gc>(Value<'gc>);
+
+impl<'gc> StrictValue<'gc> {
+    #[inline]
+    pub(crate) fn try_from_forced(val: Value<'gc>) -> Option<Self> {
+        if !val.is::<Thunk<'gc>>() {
+            Some(Self(val))
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    pub(crate) fn into_relaxed(self) -> Value<'gc> {
+        self.0
+    }
+}
+
+impl<'gc> Deref for StrictValue<'gc> {
+    type Target = Value<'gc>;
+    #[inline]
+    fn deref(&self) -> &Value<'gc> {
+        &self.0
+    }
+}
+
+impl Clone for StrictValue<'_> {
+    #[inline]
+    fn clone(&self) -> Self {
+        Self(self.0.clone())
+    }
+}
+
+impl fmt::Debug for StrictValue<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&self.0, f)
+    }
+}
+
+unsafe impl<'gc> Collect<'gc> for StrictValue<'gc> {
+    const NEEDS_TRACE: bool = true;
+    fn trace<T: gc_arena::collect::Trace<'gc>>(&self, cc: &mut T) {
+        self.0.trace(cc);
+    }
 }
--- a/fix/src/runtime/vm.rs
+++ b/fix/src/runtime/vm.rs
--- a/fix/tests/tests/io_operations.rs
+++ b/fix/tests/tests/io_operations.rs
@@ -1,5 +1,5 @@
-use fix::context::Context;
 use fix::error::Source;
+use fix::runtime::Runtime;
 use fix::value::Value;

 use crate::utils::{eval, eval_result};
@@ -97,7 +97,7 @@ fn import_with_complex_dependency_graph() {

 #[test_log::test]
 fn path_with_file() {
-    let mut ctx = Context::new().unwrap();
+    let mut ctx = Runtime::new().unwrap();
    let temp_dir = tempfile::tempdir().unwrap();
    let test_file = temp_dir.path().join("test.txt");
    std::fs::write(&test_file, "Hello, World!").unwrap();
@@ -107,7 +107,7 @@ fn path_with_file() {

    // Should return a store path string
    if let Value::String(store_path) = result {
-        assert!(store_path.starts_with(ctx.get_store_dir()));
+        assert!(store_path.starts_with("/nix/store"));
        assert!(store_path.contains("test.txt"));
    } else {
        panic!("Expected string, got {:?}", result);
@@ -136,7 +136,7 @@ fn path_with_custom_name() {

 #[test_log::test]
 fn path_with_directory_recursive() {
-    let mut ctx = Context::new().unwrap();
+    let mut ctx = Runtime::new().unwrap();
    let temp_dir = tempfile::tempdir().unwrap();
    let test_dir = temp_dir.path().join("mydir");
    std::fs::create_dir_all(&test_dir).unwrap();
@@ -150,7 +150,7 @@ fn path_with_directory_recursive() {
    let result = ctx.eval(Source::new_eval(expr).unwrap()).unwrap();

    if let Value::String(store_path) = result {
-        assert!(store_path.starts_with(ctx.get_store_dir()));
+        assert!(store_path.starts_with("/nix/store"));
        assert!(store_path.contains("mydir"));
    } else {
        panic!("Expected string, got {:?}", result);
@@ -159,7 +159,7 @@ fn path_with_directory_recursive() {

 #[test_log::test]
 fn path_flat_with_file() {
-    let mut ctx = Context::new().unwrap();
+    let mut ctx = Runtime::new().unwrap();
    let temp_dir = tempfile::tempdir().unwrap();
    let test_file = temp_dir.path().join("flat.txt");
    std::fs::write(&test_file, "Flat content").unwrap();
@@ -171,7 +171,7 @@ fn path_flat_with_file() {
    let result = ctx.eval(Source::new_eval(expr).unwrap()).unwrap();

    if let Value::String(store_path) = result {
-        assert!(store_path.starts_with(ctx.get_store_dir()));
+        assert!(store_path.starts_with("/nix/store"));
    } else {
        panic!("Expected string, got {:?}", result);
    }
--- a/fix/tests/tests/lang.rs
+++ b/fix/tests/tests/lang.rs
@@ -2,8 +2,8 @@

 use std::path::PathBuf;

-use fix::context::Context;
 use fix::error::Source;
+use fix::runtime::Runtime;
 use fix::value::Value;

 fn get_lang_dir() -> PathBuf {
@@ -16,7 +16,7 @@ fn eval_file(name: &str) -> Result<(Value, Source), String> {

    let expr = format!(r#"import "{}""#, nix_path.display());

-    let mut ctx = Context::new().map_err(|e| e.to_string())?;
+    let mut ctx = Runtime::new().map_err(|e| e.to_string())?;
    let source = Source {
        ty: fix::error::SourceType::File(nix_path.into()),
        src: expr.into(),
@@ -247,7 +247,7 @@ eval_fail_test!(fail_abort);
 eval_fail_test!(fail_addDrvOutputDependencies_empty_context);
 eval_fail_test!(fail_addDrvOutputDependencies_multi_elem_context);
 eval_fail_test!(fail_addDrvOutputDependencies_wrong_element_kind);
-eval_fail_test!(fail_addErrorContext_example);
+eval_fail_test!(fail_addErrorRuntime_example);
 eval_fail_test!(fail_assert);
 eval_fail_test!(fail_assert_equal_attrs_names);
 eval_fail_test!(fail_assert_equal_attrs_names_2);
--- a/fix/tests/tests/string_context.rs
+++ b/fix/tests/tests/string_context.rs
@@ -1,4 +1,4 @@
-use fix::context::Context;
+use fix::runtime::Runtime;
 use fix::value::Value;

 use crate::utils::eval_result;
@@ -153,8 +153,8 @@ fn string_add_merges_context() {

 #[test_log::test]
 fn context_in_derivation_args() {
-    let mut ctx = Context::new().unwrap();
-    let result = ctx
+    let mut rt = Runtime::new().unwrap();
+    let result = rt
        .eval(
            r#"
        let
@@ -173,7 +173,7 @@ fn context_in_derivation_args() {
        .unwrap();
    match result {
        Value::String(s) => {
-            assert!(s.starts_with(ctx.get_store_dir()), "Should be a store path");
+            assert!(s.starts_with("/nix/store"), "Should be a store path");
            assert!(s.ends_with(".drv"), "Should be a .drv file");
        }
        _ => panic!("Expected String, got {:?}", result),
@@ -182,8 +182,8 @@ fn context_in_derivation_args() {

 #[test_log::test]
 fn context_in_derivation_env() {
-    let mut ctx = Context::new().unwrap();
-    let result = ctx
+    let mut rt = Runtime::new().unwrap();
+    let result = rt
        .eval(
            r#"
        let
@@ -202,7 +202,7 @@ fn context_in_derivation_env() {
        .unwrap();
    match result {
        Value::String(s) => {
-            assert!(s.starts_with(ctx.get_store_dir()), "Should be a store path");
+            assert!(s.starts_with("/nix/store"), "Should be a store path");
            assert!(s.ends_with(".drv"), "Should be a .drv file");
        }
        _ => panic!("Expected String, got {:?}", result),
@@ -224,8 +224,8 @@ fn tostring_preserves_context() {

 #[test_log::test]
 fn interpolation_derivation_returns_outpath() {
-    let mut ctx = Context::new().unwrap();
-    let result = ctx
+    let mut rt = Runtime::new().unwrap();
+    let result = rt
        .eval(
            r#"
        let
@@ -238,7 +238,7 @@ fn interpolation_derivation_returns_outpath() {
        .unwrap();
    match result {
        Value::String(s) => {
-            assert!(s.starts_with(ctx.get_store_dir()), "Should be a store path");
+            assert!(s.starts_with("/nix/store"), "Should be a store path");
            assert!(s.ends_with("-test"), "Should end with derivation name");
        }
        _ => panic!("Expected String, got {:?}", result),
--- a/fix/tests/tests/utils.rs
+++ b/fix/tests/tests/utils.rs
@@ -1,31 +1,31 @@
 #![allow(dead_code)]

-use fix::context::Context;
 use fix::error::{Result, Source};
+use fix::runtime::Runtime;
 use fix::value::Value;

 pub fn eval(expr: &str) -> Value {
-    Context::new()
+    Runtime::new()
        .unwrap()
        .eval(Source::new_eval(expr.into()).unwrap())
        .unwrap()
 }

 pub fn eval_deep(expr: &str) -> Value {
-    Context::new()
+    Runtime::new()
        .unwrap()
        .eval_deep(Source::new_eval(expr.into()).unwrap())
        .unwrap()
 }

 pub fn eval_deep_result(expr: &str) -> Result<Value> {
-    Context::new()
+    Runtime::new()
        .unwrap()
        .eval_deep(Source::new_eval(expr.into()).unwrap())
 }

 pub fn eval_result(expr: &str) -> Result<Value> {
-    Context::new()
+    Runtime::new()
        .unwrap()
        .eval(Source::new_eval(expr.into()).unwrap())
 }
--- a/flake.lock
+++ b/flake.lock
@@ -8,11 +8,11 @@
        "rust-analyzer-src": "rust-analyzer-src"
      },
      "locked": {
-        "lastModified": 1770966612,
-        "narHash": "sha256-S6k14z/JsDwX6zZyLucDBTOe/9RsvxH9GTUxHn2o4vc=",
+        "lastModified": 1773471952,
+        "narHash": "sha256-kIRggXyT8RzijtfvyRIzj+zIDWM2fnCp8t0X4BkkTVc=",
        "owner": "nix-community",
        "repo": "fenix",
-        "rev": "e90d48dcfaebac7ea7a5687888a2d0733be26343",
+        "rev": "a1b770adbc3f6c27485d03b90462ec414d4e1ce5",
        "type": "github"
      },
      "original": {
@@ -37,11 +37,11 @@
    },
    "nixpkgs": {
      "locked": {
-        "lastModified": 1770841267,
-        "narHash": "sha256-9xejG0KoqsoKEGp2kVbXRlEYtFFcDTHjidiuX8hGO44=",
+        "lastModified": 1773282481,
+        "narHash": "sha256-b/GV2ysM8mKHhinse2wz+uP37epUrSE+sAKXy/xvBY4=",
        "owner": "nixos",
        "repo": "nixpkgs",
-        "rev": "ec7c70d12ce2fc37cb92aff673dcdca89d187bae",
+        "rev": "fe416aaedd397cacb33a610b33d60ff2b431b127",
        "type": "github"
      },
      "original": {
@@ -61,11 +61,11 @@
    "rust-analyzer-src": {
      "flake": false,
      "locked": {
-        "lastModified": 1770934477,
-        "narHash": "sha256-GX0cINHhhzUbQHyDYN2Mc+ovb6Sx/4yrF95VVou9aW4=",
+        "lastModified": 1773326183,
+        "narHash": "sha256-tj3piRd9RnnP36HwHmQD4O4XZeowsH/rvMeyp9Pmot0=",
        "owner": "rust-lang",
        "repo": "rust-analyzer",
-        "rev": "931cd553be123b11db1435ac7ea5657e62e5e601",
+        "rev": "6254616e97f358e67b70dfc0463687f5f7911c1a",
        "type": "github"
      },
      "original": {