refactor: reorganize crate hierarchy

fix-runtime/src/value.rs

@@ -0,0 +1,727 @@
+#![allow(dead_code)]
+
+use std::cell::RefCell;
+use std::fmt;
+use std::marker::PhantomData;
+use std::mem::size_of;
+use std::ops::Deref;
+
+use fix_lang::*;
+use gc_arena::barrier::Unlock;
+use gc_arena::collect::Trace;
+use gc_arena::{Collect, Gc, GcRefLock, Mutation, RefLock};
+use num_enum::TryFromPrimitive;
+use smallvec::SmallVec;
+use string_interner::Symbol;
+use string_interner::symbol::SymbolU32;
+
+use crate::boxing::{RawBox, RawStore, RawTag, Value as RawValue};
+use crate::string_context::StringContext;
+
+mod private {
+    pub trait Cealed {}
+}
+
+/// # Safety
+///
+/// TAG must be unique among all implementors.
+#[allow(private_interfaces)]
+pub unsafe trait Storable: private::Cealed {
+    const TAG: RawTag;
+}
+#[allow(private_bounds)]
+pub trait InlineStorable: Storable + RawStore {}
+pub trait GcStorable: Storable {}
+
+macro_rules! define_value_types {
+    (
+        inline { $($itype:ty => $itag:expr, $iname:literal;)* }
+        gc { $($gtype:ty => $gtag:expr, $gname:literal;)* }
+    ) => {
+        $(
+        #[allow(private_interfaces)]
+        unsafe impl Storable for $itype {
+            const TAG: RawTag = $itag;
+        }
+        impl InlineStorable for $itype {}
+        impl private::Cealed for $itype {}
+        )*
+        $(
+        #[allow(private_interfaces)]
+        unsafe impl Storable for $gtype {
+            const TAG: RawTag = $gtag;
+        }
+        impl GcStorable for $gtype {}
+        impl private::Cealed for $gtype {}
+        )*
+
+        const _: () = assert!(size_of::<Value<'static>>() == 8);
+        $(const _: () = assert!(size_of::<$itype>() <= 6);)*
+
+        const _: () = {
+            let tags: &[(bool, u8)] = &[$(RawTag::neg_val($itag)),*, $(RawTag::neg_val($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 {
+                    $(<$gtype as Storable>::TAG => unsafe {
+                        self.load_gc::<$gtype>().trace(cc)
+                    },)*
+                    $(<$itype as Storable>::TAG => (),)*
+                    _ => unreachable!("invalid value tag"),
+                }
+            }
+        }
+
+        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),)*
+                    _ => unreachable!("invalid value tag"),
+                }
+            }
+        }
+    };
+}
+
+define_value_types! {
+    inline {
+        i32 => RawTag::P1, "SmallInt";
+        bool => RawTag::P2, "Bool";
+        Null => RawTag::P3, "Null";
+        StringId => RawTag::P4, "SmallString";
+        PrimOp => RawTag::P5, "PrimOp";
+        Path => RawTag::N6, "Path";
+    }
+    gc {
+        i64 => RawTag::P6, "BigInt";
+        NixString => RawTag::P7, "String";
+        AttrSet<'_> => RawTag::N1, "AttrSet";
+        List<'_> => RawTag::N2, "List";
+        Thunk<'_> => RawTag::N3, "Thunk";
+        Closure<'_> => RawTag::N4, "Closure";
+        PrimOpApp<'_> => RawTag::N5, "PrimOpApp";
+    }
+}
+
+/// # Nix runtime value representation
+///
+/// NaN-boxed value fitting in 8 bytes.
+#[derive(Copy, Clone)]
+#[repr(transparent)]
+pub struct Value<'gc> {
+    raw: RawBox,
+    _marker: PhantomData<Gc<'gc, ()>>,
+}
+
+impl Default for Value<'_> {
+    #[inline(always)]
+    fn default() -> Self {
+        Self::new_inline(Null)
+    }
+}
+
+impl<'gc> Value<'gc> {
+    #[inline(always)]
+    fn from_raw_value(rv: RawValue) -> Self {
+        Self {
+            raw: RawBox::from_value(rv),
+            _marker: PhantomData,
+        }
+    }
+
+    /// 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: GcStorable>(self) -> Gc<'gc, T> {
+        unsafe {
+            let rv = self.raw.value().unwrap_unchecked();
+            let ptr: *const T = <*const T as RawStore>::from_val(rv);
+            Gc::from_ptr(ptr)
+        }
+    }
+
+    #[inline(always)]
+    const fn tag(self) -> Option<RawTag> {
+        self.raw.tag()
+    }
+}
+
+impl<'gc> Value<'gc> {
+    #[inline]
+    pub fn new_float(val: f64) -> Self {
+        Self {
+            raw: RawBox::from_float(val),
+            _marker: PhantomData,
+        }
+    }
+
+    #[inline]
+    pub fn new_inline<T: InlineStorable>(val: T) -> Self {
+        Self::from_raw_value(RawValue::store(T::TAG, val))
+    }
+
+    #[inline]
+    pub fn new_gc<T: GcStorable>(gc: Gc<'gc, T>) -> Self {
+        let ptr = Gc::as_ptr(gc);
+        Self::from_raw_value(RawValue::store(T::TAG, ptr))
+    }
+
+    #[inline]
+    pub fn make_int(val: i64, mc: &Mutation<'gc>) -> Self {
+        if val >= i32::MIN as i64 && val <= i32::MAX as i64 {
+            Value::new_inline(val as i32)
+        } else {
+            Value::new_gc(Gc::new(mc, val))
+        }
+    }
+}
+
+impl<'gc> Value<'gc> {
+    #[inline]
+    pub fn is_float(self) -> bool {
+        self.raw.is_float()
+    }
+
+    #[inline]
+    pub fn is<T: Storable>(self) -> bool {
+        self.tag() == Some(T::TAG)
+    }
+}
+
+impl<'gc> Value<'gc> {
+    #[inline]
+    pub fn as_float(self) -> Option<f64> {
+        self.raw.float().copied()
+    }
+
+    #[inline]
+    pub fn as_inline<T: InlineStorable>(self) -> Option<T> {
+        if self.is::<T>() {
+            Some(unsafe {
+                let rv = self.raw.value().unwrap_unchecked();
+                T::from_val(rv)
+            })
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    pub fn as_gc<T: GcStorable>(self) -> Option<Gc<'gc, T>> {
+        if self.is::<T>() {
+            Some(unsafe {
+                let rv = self.raw.value().unwrap_unchecked();
+                let ptr: *const T = <*const T as RawStore>::from_val(rv);
+                Gc::from_ptr(ptr)
+            })
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    pub fn to_bits(self) -> u64 {
+        self.raw.to_bits()
+    }
+
+    #[inline]
+    pub fn as_num(self) -> Option<NixNum> {
+        if let Some(i) = self.as_inline::<i32>() {
+            Some(NixNum::Int(i as i64))
+        } else if let Some(gc_i) = self.as_gc::<i64>() {
+            Some(NixNum::Int(*gc_i))
+        } else {
+            self.as_float().map(NixNum::Float)
+        }
+    }
+
+    #[inline]
+    pub fn restrict(self) -> Result<StrictValue<'gc>, Gc<'gc, Thunk<'gc>>> {
+        if let Some(thunk) = self.as_gc::<Thunk<'gc>>() {
+            Err(thunk)
+        } else {
+            Ok(StrictValue(self))
+        }
+    }
+
+    #[inline]
+    pub fn ty(self) -> NixType {
+        if self.is_float() {
+            NixType::Float
+        } else if self.is::<i32>() || self.is::<i64>() {
+            NixType::Int
+        } else if self.is::<bool>() {
+            NixType::Bool
+        } else if self.is::<Null>() {
+            NixType::Null
+        } else if self.is::<StringId>() {
+            NixType::String
+        } else if self.is::<PrimOp>() {
+            NixType::PrimOp
+        } else if self.is::<NixString>() {
+            NixType::String
+        } else if self.is::<Path>() {
+            NixType::Path
+        } else if self.is::<AttrSet>() {
+            NixType::AttrSet
+        } else if self.is::<List>() {
+            NixType::List
+        } else if self.is::<Thunk>() {
+            NixType::Thunk
+        } else if self.is::<Closure>() {
+            NixType::Closure
+        } else if self.is::<PrimOpApp>() {
+            NixType::PrimOpApp
+        } else {
+            unreachable!("value has no recognized type tag")
+        }
+    }
+
+    #[inline]
+    pub fn expect_inline<T: InlineStorable>(self) -> Result<T, NixType> {
+        self.as_inline::<T>().ok_or_else(|| self.ty())
+    }
+
+    #[inline]
+    pub fn expect_gc<T: GcStorable>(self) -> Result<Gc<'gc, T>, NixType> {
+        self.as_gc::<T>().ok_or_else(|| self.ty())
+    }
+
+    #[inline]
+    pub fn expect_num(self) -> Result<NixNum, NixType> {
+        self.as_num().ok_or_else(|| self.ty())
+    }
+
+    #[inline]
+    pub fn expect_bool(self) -> Result<bool, NixType> {
+        self.as_inline::<bool>().ok_or_else(|| self.ty())
+    }
+
+    #[inline]
+    pub fn expect_float(self) -> Result<f64, NixType> {
+        self.as_float().ok_or_else(|| self.ty())
+    }
+}
+
+#[derive(Copy, Clone, Default)]
+#[repr(transparent)]
+pub struct StaticValue(Value<'static>);
+
+impl<'gc> From<StaticValue> for Value<'gc> {
+    #[inline]
+    fn from(value: StaticValue) -> Self {
+        // SAFETY: StaticValue is guaranteed to not contain any `Gc`.
+        unsafe { std::mem::transmute::<Value<'static>, Value<'gc>>(value.0) }
+    }
+}
+
+impl StaticValue {
+    #[inline]
+    pub fn new_float(val: f64) -> Self {
+        Self(Value::new_float(val))
+    }
+    #[inline]
+    pub fn new_inline<T: InlineStorable>(val: T) -> Self {
+        Self(Value::new_inline(val))
+    }
+    #[inline]
+    pub fn new_primop(id: BuiltinId, arity: u8, dispatch_ip: u32) -> Self {
+        Self(Value::new_inline(PrimOp {
+            id,
+            arity,
+            dispatch_ip,
+        }))
+    }
+    #[inline]
+    pub fn is_float(self) -> bool {
+        self.0.is_float()
+    }
+    #[inline]
+    pub fn is<T: InlineStorable>(self) -> bool {
+        self.0.is::<T>()
+    }
+    #[inline]
+    pub fn as_float(self) -> Option<f64> {
+        self.0.as_float()
+    }
+    #[inline]
+    pub fn as_inline<T: InlineStorable>(self) -> Option<T> {
+        self.0.as_inline::<T>()
+    }
+    #[inline]
+    pub fn to_bits(self) -> u64 {
+        self.0.raw.to_bits()
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+pub struct Null;
+impl RawStore for Null {
+    fn to_val(self, value: &mut RawValue) {
+        value.set_data([0; 6]);
+    }
+    fn from_val(_: &RawValue) -> Self {
+        Self
+    }
+}
+
+impl RawStore for StringId {
+    fn to_val(self, value: &mut RawValue) {
+        (self.0.to_usize() as u32).to_val(value);
+    }
+    fn from_val(value: &RawValue) -> Self {
+        Self(
+            SymbolU32::try_from_usize(u32::from_val(value) as usize)
+                .expect("failed to read StringId from Value"),
+        )
+    }
+}
+
+/// A canonicalized absolute path. Inline value carrying an interned
+/// `StringId` whose contents are the path's absolute, dot-resolved form.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct Path(pub StringId);
+
+impl RawStore for Path {
+    fn to_val(self, value: &mut RawValue) {
+        self.0.to_val(value);
+    }
+    fn from_val(value: &RawValue) -> Self {
+        Self(StringId::from_val(value))
+    }
+}
+
+#[derive(Collect)]
+#[collect(require_static)]
+pub struct NixString {
+    data: Box<str>,
+    context: StringContext,
+}
+
+impl NixString {
+    pub fn new(s: impl Into<Box<str>>) -> Self {
+        Self {
+            data: s.into(),
+            context: StringContext::new(),
+        }
+    }
+
+    /// Construct a `NixString` whose `context` is already sorted+deduped.
+    /// The caller is responsible for invariant maintenance.
+    pub fn with_context(s: impl Into<Box<str>>, context: StringContext) -> Self {
+        Self {
+            data: s.into(),
+            context,
+        }
+    }
+
+    pub fn as_str(&self) -> &str {
+        &self.data
+    }
+
+    pub fn context(&self) -> &StringContext {
+        &self.context
+    }
+
+    pub fn has_context(&self) -> bool {
+        !self.context.is_empty()
+    }
+}
+
+impl fmt::Debug for NixString {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&self.data, f)
+    }
+}
+
+#[derive(Collect, Debug, Default)]
+#[collect(no_drop)]
+pub struct AttrSet<'gc> {
+    pub entries: SmallVec<[(StringId, Value<'gc>); 4]>,
+}
+
+impl<'gc> AttrSet<'gc> {
+    pub fn from_sorted_unchecked(entries: SmallVec<[(StringId, Value<'gc>); 4]>) -> Self {
+        debug_assert!(entries.is_sorted_by_key(|(key, _)| *key));
+        Self { entries }
+    }
+
+    pub fn lookup(&self, key: StringId) -> Option<Value<'gc>> {
+        self.entries
+            .binary_search_by_key(&key, |(k, _)| *k)
+            .ok()
+            .map(|i| self.entries[i].1)
+    }
+
+    pub fn has(&self, key: StringId) -> bool {
+        self.entries.binary_search_by_key(&key, |(k, _)| *k).is_ok()
+    }
+
+    pub 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]);
+                    i += 1;
+                }
+                Greater => {
+                    entries.push(other.entries[j]);
+                    j += 1;
+                }
+                Equal => {
+                    entries.push(other.entries[j]);
+                    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 })
+    }
+}
+
+#[derive(Collect, Debug, Default)]
+#[repr(transparent)]
+#[collect(no_drop)]
+pub struct List<'gc> {
+    pub inner: RefLock<SmallVec<[Value<'gc>; 4]>>,
+}
+
+impl<'gc> List<'gc> {
+    pub fn new(mc: &Mutation<'gc>, data: SmallVec<[Value<'gc>; 4]>) -> Gc<'gc, Self> {
+        Gc::new(
+            mc,
+            Self {
+                inner: RefLock::new(data),
+            },
+        )
+    }
+
+    pub fn new_gc(mc: &Mutation<'gc>) -> Gc<'gc, Self> {
+        Gc::new(mc, Self::default())
+    }
+}
+
+impl<'gc> Unlock for List<'gc> {
+    type Unlocked = RefCell<SmallVec<[Value<'gc>; 4]>>;
+    unsafe fn unlock_unchecked(&self) -> &Self::Unlocked {
+        unsafe { self.inner.unlock_unchecked() }
+    }
+}
+
+pub type Thunk<'gc> = RefLock<ThunkState<'gc>>;
+
+#[derive(Collect, Debug)]
+#[collect(no_drop)]
+pub enum ThunkState<'gc> {
+    Pending { ip: usize, env: GcEnv<'gc> },
+    Apply { func: Value<'gc>, arg: Value<'gc> },
+    Blackhole,
+    Evaluated(StrictValue<'gc>),
+}
+
+#[derive(Collect, Debug)]
+#[collect(no_drop)]
+pub struct Env<'gc> {
+    pub locals: SmallVec<[Value<'gc>; 4]>,
+    pub prev: Option<GcEnv<'gc>>,
+}
+pub type GcEnv<'gc> = GcRefLock<'gc, Env<'gc>>;
+
+#[derive(Collect, Debug)]
+#[collect(no_drop)]
+pub struct WithEnv<'gc> {
+    pub env: Value<'gc>,
+    pub prev: Option<GcWithEnv<'gc>>,
+}
+pub type GcWithEnv<'gc> = Gc<'gc, WithEnv<'gc>>;
+
+impl<'gc> Env<'gc> {
+    pub fn empty() -> Self {
+        Env {
+            locals: SmallVec::new(),
+            prev: None,
+        }
+    }
+
+    pub 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 struct Closure<'gc> {
+    pub ip: u32,
+    pub n_locals: u32,
+    pub env: Gc<'gc, RefLock<Env<'gc>>>,
+    pub pattern: Option<Gc<'gc, PatternInfo>>,
+}
+
+#[derive(Collect, Debug)]
+#[collect(require_static)]
+pub struct PatternInfo {
+    pub required: SmallVec<[StringId; 4]>,
+    pub optional: SmallVec<[StringId; 4]>,
+    pub ellipsis: bool,
+    pub param_spans: Box<[(StringId, u32)]>,
+}
+
+#[repr(packed, Rust)]
+#[derive(Clone, Copy, Debug, Collect)]
+#[collect(require_static)]
+pub struct PrimOp {
+    pub id: BuiltinId,
+    pub arity: u8,
+    pub dispatch_ip: u32,
+}
+
+impl RawStore for PrimOp {
+    fn to_val(self, value: &mut RawValue) {
+        let bytes = self.dispatch_ip.to_le_bytes();
+        value.set_data([
+            self.id as u8,
+            self.arity,
+            bytes[0],
+            bytes[1],
+            bytes[2],
+            bytes[3],
+        ]);
+    }
+    fn from_val(value: &RawValue) -> Self {
+        let [id, arity, bytes @ ..] = *value.data();
+        Self {
+            id: BuiltinId::try_from_primitive(id).expect("invalid BuiltinId"),
+            arity,
+            dispatch_ip: u32::from_le_bytes(bytes),
+        }
+    }
+}
+
+#[derive(Collect, Debug)]
+#[collect(no_drop)]
+pub struct PrimOpApp<'gc> {
+    pub primop: PrimOp,
+    pub arity: u8,
+    pub args: [Value<'gc>; 3],
+}
+
+#[derive(Copy, Clone, Default, Collect)]
+#[repr(transparent)]
+#[collect(no_drop)]
+pub struct StrictValue<'gc>(Value<'gc>);
+
+impl<'gc> StrictValue<'gc> {
+    #[inline]
+    pub fn relax(self) -> Value<'gc> {
+        self.0
+    }
+}
+
+impl<'gc> Deref for StrictValue<'gc> {
+    type Target = Value<'gc>;
+    #[inline]
+    fn deref(&self) -> &Value<'gc> {
+        &self.0
+    }
+}
+
+impl fmt::Debug for StrictValue<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&self.0, f)
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Collect)]
+#[collect(require_static)]
+pub enum NixType {
+    Int,
+    Float,
+    Bool,
+    Null,
+    String,
+    Path,
+    AttrSet,
+    List,
+    Thunk,
+    Closure,
+    PrimOp,
+    PrimOpApp,
+}
+
+impl NixType {
+    pub fn display(self) -> &'static str {
+        use NixType::*;
+        match self {
+            Int => "an integer",
+            Float => "a float",
+            Bool => "a boolean",
+            Null => "null",
+            String => "a string",
+            Path => "a path",
+            AttrSet => "a set",
+            List => "a list",
+            Thunk => "a thunk",
+            Closure => "a function",
+            PrimOp => "a built-in function",
+            PrimOpApp => "a partially applied built-in function",
+        }
+    }
+}
+
+impl std::fmt::Display for NixType {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.display())
+    }
+}
+
+pub enum NixNum {
+    Int(i64),
+    Float(f64),
+}