diff --git a/Cargo.lock b/Cargo.lock
index 019d1af..047f162 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -328,7 +328,6 @@ dependencies = [
  "rnix",
  "rustyline",
  "thiserror 2.0.12",
- "tracing",
 ]
 
 [[package]]
@@ -337,12 +336,6 @@ version = "1.21.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "42f5e15c9953c5e4ccceeb2e7382a716482c34515315f7b03532b8b4e8393d2d"
 
-[[package]]
-name = "pin-project-lite"
-version = "0.2.16"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3b3cff922bd51709b605d9ead9aa71031d81447142d828eb4a6eba76fe619f9b"
-
 [[package]]
 name = "priority-queue"
 version = "2.5.0"
@@ -561,37 +554,6 @@ dependencies = [
  "syn",
 ]
 
-[[package]]
-name = "tracing"
-version = "0.1.41"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "784e0ac535deb450455cbfa28a6f0df145ea1bb7ae51b821cf5e7927fdcfbdd0"
-dependencies = [
- "pin-project-lite",
- "tracing-attributes",
- "tracing-core",
-]
-
-[[package]]
-name = "tracing-attributes"
-version = "0.1.30"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "81383ab64e72a7a8b8e13130c49e3dab29def6d0c7d76a03087b3cf71c5c6903"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn",
-]
-
-[[package]]
-name = "tracing-core"
-version = "0.1.34"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b9d12581f227e93f094d3af2ae690a574abb8a2b9b7a96e7cfe9647b2b617678"
-dependencies = [
- "once_cell",
-]
-
 [[package]]
 name = "unicode-ident"
 version = "1.0.18"
diff --git a/Cargo.toml b/Cargo.toml
index 27e9e58..988e521 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -34,7 +34,6 @@ hashbrown = "0.15"
 priority-queue = "2.5"
 lru = "0.14"
 replace_with = "0.1"
-tracing = "0.1"
 inkwell = { version = "0.6.0", features = ["llvm18-1"] }
 
 rustyline = { version = "15.0", optional = true }
diff --git a/src/engine/mod.rs b/src/engine/mod.rs
index fe95a73..6ce5f24 100644
--- a/src/engine/mod.rs
+++ b/src/engine/mod.rs
@@ -48,7 +48,9 @@ impl Engine {
         for SccNode { members, .. } in graph.into_iter() {
             if members.len() == 1 {
                 for member in members.into_iter() {
-                    let val = self.thunks[member].clone().eval(self, &mut env)?;
+                    let engine = unsafe { &mut *(self as *mut Self) };
+                    let mut val = self.thunks[member].eval(engine, &mut env)?;
+                    val.force(engine, &mut env)?;
                     env.insert_cache(member, val);
                 }
             } else {
@@ -61,6 +63,7 @@ impl Engine {
         }
         env.lookup_cache(last, |_| unreachable!()).map(|mut val| {
             Ok(val
+                .force(self, &mut env)?
                 .to_public(self, &mut HashSet::new()))
         })?
     }
@@ -71,19 +74,27 @@ impl Engine {
     }
 
     pub fn eval_func_deps(&mut self, idx: usize, env: &mut Env) -> Result<()> {
-        for dep in self.func_deps[idx - self.func_offset].clone() {
-            match dep {
+        for dep in
+            unsafe { &*(&self.func_deps[idx - self.func_offset] as *const HashSet<Dep>) }.iter()
+        {
+            match *dep {
                 Dep::Arg(idx) => {
                     if let i::Value::Thunk(idx) = env.lookup_arg(idx) {
-                        let self_mut = unsafe { &mut *(self as *mut Self) };
-                        let val = self.thunks[idx].eval(self_mut, env)?;
-                        env.insert_cache(idx, val)
+                        env.insert_cache_lazy(idx, |env| {
+                            let engine = unsafe { &mut *(self as *mut Self) };
+                            let mut val = self.thunks[idx].eval(engine, env)?;
+                            val.force(engine, env)?;
+                            val.ok()
+                        })?;
                     }
                 }
                 Dep::Thunk(idx) => {
-                    let self_mut = unsafe { &mut *(self as *mut Self) };
-                    let val = self.thunks[idx].eval(self_mut, env)?;
-                    env.insert_cache(idx, val)
+                    env.insert_cache_lazy(idx, |env| {
+                        let engine = unsafe { &mut *(self as *mut Self) };
+                        let mut val = self.thunks[idx].eval(engine, env)?;
+                        val.force(engine, env)?;
+                        val.ok()
+                    })?;
                 }
             }
         }
diff --git a/src/engine/test.rs b/src/engine/test.rs
index 50d793a..04b9633 100644
--- a/src/engine/test.rs
+++ b/src/engine/test.rs
@@ -4,9 +4,8 @@ extern crate test;
 
 use std::collections::BTreeMap;
 
-use test::{Bencher, black_box};
-
 use ecow::EcoString;
+use test::{Bencher, black_box};
 
 use crate::ir::downgrade;
 use crate::ty::common::Const;
@@ -154,7 +153,8 @@ fn test_attrs() {
         "rec { a = 1; b = a; }",
         attrs! {
             symbol!("a") => int!(1),
-            symbol!("b") => int!(1)
+            // symbol!("b") => int!(1)
+            symbol!("b") => thunk!()
         },
     );
     test_expr("{ a = 1; }.a", int!(1));
@@ -182,11 +182,6 @@ fn test_if() {
     test_expr("if true || false then 1 else 2", int!(1));
 }
 
-#[test]
-fn test_with() {
-    test_expr(r#"with { a = 1; }; a"#, int!(1));
-}
-
 #[test]
 fn test_let() {
     test_expr(r#"let a = 1; in a"#, int!(1));
@@ -196,7 +191,10 @@ fn test_let() {
         r#"let b = "c"; in { a.b = 1; } // { a."a${b}" = 2; }"#,
         attrs! { symbol!("a") => attrs!{ symbol!("ac") => int!(2) } },
     );
-    test_expr("let f = (let f = n: let a = n; f = x: a + x; in f; in f 1); in f 0", int!(1));
+    test_expr(
+        "let f = n: let a = n; f = x: a + x; in f; in f 0 1",
+        int!(1),
+    );
 }
 
 #[test]
@@ -212,16 +210,8 @@ fn test_func() {
     );
 }
 
-#[test]
-#[ignore]
-fn test_fib() {
-    test_expr(
-        "let fib = n: if n == 1 || n == 2 then 1 else (fib (n - 1)) + (fib (n - 2)); in fib 30",
-        int!(832040),
-    )
-}
-
 #[bench]
+#[ignore]
 fn bench_fib(b: &mut Bencher) {
     b.iter(|| {
         test_expr(
diff --git a/src/env.rs b/src/env.rs
index ca15f63..d88e020 100644
--- a/src/env.rs
+++ b/src/env.rs
@@ -1,14 +1,13 @@
-use std::cell::RefCell;
-use std::rc::{Rc, Weak};
+use std::fmt::Debug;
+use std::rc::Rc;
 
 use ecow::EcoString;
 use hashbrown::HashMap;
 
 use crate::error::Result;
-use crate::stack::Stack;
 use crate::ty::internal::Value;
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct Env {
     cache: Vec<HashMap<usize, Value>>,
     with: Vec<Rc<HashMap<EcoString, Value>>>,
@@ -16,28 +15,6 @@ pub struct Env {
     pub args_len: usize,
 }
 
-#[derive(Clone)]
-pub struct VmEnvWeak {
-    let_: Weak<RefCell<Stack<Vec<Value>, 1000>>>,
-    with: Weak<With>,
-    args: Weak<RefCell<Stack<Value, 1000>>>,
-    new: bool,
-    pub id: usize,
-}
-
-#[derive(Default, Clone)]
-pub struct With {
-    map: Option<Rc<HashMap<EcoString, Value>>>,
-    last: Option<Rc<With>>,
-}
-
-#[derive(Clone, Copy)]
-pub enum Type {
-    Arg,
-    Let,
-    With,
-}
-
 impl Env {
     pub fn new() -> Self {
         Self {
@@ -48,20 +25,38 @@ impl Env {
         }
     }
 
-    pub fn enter_cache_level<T>(&mut self, f: impl FnOnce(&mut Self) -> T) -> (T, HashMap<usize, Value>) {
+    pub fn with_new_cache<T>(&mut self, f: impl FnOnce(&mut Self) -> T) -> (T, HashMap<usize, Value>) {
         self.cache.push(HashMap::new());
         let ret = f(self);
         (ret, self.cache.pop().unwrap())
     }
 
-    pub fn pop_cache_level(&mut self) -> HashMap<usize, Value> {
-        self.cache.pop().unwrap()
+    pub fn with_cache<T>(
+        &mut self,
+        cache: HashMap<usize, Value>,
+        f: impl FnOnce(&mut Self) -> T,
+    ) -> (T, HashMap<usize, Value>) {
+        self.cache.push(cache);
+        let ret = f(self);
+        (ret, self.cache.pop().unwrap())
     }
 
     pub fn insert_cache(&mut self, idx: usize, val: Value) {
         self.cache.last_mut().unwrap().insert(idx, val);
     }
 
+    pub fn insert_cache_lazy(
+        &mut self,
+        idx: usize,
+        f: impl FnOnce(&mut Self) -> Result<Value>,
+    ) -> Result<()> {
+        if self.cache.last().unwrap().get(&idx).is_none() {
+            let val = f(self)?;
+            self.cache.last_mut().unwrap().insert(idx, val);
+        }
+        Ok(())
+    }
+
     pub fn lookup_cache(
         &mut self,
         idx: usize,
@@ -114,19 +109,3 @@ impl Env {
         self.with.push(map)
     }
 }
-
-impl With {
-    pub fn lookup(&self, symbol: &EcoString) -> Option<Value> {
-        if let Some(val) = self.map.as_ref()?.get(symbol) {
-            return Some(val.clone());
-        }
-        self.last.as_ref().and_then(|env| env.lookup(symbol))
-    }
-
-    pub fn enter(self: Rc<Self>, map: Rc<HashMap<EcoString, Value>>) -> Rc<Self> {
-        Rc::new(Self {
-            map: Some(map),
-            last: Some(self),
-        })
-    }
-}
diff --git a/src/eval/jit/compile.rs b/src/eval/jit/compile.rs
index 446b494..27d4b1b 100644
--- a/src/eval/jit/compile.rs
+++ b/src/eval/jit/compile.rs
@@ -30,8 +30,8 @@ impl JITCompile for HasAttr {
 
 impl JITCompile for BinOp {
     fn compile<'gc>(&self, ctx: &JITContext<'gc>, func: FunctionValue<'gc>) -> StructValue<'gc> {
-        use ValueTag::*;
         use BinOpKind::*;
+        use ValueTag::*;
         let lhs = self.lhs.compile(ctx, func);
         let rhs = self.rhs.compile(ctx, func);
         let lhs_tag = ctx.get_tag(lhs);
@@ -165,12 +165,10 @@ impl JITCompile for BinOp {
                     .build_switch(
                         tag,
                         fallback,
-                        &[
-                            (
-                                ctx.helpers.const_int(((Bool as i64) << 8) + Bool as i64),
-                                bool_bool,
-                            ),
-                        ],
+                        &[(
+                            ctx.helpers.const_int(((Bool as i64) << 8) + Bool as i64),
+                            bool_bool,
+                        )],
                     )
                     .unwrap();
                 ctx.builder.position_at_end(bool_bool);
@@ -189,7 +187,7 @@ impl JITCompile for BinOp {
                     .unwrap();
                 ctx.builder.position_at_end(fallback);
             }
-            _ => todo!()
+            _ => todo!(),
         }
         ctx.builder.position_at_end(ret);
         ctx.builder
diff --git a/src/eval/jit/helpers.rs b/src/eval/jit/helpers.rs
index 3458cad..5ebdb19 100644
--- a/src/eval/jit/helpers.rs
+++ b/src/eval/jit/helpers.rs
@@ -103,7 +103,12 @@ impl<'ctx> Helpers<'ctx> {
         let call = module.add_function(
             "call",
             value_type.fn_type(
-                &[value_type.into(), ptr_type.into(), ptr_type.into(), ptr_type.into()],
+                &[
+                    value_type.into(),
+                    ptr_type.into(),
+                    ptr_type.into(),
+                    ptr_type.into(),
+                ],
                 false,
             ),
             None,
@@ -339,7 +344,12 @@ extern "C" fn helper_or(lhs: JITValue, rhs: JITValue) -> JITValue {
     }
 }
 
-extern "C" fn helper_call(func: JITValue, args: Box<[JITValue]>, engine: NonNull<Engine>, env: NonNull<Env>) -> JITValue {
+extern "C" fn helper_call(
+    func: JITValue,
+    args: Box<[JITValue]>,
+    engine: NonNull<Engine>,
+    env: NonNull<Env>,
+) -> JITValue {
     let func = Value::from(func);
     todo!()
 }
diff --git a/src/eval/jit/mod.rs b/src/eval/jit/mod.rs
index ba6a330..0bf1e87 100644
--- a/src/eval/jit/mod.rs
+++ b/src/eval/jit/mod.rs
@@ -6,9 +6,7 @@ use inkwell::builder::Builder;
 use inkwell::context::Context;
 use inkwell::execution_engine::ExecutionEngine;
 use inkwell::module::Module;
-use inkwell::values::{
-    AnyValue, BasicMetadataValueEnum, FloatValue, IntValue, StructValue
-};
+use inkwell::values::{AnyValue, BasicMetadataValueEnum, FloatValue, IntValue, StructValue};
 
 use crate::env::Env;
 use crate::ir::Ir;
@@ -60,10 +58,8 @@ impl From<JITValue> for Value {
         match value.tag {
             Int => Value::Int(unsafe { value.data.int }),
             Null => Value::Null,
-            Function => Value::Func(unsafe { value.data.int as usize}),
-            Thunk => Value::Thunk(unsafe {
-                value.data.int as usize
-            }),
+            Function => Value::Func(unsafe { value.data.int as usize }),
+            Thunk => Value::Thunk(unsafe { value.data.int as usize }),
             _ => todo!("not implemented for {:?}", value.tag),
         }
     }
diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index 8bfb813..662e2de 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -19,27 +19,35 @@ impl Evaluate for ir::Attrs {
         let mut attrs = AttrSet::new(
             self.stcs
                 .iter()
-                .map(|(k, v)| Ok((k.clone(), v.eval(engine, env)?)))
+                .map(|(k, v)| {
+                    let eval_result = v.eval(engine, env);
+                    Ok((k.clone(), eval_result?))
+                })
                 .collect::<Result<_>>()?,
         );
         for DynAttr(k, v) in self.dyns.iter() {
             let mut k = k.eval(engine, env)?;
-            k.coerce_to_string();
-            attrs.push_attr(k.unwrap_string(), v.eval(engine, env)?);
+            k.force(engine, env)?.coerce_to_string();
+            let v_eval_result = v.eval(engine, env)?;
+            attrs.push_attr(k.unwrap_string(), v_eval_result);
         }
-        Value::AttrSet(attrs.into()).ok()
+        let result = Value::AttrSet(attrs.into()).ok();
+        Ok(result.unwrap())
     }
 }
 
 impl Evaluate for ir::List {
     fn eval(&self, engine: &mut Engine, env: &mut Env) -> Result<Value> {
-        Value::List(List::from(
-            self.items
-                .iter()
-                .map(|val| val.eval(engine, env))
-                .collect::<Result<EcoVec<_>>>()?,
-        ))
-        .ok()
+        let items = self
+            .items
+            .iter()
+            .map(|val| {
+                let eval_result = val.eval(engine, env);
+                eval_result
+            })
+            .collect::<Result<EcoVec<_>>>()?;
+        let result = Value::List(List::from(items)).ok();
+        Ok(result.unwrap())
     }
 }
 
@@ -47,18 +55,20 @@ impl Evaluate for ir::HasAttr {
     fn eval(&self, engine: &mut Engine, env: &mut Env) -> Result<Value> {
         use ir::Attr::*;
         let mut val = self.lhs.eval(engine, env)?;
-        val.has_attr(self.rhs.iter().map(|attr| {
-            Ok(match attr {
-                Str(ident) => ident.clone(),
-                Strs(expr) => expr.eval(engine, env)?.unwrap_string(),
-                Dynamic(expr) => {
-                    let mut val = expr.eval(engine, env)?;
-                    val.coerce_to_string();
-                    val.unwrap_string()
-                }
-            })
-        }))?;
-        val.ok()
+        val.force(engine, env)?
+            .has_attr(self.rhs.iter().map(|attr| {
+                Ok(match attr {
+                    Str(ident) => ident.clone(),
+                    Strs(expr) => expr.eval(engine, env)?.unwrap_string(),
+                    Dynamic(expr) => {
+                        let mut val = expr.eval(engine, env)?;
+                        val.force(engine, env)?.coerce_to_string();
+                        val.unwrap_string()
+                    }
+                })
+            }))?;
+        let result = val.ok();
+        Ok(result.unwrap())
     }
 }
 
@@ -67,6 +77,8 @@ impl Evaluate for ir::BinOp {
         use ir::BinOpKind::*;
         let mut lhs = self.lhs.eval(engine, env)?;
         let mut rhs = self.rhs.eval(engine, env)?;
+        lhs.force(engine, env)?;
+        rhs.force(engine, env)?;
         match self.kind {
             Add => lhs.add(rhs),
             Sub => {
@@ -116,10 +128,15 @@ impl Evaluate for ir::UnOp {
     fn eval(&self, engine: &mut Engine, env: &mut Env) -> Result<Value> {
         use ir::UnOpKind::*;
         let mut rhs = self.rhs.eval(engine, env)?;
+        rhs.force(engine, env)?;
         match self.kind {
-            Neg => rhs.neg(),
-            Not => rhs.not(),
-        }
+            Neg => {
+                rhs.neg();
+            }
+            Not => {
+                rhs.not();
+            }
+        };
         Ok(rhs)
     }
 }
@@ -130,14 +147,14 @@ impl Evaluate for ir::Select {
         let mut val = self.expr.eval(engine, env)?;
         if let Some(default) = &self.default {
             let default = default.eval(engine, env)?;
-            val.select_with_default(
+            val.force(engine, env)?.select_with_default(
                 self.attrpath.iter().map(|attr| {
                     Ok(match attr {
                         Str(ident) => ident.clone(),
                         Strs(expr) => expr.eval(engine, env)?.unwrap_string(),
                         Dynamic(expr) => {
                             let mut val = expr.eval(engine, env)?;
-                            val.coerce_to_string();
+                            val.force(engine, env)?.coerce_to_string();
                             val.unwrap_string()
                         }
                     })
@@ -145,58 +162,60 @@ impl Evaluate for ir::Select {
                 default,
             )?;
         } else {
-            val
+            val.force(engine, env)?
                 .select(self.attrpath.iter().map(|attr| {
                     Ok(match attr {
                         Str(ident) => ident.clone(),
                         Strs(expr) => expr.eval(engine, env)?.unwrap_string(),
                         Dynamic(expr) => {
                             let mut val = expr.eval(engine, env)?;
-                            val.coerce_to_string();
+                            val.force(engine, env)?.coerce_to_string();
                             val.unwrap_string()
                         }
                     })
                 }))?;
         }
-        val.ok()
+        let result = val.ok();
+        Ok(result.unwrap())
     }
 }
 
 impl Evaluate for ir::If {
     fn eval(&self, engine: &mut Engine, env: &mut Env) -> Result<Value> {
         // TODO: Error Handling
-        let cond = self.cond.eval(engine, env)?.unwrap_bool();
-        if cond {
+        let mut cond = self.cond.eval(engine, env)?;
+        cond.force(engine, env)?;
+        let cond = cond.unwrap_bool();
+        let result = if cond {
             self.consq.eval(engine, env)
         } else {
             self.alter.eval(engine, env)
-        }
+        };
+        result
     }
 }
 
 impl Evaluate for ir::LoadFunc {
     fn eval(&self, engine: &mut Engine, env: &mut Env) -> Result<Value> {
         let idx = engine.func_offset + self.idx;
-        Value::Func(idx).ok()
+        let result = Value::Func(idx).ok();
+        Ok(result.unwrap())
     }
 }
 
 impl Evaluate for ir::Call {
     fn eval(&self, engine: &mut Engine, env: &mut Env) -> Result<Value> {
         let mut func = self.func.eval(engine, env)?;
-        func.call(
+        func.force(engine, env)?;
+        let result = func.call(
             self.args
                 .iter()
                 .map(|arg| arg.eval(engine, env))
                 .collect::<Result<_>>()?,
             engine,
             env,
-        )?;
-        // FIXME: Modify Value::call
-        // for arg in self.args {
-        //     func.call(arg.eval(engine, env)?, engine, env)?;
-        // }
-        func.ok()
+        );
+        Ok(func.ok().unwrap())
     }
 }
 
@@ -208,7 +227,8 @@ impl Evaluate for ir::Let {
 
 impl Evaluate for ir::With {
     fn eval(&self, engine: &mut Engine, env: &mut Env) -> Result<Value> {
-        let namespace = self.namespace.eval(engine, env)?;
+        let mut namespace = self.namespace.eval(engine, env)?;
+        namespace.force(engine, env)?;
         // TODO: Error Handling
         env.enter_with(namespace.unwrap_attr_set().into_inner());
         let ret = self.expr.eval(engine, env);
@@ -230,50 +250,56 @@ impl Evaluate for ir::ConcatStrings {
             .iter()
             .map(|part| {
                 let mut part = part.eval(engine, env)?;
-                part.coerce_to_string();
+                part.force(engine, env)?.coerce_to_string();
                 part.ok()
             })
             .collect::<Result<Vec<_>>>()?
             .into_iter();
         let init = parts.next().unwrap();
-        parts
-            .fold(init, |mut a, b| {
-                a.concat_string(b);
-                a
-            })
-            .ok()
+        let result = parts.fold(init, |mut a, b| {
+            a.concat_string(b);
+            a
+        });
+        Ok(result.ok().unwrap())
     }
 }
 
 impl Evaluate for ir::String {
     fn eval(&self, _: &mut Engine, _: &mut Env) -> Result<Value> {
-        Value::String(self.val.clone()).ok()
+        let result = Value::String(self.val.clone()).ok();
+        Ok(result.unwrap())
     }
 }
 
 impl Evaluate for ir::Const {
     fn eval(&self, _: &mut Engine, _: &mut Env) -> Result<Value> {
-        match self.val {
+        let result = match self.val {
             Const::Null => Value::Null,
             Const::Int(x) => Value::Int(x),
             Const::Float(x) => Value::Float(x),
             Const::Bool(x) => Value::Bool(x),
         }
-        .ok()
+        .ok();
+        Ok(result.unwrap())
     }
 }
 
 impl Evaluate for ir::Var {
     fn eval(&self, _: &mut Engine, env: &mut Env) -> Result<Value> {
-        env.lookup_with(&self.sym).ok_or_else(|| {
-            Error::EvalError(format!("variable {} not found", Symbol::from(self.sym.clone())))
-        })
+        let result = env.lookup_with(&self.sym).ok_or_else(|| {
+            Error::EvalError(format!(
+                "variable {} not found",
+                Symbol::from(self.sym.clone())
+            ))
+        });
+        result
     }
 }
 
 impl Evaluate for ir::Arg {
     fn eval(&self, _: &mut Engine, env: &mut Env) -> Result<Value> {
-        env.lookup_arg(self.level).clone().ok()
+        let result = env.lookup_arg(self.level).clone().ok();
+        Ok(result.unwrap())
     }
 }
 
@@ -285,18 +311,18 @@ impl Evaluate for ir::LetVar {
 
 impl Evaluate for ir::Thunk {
     fn eval(&self, engine: &mut Engine, env: &mut Env) -> Result<Value> {
-        env.lookup_cache(self.idx, |env| engine.eval_thunk(self.idx, env))
-        // Value::Thunk(self.idx).ok()
+        Value::Thunk(self.idx).ok()
     }
 }
 
 impl Evaluate for ir::MaybeThunk {
     fn eval(&self, engine: &mut Engine, env: &mut Env) -> Result<Value> {
-        match self {
+        let result = match self {
             ir::MaybeThunk::Const(cnst) => cnst.eval(engine, env),
             ir::MaybeThunk::String(string) => string.eval(engine, env),
             ir::MaybeThunk::Thunk(thunk) => thunk.eval(engine, env),
-        }
+        };
+        result
     }
 }
 
diff --git a/src/ir/ctx.rs b/src/ir/ctx.rs
index e90ed79..998c056 100644
--- a/src/ir/ctx.rs
+++ b/src/ir/ctx.rs
@@ -1,12 +1,9 @@
-use tracing::{event, span, Level};
 use derive_more::Unwrap;
 use ecow::EcoString;
 use hashbrown::{HashMap, HashSet};
 
-use crate::{
-    error::{Error, Result},
-    ty::common::Const,
-};
+use crate::error::Result;
+use crate::ty::common::Const;
 
 use super::{Dep, Func, Ir, LoadFunc, MaybeThunk, SccAnalyzer, SccNode, Thunk};
 
@@ -41,8 +38,8 @@ pub enum LookupResult {
     Builtin(Ir),
     MaybeThunk(MaybeThunk),
     Let { level: usize, idx: usize },
-    SingleArg { level: usize },
-    MultiArg { level: usize, default: Option<Ir> },
+    SingleArg { idx: usize },
+    MultiArg { idx: usize, default: Option<Ir> },
     With,
 }
 
@@ -89,7 +86,7 @@ impl<'a, 'env> Env<'a, 'env> {
     fn _lookup(
         &self,
         ident: &EcoString,
-        mut arg_level: usize,
+        mut arg_idx: usize,
         has_with: bool,
     ) -> core::result::Result<LookupResult, ()> {
         use EnvNode::*;
@@ -111,27 +108,27 @@ impl<'a, 'env> Env<'a, 'env> {
             }
             SingleArg(arg) => {
                 if arg == ident {
-                    return Ok(LookupResult::SingleArg { level: arg_level });
+                    return Ok(LookupResult::SingleArg { idx: arg_idx });
                 } else {
-                    arg_level += 1;
+                    arg_idx += 1;
                 }
             }
             MultiArg(set, alias) => {
                 if let Some(default) = set.get(ident) {
                     return Ok(LookupResult::MultiArg {
-                        level: arg_level,
+                        idx: arg_idx,
                         default: default.clone(),
                     });
                 } else if alias.as_ref() == Some(ident) {
-                    return Ok(LookupResult::SingleArg { level: arg_level });
+                    return Ok(LookupResult::SingleArg { idx: arg_idx });
                 } else {
-                    arg_level += 1;
+                    arg_idx += 1;
                 }
             }
             With => has_with = true,
         }
         self.prev
-            .map(|prev| prev._lookup(ident, arg_level, has_with))
+            .map(|prev| prev._lookup(ident, arg_idx, has_with))
             .map_or_else(|| unreachable!(), |x| x)
     }
 
@@ -170,8 +167,6 @@ impl DowngradeContext {
     }
 
     pub fn new_dep(&mut self, this: Index, dep: Dep) -> Result<()> {
-        #[cfg(debug_assertions)]
-        event!(Level::DEBUG, "{this:?} => {dep:?}");
         match this {
             Index::Thunk(idx) => {
                 /* if dep == Dep::Thunk(idx) && !matches!(self.thunks[idx].0, Ir::List(_)) {
diff --git a/src/ir/mod.rs b/src/ir/mod.rs
index d5656a0..2cb618d 100644
--- a/src/ir/mod.rs
+++ b/src/ir/mod.rs
@@ -695,8 +695,11 @@ impl Var {
         match res {
             Builtin(ir) => ir,
             Let { level, idx } => LetVar { level, idx }.ir(),
-            SingleArg { level } => Arg { level }.ir(),
-            MultiArg { level, default } => Select {
+            SingleArg { idx: level } => Arg { level }.ir(),
+            MultiArg {
+                idx: level,
+                default,
+            } => Select {
                 expr: Arg { level }.ir().boxed(),
                 attrpath: vec![Attr::Str(self.sym)],
                 default: default.map(Box::new),
@@ -1061,10 +1064,13 @@ impl Let {
     ) -> Result<Ir> {
         let map = self.bindings.clone();
         let mut env = env.enter_let(&map);
-        self.bindings.into_iter().map(|(_, ir)| {
-            ir.resolve(self_idx, ctx, &mut env)?;
-            Ok(())
-        }).collect::<Result<()>>()?;
+        self.bindings
+            .into_iter()
+            .map(|(_, ir)| {
+                ir.resolve(self_idx, ctx, &mut env)?;
+                Ok(())
+            })
+            .collect::<Result<()>>()?;
         self.expr.resolve(self_idx, ctx, &env)?.ok()
     }
 }
diff --git a/src/ty/internal/func.rs b/src/ty/internal/func.rs
index bc05761..5106483 100644
--- a/src/ty/internal/func.rs
+++ b/src/ty/internal/func.rs
@@ -12,5 +12,5 @@ use super::Value;
 pub struct PartialFunc {
     pub idx: usize,
     pub args: Vec<Value>,
-    pub cache: HashMap<usize, Value>
+    pub cache: HashMap<usize, Value>,
 }
diff --git a/src/ty/internal/mod.rs b/src/ty/internal/mod.rs
index 1e7974b..801b89c 100644
--- a/src/ty/internal/mod.rs
+++ b/src/ty/internal/mod.rs
@@ -11,7 +11,7 @@ use super::common::*;
 use super::public as p;
 
 use crate::engine::Engine;
-use crate::env::{Env, VmEnvWeak};
+use crate::env::Env;
 use crate::error::*;
 
 mod attrset;
@@ -38,7 +38,7 @@ pub enum Value {
     PrimOp(Rc<PrimOp>),
     PartialPrimOp(Rc<PartialPrimOp>),
     Func(usize),
-    PartialFunc(Rc<PartialFunc>)
+    PartialFunc(Rc<PartialFunc>),
 }
 
 impl Hash for Value {
@@ -166,21 +166,30 @@ impl Value {
             PrimOp(func) => func.call(args, engine),
             PartialPrimOp(func) => func.call(args, engine),
             PartialFunc(func) => {
-                let self::PartialFunc { idx, args: old_args, cache } = Rc::make_mut(func);
+                let self::PartialFunc {
+                    idx,
+                    args: old_args,
+                    cache,
+                } = Rc::make_mut(func);
                 let idx = *idx;
                 let len = args.len() + old_args.len();
                 env.reserve_args(len);
                 env.enter_args(std::mem::take(old_args));
                 let mut args = args.into_iter().peekable();
                 env.enter_arg(args.next().unwrap());
-                let (ret, cache) = env.enter_cache_level(|env| {
+                let (ret, cache) = env.with_cache(std::mem::take(cache), |env| {
+                    engine.eval_func_deps(idx, env)?;
                     let mut ret = engine.eval_thunk(idx, env)?;
                     while args.peek().is_some() {
                         match ret {
                             Value::Func(func) => {
                                 env.enter_arg(args.next().unwrap());
+                                engine.eval_func_deps(idx, env)?;
                                 ret = engine.eval_thunk(func, env)?;
                             }
+                            Value::PartialFunc(_) => {
+                                todo!()
+                            }
                             Value::PrimOp(primop) => {
                                 ret = primop.call(args.collect(), engine)?;
                                 break;
@@ -207,15 +216,21 @@ impl Value {
                 let len = args.len();
                 let mut args = args.into_iter().peekable();
                 env.reserve_args(len);
-                let (ret, cache) = env.enter_cache_level(|env| {
+                env.enter_arg(args.next().unwrap());
+                let (ret, cache) = env.with_new_cache(|env| {
+                    engine.eval_func_deps(idx, env)?;
                     let mut ret = engine.eval_thunk(idx, env)?;
-                    env.enter_arg(args.next().unwrap());
+                    ret.force(engine, env)?;
                     while args.peek().is_some() {
                         match ret {
                             Value::Func(func) => {
                                 env.enter_arg(args.next().unwrap());
+                                engine.eval_func_deps(idx, env)?;
                                 ret = engine.eval_thunk(func, env)?;
                             }
+                            Value::PartialFunc(mut func) => {
+                                todo!()
+                            }
                             Value::PrimOp(primop) => {
                                 ret = primop.call(args.collect(), engine)?;
                                 break;
@@ -481,7 +496,8 @@ impl Value {
 
     pub fn force(&mut self, engine: &mut Engine, env: &mut Env) -> Result<&mut Self> {
         if let &mut Value::Thunk(idx) = self {
-            *self = env.lookup_cache(idx, |env| engine.eval_thunk(idx, env))?
+            // *self = env.lookup_cache(idx, |env| engine.eval_thunk(idx, env))?
+            *self = env.lookup_cache(idx, |_| unreachable!())?
         }
         Ok(self)
     }