diff --git a/src/engine/mod.rs b/src/engine/mod.rs
index 239168c..4184b79 100644
--- a/src/engine/mod.rs
+++ b/src/engine/mod.rs
@@ -1,5 +1,5 @@
-use std::cell::OnceCell;
 use core::mem::MaybeUninit;
+use std::cell::OnceCell;
 use std::rc::Rc;
 
 use hashbrown::{HashMap, HashSet};
@@ -7,8 +7,8 @@ use priority_queue::PriorityQueue;
 
 use crate::env::Env;
 use crate::error::Result;
-use crate::eval::jit::{JITCompiler, JITFunc};
 use crate::eval::Evaluate;
+use crate::eval::jit::{JITCompiler, JITFunc};
 use crate::ir::{Dep, Downgraded, Ir, SccNode};
 use crate::ty::internal as i;
 use crate::ty::public::Value;
@@ -33,15 +33,22 @@ pub fn eval(downgraded: Downgraded) -> Result<Value> {
         downgraded.thunks,
         downgraded.funcs,
         downgraded.func_deps,
-        JITCompiler::new()
+        JITCompiler::new(),
     );
     engine.eval(downgraded.graph)
 }
 
 impl Engine {
-    pub fn new(thunks: Box<[Ir]>, funcs: Box<[Ir]>, func_deps: Vec<HashMap<Dep, usize>>, jit: JITCompiler) -> Self {
+    pub fn new(
+        thunks: Box<[Ir]>,
+        funcs: Box<[Ir]>,
+        func_deps: Vec<HashMap<Dep, usize>>,
+        jit: JITCompiler,
+    ) -> Self {
         Self {
-            compiled: (0..thunks.len() + funcs.len()).map(|_| OnceCell::new()).collect(),
+            compiled: (0..thunks.len() + funcs.len())
+                .map(|_| OnceCell::new())
+                .collect(),
             tasks: PriorityQueue::new(),
             thunks,
             funcs,
@@ -78,7 +85,7 @@ impl Engine {
 
     pub fn eval_thunk(&mut self, idx: usize, env: &mut Env) -> Result<i::Value> {
         let engine = self as *const Engine;
-        let func =  self.compiled[idx].get_or_init(|| self.jit.compile(&self.thunks[idx], idx));
+        let func = self.compiled[idx].get_or_init(|| self.jit.compile(&self.thunks[idx], idx));
         let mut ret: MaybeUninit<i::Value> = MaybeUninit::uninit();
         unsafe {
             func(engine, env, ret.as_mut_ptr());
@@ -88,7 +95,8 @@ impl Engine {
 
     pub fn call_func(&mut self, idx: usize, env: &mut Env) -> Result<i::Value> {
         let engine = self as *const Engine;
-        let func = self.compiled[idx + self.thunks.len()].get_or_init(|| self.jit.compile(&self.funcs[idx], idx));
+        let func = self.compiled[idx + self.thunks.len()]
+            .get_or_init(|| self.jit.compile(&self.funcs[idx], idx));
         let mut ret: MaybeUninit<i::Value> = MaybeUninit::uninit();
         unsafe {
             func(engine, env, ret.as_mut_ptr());
@@ -97,9 +105,7 @@ impl Engine {
     }
 
     pub fn eval_func_deps(&mut self, idx: usize, env: &mut Env) -> Result<()> {
-        for (&dep, _) in
-            unsafe { &*(&self.func_deps[idx] as *const HashMap<Dep, usize>) }.iter()
-        {
+        for (&dep, _) in unsafe { &*(&self.func_deps[idx] as *const HashMap<Dep, usize>) }.iter() {
             match dep {
                 Dep::Arg(idx) => {
                     if let i::Value::Thunk(idx) = env.lookup_arg(idx) {
diff --git a/src/engine/test.rs b/src/engine/test.rs
index 6f30fb6..ca04571 100644
--- a/src/engine/test.rs
+++ b/src/engine/test.rs
@@ -190,11 +190,10 @@ fn test_let() {
         r#"let b = "c"; in { a.b = 1; } // { a."a${b}" = 2; }"#,
         attrs! { symbol!("a") => attrs!{ symbol!("ac") => int!(2) } },
     );
-    // FIXME:
-    /* test_expr(
+    test_expr(
         "let f = n: let a = n; f = x: a + x; in f; in f 0 1",
         int!(1),
-    ); */
+    );
 }
 
 #[test]
diff --git a/src/eval/jit/compile.rs b/src/eval/jit/compile.rs
index 36bfa99..2272729 100644
--- a/src/eval/jit/compile.rs
+++ b/src/eval/jit/compile.rs
@@ -298,7 +298,7 @@ impl JITCompile for Attr {
         match self {
             Str(string) => ctx.create_string(string),
             Dynamic(ir) => ir.compile(ctx, engine, env),
-            Strs(strings) => strings.compile(ctx, engine, env)
+            Strs(strings) => strings.compile(ctx, engine, env),
         }
     }
 }
diff --git a/src/eval/jit/helpers.rs b/src/eval/jit/helpers.rs
index 235edcc..cb28eaf 100644
--- a/src/eval/jit/helpers.rs
+++ b/src/eval/jit/helpers.rs
@@ -1,6 +1,6 @@
+use core::{slice, str};
 use std::alloc::Layout;
 use std::alloc::alloc;
-use core::{slice, str};
 use std::mem::MaybeUninit;
 use std::ptr::NonNull;
 
@@ -18,50 +18,68 @@ pub extern "C" fn helper_call(
     // TODO: Error Handling
     let args = core::ptr::slice_from_raw_parts_mut(args_ptr, args_len);
     let args = unsafe { Box::from_raw(args) };
-    func.call(
-        args.into_iter().map(Value::from).collect(),
-        engine,
-        env
-    )
-    .unwrap();
+    func.call(args.into_iter().map(Value::from).collect(), engine, env)
+        .unwrap();
 }
 
 pub extern "C" fn helper_lookup_arg(env: &Env, level: usize, ret: &mut MaybeUninit<Value>) {
     ret.write(env.lookup_arg(level as usize));
 }
 
-pub extern "C" fn helper_lookup(env: &Env, sym_ptr: *const u8, sym_len: usize, ret: &mut MaybeUninit<Value>) {
+pub extern "C" fn helper_lookup(
+    env: &Env,
+    sym_ptr: *const u8,
+    sym_len: usize,
+    ret: &mut MaybeUninit<Value>,
+) {
     // TODO: Error Handling
     unsafe {
-        ret.write(env
-            .lookup_with(str::from_utf8_unchecked(slice::from_raw_parts(sym_ptr, sym_len)))
-            .unwrap());
+        ret.write(
+            env.lookup_with(str::from_utf8_unchecked(slice::from_raw_parts(
+                sym_ptr, sym_len,
+            )))
+            .unwrap(),
+        );
     }
 }
 
-pub extern "C" fn helper_select(val: &mut Value, path_ptr: *mut Value, path_len: usize, engine: &mut Engine, env: &mut Env) {
+pub extern "C" fn helper_select(
+    val: &mut Value,
+    path_ptr: *mut Value,
+    path_len: usize,
+    engine: &mut Engine,
+    env: &mut Env,
+) {
     let path = core::ptr::slice_from_raw_parts_mut(path_ptr, path_len);
     let path = unsafe { Box::from_raw(path) };
     val.select(path.into_iter().map(|mut val| {
         val.force(engine, env)?.coerce_to_string();
         Ok(val.unwrap_string())
-    })).unwrap();
+    }))
+    .unwrap();
 }
 
-pub extern "C" fn helper_select_with_default(val: &mut Value, path_ptr: *mut Value, path_len: usize, default: NonNull<Value>, engine: &mut Engine, env: &mut Env) {
-    let path = core::ptr::slice_from_raw_parts_mut(path_ptr, path_len);
-    let path = unsafe { Box::from_raw(path) };
-    val.select_with_default(path.into_iter().map(|mut val| {
-        val.force(engine, env)?.coerce_to_string();
-        Ok(val.unwrap_string())
-    }), unsafe { default.read() }).unwrap();
-}
-
-pub extern "C" fn helper_force(
-    thunk: &mut Value,
+pub extern "C" fn helper_select_with_default(
+    val: &mut Value,
+    path_ptr: *mut Value,
+    path_len: usize,
+    default: NonNull<Value>,
     engine: &mut Engine,
     env: &mut Env,
 ) {
+    let path = core::ptr::slice_from_raw_parts_mut(path_ptr, path_len);
+    let path = unsafe { Box::from_raw(path) };
+    val.select_with_default(
+        path.into_iter().map(|mut val| {
+            val.force(engine, env)?.coerce_to_string();
+            Ok(val.unwrap_string())
+        }),
+        unsafe { default.read() },
+    )
+    .unwrap();
+}
+
+pub extern "C" fn helper_force(thunk: &mut Value, engine: &mut Engine, env: &mut Env) {
     thunk.force(engine, env).unwrap();
 }
 
@@ -69,9 +87,15 @@ pub extern "C" fn helper_eq(lhs: &mut Value, rhs: &Value) {
     lhs.eq(rhs);
 }
 
-pub unsafe extern "C" fn helper_create_string(ptr: *const u8, len: usize, ret: &mut MaybeUninit<Value>) {
+pub unsafe extern "C" fn helper_create_string(
+    ptr: *const u8,
+    len: usize,
+    ret: &mut MaybeUninit<Value>,
+) {
     unsafe {
-        ret.write(Value::String(str::from_utf8_unchecked(slice::from_raw_parts(ptr, len)).to_string()));
+        ret.write(Value::String(
+            str::from_utf8_unchecked(slice::from_raw_parts(ptr, len)).to_string(),
+        ));
     }
 }
 
diff --git a/src/eval/jit/mod.rs b/src/eval/jit/mod.rs
index 18754ff..edefa0d 100644
--- a/src/eval/jit/mod.rs
+++ b/src/eval/jit/mod.rs
@@ -196,7 +196,10 @@ impl<'comp, 'ctx> JITContext<'comp, 'ctx> {
             .builder
             .ins()
             .stack_addr(self.compiler.ptr_type, rhs, 0);
-        let eq = self.compiler.module.declare_func_in_func(self.compiler.eq, self.builder.func);
+        let eq = self
+            .compiler
+            .module
+            .declare_func_in_func(self.compiler.eq, self.builder.func);
         self.builder.ins().call(eq, &[lhs, rhs]);
     }
 
diff --git a/src/ir/ctx.rs b/src/ir/ctx.rs
index 070cc4a..5479018 100644
--- a/src/ir/ctx.rs
+++ b/src/ir/ctx.rs
@@ -169,14 +169,16 @@ impl DowngradeContext {
         match this {
             Index::Thunk(idx) => {
                 let len = self.thunk_deps.len();
-                self.thunk_deps[idx].entry(dep.unwrap_thunk()).or_insert(len);
+                self.thunk_deps[idx]
+                    .entry(dep.unwrap_thunk())
+                    .or_insert(len);
                 len
             }
             Index::Func(idx) => {
                 let len = self.thunk_deps.len();
                 self.func_deps[idx].entry(dep).or_insert(len);
                 len
-            },
+            }
         }
     }
 
@@ -255,12 +257,12 @@ impl Downgraded {
         Self {
             graph: SccAnalyzer::new(&ctx).analyze(),
             func_deps: ctx.func_deps,
-            thunks: ctx
-                .thunks
+            thunks: ctx.thunks.into_iter().map(|(ir, _)| ir).collect(),
+            funcs: ctx
+                .funcs
                 .into_iter()
-                .map(|(ir, _)| ir)
+                .map(|Func { body, .. }| *body)
                 .collect(),
-            funcs: ctx.funcs.into_iter().map(|Func { body, .. }| *body).collect()
         }
     }
 }