diff --git a/fix-codegen/src/disassembler.rs b/fix-codegen/src/disassembler.rs
index e8052ff..57aa4c4 100644
--- a/fix-codegen/src/disassembler.rs
+++ b/fix-codegen/src/disassembler.rs
@@ -255,7 +255,9 @@ impl<'a, Ctx: DisassemblerContext> Disassembler<'a, Ctx> {
                 ("MakePatternClosure", arg_str)
             }
 
-            Op::Call => ("Call", String::new()),
+            Op::Call => {
+                ("Call", String::new())
+            },
 
             Op::MakeAttrs => {
                 let count = self.read_u32();
diff --git a/fix-codegen/src/lib.rs b/fix-codegen/src/lib.rs
index af9eab2..5192487 100644
--- a/fix-codegen/src/lib.rs
+++ b/fix-codegen/src/lib.rs
@@ -1,8 +1,8 @@
 use std::ops::Deref;
 
-use fix_builtins::{BUILTINS, BuiltinId};
+use fix_builtins::BuiltinId;
 use fix_common::StringId;
-use fix_ir::{Attr, BinOpKind, Ir, Param, RawIrRef, ThunkId, UnOpKind};
+use fix_ir::{Attr, BinOpKind, Ir, MaybeThunk, Param, RawIrRef, ThunkId, UnOpKind};
 use hashbrown::HashMap;
 use num_enum::TryFromPrimitive;
 use rnix::TextRange;
@@ -151,40 +151,35 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
         }
     }
 
-    fn classify_value(&mut self, ir: RawIrRef<'_>) -> InlineOperand {
-        match ir.deref() {
-            &Ir::Int(x) => {
+    #[must_use]
+    fn inline_maybe_thunk(&mut self, val: MaybeThunk) -> InlineOperand {
+        use MaybeThunk::*;
+        match val {
+            Int(x) => {
                 if x <= i32::MAX as i64 {
                     InlineOperand::Const(Const::Smi(x as i32))
                 } else {
                     InlineOperand::BigInt(x)
                 }
             }
-            &Ir::Float(x) => InlineOperand::Const(Const::Float(x)),
-            &Ir::Bool(b) => InlineOperand::Const(Const::Bool(b)),
-            Ir::Null => InlineOperand::Const(Const::Null),
-            Ir::Str(s) => {
-                let sid = self.ctx.intern_string(s.deref());
-                InlineOperand::Const(Const::String(sid))
-            }
-            &Ir::Thunk(id) => {
+            Float(x) => InlineOperand::Const(Const::Float(x)),
+            Bool(b) => InlineOperand::Const(Const::Bool(b)),
+            Null => InlineOperand::Const(Const::Null),
+            Str(id) => InlineOperand::Const(Const::String(id)),
+            Thunk(id) => {
                 let (layer, local) = self.resolve_thunk(id);
                 InlineOperand::Local { layer, local }
             }
-            &Ir::Arg { layer } => InlineOperand::Local {
+            Arg { layer } => InlineOperand::Local {
                 layer: layer.try_into().expect("scope too deep!"),
                 local: 0,
             },
-            &Ir::Builtin(id) => {
-                let arity = BUILTINS[id as usize].1;
-                InlineOperand::Const(Const::PrimOp { id, arity })
-            }
-            Ir::Builtins => InlineOperand::Builtins,
-            _ => panic!("cannot classify IR node as inline operand"),
+            _ => todo!(),
         }
     }
 
-    fn emit_inline_operand(&mut self, operand: InlineOperand) {
+    fn emit_maybe_thunk(&mut self, val: MaybeThunk) {
+        let operand = self.inline_maybe_thunk(val);
         match operand {
             InlineOperand::Const(val) => {
                 let idx = self.ctx.add_constant(val);
@@ -320,30 +315,15 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
                 self.count_with_thunks(*lhs) + self.count_with_thunks(*rhs)
             }
             Ir::UnOp { rhs, .. } => self.count_with_thunks(*rhs),
-            Ir::Call { func, arg, .. } => {
-                self.count_with_thunks(*func) + self.count_with_thunks(*arg)
-            }
+            Ir::Call { func, .. } => self.count_with_thunks(*func),
             Ir::Assert {
                 assertion, expr, ..
             } => self.count_with_thunks(*assertion) + self.count_with_thunks(*expr),
-            Ir::Select { expr, default, .. } => {
-                self.count_with_thunks(*expr) + default.map_or(0, |d| self.count_with_thunks(d))
-            }
+            Ir::Select { expr, .. } => self.count_with_thunks(*expr),
             Ir::HasAttr { lhs, .. } => self.count_with_thunks(*lhs),
             Ir::ConcatStrings { parts, .. } => {
                 parts.iter().map(|p| self.count_with_thunks(*p)).sum()
             }
-            Ir::Path(p) => self.count_with_thunks(*p),
-            Ir::List { items } => items.iter().map(|item| self.count_with_thunks(*item)).sum(),
-            Ir::AttrSet { stcs, dyns } => {
-                stcs.iter()
-                    .map(|(_, &(val, _))| self.count_with_thunks(val))
-                    .sum::<usize>()
-                    + dyns
-                        .iter()
-                        .map(|&(k, v, _)| self.count_with_thunks(k) + self.count_with_thunks(v))
-                        .sum::<usize>()
-            }
             _ => 0,
         }
     }
@@ -392,9 +372,8 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
                 self.collect_with_thunks_recursive(*rhs, out);
             }
             Ir::UnOp { rhs, .. } => self.collect_with_thunks_recursive(*rhs, out),
-            Ir::Call { func, arg, .. } => {
+            Ir::Call { func, .. } => {
                 self.collect_with_thunks_recursive(*func, out);
-                self.collect_with_thunks_recursive(*arg, out);
             }
             Ir::Assert {
                 assertion, expr, ..
@@ -402,11 +381,8 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
                 self.collect_with_thunks_recursive(*assertion, out);
                 self.collect_with_thunks_recursive(*expr, out);
             }
-            Ir::Select { expr, default, .. } => {
+            Ir::Select { expr, .. } => {
                 self.collect_with_thunks_recursive(*expr, out);
-                if let Some(d) = default {
-                    self.collect_with_thunks_recursive(*d, out);
-                }
             }
             Ir::HasAttr { lhs, .. } => self.collect_with_thunks_recursive(*lhs, out),
             Ir::ConcatStrings { parts, .. } => {
@@ -414,22 +390,7 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
                     self.collect_with_thunks_recursive(*p, out);
                 }
             }
-            Ir::Path(p) => self.collect_with_thunks_recursive(*p, out),
-            Ir::List { items } => {
-                for item in items.iter() {
-                    self.collect_with_thunks_recursive(*item, out);
-                }
-            }
-            Ir::AttrSet { stcs, dyns } => {
-                for (_, &(val, _)) in stcs.iter() {
-                    self.collect_with_thunks_recursive(val, out);
-                }
-                for &(key, val, _) in dyns.iter() {
-                    self.collect_with_thunks_recursive(key, out);
-                    self.collect_with_thunks_recursive(val, out);
-                }
-            }
-            _ => {}
+            _ => (),
         }
     }
 
@@ -512,10 +473,9 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
             &Ir::Bool(true) => self.emit_op(Op::PushTrue),
             &Ir::Bool(false) => self.emit_op(Op::PushFalse),
             Ir::Null => self.emit_op(Op::PushNull),
-            Ir::Str(s) => {
-                let idx = self.ctx.intern_string(s.deref());
+            &Ir::Str(id) => {
                 self.emit_op(Op::PushString);
-                self.emit_str_id(idx);
+                self.emit_str_id(id);
             }
             &Ir::Path(p) => {
                 self.emit_expr(p);
@@ -572,15 +532,14 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
                     self.emit_op(Op::MakeList);
                     self.emit_u32(items.len() as u32);
                     for &item in items.iter() {
-                        let operand = self.classify_value(item);
-                        self.emit_inline_operand(operand);
+                        self.emit_maybe_thunk(item);
                     }
                 }
             }
             &Ir::Call { func, arg, .. } => {
-                self.emit_expr(arg);
                 self.emit_expr(func);
                 self.emit_op(Op::Call);
+                self.emit_maybe_thunk(arg);
             }
             &Ir::Arg { layer } => {
                 self.emit_load(layer.try_into().expect("scope too deep!"), 0);
@@ -616,16 +575,17 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
                 );
             }
             &Ir::ConcatStrings {
-                ref parts,
-                force_string,
+                parts: _,
+                force_string: _,
             } => {
-                self.emit_op(Op::ConcatStrings);
-                self.emit_u16(parts.len() as u16);
-                self.emit_u8(if force_string { 1 } else { 0 });
-                for &part in parts.iter() {
-                    let operand = self.classify_value(part);
-                    self.emit_inline_operand(operand);
-                }
+                todo!("redesign ConcatStrings");
+                // self.emit_op(Op::ConcatStrings);
+                // self.emit_u16(parts.len() as u16);
+                // self.emit_u8(if force_string { 1 } else { 0 });
+                // for &part in parts.iter() {
+                //     let operand = self.inline_maybe_thunk(part);
+                //     self.emit_inline_operand(operand);
+                // }
             }
             &Ir::HasAttr { lhs, ref rhs } => {
                 self.emit_has_attr(lhs, rhs);
@@ -732,14 +692,16 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
                 self.patch_i32(end_placeholder, end_offset);
             }
             PipeL => {
-                self.emit_expr(rhs);
-                self.emit_expr(lhs);
-                self.emit_op(Op::Call);
+                todo!("new call");
+                // self.emit_expr(rhs);
+                // self.emit_expr(lhs);
+                // self.emit_op(Op::Call);
             }
             PipeR => {
-                self.emit_expr(lhs);
-                self.emit_expr(rhs);
-                self.emit_op(Op::Call);
+                todo!("new call");
+                // self.emit_expr(lhs);
+                // self.emit_expr(rhs);
+                // self.emit_op(Op::Call);
             }
             _ => {
                 self.emit_expr(lhs);
@@ -817,8 +779,8 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
 
     fn emit_attrset(
         &mut self,
-        stcs: &fix_ir::HashMap<'_, StringId, (RawIrRef<'_>, TextRange)>,
-        dyns: &[(RawIrRef<'_>, RawIrRef<'_>, TextRange)],
+        stcs: &fix_ir::HashMap<'_, StringId, (MaybeThunk, TextRange)>,
+        dyns: &[(RawIrRef<'_>, MaybeThunk, TextRange)],
     ) {
         if stcs.is_empty() && dyns.is_empty() {
             self.emit_op(Op::MakeEmptyAttrs);
@@ -832,19 +794,18 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
         for (&sym, &(val, span)) in stcs.iter() {
             self.emit_u8(AttrKeyType::Static as u8);
             self.emit_str_id(sym);
-            let val_operand = self.classify_value(val);
-            self.emit_inline_operand(val_operand);
+            self.emit_maybe_thunk(val);
             let span_id = self.ctx.register_span(span);
             self.emit_u32(span_id);
         }
-        for &(key, val, span) in dyns.iter() {
-            self.emit_u8(AttrKeyType::Dynamic as u8);
-            let key_operand = self.classify_value(key);
-            self.emit_inline_operand(key_operand);
-            let val_operand = self.classify_value(val);
-            self.emit_inline_operand(val_operand);
-            let span_id = self.ctx.register_span(span);
-            self.emit_u32(span_id);
+        for &(_key, _val, _span) in dyns.iter() {
+            todo!("redesign dynamic attr key");
+            // self.emit_u8(AttrKeyType::Dynamic as u8);
+            // self.emit_maybe_thunk(key);
+            // let val_operand = self.inline_maybe_thunk(val);
+            // self.emit_maybe_thunk(val);
+            // let span_id = self.ctx.register_span(span);
+            // self.emit_u32(span_id);
         }
     }
 
@@ -910,12 +871,12 @@ impl<'a, Ctx: BytecodeContext> BytecodeEmitter<'a, Ctx> {
 
     fn emit_with(
         &mut self,
-        namespace: RawIrRef<'_>,
+        namespace: MaybeThunk,
         body: RawIrRef<'_>,
         thunks: &[(ThunkId, RawIrRef<'_>)],
     ) {
-        self.emit_expr(namespace);
         self.emit_op(Op::PushWith);
+        self.emit_maybe_thunk(namespace);
         self.emit_scope_thunks(thunks);
         self.emit_expr(body);
         self.emit_op(Op::PopWith);
diff --git a/fix-ir/src/downgrade.rs b/fix-ir/src/downgrade.rs
index e103f46..66e4b71 100644
--- a/fix-ir/src/downgrade.rs
+++ b/fix-ir/src/downgrade.rs
@@ -1,4 +1,3 @@
-use bumpalo::boxed::Box;
 use bumpalo::collections::{CollectIn, Vec};
 use fix_builtins::BuiltinId;
 use fix_common::Symbol;
@@ -6,7 +5,7 @@ use fix_error::{Error, Result, Source};
 use hashbrown::HashSet;
 use hashbrown::hash_map::Entry;
 use rnix::TextRange;
-use rnix::ast::{self, Expr, HasEntry};
+use rnix::ast::{self, AstToken, Expr, HasEntry};
 use rowan::ast::AstNode;
 
 use super::*;
@@ -39,20 +38,13 @@ impl<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>, T, E: std::fmt::Display>
     }
 }
 
-trait BoxIn: Sized {
-    fn box_in(self, bump: &bumpalo::Bump) -> Box<'_, Self> {
-        Box::new_in(self, bump)
-    }
-}
-impl<T: Sized> BoxIn for T {}
-
 pub trait DowngradeContext<'id: 'ir, 'ir> {
     fn new_expr(&self, expr: Ir<'ir, IrRef<'id, 'ir>>) -> IrRef<'id, 'ir>;
-    fn maybe_thunk(&mut self, ir: IrRef<'id, 'ir>) -> IrRef<'id, 'ir>;
+    fn maybe_thunk(&mut self, ir: IrRef<'id, 'ir>) -> MaybeThunk;
 
-    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 intern_string(&mut self, sym: impl AsRef<str>) -> StringId;
+    fn resolve_sym(&self, id: StringId) -> Symbol<'_>;
+    fn lookup(&self, sym: StringId, span: TextRange) -> Result<MaybeThunk>;
 
     fn get_current_source(&self) -> Source;
 
@@ -165,14 +157,15 @@ impl<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>> Downgrade<'id, 'ir, Ctx> fo
         let path = {
             let temp = self.content().require(ctx, span)?;
             let text = temp.text();
-            ctx.new_expr(Ir::Str(
-                text[1..text.len() - 1].to_string().box_in(ctx.bump()),
-            ))
+            let id = ctx.intern_string(&text[1..text.len() - 1]);
+            let expr = ctx.new_expr(Ir::Str(id));
+            ctx.maybe_thunk(expr)
         };
         // HACK: disgusting eww
         let find_file = ctx.new_expr(Ir::Builtin(BuiltinId::FindFile));
-        let sym = ctx.new_sym("nixPath".into());
+        let sym = ctx.intern_string("nixPath");
         let nix_path = ctx.new_expr(Ir::BuiltinConst(sym));
+        let nix_path = ctx.maybe_thunk(nix_path);
         let call = ctx.new_expr(Ir::Call {
             func: find_file,
             arg: nix_path,
@@ -194,14 +187,14 @@ impl<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>> Downgrade<'id, 'ir, Ctx> fo
 
         let bump = ctx.bump();
         let mut parts = normalized.into_iter().map(|part| match part {
-            ast::InterpolPart::Literal(lit) => Ok(ctx.new_expr(Ir::Str(lit.box_in(bump)))),
-            ast::InterpolPart::Interpolation(interpol) => {
-                let inner = interpol
-                    .expr()
-                    .require(ctx, interpol.syntax().text_range())?
-                    .downgrade(ctx)?;
-                Ok(ctx.maybe_thunk(inner))
+            ast::InterpolPart::Literal(lit) => {
+                let id = ctx.intern_string(lit);
+                Ok(ctx.new_expr(Ir::Str(id)))
             }
+            ast::InterpolPart::Interpolation(interpol) => interpol
+                .expr()
+                .require(ctx, interpol.syntax().text_range())?
+                .downgrade(ctx),
         });
 
         Ok(if is_single_literal {
@@ -219,11 +212,15 @@ impl<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>> Downgrade<'id, 'ir, Ctx> fo
 impl<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>> Downgrade<'id, 'ir, Ctx> for ast::Literal {
     fn downgrade(self, ctx: &mut Ctx) -> Result<IrRef<'id, 'ir>> {
         let span = self.syntax().text_range();
-        Ok(ctx.new_expr(match self.kind() {
+        let expr = match self.kind() {
             ast::LiteralKind::Integer(int) => Ir::Int(int.value().require(ctx, span)?),
             ast::LiteralKind::Float(float) => Ir::Float(float.value().require(ctx, span)?),
-            ast::LiteralKind::Uri(uri) => Ir::Str(uri.to_string().box_in(ctx.bump())),
-        }))
+            ast::LiteralKind::Uri(uri) => {
+                let id = ctx.intern_string(uri.syntax().text());
+                Ir::Str(id)
+            }
+        };
+        Ok(ctx.new_expr(expr))
     }
 }
 
@@ -231,8 +228,8 @@ impl<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>> Downgrade<'id, 'ir, Ctx> fo
     fn downgrade(self, ctx: &mut Ctx) -> Result<IrRef<'id, 'ir>> {
         let span = self.syntax().text_range();
         let text = self.ident_token().require(ctx, span)?.to_string();
-        let sym = ctx.new_sym(text);
-        ctx.lookup(sym, span)
+        let sym = ctx.intern_string(text);
+        ctx.lookup(sym, span).map(|thunk| thunk.to_ir(ctx))
     }
 }
 
@@ -299,12 +296,10 @@ impl<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>> Downgrade<'id, 'ir, Ctx> fo
         let span = self.syntax().text_range();
         let expr = self.expr().require(ctx, span)?.downgrade(ctx)?;
         let attrpath = downgrade_attrpath(self.attrpath().require(ctx, span)?, ctx)?;
-        let default = if let Some(default) = self.default_expr() {
-            let default_expr = default.downgrade(ctx)?;
-            Some(ctx.maybe_thunk(default_expr))
-        } else {
-            None
-        };
+        let default = self
+            .default_expr()
+            .map(|expr| expr.downgrade(ctx))
+            .transpose()?;
         let span = self.syntax().text_range();
         Ok(ctx.new_expr(Ir::Select {
             expr,
@@ -331,7 +326,7 @@ impl<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>> Downgrade<'id, 'ir, Ctx> fo
             Ok(ctx.new_expr(Ir::AttrSet { stcs, dyns }))
         })?;
 
-        let body_sym = ctx.new_sym("body".to_string());
+        let body_sym = ctx.intern_string("body");
         Ok(ctx.new_expr(Ir::Select {
             expr: attrset_expr,
             attrpath: Vec::from_iter_in(
@@ -390,7 +385,7 @@ impl<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>> Downgrade<'id, 'ir, Ctx> fo
 
             match raw_param {
                 ast::Param::IdentParam(id) => {
-                    let param_sym = ctx.new_sym(id.to_string());
+                    let param_sym = ctx.intern_string(id.to_string());
                     param = None;
 
                     body = ctx.with_param_scope(param_sym, |ctx| body_ast.downgrade(ctx))?;
@@ -400,7 +395,7 @@ impl<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>> Downgrade<'id, 'ir, Ctx> fo
                         .pat_bind()
                         .map(|alias| {
                             let ident = alias.ident().require(ctx, alias.syntax().text_range())?;
-                            Ok::<_, std::boxed::Box<Error>>(ctx.new_sym(ident.to_string()))
+                            Ok::<_, std::boxed::Box<Error>>(ctx.intern_string(ident.to_string()))
                         })
                         .transpose()?;
 
@@ -484,7 +479,7 @@ impl<'id: 'ir, 'ir> PendingAttrSet<'ir> {
 
         match first {
             ast::Attr::Ident(ident) => {
-                let sym = ctx.new_sym(ident.to_string());
+                let sym = ctx.intern_string(ident.to_string());
                 self.insert_static(sym, span, rest, value, ctx)
             }
             ast::Attr::Str(string) => {
@@ -493,7 +488,7 @@ impl<'id: 'ir, 'ir> PendingAttrSet<'ir> {
                     && let ast::InterpolPart::Literal(lit) =
                         parts.into_iter().next().expect("len checked")
                 {
-                    let sym = ctx.new_sym(lit);
+                    let sym = ctx.intern_string(lit);
                     return self.insert_static(sym, span, rest, value, ctx);
                 }
                 self.insert_dynamic(first.clone(), span, rest, value, ctx)
@@ -736,14 +731,14 @@ impl<'id: 'ir, 'ir> PendingAttrSet<'ir> {
         for attr in inherit.attrs() {
             let span = attr.syntax().text_range();
             let sym = match &attr {
-                ast::Attr::Ident(ident) => ctx.new_sym(ident.to_string()),
+                ast::Attr::Ident(ident) => ctx.intern_string(ident.to_string()),
                 ast::Attr::Str(s) => {
                     let parts = s.normalized_parts();
                     if parts.len() == 1
                         && let ast::InterpolPart::Literal(lit) =
                             parts.into_iter().next().expect("len checked")
                     {
-                        ctx.new_sym(lit)
+                        ctx.intern_string(lit)
                     } else {
                         return Err(Error::downgrade_error(
                             "dynamic attributes not allowed in inherit".to_string(),
@@ -763,7 +758,7 @@ impl<'id: 'ir, 'ir> PendingAttrSet<'ir> {
 
             if self.stcs.contains_key(&sym) {
                 return Err(Error::downgrade_error(
-                    format!("attribute '{}' already defined", ctx.get_sym(sym)),
+                    format!("attribute '{}' already defined", ctx.resolve_sym(sym)),
                     ctx.get_current_source(),
                     span,
                 ));
@@ -840,8 +835,8 @@ fn make_attrpath_value_entry<'ir>(path: Vec<'ir, ast::Attr>, value: ast::Expr) -
 }
 
 struct FinalizedAttrSet<'id, 'ir> {
-    stcs: HashMap<'ir, StringId, (IrRef<'id, 'ir>, TextRange)>,
-    dyns: Vec<'ir, (IrRef<'id, 'ir>, IrRef<'id, 'ir>, TextRange)>,
+    stcs: HashMap<'ir, StringId, (MaybeThunk, TextRange)>,
+    dyns: Vec<'ir, (IrRef<'id, 'ir>, MaybeThunk, TextRange)>,
 }
 
 fn downgrade_attrs<'id, 'ir>(
@@ -861,17 +856,17 @@ fn downgrade_attr<'id, 'ir>(
     use ast::InterpolPart::*;
     match attr {
         Ident(ident) => Ok(Attr::Str(
-            ctx.new_sym(ident.to_string()),
+            ctx.intern_string(ident.to_string()),
             ident.syntax().text_range(),
         )),
         Str(string) => {
             let parts = string.normalized_parts();
             let span = string.syntax().text_range();
             if parts.is_empty() {
-                Ok(Attr::Str(ctx.new_sym("".to_string()), span))
+                Ok(Attr::Str(ctx.intern_string(""), span))
             } else if parts.len() == 1 {
                 match parts.into_iter().next().expect("len checked") {
-                    Literal(ident) => Ok(Attr::Str(ctx.new_sym(ident), span)),
+                    Literal(ident) => Ok(Attr::Str(ctx.intern_string(ident), span)),
                     Interpolation(interpol) => Ok(Attr::Dynamic(
                         interpol
                             .expr()
@@ -885,7 +880,10 @@ fn downgrade_attr<'id, 'ir>(
                 let parts = parts
                     .into_iter()
                     .map(|part| match part {
-                        Literal(lit) => Ok(ctx.new_expr(Ir::Str(lit.box_in(bump)))),
+                        Literal(lit) => {
+                            let id = ctx.intern_string(lit);
+                            Ok(ctx.new_expr(Ir::Str(id)))
+                        }
                         Interpolation(interpol) => interpol
                             .expr()
                             .require(ctx, interpol.syntax().text_range())?
@@ -950,13 +948,13 @@ where
     for entry in pat_entries {
         let ident = entry.ident().require(ctx, entry.syntax().text_range())?;
         let sym_span = ident.syntax().text_range();
-        let sym = ctx.new_sym(ident.syntax().text().to_string());
+        let sym = ctx.intern_string(ident.syntax().text().to_string());
         let default = entry.default();
         let span = entry.syntax().text_range();
 
         if !seen_params.insert(sym) {
             return Err(Error::downgrade_error(
-                format!("duplicate parameter '{}'", ctx.get_sym(sym)),
+                format!("duplicate parameter '{}'", ctx.resolve_sym(sym)),
                 ctx.get_current_source(),
                 span,
             ));
@@ -1001,12 +999,13 @@ where
                     default,
                     span,
                 } = param;
-                let default = if let Some(default) = default {
-                    let default = default.clone().downgrade(ctx)?;
-                    Some(ctx.maybe_thunk(default))
-                } else {
-                    None
-                };
+                let default = default.map(|default| default.downgrade(ctx)).transpose()?;
+                // let default = if let Some(default) = default {
+                //     let default = default.clone().downgrade(ctx)?;
+                //     Some(ctx.maybe_thunk(default))
+                // } else {
+                //     None
+                // };
 
                 Ok(ctx.new_expr(Ir::Select {
                     expr: arg,
@@ -1075,7 +1074,7 @@ where
     F: FnOnce(
         &mut Ctx,
         &[StringId],
-        &[(IrRef<'id, 'ir>, IrRef<'id, 'ir>, TextRange)],
+        &[(IrRef<'id, 'ir>, MaybeThunk, TextRange)],
     ) -> Result<IrRef<'id, 'ir>>,
 {
     let mut pending = PendingAttrSet::new_in(ctx.bump());
@@ -1088,18 +1087,21 @@ where
 
     ctx.with_let_scope(&keys, |ctx| {
         let finalized = finalize_pending_set::<_, ALLOW_DYN>(pending, &inherit_lookups, ctx)?;
-        let vals = keys
-            .iter()
-            .map(|sym| finalized.stcs.get(sym).expect("WTF").0)
-            .collect_in(ctx.bump());
+        let vals = {
+            let mut temp = Vec::with_capacity_in(keys.len(), ctx.bump());
+            for sym in &keys {
+                temp.push(finalized.stcs.get(sym).expect("WTF").0.to_ir(ctx));
+            }
+            temp
+        };
         body_fn(ctx, &keys, &finalized.dyns).map(|body| (vals, body))
     })
 }
 
-fn collect_inherit_lookups<'id, 'ir, Ctx: DowngradeContext<'id, 'ir>>(
+fn collect_inherit_lookups<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>>(
     entries: &[ast::Entry],
     ctx: &mut Ctx,
-) -> Result<HashMap<'ir, StringId, (IrRef<'id, 'ir>, TextRange)>> {
+) -> Result<HashMap<'ir, StringId, (MaybeThunk, TextRange)>> {
     let mut inherit_lookups = HashMap::new_in(ctx.bump());
     for entry in entries {
         if let ast::Entry::Inherit(inherit) = entry
@@ -1108,7 +1110,7 @@ fn collect_inherit_lookups<'id, 'ir, Ctx: DowngradeContext<'id, 'ir>>(
             for attr in inherit.attrs() {
                 if let ast::Attr::Ident(ident) = attr {
                     let attr_span = ident.syntax().text_range();
-                    let sym = ctx.new_sym(ident.to_string());
+                    let sym = ctx.intern_string(ident.to_string());
                     let expr = ctx.lookup(sym, attr_span)?;
                     inherit_lookups.insert(sym, (expr, attr_span));
                 }
@@ -1127,7 +1129,7 @@ fn collect_binding_syms<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>, const AL
     for (sym, (_, span)) in &pending.stcs {
         if !binding_syms.insert(*sym) {
             return Err(Error::downgrade_error(
-                format!("attribute '{}' already defined", ctx.get_sym(*sym)),
+                format!("attribute '{}' already defined", ctx.resolve_sym(*sym)),
                 ctx.get_current_source(),
                 *span,
             ));
@@ -1139,15 +1141,15 @@ 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<StringId, (IrRef<'id, 'ir>, TextRange)>,
+    inherit_lookups: &HashMap<StringId, (MaybeThunk, TextRange)>,
     ctx: &mut Ctx,
 ) -> Result<FinalizedAttrSet<'id, 'ir>> {
     let mut stcs = HashMap::new_in(ctx.bump());
     let mut dyns = Vec::new_in(ctx.bump());
 
     for (sym, (value, value_span)) in pending.stcs {
-        let expr_id = finalize_pending_value::<_, ALLOW_DYN>(value, inherit_lookups, ctx)?;
-        stcs.insert(sym, (expr_id, value_span));
+        let expr = finalize_pending_value::<_, ALLOW_DYN>(value, inherit_lookups, ctx)?;
+        stcs.insert(sym, (ctx.maybe_thunk(expr), value_span));
     }
 
     if ALLOW_DYN {
@@ -1155,12 +1157,10 @@ fn finalize_pending_set<'id, 'ir, Ctx: DowngradeContext<'id, 'ir>, const ALLOW_D
             let key_id = downgrade_attr(attr, ctx)?;
             let key_expr = match key_id {
                 Attr::Dynamic(id, _) => id,
-                Attr::Str(sym, _attr_span) => {
-                    ctx.new_expr(Ir::Str(ctx.get_sym(sym).to_string().box_in(ctx.bump())))
-                }
+                Attr::Str(sym, _attr_span) => ctx.new_expr(Ir::Str(sym)),
             };
-            let value_id = finalize_pending_value::<_, ALLOW_DYN>(value, inherit_lookups, ctx)?;
-            dyns.push((key_expr, value_id, value_span));
+            let value = finalize_pending_value::<_, ALLOW_DYN>(value, inherit_lookups, ctx)?;
+            dyns.push((key_expr, ctx.maybe_thunk(value), value_span));
         }
     }
 
@@ -1169,30 +1169,25 @@ 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<StringId, (IrRef<'id, 'ir>, TextRange)>,
+    inherit_lookups: &HashMap<StringId, (MaybeThunk, TextRange)>,
     ctx: &mut Ctx,
 ) -> Result<IrRef<'id, 'ir>> {
     match value {
-        PendingValue::Expr(expr) => {
-            let id = Downgrade::downgrade(expr, ctx)?;
-            Ok(ctx.maybe_thunk(id))
-        }
+        PendingValue::Expr(expr) => expr.downgrade(ctx),
         PendingValue::InheritFrom(from_expr, sym, span) => {
-            let from_id = Downgrade::downgrade(from_expr, ctx)?;
-            let select_id = ctx.new_expr(Ir::Select {
-                expr: from_id,
+            let from = Downgrade::downgrade(from_expr, ctx)?;
+            Ok(ctx.new_expr(Ir::Select {
+                expr: from,
                 attrpath: Vec::from_iter_in([Attr::Str(sym, span)], ctx.bump()),
                 default: None,
                 span,
-            });
-            Ok(ctx.maybe_thunk(select_id))
+            }))
         }
         PendingValue::InheritScope(sym, span) => {
             if let Some(&(expr, _)) = inherit_lookups.get(&sym) {
-                Ok(ctx.maybe_thunk(expr))
+                Ok(expr.to_ir(ctx))
             } else {
-                let lookup_id = ctx.lookup(sym, span)?;
-                Ok(ctx.maybe_thunk(lookup_id))
+                ctx.lookup(sym, span).map(|val| val.to_ir(ctx))
             }
         }
         PendingValue::Set(set) => {
@@ -1221,7 +1216,8 @@ fn downgrade_path<'id, 'ir>(
         .into_iter()
         .map(|part| match part {
             ast::InterpolPart::Literal(lit) => {
-                Ok(ctx.new_expr(Ir::Str(lit.text().to_string().box_in(ctx.bump()))))
+                let id = ctx.intern_string(lit.text());
+                Ok(ctx.new_expr(Ir::Str(id)))
             }
             ast::InterpolPart::Interpolation(interpol) => interpol
                 .expr()
diff --git a/fix-ir/src/lib.rs b/fix-ir/src/lib.rs
index bc3c76a..0336568 100644
--- a/fix-ir/src/lib.rs
+++ b/fix-ir/src/lib.rs
@@ -2,7 +2,6 @@ use std::hash::Hash;
 use std::ops::Deref;
 
 use bumpalo::Bump;
-use bumpalo::boxed::Box;
 use bumpalo::collections::Vec;
 use fix_builtins::{BUILTINS, BuiltinId};
 use fix_common::StringId;
@@ -11,6 +10,8 @@ use num_enum::TryFromPrimitive as _;
 use rnix::{TextRange, ast};
 use string_interner::DefaultStringInterner;
 
+use crate::downgrade::DowngradeContext;
+
 pub mod downgrade;
 
 pub type HashMap<'ir, K, V> = hashbrown::HashMap<K, V, hashbrown::DefaultHashBuilder, &'ir Bump>;
@@ -62,6 +63,46 @@ impl<'ir> Deref for RawIrRef<'ir> {
     }
 }
 
+#[repr(C)]
+#[derive(Debug, Clone, Copy)]
+pub enum MaybeThunk {
+    Int(i64),
+    Float(f64),
+    Bool(bool),
+    Null,
+    Str(StringId),
+    Path(StringId),
+    Thunk(ThunkId),
+    Arg { layer: usize },
+    Builtin(BuiltinId),
+    Builtins,
+    ReplBinding(StringId),
+    ScopedImportBinding(StringId),
+    WithLookup(StringId),
+}
+
+impl MaybeThunk {
+    fn to_ir<'id, 'ir>(self, ctx: &mut impl DowngradeContext<'id, 'ir>) -> IrRef<'id, 'ir> {
+        use MaybeThunk::*;
+        let ir = match self {
+            Int(x) => Ir::Int(x),
+            Float(x) => Ir::Float(x),
+            Bool(x) => Ir::Bool(x),
+            Null => Ir::Null,
+            Str(x) => Ir::Str(x),
+            Path(x) => Ir::Path(ctx.new_expr(Ir::Str(x))),
+            Thunk(x) => Ir::Thunk(x),
+            Arg { layer } => Ir::Arg { layer },
+            Builtin(x) => Ir::Builtin(x),
+            Builtins => Ir::Builtins,
+            ReplBinding(x) => Ir::ReplBinding(x),
+            ScopedImportBinding(x) => Ir::ScopedImportBinding(x),
+            WithLookup(x) => Ir::WithLookup(x),
+        };
+        ctx.new_expr(ir)
+    }
+}
+
 #[repr(C)]
 #[derive(Debug)]
 pub enum Ir<'ir, Ref> {
@@ -69,15 +110,15 @@ pub enum Ir<'ir, Ref> {
     Float(f64),
     Bool(bool),
     Null,
-    Str(Box<'ir, String>),
+    Str(StringId),
+    Path(Ref),
     AttrSet {
-        stcs: HashMap<'ir, StringId, (Ref, TextRange)>,
-        dyns: Vec<'ir, (Ref, Ref, TextRange)>,
+        stcs: HashMap<'ir, StringId, (MaybeThunk, TextRange)>,
+        dyns: Vec<'ir, (Ref, MaybeThunk, TextRange)>,
     },
     List {
-        items: Vec<'ir, Ref>,
+        items: Vec<'ir, MaybeThunk>,
     },
-    Path(Ref),
     ConcatStrings {
         parts: Vec<'ir, Ref>,
         force_string: bool,
@@ -118,7 +159,7 @@ pub enum Ir<'ir, Ref> {
     },
 
     With {
-        namespace: Ref,
+        namespace: MaybeThunk,
         body: Ref,
         thunks: Vec<'ir, (ThunkId, Ref)>,
     },
@@ -135,7 +176,7 @@ pub enum Ir<'ir, Ref> {
     },
     Call {
         func: Ref,
-        arg: Ref,
+        arg: MaybeThunk,
         span: TextRange,
     },
 
diff --git a/fix-vm/src/lib.rs b/fix-vm/src/lib.rs
index f8582e0..061229b 100644
--- a/fix-vm/src/lib.rs
+++ b/fix-vm/src/lib.rs
@@ -413,9 +413,7 @@ impl<'gc> GcRoot<'gc> {
                     let Ok(ty) = AttrKeyType::try_from_primitive(tag)
                         .map_err(|err| panic!("unknown key tag: {:#04x}", err.number));
                     match ty {
-                        AttrKeyType::Static => {
-                            keys.push(SelectKeyData::Static(read!(StringId)))
-                        }
+                        AttrKeyType::Static => keys.push(SelectKeyData::Static(read!(StringId))),
                         AttrKeyType::Dynamic => keys.push(SelectKeyData::Dynamic),
                     };
                 }
@@ -598,14 +596,15 @@ impl<'gc> GcRoot<'gc> {
                 }
 
                 Call => {
-                    // force func
                     try_force!(0, inst_start_pc);
                     if self.call_depth > 10000 {
-                        return Action::Done(Err(Error::eval_error("stack overflow; max-call-depth exceeded")))
+                        return Action::Done(Err(Error::eval_error(
+                            "stack overflow; max-call-depth exceeded",
+                        )));
                     }
                     self.call_depth += 1;
                     let func = self.pop_stack();
-                    let arg = self.pop_stack();
+                    let arg = read!(OperandData).resolve(mc, self);
                     if let Some(closure) = func.as_gc::<Closure>() {
                         let ip = closure.ip;
                         let n_locals = closure.n_locals;
@@ -783,16 +782,17 @@ impl<'gc> GcRoot<'gc> {
                         };
 
                         if let Some(attrset) = current_val.as_gc::<AttrSet>()
-                            && let Some(v) = attrset.lookup(key_sid) {
-                                if i < n - 1 {
-                                    current_val = v.restrict().unwrap_or_else(|_| {
-                                        panic!("intermediate select values must be forced")
-                                    });
-                                } else {
-                                    result_val = Some(v);
-                                }
-                                continue;
+                            && let Some(v) = attrset.lookup(key_sid)
+                        {
+                            if i < n - 1 {
+                                current_val = v.restrict().unwrap_or_else(|_| {
+                                    panic!("intermediate select values must be forced")
+                                });
+                            } else {
+                                result_val = Some(v);
                             }
+                            continue;
+                        }
 
                         use_default = true;
                         break;
@@ -992,7 +992,7 @@ impl<'gc> GcRoot<'gc> {
                 }
 
                 PushWith => {
-                    let env = self.pop_stack();
+                    let env = read!(OperandData).resolve(mc, self);
                     let scope = Gc::new(
                         mc,
                         WithEnv {
diff --git a/fix/src/lib.rs b/fix/src/lib.rs
index fafcc52..ce6bb2e 100644
--- a/fix/src/lib.rs
+++ b/fix/src/lib.rs
@@ -7,7 +7,7 @@ use fix_codegen::{BytecodeContext, InstructionPtr};
 use fix_common::{StringId, Symbol};
 use fix_error::{Error, Result, Source};
 use fix_ir::downgrade::{Downgrade as _, DowngradeContext};
-use fix_ir::{Ir, IrRef, RawIrRef, ThunkId};
+use fix_ir::{Ir, IrRef, MaybeThunk, RawIrRef, ThunkId};
 use fix_vm::{ForceMode, StaticValue, Vm, VmContext};
 use ghost_cell::{GhostCell, GhostToken};
 use hashbrown::{HashMap, HashSet};
@@ -294,56 +294,66 @@ impl<'ctx: 'ir, 'id, 'ir> DowngradeContext<'id, 'ir> for DowngradeCtx<'ctx, 'id,
         IrRef::new(self.bump.alloc(GhostCell::new(expr)))
     }
 
-    fn maybe_thunk(&mut self, ir: IrRef<'id, 'ir>) -> IrRef<'id, 'ir> {
-        if !should_thunk(ir, &self.token) {
-            return ir;
+    fn maybe_thunk(&mut self, ir: IrRef<'id, 'ir>) -> MaybeThunk {
+        use MaybeThunk::*;
+        match *ir.borrow(&self.token) {
+            Ir::Builtin(x) => return Builtin(x),
+            Ir::Int(x) => return Int(x),
+            Ir::Float(x) => return Float(x),
+            Ir::Bool(x) => return Bool(x),
+            Ir::Str(x) => return Str(x),
+            Ir::Thunk(x) => return Thunk(x),
+            Ir::Arg { layer } => return Arg { layer },
+            Ir::Builtins => return Builtins,
+            Ir::Null => return Null,
+            _ => (),
         }
-
         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))
+        Thunk(id)
     }
 
-    fn new_sym(&mut self, sym: String) -> StringId {
+    fn intern_string(&mut self, sym: impl AsRef<str>) -> StringId {
         StringId(self.strings.get_or_intern(sym))
     }
 
-    fn get_sym(&self, id: StringId) -> Symbol<'_> {
+    fn resolve_sym(&self, id: StringId) -> Symbol<'_> {
         self.strings.resolve(id.0).expect("no symbol found").into()
     }
 
-    fn lookup(&self, sym: StringId, span: rnix::TextRange) -> Result<IrRef<'id, 'ir>> {
+    fn lookup(&self, sym: StringId, span: rnix::TextRange) -> Result<MaybeThunk> {
         for scope in self.scopes.iter().rev() {
             match scope {
                 &Scope::Global(global_scope) => {
+                    use MaybeThunk::*;
                     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,
+                        let val = match expr {
+                            Ir::Builtins => Builtins,
+                            Ir::Builtin(s) => Builtin(*s),
+                            Ir::Bool(b) => Bool(*b),
+                            Ir::Null => Null,
                             _ => unreachable!("globals should only contain leaf IR nodes"),
                         };
-                        return Ok(self.new_expr(ir));
+                        return Ok(val);
                     }
                 }
                 &Scope::Repl(repl_bindings) => {
                     if repl_bindings.contains(&sym) {
-                        return Ok(self.new_expr(Ir::ReplBinding(sym)));
+                        return Ok(MaybeThunk::ReplBinding(sym));
                     }
                 }
                 Scope::ScopedImport(scoped_bindings) => {
                     if scoped_bindings.contains(&sym) {
-                        return Ok(self.new_expr(Ir::ScopedImportBinding(sym)));
+                        return Ok(MaybeThunk::ScopedImportBinding(sym));
                     }
                 }
                 Scope::Let(let_scope) => {
                     if let Some(&expr) = let_scope.get(&sym) {
-                        return Ok(self.new_expr(Ir::Thunk(expr)));
+                        return Ok(MaybeThunk::Thunk(expr));
                     }
                 }
                 &Scope::Param {
@@ -351,19 +361,19 @@ impl<'ctx: 'ir, 'id, 'ir> DowngradeContext<'id, 'ir> for DowngradeCtx<'ctx, 'id,
                     abs_layer,
                 } => {
                     if param_sym == sym {
-                        return Ok(self.new_expr(Ir::Arg {
+                        return Ok(MaybeThunk::Arg {
                             layer: self.thunk_scopes.len() - abs_layer,
-                        }));
+                        });
                     }
                 }
             }
         }
 
         if self.with_scope_count > 0 {
-            Ok(self.new_expr(Ir::WithLookup(sym)))
+            Ok(MaybeThunk::WithLookup(sym))
         } else {
             Err(Error::downgrade_error(
-                format!("'{}' not found", self.get_sym(sym)),
+                format!("'{}' not found", self.resolve_sym(sym)),
                 self.get_current_source(),
                 span,
             ))