refactor(downgrade): MaybeThunk

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,
             ))