refactor: use GAT in enum Ir

fix-ir/src/downgrade.rs

@@ -39,12 +39,12 @@ impl<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>, T, E: std::fmt::Display>
 }
 
 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>) -> MaybeThunk;
+    fn new_expr(&self, expr: Ir<'ir, GhostRef<'id, 'ir>>) -> IrRef<'id, 'ir>;
+    fn maybe_thunk(&mut self, ir: IrRef<'id, 'ir>) -> GhostMaybeThunkRef<'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 lookup(&self, sym: StringId, span: TextRange) -> Result<GhostMaybeThunkRef<'id, 'ir>>;
 
     fn get_current_source(&self) -> Source;
 
@@ -229,7 +229,8 @@ impl<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>> Downgrade<'id, 'ir, Ctx> fo
         let span = self.syntax().text_range();
         let text = self.ident_token().require(ctx, span)?.to_string();
         let sym = ctx.intern_string(text);
-        ctx.lookup(sym, span).map(|thunk| thunk.to_ir(ctx))
+        ctx.lookup(sym, span)
+            .map(|thunk| ctx.new_expr(Ir::MaybeThunk(thunk)))
     }
 }
 
@@ -835,8 +836,8 @@ fn make_attrpath_value_entry<'ir>(path: Vec<'ir, ast::Attr>, value: ast::Expr) -
 }
 
 struct FinalizedAttrSet<'id, 'ir> {
-    stcs: HashMap<'ir, StringId, (MaybeThunk, TextRange)>,
-    dyns: Vec<'ir, (IrRef<'id, 'ir>, MaybeThunk, TextRange)>,
+    stcs: HashMap<'ir, StringId, (GhostMaybeThunkRef<'id, 'ir>, TextRange)>,
+    dyns: Vec<'ir, (IrRef<'id, 'ir>, GhostMaybeThunkRef<'id, 'ir>, TextRange)>,
 }
 
 fn downgrade_attrs<'id, 'ir>(
@@ -1074,7 +1075,7 @@ where
     F: FnOnce(
         &mut Ctx,
         &[StringId],
-        &[(IrRef<'id, 'ir>, MaybeThunk, TextRange)],
+        &[(IrRef<'id, 'ir>, GhostMaybeThunkRef<'id, 'ir>, TextRange)],
     ) -> Result<IrRef<'id, 'ir>>,
 {
     let mut pending = PendingAttrSet::new_in(ctx.bump());
@@ -1090,7 +1091,7 @@ where
         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.push(ctx.new_expr(Ir::MaybeThunk(finalized.stcs.get(sym).expect("WTF").0)));
             }
             temp
         };
@@ -1101,7 +1102,7 @@ where
 fn collect_inherit_lookups<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>>(
     entries: &[ast::Entry],
     ctx: &mut Ctx,
-) -> Result<HashMap<'ir, StringId, (MaybeThunk, TextRange)>> {
+) -> Result<HashMap<'ir, StringId, (GhostMaybeThunkRef<'id, 'ir>, TextRange)>> {
     let mut inherit_lookups = HashMap::new_in(ctx.bump());
     for entry in entries {
         if let ast::Entry::Inherit(inherit) = entry
@@ -1141,7 +1142,7 @@ 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, (MaybeThunk, TextRange)>,
+    inherit_lookups: &HashMap<StringId, (GhostMaybeThunkRef<'id, 'ir>, TextRange)>,
     ctx: &mut Ctx,
 ) -> Result<FinalizedAttrSet<'id, 'ir>> {
     let mut stcs = HashMap::new_in(ctx.bump());
@@ -1169,7 +1170,7 @@ 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, (MaybeThunk, TextRange)>,
+    inherit_lookups: &HashMap<StringId, (GhostMaybeThunkRef<'id, 'ir>, TextRange)>,
     ctx: &mut Ctx,
 ) -> Result<IrRef<'id, 'ir>> {
     match value {
@@ -1185,9 +1186,10 @@ fn finalize_pending_value<'id, 'ir, Ctx: DowngradeContext<'id, 'ir>, const ALLOW
         }
         PendingValue::InheritScope(sym, span) => {
             if let Some(&(expr, _)) = inherit_lookups.get(&sym) {
-                Ok(expr.to_ir(ctx))
+                Ok(ctx.new_expr(Ir::MaybeThunk(expr)))
             } else {
-                ctx.lookup(sym, span).map(|val| val.to_ir(ctx))
+                ctx.lookup(sym, span)
+                    .map(|val| ctx.new_expr(Ir::MaybeThunk(val)))
             }
         }
         PendingValue::Set(set) => {