refactor with

fix-ir/src/downgrade.rs

@@ -44,7 +44,7 @@ pub trait DowngradeContext<'id: 'ir, '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<GhostRoMaybeThunkRef<'id, 'ir>>;
+    fn lookup(&mut self, sym: StringId, span: TextRange) -> Result<GhostRoMaybeThunkRef<'id, 'ir>>;
 
     fn get_current_source(&self) -> Source;
 
@@ -54,7 +54,7 @@ pub trait DowngradeContext<'id: 'ir, 'ir> {
     fn with_let_scope<F, R>(&mut self, bindings: &[StringId], f: F) -> Result<R>
     where
         F: FnOnce(&mut Self) -> Result<(Vec<'ir, GhostRoMaybeThunkRef<'id, 'ir>>, R)>;
-    fn with_with_scope<F, R>(&mut self, f: F) -> R
+    fn with_with_scope<F, R>(&mut self, namespace: GhostRoMaybeThunkRef<'id, 'ir>, f: F) -> R
     where
         F: FnOnce(&mut Self) -> R;
     fn with_thunk_scope<F, R>(&mut self, f: F) -> (R, Vec<'ir, (ThunkId, GhostRoIrRef<'id, 'ir>)>)
@@ -448,15 +448,7 @@ impl<'id: 'ir, 'ir, Ctx: DowngradeContext<'id, 'ir>> Downgrade<'id, 'ir, Ctx> fo
         let namespace = ctx.maybe_thunk(namespace);
 
         let body_expr = self.body().require(ctx, span)?;
-        let (body, thunks) =
-            ctx.with_thunk_scope(|ctx| ctx.with_with_scope(|ctx| body_expr.downgrade(ctx)));
-        let body = body?;
-
-        Ok(ctx.new_expr(Ir::With {
-            namespace,
-            body,
-            thunks,
-        }))
+        ctx.with_with_scope(namespace, |ctx| body_expr.downgrade(ctx))
     }
 }