try enabling typeof for fun error messages

Author: yaahc

compiler/rustc_typeck/src/astconv/mod.rs

@@ -2277,9 +2277,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(&ty), length));
                 self.normalize_ty(ast_ty.span, array_ty)
             }
-            hir::TyKind::Typeof(ref _e) => {
+            hir::TyKind::Typeof(ref e) => {
                 tcx.sess.emit_err(TypeofReservedKeywordUsed { span: ast_ty.span });
-                tcx.ty_error()
+                tcx.type_of(e.hir_id.owner)
             }
             hir::TyKind::Infer => {
                 // Infer also appears as the type of arguments or return

compiler/rustc_typeck/src/collect/type_of.rs

@@ -417,12 +417,16 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
             let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id));
             match parent_node {
                 Node::Ty(&Ty { kind: TyKind::Array(_, ref constant), .. })
-                | Node::Ty(&Ty { kind: TyKind::Typeof(ref constant), .. })
                 | Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
                     if constant.hir_id == hir_id =>
                 {
                     tcx.types.usize
                 }
+                Node::Ty(&Ty { kind: TyKind::Typeof(ref constant), .. })
+                    if constant.hir_id == hir_id =>
+                {
+                    tcx.typeck(def_id).node_type(constant.hir_id)
+                }
 
                 Node::Expr(&Expr { kind: ExprKind::ConstBlock(ref anon_const), .. })
                     if anon_const.hir_id == hir_id =>