Add some type-alias-impl-trait regression tests

[rust.git] / src / librustc_ast_lowering / lib.rs

diff --git a/src/librustc_ast_lowering/lib.rs b/src/librustc_ast_lowering/lib.rs
index 90560c371e29221569f789f3f98feedc8e543ba3..284ede3b4fa1a119d92a81f3794da7c370aa7f2a 100644 (file)
--- a/src/librustc_ast_lowering/lib.rs
+++ b/src/librustc_ast_lowering/lib.rs
@@ -41,7 +41,6 @@
 use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sync::Lrc;
-use rustc_error_codes::*;
 use rustc_errors::struct_span_err;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Namespace, PartialRes, PerNS, Res};
@@ -1254,7 +1253,12 @@ fn lower_ty_direct(&mut self, t: &Ty, mut itctx: ImplTraitContext<'_, 'hir>) ->
                                 | GenericBound::Trait(ref ty, TraitBoundModifier::MaybeConst) => {
                                     Some(this.lower_poly_trait_ref(ty, itctx.reborrow()))
                                 }
-                                GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
+                                // `?const ?Bound` will cause an error during AST validation
+                                // anyways, so treat it like `?Bound` as compilation proceeds.
+                                GenericBound::Trait(_, TraitBoundModifier::Maybe)
+                                | GenericBound::Trait(_, TraitBoundModifier::MaybeConstMaybe) => {
+                                    None
+                                }
                                 GenericBound::Outlives(ref lifetime) => {
                                     if lifetime_bound.is_none() {
                                         lifetime_bound = Some(this.lower_lifetime(lifetime));
@@ -2297,8 +2301,13 @@ fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource {
     fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier {
         match f {
             TraitBoundModifier::None => hir::TraitBoundModifier::None,
-            TraitBoundModifier::Maybe => hir::TraitBoundModifier::Maybe,
             TraitBoundModifier::MaybeConst => hir::TraitBoundModifier::MaybeConst,
+
+            // `MaybeConstMaybe` will cause an error during AST validation, but we need to pick a
+            // placeholder for compilation to proceed.
+            TraitBoundModifier::MaybeConstMaybe | TraitBoundModifier::Maybe => {
+                hir::TraitBoundModifier::Maybe
+            }
         }
     }