Rollup merge of #125807 - oli-obk:resolve_const_types, r=compiler-errors

Also resolve the type of constants, even if we already turned it into an error constant

error constants can still have arbitrary types, and in this case it was turned into an error constant because there was an infer var in the *type* not the *const*.

fixes #125760

4 files changed, 44 insertions, 0 deletions

diff --git a/compiler/rustc_hir_typeck/src/writeback.rs b/compiler/rustc_hir_typeck/src/writeback.rs
index 31caa52d267..e337105f011 100644
--- a/compiler/rustc_hir_typeck/src/writeback.rs
+++ b/compiler/rustc_hir_typeck/src/writeback.rs
@@ -865,6 +865,7 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Resolver<'cx, 'tcx> {
         self.handle_term(ct, ty::Const::outer_exclusive_binder, |tcx, guar| {
             ty::Const::new_error(tcx, guar, ct.ty())
         })
+        .super_fold_with(self)
     }
 
     fn fold_predicate(&mut self, predicate: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
diff --git a/tests/ui/type-alias-impl-trait/const_generic_type.infer.stderr b/tests/ui/type-alias-impl-trait/const_generic_type.infer.stderr
new file mode 100644
index 00000000000..6a1a770228d
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/const_generic_type.infer.stderr
@@ -0,0 +1,10 @@
+error: `Bar` is forbidden as the type of a const generic parameter
+  --> $DIR/const_generic_type.rs:7:24
+   |
+LL | async fn test<const N: crate::Bar>() {
+   |                        ^^^^^^^^^^
+   |
+   = note: the only supported types are integers, `bool` and `char`
+
+error: aborting due to 1 previous error
+
diff --git a/tests/ui/type-alias-impl-trait/const_generic_type.no_infer.stderr b/tests/ui/type-alias-impl-trait/const_generic_type.no_infer.stderr
new file mode 100644
index 00000000000..a1a69bfaca3
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/const_generic_type.no_infer.stderr
@@ -0,0 +1,19 @@
+error[E0283]: type annotations needed
+  --> $DIR/const_generic_type.rs:7:1
+   |
+LL | async fn test<const N: crate::Bar>() {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot infer type
+   |
+   = note: cannot satisfy `_: std::fmt::Display`
+
+error: `Bar` is forbidden as the type of a const generic parameter
+  --> $DIR/const_generic_type.rs:7:24
+   |
+LL | async fn test<const N: crate::Bar>() {
+   |                        ^^^^^^^^^^
+   |
+   = note: the only supported types are integers, `bool` and `char`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0283`.
diff --git a/tests/ui/type-alias-impl-trait/const_generic_type.rs b/tests/ui/type-alias-impl-trait/const_generic_type.rs
new file mode 100644
index 00000000000..95a5e1c6286
--- /dev/null
+++ b/tests/ui/type-alias-impl-trait/const_generic_type.rs
@@ -0,0 +1,14 @@
+//@edition: 2021
+//@revisions: infer no_infer
+
+#![feature(type_alias_impl_trait)]
+type Bar = impl std::fmt::Display;
+
+async fn test<const N: crate::Bar>() {
+    //[no_infer]~^ ERROR: type annotations needed
+    //~^^ ERROR: `Bar` is forbidden as the type of a const generic parameter
+    #[cfg(infer)]
+    let x: u32 = N;
+}
+
+fn main() {}