Don't ICE for kind mismatches during error rendering

Author: oli-obk

compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs

@@ -1974,6 +1974,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     for (obligation_arg, impl_arg) in
                         std::iter::zip(obligation_trait_ref.args, impl_trait_ref.args)
                     {
+                        if (obligation_arg, impl_arg).references_error() {
+                            return false;
+                        }
                         if let Err(terr) =
                             ocx.eq(&ObligationCause::dummy(), param_env, impl_arg, obligation_arg)
                         {

tests/ui/const-generics/kind_mismatch.rs

@@ -0,0 +1,23 @@
+//! THis test used to ICE in typeck because of the type/const mismatch,
+//! even though wfcheck already errored.
+
+pub struct KeyHolder<const K: u8> {}
+
+pub trait ContainsKey<const K: u8> {}
+
+pub trait SubsetExcept<P> {}
+
+impl<K> ContainsKey<K> for KeyHolder<K> {}
+//~^ ERROR: type provided when a constant was expected
+//~| ERROR: type provided when a constant was expected
+
+impl<P, T: ContainsKey<0>> SubsetExcept<P> for T {}
+
+pub fn remove_key<K, S: SubsetExcept<K>>() -> S {
+    loop {}
+}
+
+fn main() {
+    let map: KeyHolder<0> = remove_key::<_, _>();
+    //~^ ERROR: the trait bound `KeyHolder<0>: SubsetExcept<_>` is not satisfied
+}

tests/ui/const-generics/kind_mismatch.stderr

@@ -0,0 +1,39 @@
+error[E0747]: type provided when a constant was expected
+  --> $DIR/kind_mismatch.rs:10:38
+   |
+LL | impl<K> ContainsKey<K> for KeyHolder<K> {}
+   |      -                               ^
+   |      |
+   |      help: consider changing this type parameter to a const parameter: `const K: u8`
+
+error[E0747]: type provided when a constant was expected
+  --> $DIR/kind_mismatch.rs:10:21
+   |
+LL | impl<K> ContainsKey<K> for KeyHolder<K> {}
+   |      -              ^
+   |      |
+   |      help: consider changing this type parameter to a const parameter: `const K: u8`
+
+error[E0277]: the trait bound `KeyHolder<0>: SubsetExcept<_>` is not satisfied
+  --> $DIR/kind_mismatch.rs:21:45
+   |
+LL |     let map: KeyHolder<0> = remove_key::<_, _>();
+   |                                             ^ the trait `ContainsKey<0>` is not implemented for `KeyHolder<0>`, which is required by `KeyHolder<0>: SubsetExcept<_>`
+   |
+note: required for `KeyHolder<0>` to implement `SubsetExcept<_>`
+  --> $DIR/kind_mismatch.rs:14:28
+   |
+LL | impl<P, T: ContainsKey<0>> SubsetExcept<P> for T {}
+   |            --------------  ^^^^^^^^^^^^^^^     ^
+   |            |
+   |            unsatisfied trait bound introduced here
+note: required by a bound in `remove_key`
+  --> $DIR/kind_mismatch.rs:16:25
+   |
+LL | pub fn remove_key<K, S: SubsetExcept<K>>() -> S {
+   |                         ^^^^^^^^^^^^^^^ required by this bound in `remove_key`
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0277, E0747.
+For more information about an error, try `rustc --explain E0277`.