Auto merge of #109740 - compiler-errors:new-solver-deep-reject-placeholder-consts, r=lcnr

Don't ICE on placeholder consts in deep reject

Since we canonicalize const params into placeholder consts, we need to be able to handle them during deep reject.

r? `@lcnr` (though maybe `@oli-obk` can look at this one too, if he wants 😸)

Fixes compiler-errors/next-solver-hir-issues#10

1 files changed, 5 insertions, 1 deletions

diff --git a/compiler/rustc_middle/src/ty/fast_reject.rs b/compiler/rustc_middle/src/ty/fast_reject.rs
index 0a6e94248e6..61cde923e9a 100644
--- a/compiler/rustc_middle/src/ty/fast_reject.rs
+++ b/compiler/rustc_middle/src/ty/fast_reject.rs
@@ -312,6 +312,7 @@ impl DeepRejectCtxt {
             // Impls cannot contain these types as these cannot be named directly.
             ty::FnDef(..) | ty::Closure(..) | ty::Generator(..) => false,
 
+            // Placeholder types don't unify with anything on their own
             ty::Placeholder(..) | ty::Bound(..) => false,
 
             // Depending on the value of `treat_obligation_params`, we either
@@ -359,6 +360,9 @@ impl DeepRejectCtxt {
                 TreatParams::AsCandidateKey => true,
             },
 
+            // Placeholder consts don't unify with anything on their own
+            ty::ConstKind::Placeholder(_) => false,
+
             // As we don't necessarily eagerly evaluate constants,
             // they might unify with any value.
             ty::ConstKind::Expr(_) | ty::ConstKind::Unevaluated(_) | ty::ConstKind::Error(_) => {
@@ -371,7 +375,7 @@ impl DeepRejectCtxt {
 
             ty::ConstKind::Infer(_) => true,
 
-            ty::ConstKind::Bound(..) | ty::ConstKind::Placeholder(_) => {
+            ty::ConstKind::Bound(..) => {
                 bug!("unexpected obl const: {:?}", obligation_ct)
             }
         }