trait_selection: fix type-const eval ICE

Author: JohnTitor

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -720,6 +720,25 @@ pub fn try_evaluate_const<'tcx>(
                 }
             };
 
+            if tcx.is_type_const(uv.def) {
+                match ty::Instance::try_resolve(tcx, typing_env, uv.def, args) {
+                    Ok(Some(instance)) => {
+                        let ct =
+                            tcx.const_of_item(instance.def_id()).instantiate(tcx, instance.args);
+                        return try_evaluate_const(infcx, ct, param_env);
+                    }
+                    Ok(None) => return Err(EvaluateConstErr::HasGenericsOrInfers),
+                    Err(err) => {
+                        return Err(EvaluateConstErr::EvaluationFailure(
+                            rustc_middle::mir::interpret::ReportedErrorInfo::non_const_eval_error(
+                                err,
+                            )
+                            .into(),
+                        ));
+                    }
+                }
+            }
+
             let uv = ty::UnevaluatedConst::new(uv.def, args);
             let erased_uv = tcx.erase_and_anonymize_regions(uv);
 

tests/ui/const-generics/type-const-ice-issue-151631.rs

@@ -0,0 +1,38 @@
+//@ compile-flags: -Znext-solver=globally
+#![feature(generic_const_items, min_generic_const_args)]
+#![feature(adt_const_params)]
+#![allow(incomplete_features)]
+#![allow(dead_code)]
+
+trait Owner: NewTrait {
+    #[type_const]
+    const C<const N: u32>: u32;
+    #[type_const]
+    const K<const N: u32>: u32;
+}
+
+trait NewTrait {}
+
+impl NewTrait for () {}
+
+impl Owner for () {
+    #[type_const]
+    const C<const N: u32>: u32 = N;
+    #[type_const]
+    const K<const N: u32>: u32 = const { 99 + 1 };
+}
+
+fn take0<const N: u32>(_: impl Owner<C<N> = { N }>) {}
+fn take1(_: impl Owner<K<99> = 100>) {}
+
+#[derive(PartialEq, Eq, std::marker::ConstParamTy)]
+enum Maybe<T> {
+    Nothing,
+    Just(T),
+}
+
+fn main() {
+    take0::<128>(());
+    take1(());
+    //~^ ERROR type mismatch resolving `const { 99 + 1 } == 100`
+}

tests/ui/const-generics/type-const-ice-issue-151631.stderr

@@ -0,0 +1,17 @@
+error[E0271]: type mismatch resolving `const { 99 + 1 } == 100`
+  --> $DIR/type-const-ice-issue-151631.rs:36:11
+   |
+LL |     take1(());
+   |     ----- ^^ types differ
+   |     |
+   |     required by a bound introduced by this call
+   |
+note: required by a bound in `take1`
+  --> $DIR/type-const-ice-issue-151631.rs:26:24
+   |
+LL | fn take1(_: impl Owner<K<99> = 100>) {}
+   |                        ^^^^^^^^^^^ required by this bound in `take1`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0271`.