Rollup merge of #150554 - Dushyanthyadav:ice-issue-150409-regression-test, r=davidtwco

test: add regression cases for valtree hashing ICE

This PR extends the existing regression test `printing_valtrees_supports_non_values.rs` to cover cases that previously caused an ICE in `const_kind.rs` due to hashing inference variables.

It specifically adds:

A case where an associated constant is used without the required trait bound.

The `0: _` case as suggested in [Here](#150409 (comment))

Fixes #150409

Author: matthiaskrgr

tests/ui/const-generics/mgca/printing_valtrees_supports_non_values.rs

@@ -25,3 +25,14 @@ fn baz<T: Trait>() {
 }
 
 fn main() {}
+
+fn test_ice_missing_bound<T>() {
+    foo::<{Option::Some::<u32>{0: <T as Trait>::ASSOC}}>();
+    //~^ ERROR the trait bound `T: Trait` is not satisfied
+    //~| ERROR the constant `Option::<u32>::Some(_)` is not of type `Foo`
+}
+
+fn test_underscore_inference() {
+    foo::<{ Option::Some::<u32> { 0: _ } }>();
+    //~^ ERROR the constant `Option::<u32>::Some(_)` is not of type `Foo`
+}

tests/ui/const-generics/mgca/printing_valtrees_supports_non_values.stderr

@@ -22,5 +22,41 @@ note: required by a const generic parameter in `foo`
 LL | fn foo<const N: Foo>() {}
    |        ^^^^^^^^^^^^ required by this const generic parameter in `foo`
 
-error: aborting due to 2 previous errors
+error[E0277]: the trait bound `T: Trait` is not satisfied
+  --> $DIR/printing_valtrees_supports_non_values.rs:30:5
+   |
+LL |     foo::<{Option::Some::<u32>{0: <T as Trait>::ASSOC}}>();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for `T`
+   |
+help: consider restricting type parameter `T` with trait `Trait`
+   |
+LL | fn test_ice_missing_bound<T: Trait>() {
+   |                            +++++++
+
+error: the constant `Option::<u32>::Some(_)` is not of type `Foo`
+  --> $DIR/printing_valtrees_supports_non_values.rs:30:12
+   |
+LL |     foo::<{Option::Some::<u32>{0: <T as Trait>::ASSOC}}>();
+   |            ^^^^^^^^^^^^^^^^^^^ expected `Foo`, found `Option<u32>`
+   |
+note: required by a const generic parameter in `foo`
+  --> $DIR/printing_valtrees_supports_non_values.rs:15:8
+   |
+LL | fn foo<const N: Foo>() {}
+   |        ^^^^^^^^^^^^ required by this const generic parameter in `foo`
+
+error: the constant `Option::<u32>::Some(_)` is not of type `Foo`
+  --> $DIR/printing_valtrees_supports_non_values.rs:36:13
+   |
+LL |     foo::<{ Option::Some::<u32> { 0: _ } }>();
+   |             ^^^^^^^^^^^^^^^^^^^ expected `Foo`, found `Option<u32>`
+   |
+note: required by a const generic parameter in `foo`
+  --> $DIR/printing_valtrees_supports_non_values.rs:15:8
+   |
+LL | fn foo<const N: Foo>() {}
+   |        ^^^^^^^^^^^^ required by this const generic parameter in `foo`
+
+error: aborting due to 5 previous errors
 
+For more information about this error, try `rustc --explain E0277`.