add test for Inconsistent rustc_transmute::is_transmutable(...) result, got Yes

Fixes #110969

Author: matthiaskrgr

tests/ui/const-generics/adt_const_params/transmutable-ice-110969.rs

@@ -0,0 +1,32 @@
+// ICE Inconsistent rustc_transmute::is_transmutable(...) result, got Yes
+// issue: rust-lang/rust#110969
+#![feature(adt_const_params, generic_const_exprs, transmutability)]
+#![allow(incomplete_features, unstable_features)]
+
+mod assert {
+    use std::mem::BikeshedIntrinsicFrom;
+
+    pub fn is_transmutable<Src, Dst, Context, const ASSUME: std::mem::Assume>()
+    where
+        Dst: BikeshedIntrinsicFrom<Src, Context, ASSUME>,
+        //~^ ERROR trait takes at most 2 generic arguments but 3 generic arguments were supplied
+    {
+    }
+}
+
+fn via_associated_const() {
+    struct Context;
+    #[repr(C)]
+    struct Src;
+    #[repr(C)]
+    struct Dst;
+
+    trait Trait {
+        const FALSE: bool = assert::is_transmutable::<Src, Dst, Context, {}>();
+        //~^ ERROR mismatched types
+        //~| ERROR `Src` cannot be safely transmuted into `Dst`
+        //~| ERROR mismatched types
+    }
+}
+
+pub fn main() {}

tests/ui/const-generics/adt_const_params/transmutable-ice-110969.stderr

@@ -0,0 +1,39 @@
+error[E0107]: trait takes at most 2 generic arguments but 3 generic arguments were supplied
+  --> $DIR/transmutable-ice-110969.rs:11:14
+   |
+LL |         Dst: BikeshedIntrinsicFrom<Src, Context, ASSUME>,
+   |              ^^^^^^^^^^^^^^^^^^^^^               ------ help: remove this generic argument
+   |              |
+   |              expected at most 2 generic arguments
+
+error[E0308]: mismatched types
+  --> $DIR/transmutable-ice-110969.rs:25:74
+   |
+LL |         const FALSE: bool = assert::is_transmutable::<Src, Dst, Context, {}>();
+   |                                                                          ^^ expected `Assume`, found `()`
+
+error[E0277]: `Src` cannot be safely transmuted into `Dst`
+  --> $DIR/transmutable-ice-110969.rs:25:60
+   |
+LL |         const FALSE: bool = assert::is_transmutable::<Src, Dst, Context, {}>();
+   |                                                            ^^^ `Dst` may carry safety invariants
+   |
+note: required by a bound in `is_transmutable`
+  --> $DIR/transmutable-ice-110969.rs:11:14
+   |
+LL |     pub fn is_transmutable<Src, Dst, Context, const ASSUME: std::mem::Assume>()
+   |            --------------- required by a bound in this function
+LL |     where
+LL |         Dst: BikeshedIntrinsicFrom<Src, Context, ASSUME>,
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_transmutable`
+
+error[E0308]: mismatched types
+  --> $DIR/transmutable-ice-110969.rs:25:29
+   |
+LL |         const FALSE: bool = assert::is_transmutable::<Src, Dst, Context, {}>();
+   |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `bool`, found `()`
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0107, E0277, E0308.
+For more information about an error, try `rustc --explain E0107`.