add a ui test for #101739

Author: TaKO8Ki

src/test/ui/transmutability/issues-101739.rs

@@ -0,0 +1,21 @@
+#![feature(transmutability)]
+
+mod assert {
+    use std::mem::BikeshedIntrinsicFrom;
+
+    pub fn is_transmutable<Src, Context, const ASSUME_ALIGNMENT: bool>()
+    where
+        Dst: BikeshedIntrinsicFrom<Src, Context, ASSUME_ALIGNMENT>, //~ ERROR cannot find type `Dst` in this scope
+        //~^ ERROR mismatched types
+    {
+    }
+}
+
+fn via_const() {
+    struct Context;
+    struct Src;
+
+    assert::is_transmutable::<Src, Context, false>();
+}
+
+fn main() {}

src/test/ui/transmutability/issues-101739.stderr

@@ -0,0 +1,16 @@
+error[E0412]: cannot find type `Dst` in this scope
+  --> $DIR/issues-101739.rs:8:9
+   |
+LL |         Dst: BikeshedIntrinsicFrom<Src, Context, ASSUME_ALIGNMENT>,
+   |         ^^^ not found in this scope
+
+error[E0308]: mismatched types
+  --> $DIR/issues-101739.rs:8:50
+   |
+LL |         Dst: BikeshedIntrinsicFrom<Src, Context, ASSUME_ALIGNMENT>,
+   |                                                  ^^^^^^^^^^^^^^^^ expected struct `Assume`, found `bool`
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0308, E0412.
+For more information about an error, try `rustc --explain E0308`.