safe transmute: test when ASSUME params are passed indirectly

ref: https://github.com/rust-lang/rust/pull/92268/files#r925258420

Author: jswrenn

src/test/ui/transmutability/abstraction/abstracted_assume.rs

@@ -0,0 +1,73 @@
+// check-pass
+//! The implementation should behave correctly when the `ASSUME` parameters are
+//! provided indirectly through an abstraction.
+
+#![crate_type = "lib"]
+#![feature(transmutability)]
+#![allow(dead_code, incomplete_features, non_camel_case_types)]
+
+mod assert {
+    use std::mem::BikeshedIntrinsicFrom;
+
+    pub fn is_transmutable<
+        Src,
+        Dst,
+        Context,
+        const ASSUME_ALIGNMENT: bool,
+        const ASSUME_LIFETIMES: bool,
+        const ASSUME_VALIDITY: bool,
+        const ASSUME_VISIBILITY: bool,
+    >()
+    where
+        Dst: BikeshedIntrinsicFrom<
+            Src,
+            Context,
+            ASSUME_ALIGNMENT,
+            ASSUME_LIFETIMES,
+            ASSUME_VALIDITY,
+            ASSUME_VISIBILITY,
+        >,
+    {}
+}
+
+fn direct() {
+    struct Context;
+    #[repr(C)] struct Src;
+    #[repr(C)] struct Dst;
+
+    assert::is_transmutable::<Src, Dst, Context, false, false, false, false>();
+}
+
+fn via_const() {
+    struct Context;
+    #[repr(C)] struct Src;
+    #[repr(C)] struct Dst;
+
+    const FALSE: bool = false;
+
+    assert::is_transmutable::<Src, Dst, Context, FALSE, FALSE, FALSE, FALSE>();
+}
+
+fn via_associated_const() {
+    struct Context;
+    #[repr(C)] struct Src;
+    #[repr(C)] struct Dst;
+
+    trait Trait {
+        const FALSE: bool = true;
+    }
+
+    struct Ty;
+
+    impl Trait for Ty {}
+
+    assert::is_transmutable::<
+        Src,
+        Dst,
+        Context,
+        {Ty::FALSE},
+        {Ty::FALSE},
+        {Ty::FALSE},
+        {Ty::FALSE}
+    >();
+}