Rollup merge of #137728 - Darksonn:no-tuple-unsize, r=oli-obk

Remove unsizing coercions for tuples

See https://github.com/rust-lang/rust/issues/42877#issuecomment-2686010847 and below comments for justification.

Tracking issue: #42877
Fixes: #135217

2 files changed, 1 insertions, 17 deletions

diff --git a/tests/ui/cast/cast-rfc0401-vtable-kinds.rs b/tests/ui/cast/cast-rfc0401-vtable-kinds.rs
index 5704a33cc87..78f6dca1818 100644
--- a/tests/ui/cast/cast-rfc0401-vtable-kinds.rs
+++ b/tests/ui/cast/cast-rfc0401-vtable-kinds.rs
@@ -2,8 +2,6 @@
 // Check that you can cast between different pointers to trait objects
 // whose vtable have the same kind (both lengths, or both trait pointers).
 
-#![feature(unsized_tuple_coercion)]
-
 trait Bar { //~ WARN trait `Bar` is never used
     fn bar(&self) { println!("Bar!"); }
 }
@@ -19,10 +17,6 @@ fn foo_to_bar<T:?Sized>(u: *const FooS<T>) -> *const BarS<T> {
     u as *const BarS<T>
 }
 
-fn tuple_i32_to_u32<T:?Sized>(u: *const (i32, T)) -> *const (u32, T) {
-    u as *const (u32, T)
-}
-
 
 fn main() {
     let s = FooS([0,1,2]);
@@ -31,14 +25,4 @@ fn main() {
     let bar_ref : *const BarS<[u32]> = foo_to_bar(u);
     let z : &BarS<[u32]> = unsafe{&*bar_ref};
     assert_eq!(&z.0, &[0,1,2]);
-
-    // this assumes that tuple reprs for (i32, _) and (u32, _) are
-    // the same.
-    let s = (0i32, [0, 1, 2]);
-    let u: &(i32, [u8]) = &s;
-    let u: *const (i32, [u8]) = u;
-    let u_u32 : *const (u32, [u8]) = tuple_i32_to_u32(u);
-    unsafe {
-        assert_eq!(&(*u_u32).1, &[0, 1, 2]);
-    }
 }
diff --git a/tests/ui/cast/cast-rfc0401-vtable-kinds.stderr b/tests/ui/cast/cast-rfc0401-vtable-kinds.stderr
index 4f57e2e7df7..01277fd632e 100644
--- a/tests/ui/cast/cast-rfc0401-vtable-kinds.stderr
+++ b/tests/ui/cast/cast-rfc0401-vtable-kinds.stderr
@@ -1,5 +1,5 @@
 warning: trait `Bar` is never used
-  --> $DIR/cast-rfc0401-vtable-kinds.rs:7:7
+  --> $DIR/cast-rfc0401-vtable-kinds.rs:5:7
    |
 LL | trait Bar {
    |       ^^^