Add tests for *const Trait<'a> -> *const Trait<'b> and similar casts

tests/ui/cast/ptr-to-trait-obj-add-auto.rs

@@ -0,0 +1,9 @@
+// check-pass
+
+trait Trait<'a> {}
+
+fn add_auto<'a>(x: *mut dyn Trait<'a>) -> *mut (dyn Trait<'a> + Send) {
+    x as _
+}
+
+fn main() {}

tests/ui/cast/ptr-to-trait-obj-different-args.rs

@@ -28,3 +28,11 @@ fn generic<T>(x: *const dyn Trait<X>, t: *const dyn Trait<T>) {
     let _: *const dyn Trait<T> = x as _; //~ error: casting `*const (dyn Trait<X> + 'static)` as `*const dyn Trait<T>` is invalid
     let _: *const dyn Trait<X> = t as _; //~ error: casting `*const (dyn Trait<T> + 'static)` as `*const dyn Trait<X>` is invalid
 }
+
+trait Assocked {
+    type Assoc: ?Sized;
+}
+
+fn change_assoc(x: *mut dyn Assocked<Assoc = u8>) -> *mut dyn Assocked<Assoc = u32> {
+    x as _
+}

tests/ui/cast/ptr-to-trait-obj-different-regions-lt-ext.rs

@@ -0,0 +1,31 @@
+// check-pass
+//
+// issue: <https://github.com/rust-lang/rust/issues/120217>
+
+#![feature(arbitrary_self_types)]
+
+trait Static<'a> {
+    fn proof(self: *const Self, s: &'a str) -> &'static str;
+}
+
+fn bad_cast<'a>(x: *const dyn Static<'static>) -> *const dyn Static<'a> {
+    x as _
+}
+
+impl Static<'static> for () {
+    fn proof(self: *const Self, s: &'static str) -> &'static str {
+        s
+    }
+}
+
+fn extend_lifetime(s: &str) -> &'static str {
+    bad_cast(&()).proof(s)
+}
+
+fn main() {
+    let s = String::from("Hello World");
+    let slice = extend_lifetime(&s);
+    println!("Now it exists: {slice}");
+    drop(s);
+    println!("Now it’s gone: {slice}");
+}

tests/ui/cast/ptr-to-trait-obj-different-regions-misc.rs

@@ -0,0 +1,34 @@
+// check-pass
+
+trait Trait<'a> {}
+
+fn change_lt<'a, 'b>(x: *mut dyn Trait<'a>) -> *mut dyn Trait<'b> {
+    x as _
+}
+
+fn change_lt_ab<'a: 'b, 'b>(x: *mut dyn Trait<'a>) -> *mut dyn Trait<'b> {
+    x as _
+}
+
+fn change_lt_ba<'a, 'b: 'a>(x: *mut dyn Trait<'a>) -> *mut dyn Trait<'b> {
+    x as _
+}
+
+trait Assocked {
+    type Assoc: ?Sized;
+}
+
+fn change_assoc_0<'a, 'b>(
+    x: *mut dyn Assocked<Assoc = dyn Send + 'a>,
+) -> *mut dyn Assocked<Assoc = dyn Send + 'b> {
+    x as _
+}
+
+fn change_assoc_1<'a, 'b>(
+    x: *mut dyn Assocked<Assoc = dyn Trait<'a>>,
+) -> *mut dyn Assocked<Assoc = dyn Trait<'b>> {
+    x as _
+}
+
+
+fn main() {}

tests/ui/cast/ptr-to-trait-obj-ok.rs

@@ -0,0 +1,17 @@
+// check-pass
+
+trait Trait<'a> {}
+
+fn remove_auto<'a>(x: *mut (dyn Trait<'a> + Send)) -> *mut dyn Trait<'a> {
+    x as _
+}
+
+fn cast_inherent_lt<'a, 'b>(x: *mut (dyn Trait<'static> + 'a)) -> *mut (dyn Trait<'static> + 'b) {
+    x as _
+}
+
+fn unprincipled<'a, 'b>(x: *mut (dyn Send + 'a)) -> *mut (dyn Sync + 'b) {
+    x as _
+}
+
+fn main() {}