Rollup merge of #103699 - compiler-errors:dyn-star-cast-bad, r=TaKO8Ki

Emit proper error when casting to `dyn*`

Fixes #103679

4 files changed, 58 insertions, 0 deletions

diff --git a/src/test/ui/dyn-star/no-explicit-dyn-star-cast.rs b/src/test/ui/dyn-star/no-explicit-dyn-star-cast.rs
new file mode 100644
index 00000000000..67240c8e8da
--- /dev/null
+++ b/src/test/ui/dyn-star/no-explicit-dyn-star-cast.rs
@@ -0,0 +1,13 @@
+use std::fmt::Debug;
+
+fn make_dyn_star() {
+    let i = 42usize;
+    let dyn_i: dyn* Debug = i as dyn* Debug;
+    //~^ ERROR casting `usize` as `dyn* Debug` is invalid
+    //~| ERROR dyn* trait objects are unstable
+    //~| ERROR dyn* trait objects are unstable
+}
+
+fn main() {
+    make_dyn_star();
+}
diff --git a/src/test/ui/dyn-star/no-explicit-dyn-star-cast.stderr b/src/test/ui/dyn-star/no-explicit-dyn-star-cast.stderr
new file mode 100644
index 00000000000..687d7db0464
--- /dev/null
+++ b/src/test/ui/dyn-star/no-explicit-dyn-star-cast.stderr
@@ -0,0 +1,28 @@
+error[E0658]: dyn* trait objects are unstable
+  --> $DIR/no-explicit-dyn-star-cast.rs:5:16
+   |
+LL |     let dyn_i: dyn* Debug = i as dyn* Debug;
+   |                ^^^^^^^^^^
+   |
+   = note: see issue #91611 <https://github.com/rust-lang/rust/issues/91611> for more information
+   = help: add `#![feature(dyn_star)]` to the crate attributes to enable
+
+error[E0658]: dyn* trait objects are unstable
+  --> $DIR/no-explicit-dyn-star-cast.rs:5:34
+   |
+LL |     let dyn_i: dyn* Debug = i as dyn* Debug;
+   |                                  ^^^^^^^^^^
+   |
+   = note: see issue #91611 <https://github.com/rust-lang/rust/issues/91611> for more information
+   = help: add `#![feature(dyn_star)]` to the crate attributes to enable
+
+error[E0606]: casting `usize` as `dyn* Debug` is invalid
+  --> $DIR/no-explicit-dyn-star-cast.rs:5:29
+   |
+LL |     let dyn_i: dyn* Debug = i as dyn* Debug;
+   |                             ^^^^^^^^^^^^^^^
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0606, E0658.
+For more information about an error, try `rustc --explain E0606`.
diff --git a/src/test/ui/dyn-star/no-explicit-dyn-star.rs b/src/test/ui/dyn-star/no-explicit-dyn-star.rs
new file mode 100644
index 00000000000..4f726b7c6a6
--- /dev/null
+++ b/src/test/ui/dyn-star/no-explicit-dyn-star.rs
@@ -0,0 +1,8 @@
+// aux-build:dyn-star-foreign.rs
+
+extern crate dyn_star_foreign;
+
+fn main() {
+    dyn_star_foreign::require_dyn_star_display(1usize as _);
+    //~^ ERROR casting `usize` as `dyn* std::fmt::Display` is invalid
+}
diff --git a/src/test/ui/dyn-star/no-explicit-dyn-star.stderr b/src/test/ui/dyn-star/no-explicit-dyn-star.stderr
new file mode 100644
index 00000000000..49706fae19e
--- /dev/null
+++ b/src/test/ui/dyn-star/no-explicit-dyn-star.stderr
@@ -0,0 +1,9 @@
+error[E0606]: casting `usize` as `dyn* std::fmt::Display` is invalid
+  --> $DIR/no-explicit-dyn-star.rs:6:48
+   |
+LL |     dyn_star_foreign::require_dyn_star_display(1usize as _);
+   |                                                ^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0606`.