Rollup merge of #144804 - WaffleLapkin:reach-for-the-casts, r=compiler-errors

Don't warn on never to any `as` casts as unreachable

I'm doing this while being sleep deprived on a night train, let's hope this is coherent.

Fixes rust-lang/rust#67227

4 files changed, 22 insertions, 39 deletions

diff --git a/tests/ui/reachable/expr_cast.rs b/tests/ui/reachable/expr_cast.rs
index e8e477ea4f6..aa412c99b2e 100644
--- a/tests/ui/reachable/expr_cast.rs
+++ b/tests/ui/reachable/expr_cast.rs
@@ -1,13 +1,21 @@
-#![allow(unused_variables)]
-#![allow(unused_assignments)]
-#![allow(dead_code)]
+//@ check-pass
+//@ edition: 2024
+//
+// Check that we don't warn on `as` casts of never to any as unreachable.
+// While they *are* unreachable, sometimes they are required to appeal typeck.
 #![deny(unreachable_code)]
-#![feature(never_type, type_ascription)]
 
 fn a() {
-    // the cast is unreachable:
-    let x = {return} as !; //~ ERROR unreachable
-    //~| ERROR non-primitive cast
+    _ = {return} as u32;
 }
 
-fn main() { }
+fn b() {
+    (return) as u32;
+}
+
+// example that needs an explicit never-to-any `as` cast
+fn example() -> impl Iterator<Item = u8> {
+    todo!() as std::iter::Empty<_>
+}
+
+fn main() {}
diff --git a/tests/ui/reachable/expr_cast.stderr b/tests/ui/reachable/expr_cast.stderr
deleted file mode 100644
index 6643f1784a1..00000000000
--- a/tests/ui/reachable/expr_cast.stderr
+++ /dev/null
@@ -1,24 +0,0 @@
-error: unreachable expression
-  --> $DIR/expr_cast.rs:9:13
-   |
-LL |     let x = {return} as !;
-   |             ^------^^^^^^
-   |             ||
-   |             |any code following this expression is unreachable
-   |             unreachable expression
-   |
-note: the lint level is defined here
-  --> $DIR/expr_cast.rs:4:9
-   |
-LL | #![deny(unreachable_code)]
-   |         ^^^^^^^^^^^^^^^^
-
-error[E0605]: non-primitive cast: `()` as `!`
-  --> $DIR/expr_cast.rs:9:13
-   |
-LL |     let x = {return} as !;
-   |             ^^^^^^^^^^^^^ an `as` expression can only be used to convert between primitive types or to coerce to a specific trait object
-
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0605`.
diff --git a/tests/ui/reachable/unreachable-try-pattern.rs b/tests/ui/reachable/unreachable-try-pattern.rs
index 22cbfb95af0..1358722e229 100644
--- a/tests/ui/reachable/unreachable-try-pattern.rs
+++ b/tests/ui/reachable/unreachable-try-pattern.rs
@@ -18,7 +18,7 @@ fn bar(x: Result<!, i32>) -> Result<u32, i32> {
 fn foo(x: Result<!, i32>) -> Result<u32, i32> {
     let y = (match x { Ok(n) => Ok(n as u32), Err(e) => Err(e) })?;
     //~^ WARN unreachable pattern
-    //~| WARN unreachable expression
+    //~| WARN unreachable call
     Ok(y)
 }
 
diff --git a/tests/ui/reachable/unreachable-try-pattern.stderr b/tests/ui/reachable/unreachable-try-pattern.stderr
index 40b11613105..468af427249 100644
--- a/tests/ui/reachable/unreachable-try-pattern.stderr
+++ b/tests/ui/reachable/unreachable-try-pattern.stderr
@@ -1,11 +1,10 @@
-warning: unreachable expression
-  --> $DIR/unreachable-try-pattern.rs:19:36
+warning: unreachable call
+  --> $DIR/unreachable-try-pattern.rs:19:33
    |
 LL |     let y = (match x { Ok(n) => Ok(n as u32), Err(e) => Err(e) })?;
-   |                                    -^^^^^^^
-   |                                    |
-   |                                    unreachable expression
-   |                                    any code following this expression is unreachable
+   |                                 ^^ - any code following this expression is unreachable
+   |                                 |
+   |                                 unreachable call
    |
 note: the lint level is defined here
   --> $DIR/unreachable-try-pattern.rs:3:9