Auto merge of #54810 - 1aim:unused-impl-trait, r=oli-obk

Fix dead code lint for functions using impl Trait

Fixes https://github.com/rust-lang/rust/issues/54754

This is a minimal fix that doesn't add any new queries or touches unnecessary code. Please nominate for beta backport if wanted.

src/test/run-pass/async-await.rs

@@ -170,6 +170,7 @@ fn main() {
         async_closure,
         async_fn,
         async_fn_with_internal_borrow,
+        Foo::async_method,
         |x| {
             async move {
                 unsafe { await!(unsafe_async_fn(x)) }

src/test/ui/impl-trait/existential-minimal.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// run-pass
+// compile-pass
 
 fn main() {}
 

src/test/ui/impl-trait/issue-42479.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// run-pass
+// compile-pass
 
 use std::iter::once;
 

src/test/ui/impl-trait/issue-49376.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// run-pass
+// compile-pass
 
 // Tests for nested self-reference which caused a stack overflow.
 

src/test/ui/issue-49556.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// run-pass
+// compile-pass
 fn iter<'a>(data: &'a [usize]) -> impl Iterator<Item = usize> + 'a {
     data.iter()
         .map(

src/test/ui/lint/lint-dead-code-1.rs

@@ -109,6 +109,10 @@ fn bar() { //~ ERROR: function is never used
     foo();
 }
 
+fn baz() -> impl Copy { //~ ERROR: function is never used
+    "I'm unused, too"
+}
+
 // Code with #[allow(dead_code)] should be marked live (and thus anything it
 // calls is marked live)
 #[allow(dead_code)]

src/test/ui/lint/lint-dead-code-1.stderr

@@ -58,5 +58,11 @@ error: function is never used: `bar`
 LL | fn bar() { //~ ERROR: function is never used
    | ^^^^^^^^
 
-error: aborting due to 9 previous errors
+error: function is never used: `baz`
+  --> $DIR/lint-dead-code-1.rs:112:1
+   |
+LL | fn baz() -> impl Copy { //~ ERROR: function is never used
+   | ^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 10 previous errors
 

src/test/ui/traits/conservative_impl_trait.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// run-pass
+// compile-pass
 // #39665
 
 fn batches(n: &u32) -> impl Iterator<Item=&u32> {