Rollup merge of #136598 - compiler-errors:unit-fallback, r=WaffleLapkin

Fix suggestion for `dependency_on_unit_never_type_fallback` involving closures + format args expansions

fixes #136562

r? wafflelapkin or reassign

4 files changed, 46 insertions, 8 deletions

diff --git a/tests/ui/never_type/dont-suggest-turbofish-from-expansion.rs b/tests/ui/never_type/dont-suggest-turbofish-from-expansion.rs
new file mode 100644
index 00000000000..9a53358464d
--- /dev/null
+++ b/tests/ui/never_type/dont-suggest-turbofish-from-expansion.rs
@@ -0,0 +1,20 @@
+#![deny(dependency_on_unit_never_type_fallback)]
+
+fn create_ok_default<C>() -> Result<C, ()>
+where
+    C: Default,
+{
+    Ok(C::default())
+}
+
+fn main() -> Result<(), ()> {
+    //~^ ERROR this function depends on never type fallback being `()`
+    //~| WARN this was previously accepted by the compiler but is being phased out
+    let (returned_value, _) = (|| {
+        let created = create_ok_default()?;
+        Ok((created, ()))
+    })()?;
+
+    let _ = format_args!("{:?}", returned_value);
+    Ok(())
+}
diff --git a/tests/ui/never_type/dont-suggest-turbofish-from-expansion.stderr b/tests/ui/never_type/dont-suggest-turbofish-from-expansion.stderr
new file mode 100644
index 00000000000..3fe642a8401
--- /dev/null
+++ b/tests/ui/never_type/dont-suggest-turbofish-from-expansion.stderr
@@ -0,0 +1,26 @@
+error: this function depends on never type fallback being `()`
+  --> $DIR/dont-suggest-turbofish-from-expansion.rs:10:1
+   |
+LL | fn main() -> Result<(), ()> {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in Rust 2024 and in a future release in all editions!
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2024/never-type-fallback.html>
+   = help: specify the types explicitly
+note: in edition 2024, the requirement `!: Default` will fail
+  --> $DIR/dont-suggest-turbofish-from-expansion.rs:14:23
+   |
+LL |         let created = create_ok_default()?;
+   |                       ^^^^^^^^^^^^^^^^^^^
+note: the lint level is defined here
+  --> $DIR/dont-suggest-turbofish-from-expansion.rs:1:9
+   |
+LL | #![deny(dependency_on_unit_never_type_fallback)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: use `()` annotations to avoid fallback changes
+   |
+LL |         let created: () = create_ok_default()?;
+   |                    ++++
+
+error: aborting due to 1 previous error
+
diff --git a/tests/ui/never_type/lint-never-type-fallback-flowing-into-unsafe.e2015.stderr b/tests/ui/never_type/lint-never-type-fallback-flowing-into-unsafe.e2015.stderr
index 04cd2fcafd6..49b966f32ce 100644
--- a/tests/ui/never_type/lint-never-type-fallback-flowing-into-unsafe.e2015.stderr
+++ b/tests/ui/never_type/lint-never-type-fallback-flowing-into-unsafe.e2015.stderr
@@ -130,10 +130,6 @@ LL |         msg_send!();
    = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2024/never-type-fallback.html>
    = help: specify the type explicitly
    = note: this warning originates in the macro `msg_send` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: use `()` annotations to avoid fallback changes
-   |
-LL |             match send_message::<() /* ?0 */>() {
-   |                                  ~~
 
 warning: 10 warnings emitted
 
diff --git a/tests/ui/never_type/lint-never-type-fallback-flowing-into-unsafe.e2024.stderr b/tests/ui/never_type/lint-never-type-fallback-flowing-into-unsafe.e2024.stderr
index 7adba2cc709..4d3692a7b04 100644
--- a/tests/ui/never_type/lint-never-type-fallback-flowing-into-unsafe.e2024.stderr
+++ b/tests/ui/never_type/lint-never-type-fallback-flowing-into-unsafe.e2024.stderr
@@ -130,10 +130,6 @@ LL |         msg_send!();
    = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2024/never-type-fallback.html>
    = help: specify the type explicitly
    = note: this error originates in the macro `msg_send` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: use `()` annotations to avoid fallback changes
-   |
-LL |             match send_message::<() /* ?0 */>() {
-   |                                  ~~
 
 warning: the type `!` does not permit zero-initialization
   --> $DIR/lint-never-type-fallback-flowing-into-unsafe.rs:12:18