Rollup merge of rust-lang#142025 - m-ou-se:which-local-binding, r=jdonszelmann

Don't refer to 'local binding' in extern macro.

When it comes from a macro expansion, the user has no clue what 'local binding' the compiler is talking about, if they don't know the expansion of the macro. Better to just say 'temporary value'.

Author: matthiaskrgr

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -3314,7 +3314,13 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                     "function parameter".to_string(),
                     "function parameter borrowed here".to_string(),
                 ),
-                LocalKind::Temp if self.body.local_decls[local].is_user_variable() => {
+                LocalKind::Temp
+                    if self.body.local_decls[local].is_user_variable()
+                        && !self.body.local_decls[local]
+                            .source_info
+                            .span
+                            .in_external_macro(self.infcx.tcx.sess.source_map()) =>
+                {
                     ("local binding".to_string(), "local binding introduced here".to_string())
                 }
                 LocalKind::ReturnPointer | LocalKind::Temp => {

tests/ui/macros/return_from_external_macro.rs

@@ -5,7 +5,7 @@ extern crate ret_from_ext;
 
 fn foo() -> impl Sized {
     drop(|| ret_from_ext::foo!());
-    //~^ ERROR cannot return reference to local binding
+    //~^ ERROR cannot return reference to temporary value
 
     ret_from_ext::foo!()
     //~^ ERROR temporary value dropped while borrowed

tests/ui/macros/return_from_external_macro.stderr

@@ -1,11 +1,11 @@
-error[E0515]: cannot return reference to local binding
+error[E0515]: cannot return reference to temporary value
   --> $DIR/return_from_external_macro.rs:7:13
    |
 LL |     drop(|| ret_from_ext::foo!());
    |             ^^^^^^^^^^^^^^^^^^^^
    |             |
    |             returns a reference to data owned by the current function
-   |             local binding introduced here
+   |             temporary value created here
    |
    = note: this error originates in the macro `ret_from_ext::foo` (in Nightly builds, run with -Z macro-backtrace for more info)