Dont suggest use<APIT>

Author: compiler-errors

compiler/rustc_borrowck/src/diagnostics/opaque_suggestions.rs

@@ -97,7 +97,18 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                             })
                             .map(|arg| arg.to_string()),
                     );
-                    if opaque_def_id.is_local() {
+                    if seen_generics.iter().any(|name| name.starts_with("impl ")) {
+                        // FIXME: This should be a dedicated suggestion, but that
+                        // requires a lot of moving parts :/
+                        diag.span_help(
+                            tcx.def_span(opaque_def_id),
+                            format!(
+                                "add a precise capturing bound to avoid overcapturing, \
+                                after turning all argument-position impl traits into \
+                                type parameters: `+ use</* Args */>`",
+                            ),
+                        );
+                    } else if opaque_def_id.is_local() {
                         diag.span_suggestion_verbose(
                             tcx.def_span(opaque_def_id).shrink_to_hi(),
                             "add a precise capturing bound to avoid overcapturing",

tests/ui/impl-trait/precise-capturing/migration-note.rs

@@ -187,4 +187,19 @@ fn returned() -> impl Sized {
 }
 //~^ NOTE `x` dropped here while still borrowed
 
+fn capture_apit(x: &impl Sized) -> impl Sized {}
+//~^ NOTE in this expansion of desugaring of `impl Trait`
+
+fn test_apit() {
+    let x = String::new();
+    //~^ NOTE binding `x` declared here
+    let y = capture_apit(&x);
+    //~^ NOTE borrow of `x` occurs here
+    //~| NOTE this call may capture more lifetimes than intended
+    drop(x);
+    //~^ ERROR cannot move out of `x` because it is borrowed
+    //~| NOTE move out of `x` occurs here
+}
+//~^ NOTE borrow might be used here, when `y` is dropped
+
 fn main() {}

tests/ui/impl-trait/precise-capturing/migration-note.stderr

@@ -278,7 +278,37 @@ help: add a precise capturing bound to avoid overcapturing
 LL | fn display_len<T>(x: &Vec<T>) -> impl Display + use<T> {
    |                                               ++++++++
 
-error: aborting due to 12 previous errors
+error[E0505]: cannot move out of `x` because it is borrowed
+  --> $DIR/migration-note.rs:199:10
+   |
+LL |     let x = String::new();
+   |         - binding `x` declared here
+LL |
+LL |     let y = capture_apit(&x);
+   |                          -- borrow of `x` occurs here
+...
+LL |     drop(x);
+   |          ^ move out of `x` occurs here
+...
+LL | }
+   | - borrow might be used here, when `y` is dropped and runs the destructor for type `impl Sized`
+   |
+note: this call may capture more lifetimes than intended, because Rust 2024 has adjusted the `impl Trait` lifetime capture rules
+  --> $DIR/migration-note.rs:196:13
+   |
+LL |     let y = capture_apit(&x);
+   |             ^^^^^^^^^^^^^^^^
+help: add a precise capturing bound to avoid overcapturing, after turning all argument-position impl traits into type parameters: `+ use</* Args */>`
+  --> $DIR/migration-note.rs:190:36
+   |
+LL | fn capture_apit(x: &impl Sized) -> impl Sized {}
+   |                                    ^^^^^^^^^^
+help: consider cloning the value if the performance cost is acceptable
+   |
+LL |     let y = capture_apit(&x.clone());
+   |                            ++++++++
+
+error: aborting due to 13 previous errors
 
 Some errors have detailed explanations: E0499, E0502, E0503, E0505, E0506, E0597, E0716.
 For more information about an error, try `rustc --explain E0499`.