From 0dc6c1e59421e44e15cda1cef307b0381ba12468 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Tue, 12 Nov 2024 02:54:42 +0000
Subject: [PATCH] Make precise capturing suggestion machine-applicable only if
 it has not APITs

---
 compiler/rustc_trait_selection/src/errors.rs  | 10 ++++++-
 ...overcaptures-2024-machine-applicable.fixed | 13 ++++++++++
 .../overcaptures-2024-machine-applicable.rs   | 13 ++++++++++
 ...vercaptures-2024-machine-applicable.stderr | 26 +++++++++++++++++++
 4 files changed, 61 insertions(+), 1 deletion(-)
 create mode 100644 tests/ui/impl-trait/precise-capturing/overcaptures-2024-machine-applicable.fixed
 create mode 100644 tests/ui/impl-trait/precise-capturing/overcaptures-2024-machine-applicable.rs
 create mode 100644 tests/ui/impl-trait/precise-capturing/overcaptures-2024-machine-applicable.stderr

diff --git a/compiler/rustc_trait_selection/src/errors.rs b/compiler/rustc_trait_selection/src/errors.rs
index 3e06d0807d8..afac6fc6004 100644
--- a/compiler/rustc_trait_selection/src/errors.rs
+++ b/compiler/rustc_trait_selection/src/errors.rs
@@ -1907,10 +1907,18 @@ impl Subdiagnostic for AddPreciseCapturingForOvercapture {
         diag: &mut Diag<'_, G>,
         _f: &F,
     ) {
+        let applicability = if self.apit_spans.is_empty() {
+            Applicability::MachineApplicable
+        } else {
+            // If there are APIT that are converted to regular parameters,
+            // then this may make the API turbofishable in ways that were
+            // not intended.
+            Applicability::MaybeIncorrect
+        };
         diag.multipart_suggestion_verbose(
             fluent::trait_selection_precise_capturing_overcaptures,
             self.suggs,
-            Applicability::MaybeIncorrect,
+            applicability,
         );
         if !self.apit_spans.is_empty() {
             diag.span_note(
diff --git a/tests/ui/impl-trait/precise-capturing/overcaptures-2024-machine-applicable.fixed b/tests/ui/impl-trait/precise-capturing/overcaptures-2024-machine-applicable.fixed
new file mode 100644
index 00000000000..960f2f1bb13
--- /dev/null
+++ b/tests/ui/impl-trait/precise-capturing/overcaptures-2024-machine-applicable.fixed
@@ -0,0 +1,13 @@
+//@ run-rustfix
+//@ rustfix-only-machine-applicable
+
+// Make sure that simple overcapture suggestions remain machine applicable.
+
+#![allow(unused)]
+#![deny(impl_trait_overcaptures)]
+
+fn named<'a>(x: &'a i32) -> impl Sized + use<> { *x }
+//~^ ERROR `impl Sized` will capture more lifetimes than possibly intended in edition 2024
+//~| WARN this changes meaning in Rust 2024
+
+fn main() {}
diff --git a/tests/ui/impl-trait/precise-capturing/overcaptures-2024-machine-applicable.rs b/tests/ui/impl-trait/precise-capturing/overcaptures-2024-machine-applicable.rs
new file mode 100644
index 00000000000..dc9efbf3b95
--- /dev/null
+++ b/tests/ui/impl-trait/precise-capturing/overcaptures-2024-machine-applicable.rs
@@ -0,0 +1,13 @@
+//@ run-rustfix
+//@ rustfix-only-machine-applicable
+
+// Make sure that simple overcapture suggestions remain machine applicable.
+
+#![allow(unused)]
+#![deny(impl_trait_overcaptures)]
+
+fn named<'a>(x: &'a i32) -> impl Sized { *x }
+//~^ ERROR `impl Sized` will capture more lifetimes than possibly intended in edition 2024
+//~| WARN this changes meaning in Rust 2024
+
+fn main() {}
diff --git a/tests/ui/impl-trait/precise-capturing/overcaptures-2024-machine-applicable.stderr b/tests/ui/impl-trait/precise-capturing/overcaptures-2024-machine-applicable.stderr
new file mode 100644
index 00000000000..35fff9ef170
--- /dev/null
+++ b/tests/ui/impl-trait/precise-capturing/overcaptures-2024-machine-applicable.stderr
@@ -0,0 +1,26 @@
+error: `impl Sized` will capture more lifetimes than possibly intended in edition 2024
+  --> $DIR/overcaptures-2024-machine-applicable.rs:9:29
+   |
+LL | fn named<'a>(x: &'a i32) -> impl Sized { *x }
+   |                             ^^^^^^^^^^
+   |
+   = warning: this changes meaning in Rust 2024
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2024/rpit-lifetime-capture.html>
+note: specifically, this lifetime is in scope but not mentioned in the type's bounds
+  --> $DIR/overcaptures-2024-machine-applicable.rs:9:10
+   |
+LL | fn named<'a>(x: &'a i32) -> impl Sized { *x }
+   |          ^^
+   = note: all lifetimes in scope will be captured by `impl Trait`s in edition 2024
+note: the lint level is defined here
+  --> $DIR/overcaptures-2024-machine-applicable.rs:7:9
+   |
+LL | #![deny(impl_trait_overcaptures)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^
+help: use the precise capturing `use<...>` syntax to make the captures explicit
+   |
+LL | fn named<'a>(x: &'a i32) -> impl Sized + use<> { *x }
+   |                                        +++++++
+
+error: aborting due to 1 previous error
+