Rollup merge of #153887 - estebank:as_ref-suggestion, r=JohnTitor

matthiaskrgr · web-flow · commit 6da1cc247ce8 · 2026-03-15T16:52:45.000+01:00
Turn label into structured suggestion for `.as_ref()` and `.as_mut()`

```
error[E0382]: use of moved value: `foo`
  --&gt; $DIR/as-ref-2.rs:10:14
   |
LL |     let foo = Some(Struct);
   |         --- move occurs because `foo` has type `Option&lt;Struct&gt;`, which does not implement the `Copy` trait
LL |     let _x: Option&lt;Struct&gt; = foo.map(|s| bar(&amp;s));
   |                                  ---------------- `foo` moved due to this method call
LL |     let _y = foo;
   |              ^^^ value used here after move
   |
note: `Option::&lt;T&gt;::map` takes ownership of the receiver `self`, which moves `foo`
  --&gt; $SRC_DIR/core/src/option.rs:LL:COL
help: consider calling `.as_ref()` to borrow the value's contents
   |
LL |     let _x: Option&lt;Struct&gt; = foo.as_ref().map(|s| bar(&amp;s));
   |                                 +++++++++
help: consider calling `.as_mut()` to mutably borrow the value's contents
   |
LL |     let _x: Option&lt;Struct&gt; = foo.as_mut().map(|s| bar(&amp;s));
   |                                 +++++++++
```
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -1377,7 +1377,9 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                         matches!(tcx.get_diagnostic_name(def_id), Some(sym::Option | sym::Result))
                     });
                     if is_option_or_result && maybe_reinitialized_locations_is_empty {
-                        err.subdiagnostic(CaptureReasonLabel::BorrowContent { var_span });
+                        err.subdiagnostic(CaptureReasonLabel::BorrowContent {
+                            var_span: var_span.shrink_to_hi(),
+                        });
                     }
                     if let Some((CallDesugaringKind::ForLoopIntoIter, _)) = desugaring {
                         let ty = moved_place.ty(self.body, tcx).ty;
diff --git a/compiler/rustc_borrowck/src/session_diagnostics.rs b/compiler/rustc_borrowck/src/session_diagnostics.rs
@@ -456,7 +456,18 @@ pub(crate) enum CaptureReasonLabel<'a> {
         is_move_msg: bool,
         is_loop_message: bool,
     },
-    #[label("help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents")]
+    #[suggestion(
+        "consider calling `.as_ref()` to borrow the value's contents",
+        applicability = "maybe-incorrect",
+        code = ".as_ref()",
+        style = "verbose"
+    )]
+    #[suggestion(
+        "consider calling `.as_mut()` to mutably borrow the value's contents",
+        applicability = "maybe-incorrect",
+        code = ".as_mut()",
+        style = "verbose"
+    )]
     BorrowContent {
         #[primary_span]
         var_span: Span,
diff --git a/tests/ui/borrowck/suggest-as-ref-on-mut-closure.stderr b/tests/ui/borrowck/suggest-as-ref-on-mut-closure.stderr
@@ -4,11 +4,18 @@ error[E0507]: cannot move out of `*cb` which is behind a mutable reference
 LL |     cb.map(|cb| cb());
    |     ^^ -------------- `*cb` moved due to this method call
    |     |
-   |     help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents
    |     move occurs because `*cb` has type `Option<&mut dyn FnMut()>`, which does not implement the `Copy` trait
    |
 note: `Option::<T>::map` takes ownership of the receiver `self`, which moves `*cb`
   --> $SRC_DIR/core/src/option.rs:LL:COL
+help: consider calling `.as_ref()` to borrow the value's contents
+   |
+LL |     cb.as_ref().map(|cb| cb());
+   |       +++++++++
+help: consider calling `.as_mut()` to mutably borrow the value's contents
+   |
+LL |     cb.as_mut().map(|cb| cb());
+   |       +++++++++
 help: you could `clone` the value and consume it, if the `&mut dyn FnMut(): Clone` trait bound could be satisfied
    |
 LL |     <Option<&mut dyn FnMut()> as Clone>::clone(&cb).map(|cb| cb());
diff --git a/tests/ui/suggestions/as-ref-2.stderr b/tests/ui/suggestions/as-ref-2.stderr
@@ -4,14 +4,20 @@ error[E0382]: use of moved value: `foo`
 LL |     let foo = Some(Struct);
    |         --- move occurs because `foo` has type `Option<Struct>`, which does not implement the `Copy` trait
 LL |     let _x: Option<Struct> = foo.map(|s| bar(&s));
-   |                              --- ---------------- `foo` moved due to this method call
-   |                              |
-   |                              help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents
+   |                                  ---------------- `foo` moved due to this method call
 LL |     let _y = foo;
    |              ^^^ value used here after move
    |
 note: `Option::<T>::map` takes ownership of the receiver `self`, which moves `foo`
   --> $SRC_DIR/core/src/option.rs:LL:COL
+help: consider calling `.as_ref()` to borrow the value's contents
+   |
+LL |     let _x: Option<Struct> = foo.as_ref().map(|s| bar(&s));
+   |                                 +++++++++
+help: consider calling `.as_mut()` to mutably borrow the value's contents
+   |
+LL |     let _x: Option<Struct> = foo.as_mut().map(|s| bar(&s));
+   |                                 +++++++++
 help: you could `clone` the value and consume it, if the `Struct: Clone` trait bound could be satisfied
    |
 LL |     let _x: Option<Struct> = foo.clone().map(|s| bar(&s));
diff --git a/tests/ui/suggestions/option-content-move.fixed b/tests/ui/suggestions/option-content-move.fixed
@@ -7,7 +7,7 @@ impl LipogramCorpora {
     pub fn validate_all(&mut self) -> Result<(), char> {
         for selection in &self.selections {
             if selection.1.is_some() {
-                if <Option<String> as Clone>::clone(&selection.1.clone()).unwrap().contains(selection.0) {
+                if <Option<String> as Clone>::clone(&selection.1.clone()).as_mut().as_ref().unwrap().contains(selection.0) {
                 //~^ ERROR cannot move out of `selection.1`
                     return Err(selection.0);
                 }
@@ -25,7 +25,7 @@ impl LipogramCorpora2 {
     pub fn validate_all(&mut self) -> Result<(), char> {
         for selection in &self.selections {
             if selection.1.is_ok() {
-                if <Result<String, String> as Clone>::clone(&selection.1.clone()).unwrap().contains(selection.0) {
+                if <Result<String, String> as Clone>::clone(&selection.1.clone()).as_mut().as_ref().unwrap().contains(selection.0) {
                 //~^ ERROR cannot move out of `selection.1`
                     return Err(selection.0);
                 }
diff --git a/tests/ui/suggestions/option-content-move.stderr b/tests/ui/suggestions/option-content-move.stderr
@@ -4,11 +4,18 @@ error[E0507]: cannot move out of `selection.1` which is behind a shared referenc
 LL |                 if selection.1.unwrap().contains(selection.0) {
    |                    ^^^^^^^^^^^ -------- `selection.1` moved due to this method call
    |                    |
-   |                    help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents
    |                    move occurs because `selection.1` has type `Option<String>`, which does not implement the `Copy` trait
    |
 note: `Option::<T>::unwrap` takes ownership of the receiver `self`, which moves `selection.1`
   --> $SRC_DIR/core/src/option.rs:LL:COL
+help: consider calling `.as_ref()` to borrow the value's contents
+   |
+LL |                 if selection.1.as_ref().unwrap().contains(selection.0) {
+   |                               +++++++++
+help: consider calling `.as_mut()` to mutably borrow the value's contents
+   |
+LL |                 if selection.1.as_mut().unwrap().contains(selection.0) {
+   |                               +++++++++
 help: you can `clone` the value and consume it, but this might not be your desired behavior
    |
 LL |                 if <Option<String> as Clone>::clone(&selection.1).unwrap().contains(selection.0) {
@@ -24,11 +31,18 @@ error[E0507]: cannot move out of `selection.1` which is behind a shared referenc
 LL |                 if selection.1.unwrap().contains(selection.0) {
    |                    ^^^^^^^^^^^ -------- `selection.1` moved due to this method call
    |                    |
-   |                    help: consider calling `.as_ref()` or `.as_mut()` to borrow the type's contents
    |                    move occurs because `selection.1` has type `Result<String, String>`, which does not implement the `Copy` trait
    |
 note: `Result::<T, E>::unwrap` takes ownership of the receiver `self`, which moves `selection.1`
   --> $SRC_DIR/core/src/result.rs:LL:COL
+help: consider calling `.as_ref()` to borrow the value's contents
+   |
+LL |                 if selection.1.as_ref().unwrap().contains(selection.0) {
+   |                               +++++++++
+help: consider calling `.as_mut()` to mutably borrow the value's contents
+   |
+LL |                 if selection.1.as_mut().unwrap().contains(selection.0) {
+   |                               +++++++++
 help: you can `clone` the value and consume it, but this might not be your desired behavior
    |
 LL |                 if <Result<String, String> as Clone>::clone(&selection.1).unwrap().contains(selection.0) {
