Auto merge of #61147 - estebank:suggest-as-ref, r=oli-obk

When encountering move error on an `Option`, suggest using `as_ref`

Fix #61109, cc #15457.

src/librustc_mir/borrow_check/move_errors.rs

@@ -242,12 +242,7 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
         let (mut err, err_span) = {
             let (span, original_path, kind): (Span, &Place<'tcx>, &IllegalMoveOriginKind<'_>) =
                 match error {
-                    GroupedMoveError::MovesFromPlace {
-                        span,
-                        ref original_path,
-                        ref kind,
-                        ..
-                    } |
+                    GroupedMoveError::MovesFromPlace { span, ref original_path, ref kind, .. } |
                     GroupedMoveError::MovesFromValue { span, ref original_path, ref kind, .. } |
                     GroupedMoveError::OtherIllegalMove { span, ref original_path, ref kind } => {
                         (span, original_path, kind)
@@ -257,8 +252,7 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
             debug!("report: original_path={:?} span={:?}, kind={:?} \
                    original_path.is_upvar_field_projection={:?}", original_path, span, kind,
                    self.is_upvar_field_projection(original_path));
-            (
-                match kind {
+            let err = match kind {
                 IllegalMoveOriginKind::Static => {
                     self.infcx.tcx.cannot_move_out_of(span, "static item", origin)
                 }
@@ -271,7 +265,7 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
                         self.prefixes(&original_path, PrefixSet::All)
                         .any(|p| self.is_upvar_field_projection(p).is_some());
                     debug!("report: ty={:?}", ty);
-                        match ty.sty {
+                    let mut err = match ty.sty {
                         ty::Array(..) | ty::Slice(..) =>
                             self.infcx.tcx.cannot_move_out_of_interior_noncopy(
                                 span, ty, None, origin
@@ -319,7 +313,27 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
                                 span, &source.to_string(), origin
                             )
                         },
+                    };
+                    let orig_path_ty = format!(
+                        "{:?}",
+                        original_path.ty(self.mir, self.infcx.tcx).ty,
+                    );
+                    let snippet = self.infcx.tcx.sess.source_map().span_to_snippet(span).unwrap();
+                    let is_option = orig_path_ty.starts_with("std::option::Option");
+                    let is_result = orig_path_ty.starts_with("std::result::Result");
+                    if  is_option || is_result {
+                        err.span_suggestion(
+                            span,
+                            &format!("consider borrowing the `{}`'s content", if is_option {
+                                "Option"
+                            } else {
+                                "Result"
+                            }),
+                            format!("{}.as_ref()", snippet),
+                            Applicability::MaybeIncorrect,
+                        );
                     }
+                    err
                 }
                 IllegalMoveOriginKind::InteriorOfTypeWithDestructor { container_ty: ty } => {
                     self.infcx.tcx
@@ -329,9 +343,8 @@ impl<'a, 'gcx, 'tcx> MirBorrowckCtxt<'a, 'gcx, 'tcx> {
                     self.infcx.tcx.cannot_move_out_of_interior_noncopy(
                         span, ty, Some(*is_index), origin
                     ),
-                },
-                span,
-            )
+            };
+            (err, span)
         };
 
         self.add_move_hints(error, &mut err, err_span);

src/test/ui/suggestions/option-content-move.fixed

@@ -0,0 +1,39 @@
+//run-rustfix
+
+pub struct LipogramCorpora {
+    selections: Vec<(char, Option<String>)>,
+}
+
+impl LipogramCorpora {
+    pub fn validate_all(&mut self) -> Result<(), char> {
+        for selection in &self.selections {
+            if selection.1.is_some() {
+                if selection.1.as_ref().unwrap().contains(selection.0) {
+                //~^ ERROR cannot move out of borrowed content
+                    return Err(selection.0);
+                }
+            }
+        }
+        Ok(())
+    }
+}
+
+pub struct LipogramCorpora2 {
+    selections: Vec<(char, Result<String, String>)>,
+}
+
+impl LipogramCorpora2 {
+    pub fn validate_all(&mut self) -> Result<(), char> {
+        for selection in &self.selections {
+            if selection.1.is_ok() {
+                if selection.1.as_ref().unwrap().contains(selection.0) {
+                //~^ ERROR cannot move out of borrowed content
+                    return Err(selection.0);
+                }
+            }
+        }
+        Ok(())
+    }
+}
+
+fn main() {}

src/test/ui/suggestions/option-content-move.rs

@@ -0,0 +1,39 @@
+//run-rustfix
+
+pub struct LipogramCorpora {
+    selections: Vec<(char, Option<String>)>,
+}
+
+impl LipogramCorpora {
+    pub fn validate_all(&mut self) -> Result<(), char> {
+        for selection in &self.selections {
+            if selection.1.is_some() {
+                if selection.1.unwrap().contains(selection.0) {
+                //~^ ERROR cannot move out of borrowed content
+                    return Err(selection.0);
+                }
+            }
+        }
+        Ok(())
+    }
+}
+
+pub struct LipogramCorpora2 {
+    selections: Vec<(char, Result<String, String>)>,
+}
+
+impl LipogramCorpora2 {
+    pub fn validate_all(&mut self) -> Result<(), char> {
+        for selection in &self.selections {
+            if selection.1.is_ok() {
+                if selection.1.unwrap().contains(selection.0) {
+                //~^ ERROR cannot move out of borrowed content
+                    return Err(selection.0);
+                }
+            }
+        }
+        Ok(())
+    }
+}
+
+fn main() {}

src/test/ui/suggestions/option-content-move.stderr

@@ -0,0 +1,21 @@
+error[E0507]: cannot move out of borrowed content
+  --> $DIR/option-content-move.rs:11:20
+   |
+LL |                 if selection.1.unwrap().contains(selection.0) {
+   |                    ^^^^^^^^^^^
+   |                    |
+   |                    cannot move out of borrowed content
+   |                    help: consider borrowing the `Option`'s content: `selection.1.as_ref()`
+
+error[E0507]: cannot move out of borrowed content
+  --> $DIR/option-content-move.rs:29:20
+   |
+LL |                 if selection.1.unwrap().contains(selection.0) {
+   |                    ^^^^^^^^^^^
+   |                    |
+   |                    cannot move out of borrowed content
+   |                    help: consider borrowing the `Result`'s content: `selection.1.as_ref()`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0507`.