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Improve suggestion to change struct field to &mut
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23c2723269
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@ -229,15 +229,15 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
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} => {
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err.span_label(span, format!("cannot {ACT}", ACT = act));
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if let Some((span, message)) = annotate_struct_field(
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if let Some(span) = get_mut_span_in_struct_field(
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self.infcx.tcx,
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Place::ty_from(local, proj_base, self.body, self.infcx.tcx).ty,
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field,
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) {
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err.span_suggestion(
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err.span_suggestion_verbose(
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span,
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"consider changing this to be mutable",
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message,
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"mut ".into(),
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Applicability::MaybeIncorrect,
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);
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}
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@ -1059,18 +1059,18 @@ fn is_closure_or_generator(ty: Ty<'_>) -> bool {
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ty.is_closure() || ty.is_generator()
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}
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/// Adds a suggestion to a struct definition given a field access to a local.
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/// This function expects the local to be a reference to a struct in order to produce a suggestion.
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/// Given a field that needs to be mutuable, returns a span where the mut could go.
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/// This function expects the local to be a reference to a struct in order to produce a span.
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///
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/// ```text
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/// LL | s: &'a String
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/// | ---------- use `&'a mut String` here to make mutable
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/// | ^ returns a span pointing here
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/// ```
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fn annotate_struct_field<'tcx>(
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fn get_mut_span_in_struct_field<'tcx>(
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tcx: TyCtxt<'tcx>,
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ty: Ty<'tcx>,
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field: &mir::Field,
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) -> Option<(Span, String)> {
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) -> Option<Span> {
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// Expect our local to be a reference to a struct of some kind.
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if let ty::Ref(_, ty, _) = ty.kind() {
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if let ty::Adt(def, _) = ty.kind() {
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@ -1081,25 +1081,12 @@ fn annotate_struct_field<'tcx>(
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// Now we're dealing with the actual struct that we're going to suggest a change to,
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// we can expect a field that is an immutable reference to a type.
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if let hir::Node::Field(field) = node {
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if let hir::TyKind::Rptr(
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lifetime,
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hir::MutTy { mutbl: hir::Mutability::Not, ref ty },
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) = field.ty.kind
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if let hir::TyKind::Rptr(lifetime, hir::MutTy { mutbl: hir::Mutability::Not, .. }) =
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field.ty.kind
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{
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// Get the snippets in two parts - the named lifetime (if there is one) and
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// type being referenced, that way we can reconstruct the snippet without loss
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// of detail.
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let type_snippet = tcx.sess.source_map().span_to_snippet(ty.span).ok()?;
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let lifetime_snippet = if !lifetime.is_elided() {
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format!("{} ", tcx.sess.source_map().span_to_snippet(lifetime.span).ok()?)
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} else {
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String::new()
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};
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return Some((
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field.ty.span,
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format!("&{}mut {}", lifetime_snippet, &*type_snippet,),
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));
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return Some(
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lifetime.span.with_hi(lifetime.span.hi() + BytePos(1)).shrink_to_hi(),
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);
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}
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}
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}
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@ -1,11 +1,16 @@
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struct Bar<'a> {
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s: &'a String
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s: &'a String,
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// use wonky spaces to ensure we are creating the span correctly
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longer_name: & 'a Vec<u8>
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}
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impl<'a> Bar<'a> {
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fn f(&mut self) {
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self.s.push('x');
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//~^ ERROR cannot borrow `*self.s` as mutable, as it is behind a `&` reference
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self.longer_name.push(13);
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//~^ ERROR cannot borrow `*self.longer_name` as mutable, as it is behind a `&` reference
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}
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}
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@ -1,12 +1,25 @@
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error[E0596]: cannot borrow `*self.s` as mutable, as it is behind a `&` reference
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--> $DIR/issue-38147-2.rs:7:9
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--> $DIR/issue-38147-2.rs:9:9
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LL | s: &'a String
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| ---------- help: consider changing this to be mutable: `&'a mut String`
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...
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LL | self.s.push('x');
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| ^^^^^^^^^^^^^^^^ cannot borrow as mutable
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help: consider changing this to be mutable
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LL | s: &'a mut String,
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| +++
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error: aborting due to previous error
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error[E0596]: cannot borrow `*self.longer_name` as mutable, as it is behind a `&` reference
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--> $DIR/issue-38147-2.rs:12:9
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LL | self.longer_name.push(13);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^ cannot borrow as mutable
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help: consider changing this to be mutable
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LL | longer_name: & 'a mut Vec<u8>
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| +++
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0596`.
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@ -1,11 +1,13 @@
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error[E0596]: cannot borrow `*self.s` as mutable, as it is behind a `&` reference
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--> $DIR/issue-38147-3.rs:7:9
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LL | s: &'a String
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| ---------- help: consider changing this to be mutable: `&'a mut String`
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...
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LL | self.s.push('x');
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| ^^^^^^^^^^^^^^^^ cannot borrow as mutable
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help: consider changing this to be mutable
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LL | s: &'a mut String
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| +++
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error: aborting due to previous error
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