Add suggestion to use a closure arg instead of a capture on bck error
This commit is contained in:
Maybe Waffle
parent
cfe5c3ca6c
commit
102c0af5a7
4 changed files with 237 additions and 8 deletions
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@ -1,3 +1,5 @@
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use std::iter;
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use either::Either;
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use rustc_data_structures::captures::Captures;
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use rustc_data_structures::fx::FxIndexSet;
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@ -10,25 +12,25 @@ use rustc_hir::intravisit::{walk_block, walk_expr, Visitor};
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use rustc_hir::{AsyncGeneratorKind, GeneratorKind, LangItem};
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use rustc_infer::infer::TyCtxtInferExt;
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use rustc_infer::traits::ObligationCause;
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use rustc_middle::hir::nested_filter::OnlyBodies;
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use rustc_middle::mir::tcx::PlaceTy;
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use rustc_middle::mir::{
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self, AggregateKind, BindingForm, BorrowKind, ClearCrossCrate, ConstraintCategory,
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FakeReadCause, LocalDecl, LocalInfo, LocalKind, Location, Operand, Place, PlaceRef,
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ProjectionElem, Rvalue, Statement, StatementKind, Terminator, TerminatorKind, VarBindingForm,
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};
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use rustc_middle::ty::{self, suggest_constraining_type_params, PredicateKind, Ty};
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use rustc_middle::ty::{self, suggest_constraining_type_params, PredicateKind, Ty, TypeckResults};
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use rustc_middle::util::CallKind;
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use rustc_mir_dataflow::move_paths::{InitKind, MoveOutIndex, MovePathIndex};
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use rustc_span::def_id::LocalDefId;
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use rustc_span::hygiene::DesugaringKind;
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use rustc_span::symbol::{kw, sym};
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use rustc_span::symbol::{kw, sym, Ident};
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use rustc_span::{BytePos, Span, Symbol};
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use rustc_trait_selection::infer::InferCtxtExt;
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use rustc_trait_selection::traits::ObligationCtxt;
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use crate::borrow_set::TwoPhaseActivation;
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use crate::borrowck_errors;
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use crate::diagnostics::conflict_errors::StorageDeadOrDrop::LocalStorageDead;
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use crate::diagnostics::{find_all_local_uses, CapturedMessageOpt};
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use crate::{
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@ -959,6 +961,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
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None,
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);
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self.suggest_binding_for_closure_capture_self(&mut err, &issued_spans);
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self.suggest_using_closure_argument_instead_of_capture(
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&mut err,
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issued_borrow.borrowed_place,
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&issued_spans,
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);
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err
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}
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@ -977,6 +984,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
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place,
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issued_borrow.borrowed_place,
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);
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self.suggest_using_closure_argument_instead_of_capture(
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&mut err,
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issued_borrow.borrowed_place,
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&issued_spans,
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);
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err
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}
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@ -1263,6 +1275,173 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
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}
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}
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/// Suggest using closure argument instead of capture.
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///
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/// For example:
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/// ```ignore (illustrative)
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/// struct S;
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///
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/// impl S {
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/// fn call(&mut self, f: impl Fn(&mut Self)) { /* ... */ }
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/// fn x(&self) {}
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/// }
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///
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/// let mut v = S;
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/// v.call(|this: &mut S| v.x());
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/// // ^\ ^-- help: try using the closure argument: `this`
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/// // *-- error: cannot borrow `v` as mutable because it is also borrowed as immutable
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/// ```
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fn suggest_using_closure_argument_instead_of_capture(
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&self,
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err: &mut Diagnostic,
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borrowed_place: Place<'tcx>,
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issued_spans: &UseSpans<'tcx>,
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) {
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let &UseSpans::ClosureUse { capture_kind_span, .. } = issued_spans else { return };
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let tcx = self.infcx.tcx;
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let hir = tcx.hir();
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// Get the type of the local that we are trying to borrow
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let local = borrowed_place.local;
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let local_ty = self.body.local_decls[local].ty;
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// Get the body the error happens in
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let &body_id =
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if let hir::Node::Item(hir::Item { kind, .. }) = hir.get(self.mir_hir_id())
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&& let hir::ItemKind::Static(_, _, body_id)
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| hir::ItemKind::Const(_, body_id)
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| hir::ItemKind::Fn(_, _, body_id) = kind
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{
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body_id
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} else if let hir::Node::TraitItem(hir::TraitItem { kind, .. }) = hir.get(self.mir_hir_id())
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&& let hir::TraitItemKind::Const(_, Some(body_id))
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| hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(body_id)) = kind
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{
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body_id
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}else if let hir::Node::ImplItem(hir::ImplItem { kind, .. }) = hir.get(self.mir_hir_id())
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&& let hir::ImplItemKind::Const(_, body_id)
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| hir::ImplItemKind::Fn(_, body_id) = kind
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{
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body_id
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} else {
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return
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};
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let body_expr = hir.body(body_id).value;
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struct ClosureFinder<'hir> {
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hir: rustc_middle::hir::map::Map<'hir>,
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borrow_span: Span,
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res: Option<(&'hir hir::Expr<'hir>, &'hir hir::Closure<'hir>)>,
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/// The path expression with the `borrow_span` span
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error_path: Option<(&'hir hir::Expr<'hir>, &'hir hir::QPath<'hir>)>,
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}
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impl<'hir> Visitor<'hir> for ClosureFinder<'hir> {
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type NestedFilter = OnlyBodies;
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fn nested_visit_map(&mut self) -> Self::Map {
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self.hir
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}
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fn visit_expr(&mut self, ex: &'hir hir::Expr<'hir>) {
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if let hir::ExprKind::Path(qpath) = &ex.kind
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&& ex.span == self.borrow_span
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{
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self.error_path = Some((ex, qpath));
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}
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if let hir::ExprKind::Closure(closure) = ex.kind
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&& ex.span.contains(self.borrow_span)
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// To support cases like `|| { v.call(|this| v.get()) }`
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// FIXME: actually support such cases (need to figure out how to move from the capture place to original local)
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&& self.res.as_ref().map_or(true, |(prev_res, _)| prev_res.span.contains(ex.span))
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{
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self.res = Some((ex, closure));
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}
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hir::intravisit::walk_expr(self, ex);
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}
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}
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// Find the closure that most tightly wraps `capture_kind_span`
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let mut finder =
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ClosureFinder { hir, borrow_span: capture_kind_span, res: None, error_path: None };
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finder.visit_expr(body_expr);
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let Some((closure_expr, closure)) = finder.res else { return };
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let typeck_results: &TypeckResults<'_> =
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tcx.typeck_opt_const_arg(self.body.source.with_opt_param().as_local().unwrap());
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// Check that the parent of the closure is a method call,
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// with receiver matching with local's type (modulo refs)
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let parent = hir.parent_id(closure_expr.hir_id);
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if let hir::Node::Expr(parent) = hir.get(parent) {
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if let hir::ExprKind::MethodCall(_, recv, ..) = parent.kind {
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let recv_ty = typeck_results.expr_ty(recv);
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if recv_ty.peel_refs() != local_ty {
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return;
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}
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}
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}
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// Get closure's arguments
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let ty::Closure(_, substs) = typeck_results.expr_ty(closure_expr).kind() else { unreachable!() };
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let sig = substs.as_closure().sig();
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let tupled_params =
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tcx.erase_late_bound_regions(sig.inputs().iter().next().unwrap().map_bound(|&b| b));
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let ty::Tuple(params) = tupled_params.kind() else { return };
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// Find the first argument with a matching type, get its name
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let Some((_, this_name)) = params
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.iter()
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.zip(hir.body_param_names(closure.body))
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.find(|(param_ty, name)|{
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// FIXME: also support deref for stuff like `Rc` arguments
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param_ty.peel_refs() == local_ty && name != &Ident::empty()
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})
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else { return };
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let spans;
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if let Some((_path_expr, qpath)) = finder.error_path
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&& let hir::QPath::Resolved(_, path) = qpath
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&& let hir::def::Res::Local(local_id) = path.res
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{
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// Find all references to the problematic variable in this closure body
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struct VariableUseFinder {
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local_id: hir::HirId,
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spans: Vec<Span>,
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}
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impl<'hir> Visitor<'hir> for VariableUseFinder {
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fn visit_expr(&mut self, ex: &'hir hir::Expr<'hir>) {
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if let hir::ExprKind::Path(qpath) = &ex.kind
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&& let hir::QPath::Resolved(_, path) = qpath
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&& let hir::def::Res::Local(local_id) = path.res
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&& local_id == self.local_id
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{
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self.spans.push(ex.span);
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}
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hir::intravisit::walk_expr(self, ex);
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}
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}
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let mut finder = VariableUseFinder { local_id, spans: Vec::new() };
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finder.visit_expr(hir.body(closure.body).value);
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spans = finder.spans;
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} else {
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spans = vec![capture_kind_span];
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}
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err.multipart_suggestion(
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"try using the closure argument",
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iter::zip(spans, iter::repeat(this_name.to_string())).collect(),
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Applicability::MaybeIncorrect,
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);
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}
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fn suggest_binding_for_closure_capture_self(
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&self,
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err: &mut Diagnostic,
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