Suggest borrowing on fn argument that is impl AsRef · rust-lang/rust@2df4f7d (original) (raw)
`@@ -449,31 +449,81 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
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`} else {
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`(None, &[][..], 0)
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`};
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let mut can_suggest_clone = true;
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`if let Some(def_id) = def_id
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` && let node = self.infcx.tcx.hir_node_by_def_id(def_id)
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` && let Some(fn_sig) = node.fn_sig()
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` && let Some(ident) = node.ident()
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` && let Some(pos) = args.iter().position(|arg| arg.hir_id == expr.hir_id)
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` && let Some(arg) = fn_sig.decl.inputs.get(pos + offset)
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`{
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``
`-
let mut span: MultiSpan = arg.span.into();
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``
`-
span.push_span_label(
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``
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arg.span,
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``
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"this parameter takes ownership of the value".to_string(),
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``
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);
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``
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let descr = match node.fn_kind() {
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``
`-
Some(hir::intravisit::FnKind::ItemFn(..)) | None => "function",
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``
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Some(hir::intravisit::FnKind::Method(..)) => "method",
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``
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Some(hir::intravisit::FnKind::Closure) => "closure",
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``
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};
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``
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span.push_span_label(ident.span, format!("in this {descr}"));
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``
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err.span_note(
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span,
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``
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format!(
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`` -
"consider changing this parameter type in {descr} {ident} to borrow \
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instead if owning the value isn't necessary",
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``
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),
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``
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);
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let mut is_mut = false;
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if let hir::TyKind::Path(hir::QPath::Resolved(None, path)) = arg.kind
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&& let Res::Def(DefKind::TyParam, param_def_id) = path.res
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&& self
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.infcx
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.tcx
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.predicates_of(def_id)
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.instantiate_identity(self.infcx.tcx)
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.predicates
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.into_iter()
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.any(|pred| {
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if let ty::ClauseKind::Trait(predicate) = pred.kind().skip_binder()
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&& [
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self.infcx.tcx.get_diagnostic_item(sym::AsRef),
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self.infcx.tcx.get_diagnostic_item(sym::AsMut),
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self.infcx.tcx.get_diagnostic_item(sym::Borrow),
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self.infcx.tcx.get_diagnostic_item(sym::BorrowMut),
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]
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.contains(&Some(predicate.def_id()))
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&& let ty::Param(param) = predicate.self_ty().kind()
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&& let generics = self.infcx.tcx.generics_of(def_id)
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&& let param = generics.type_param(*param, self.infcx.tcx)
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&& param.def_id == param_def_id
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{
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if [
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self.infcx.tcx.get_diagnostic_item(sym::AsMut),
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self.infcx.tcx.get_diagnostic_item(sym::BorrowMut),
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]
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.contains(&Some(predicate.def_id()))
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{
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is_mut = true;
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}
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true
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} else {
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false
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}
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})
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{
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// The type of the argument corresponding to the expression that got moved
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// is a type parameter T, which is has a T: AsRef obligation.
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err.span_suggestion_verbose(
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expr.span.shrink_to_lo(),
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"borrow the value to avoid moving it",
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format!("&{}", if is_mut { "mut " } else { "" }),
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Applicability::MachineApplicable,
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);
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can_suggest_clone = is_mut;
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} else {
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let mut span: MultiSpan = arg.span.into();
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span.push_span_label(
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arg.span,
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"this parameter takes ownership of the value".to_string(),
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);
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let descr = match node.fn_kind() {
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Some(hir::intravisit::FnKind::ItemFn(..)) | None => "function",
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Some(hir::intravisit::FnKind::Method(..)) => "method",
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Some(hir::intravisit::FnKind::Closure) => "closure",
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};
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span.push_span_label(ident.span, format!("in this {descr}"));
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err.span_note(
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span,
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format!(
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"consider changing this parameter type in {descr} {ident} to \
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borrow instead if owning the value isn't necessary",
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),
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);
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}
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`}
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`let place = &self.move_data.move_paths[mpi].place;
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`let ty = place.ty(self.body, self.infcx.tcx).ty;
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`@@ -491,9 +541,10 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
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`ClosureKind::Coroutine(CoroutineKind::Desugared(_, CoroutineSource::Block)),
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` ..
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`} = move_spans
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&& can_suggest_clone
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`{
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`self.suggest_cloning(err, ty, expr, None, Some(move_spans));
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`-
} else if self.suggest_hoisting_call_outside_loop(err, expr) {
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} else if self.suggest_hoisting_call_outside_loop(err, expr) && can_suggest_clone {
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`// The place where the type moves would be misleading to suggest clone.
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`// #121466
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`self.suggest_cloning(err, ty, expr, None, Some(move_spans));
`