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Simpler diagnostic when passing arg to closure and missing borrow #76362

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Simpler diagnostic when passing arg to closure and missing borrow #76362

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8 changes: 7 additions & 1 deletion compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -685,6 +685,11 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
_ => None,
};

let found_node = match found_did {
Some(found_did) => self.tcx.hir().get_if_local(found_did),
None => None,
};

let found_span = found_did
.and_then(|did| self.tcx.hir().span_if_local(did))
.map(|sp| self.tcx.sess.source_map().guess_head_span(sp)); // the sp could be an fn def
Expand All @@ -694,7 +699,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
// but we want to complain about them only once.
return;
}

self.reported_closure_mismatch.borrow_mut().insert((span, found_span));

let found = match found_trait_ref.skip_binder().substs.type_at(1).kind() {
Expand All @@ -717,6 +722,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
found_span,
found_trait_ref,
expected_trait_ref,
found_node,
)
} else {
let (closure_span, found) = found_did
Expand Down
58 changes: 57 additions & 1 deletion compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,8 @@ use rustc_hir::def::DefKind;
use rustc_hir::def_id::DefId;
use rustc_hir::intravisit::Visitor;
use rustc_hir::lang_items::LangItem;
use rustc_hir::ExprKind;
// use rustc_hir::TyKind;
use rustc_hir::{AsyncGeneratorKind, GeneratorKind, Node};
use rustc_middle::ty::{
self, suggest_constraining_type_param, AdtKind, DefIdTree, Infer, InferTy, ToPredicate, Ty,
Expand Down Expand Up @@ -121,6 +123,7 @@ pub trait InferCtxtExt<'tcx> {
found_span: Option<Span>,
expected_ref: ty::PolyTraitRef<'tcx>,
found: ty::PolyTraitRef<'tcx>,
found_node: Option<Node<'tcx>>,
) -> DiagnosticBuilder<'tcx>;

fn suggest_fully_qualified_path(
Expand Down Expand Up @@ -907,7 +910,11 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
_ => return None,
};

if let hir::FnRetTy::Return(ret_ty) = sig.decl.output { Some(ret_ty.span) } else { None }
if let hir::FnRetTy::Return(ret_ty) = sig.decl.output {
Some(ret_ty.span)
} else {
None
}
}

/// If all conditions are met to identify a returned `dyn Trait`, suggest using `impl Trait` if
Expand Down Expand Up @@ -1145,6 +1152,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
found_span: Option<Span>,
expected_ref: ty::PolyTraitRef<'tcx>,
found: ty::PolyTraitRef<'tcx>,
found_node: Option<Node<'tcx>>,
) -> DiagnosticBuilder<'tcx> {
crate fn build_fn_sig_string<'tcx>(
tcx: TyCtxt<'tcx>,
Expand Down Expand Up @@ -1193,6 +1201,54 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
);
err.span_label(found_span, expected_str);

if let Some(node) = found_node {
match node {
Node::Expr(param) => match param.kind {
ExprKind::Closure(_, _fn_decl_input, _, _, _) => {
// Input are in closure with _fn_decl_input inputs itself
let expected = expected_ref.skip_binder().substs.type_at(1); // ?

// let inputs = expected_ref.skip_binder().substs.type_at(1);
// let sig = if let ty::Tuple(inputs) = inputs.kind() {
// inputs.iter().map(|k| k.expect_ty())
// } else {
// ::std::iter::once(inputs)
// };

match expected.kind() {
ty::Closure(_did, substs) => {
let msg = format!(
"closure -> & {:?}",
substs
);
err.span_suggestion_verbose(
span.shrink_to_lo(),
"hint: add missing borrow here:",
msg,
Applicability::MaybeIncorrect,
);
}
ty::Ref(_region, ty, _) => {
let msg = format!(
"ref -> & {:?}",
ty
);
err.span_suggestion_verbose(
span.shrink_to_lo(),
"hint: add missing borrow here:",
msg,
Applicability::MaybeIncorrect,
);
}
_ => {}
}
}
_ => {}
},
_ => {}
}
};

err
}

Expand Down