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@estebank
estebank committed Nov 17, 2019
1 parent 0487f0c commit d7efa5b
Showing 1 changed file with 91 additions and 81 deletions.
172 changes: 91 additions & 81 deletions src/librustc/traits/error_reporting.rs
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Expand Up @@ -1230,6 +1230,24 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
}
}

fn mk_obligation_for_def_id(
&self,
def_id: DefId,
output_ty: Ty<'tcx>,
cause: ObligationCause<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> PredicateObligation<'tcx> {
let new_trait_ref = ty::TraitRef {
def_id,
substs: self.tcx.mk_substs_trait(output_ty, &[]),
};
Obligation::new(cause, param_env, new_trait_ref.to_predicate())
}


/// We tried to apply the bound to an `fn` or closure. Check whether calling it would
/// evaluate to a type that *would* satisfy the trait binding. If it would, suggest calling
/// it: `bar(foo)` → `bar(foo())`. This case is *very* likely to be hit if `foo` is `async`.
fn suggest_fn_call(
&self,
obligation: &PredicateObligation<'tcx>,
Expand All @@ -1248,19 +1266,14 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
_ => return,
};
let msg = format!("use parentheses to call the {}", callable);
// We tried to apply the bound to an `fn` or closure. Check whether calling it would
// evaluate to a type that *would* satisfy the trait binding. If it would, suggest calling
// it: `bar(foo)` → `bar(foo())`. This case is *very* likely to be hit if `foo` is `async`.

let new_trait_ref = ty::TraitRef {
def_id: trait_ref.def_id(),
substs: self.tcx.mk_substs_trait(output_ty.skip_binder(), &[]),
};
let obligation = Obligation::new(
let obligation = self.mk_obligation_for_def_id(
trait_ref.def_id(),
output_ty.skip_binder(),
obligation.cause.clone(),
obligation.param_env,
new_trait_ref.to_predicate(),
);

let get_name = |err: &mut DiagnosticBuilder<'_>, kind: &hir::PatKind| -> Option<String> {
// Get the local name of this closure. This can be inaccurate because
// of the possibility of reassignment, but this should be good enough.
Expand All @@ -1277,73 +1290,72 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
match self.evaluate_obligation(&obligation) {
Ok(EvaluationResult::EvaluatedToOk) |
Ok(EvaluationResult::EvaluatedToOkModuloRegions) |
Ok(EvaluationResult::EvaluatedToAmbig) => {
let hir = self.tcx.hir();
// Get the name of the callable and the arguments to be used in the suggestion.
let snippet = match hir.get_if_local(def_id) {
Some(hir::Node::Expr(hir::Expr {
kind: hir::ExprKind::Closure(_, decl, _, span, ..),
..
})) => {
err.span_label(*span, "consider calling this closure");
let hir_id = match hir.as_local_hir_id(def_id) {
Some(hir_id) => hir_id,
None => return,
};
let parent_node = hir.get_parent_node(hir_id);
let name = match hir.find(parent_node) {
Some(hir::Node::Stmt(hir::Stmt {
kind: hir::StmtKind::Local(local), ..
})) => match get_name(err, &local.pat.kind) {
Some(name) => name,
None => return,
},
// Different to previous arm because one is `&hir::Local` and the other
// is `P<hir::Local>`.
Some(hir::Node::Local(local)) => match get_name(err, &local.pat.kind) {
Some(name) => name,
None => return,
},
_ => return,
};
let args = decl.inputs.iter()
.map(|_| "_")
.collect::<Vec<_>>().join(", ");
format!("{}({})", name, args)
}
Some(hir::Node::Item(hir::Item {
ident,
kind: hir::ItemKind::Fn(.., body_id),
..
})) => {
err.span_label(ident.span, "consider calling this function");
let body = hir.body(*body_id);
let args = body.params.iter()
.map(|arg| match &arg.pat.kind {
hir::PatKind::Binding(_, _, ident, None)
if ident.name != kw::SelfLower => ident.to_string(),
_ => "_".to_string(),
}).collect::<Vec<_>>().join(", ");
format!("{}({})", ident, args)
}
Ok(EvaluationResult::EvaluatedToAmbig) => {}
_ => return,
}
let hir = self.tcx.hir();
// Get the name of the callable and the arguments to be used in the suggestion.
let snippet = match hir.get_if_local(def_id) {
Some(hir::Node::Expr(hir::Expr {
kind: hir::ExprKind::Closure(_, decl, _, span, ..),
..
})) => {
err.span_label(*span, "consider calling this closure");
let hir_id = match hir.as_local_hir_id(def_id) {
Some(hir_id) => hir_id,
None => return,
};
let parent_node = hir.get_parent_node(hir_id);
let name = match hir.find(parent_node) {
Some(hir::Node::Stmt(hir::Stmt {
kind: hir::StmtKind::Local(local), ..
})) => match get_name(err, &local.pat.kind) {
Some(name) => name,
None => return,
},
// Different to previous arm because one is `&hir::Local` and the other
// is `P<hir::Local>`.
Some(hir::Node::Local(local)) => match get_name(err, &local.pat.kind) {
Some(name) => name,
None => return,
},
_ => return,
};
if points_at_arg {
// When the obligation error has been ensured to have been caused by
// an argument, the `obligation.cause.span` points at the expression
// of the argument, so we can provide a suggestion. This is signaled
// by `points_at_arg`. Otherwise, we give a more general note.
err.span_suggestion(
obligation.cause.span,
&msg,
snippet,
Applicability::HasPlaceholders,
);
} else {
err.help(&format!("{}: `{}`", msg, snippet));
}
let args = decl.inputs.iter()
.map(|_| "_")
.collect::<Vec<_>>().join(", ");
format!("{}({})", name, args)
}
Some(hir::Node::Item(hir::Item {
ident,
kind: hir::ItemKind::Fn(.., body_id),
..
})) => {
err.span_label(ident.span, "consider calling this function");
let body = hir.body(*body_id);
let args = body.params.iter()
.map(|arg| match &arg.pat.kind {
hir::PatKind::Binding(_, _, ident, None)
if ident.name != kw::SelfLower => ident.to_string(),
_ => "_".to_string(),
}).collect::<Vec<_>>().join(", ");
format!("{}({})", ident, args)
}
_ => {}
_ => return,
};
if points_at_arg {
// When the obligation error has been ensured to have been caused by
// an argument, the `obligation.cause.span` points at the expression
// of the argument, so we can provide a suggestion. This is signaled
// by `points_at_arg`. Otherwise, we give a more general note.
err.span_suggestion(
obligation.cause.span,
&msg,
snippet,
Applicability::HasPlaceholders,
);
} else {
err.help(&format!("{}: `{}`", msg, snippet));
}
}

Expand Down Expand Up @@ -1377,12 +1389,11 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
if let ty::Ref(_, t_type, _) = trait_type.kind {
trait_type = t_type;

let substs = self.tcx.mk_substs_trait(trait_type, &[]);
let new_trait_ref = ty::TraitRef::new(trait_ref.def_id, substs);
let new_obligation = Obligation::new(
let new_obligation = self.mk_obligation_for_def_id(
trait_ref.def_id,
trait_type,
ObligationCause::dummy(),
obligation.param_env,
new_trait_ref.to_predicate(),
);

if self.predicate_may_hold(&new_obligation) {
Expand Down Expand Up @@ -1440,12 +1451,11 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
hir::Mutability::Immutable => self.tcx.mk_mut_ref(region, t_type),
};

let substs = self.tcx.mk_substs_trait(&trait_type, &[]);
let new_trait_ref = ty::TraitRef::new(trait_ref.skip_binder().def_id, substs);
let new_obligation = Obligation::new(
let new_obligation = self.mk_obligation_for_def_id(
trait_ref.skip_binder().def_id,
trait_type,
ObligationCause::dummy(),
obligation.param_env,
new_trait_ref.to_predicate(),
);

if self.evaluate_obligation_no_overflow(
Expand Down

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