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Suggest turbofish for uninferred const argument

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This commit is contained in:
Justus K 2020-10-08 22:23:01 +02:00
parent b5c37e86ff
commit 4379a43e46
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12 changed files with 110 additions and 8 deletions
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32
compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
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@ -124,6 +124,11 @@ impl<'a, 'tcx> Visitor<'tcx> for FindHirNodeVisitor<'a, 'tcx> {
return;
}
}
// FIXME(const_generics): Currently, any uninferred `const` generics arguments
// are handled specially, but instead they should be handled in `annotate_method_call`,
// which currently doesn't work because this evaluates to `false` for const arguments.
// See https://github.com/rust-lang/rust/pull/77758 for more details.
if self.node_ty_contains_target(expr.hir_id).is_some() {
match expr.kind {
ExprKind::Closure(..) => self.found_closure = Some(&expr),
@ -345,11 +350,6 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
) -> DiagnosticBuilder<'tcx> {
let arg = self.resolve_vars_if_possible(arg);
let arg_data = self.extract_inference_diagnostics_data(arg, None);
let kind_str = match arg.unpack() {
GenericArgKind::Type(_) => "type",
GenericArgKind::Const(_) => "the value",
GenericArgKind::Lifetime(_) => bug!("unexpected lifetime"),
};
let mut local_visitor = FindHirNodeVisitor::new(&self, arg, span);
let ty_to_string = |ty: Ty<'tcx>| -> String {
@ -618,6 +618,28 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
.any(|span_label| span_label.label.is_some() && span_label.span == span)
&& local_visitor.found_arg_pattern.is_none()
{
let (kind_str, const_value) = match arg.unpack() {
GenericArgKind::Type(_) => ("type", None),
GenericArgKind::Const(_) => ("the value", Some(())),
GenericArgKind::Lifetime(_) => bug!("unexpected lifetime"),
};
// FIXME(const_generics): we would like to handle const arguments
// as part of the normal diagnostics flow below, but there appear to
// be subtleties in doing so, so for now we special-case const args
// here.
if let Some(suggestion) = const_value
.and_then(|_| arg_data.parent_name.as_ref())
.map(|parent| format!("{}::<{}>", parent, arg_data.name))
{
err.span_suggestion_verbose(
span,
"consider specifying the const argument",
suggestion,
Applicability::MaybeIncorrect,
);
}
// Avoid multiple labels pointing at `span`.
err.span_label(
span,