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Rollup merge of #89528 - FabianWolff:issue-89497, r=jackh726

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Fix suggestion to borrow when casting from pointer to reference

Fixes #89497.
This commit is contained in:
Manish Goregaokar 2021-10-06 12:33:21 -07:00 • committed by GitHub
commit f5bfa3450a
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7 changed files with 80 additions and 14 deletions
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44
compiler/rustc_typeck/src/check/cast.rs
View file

@ -351,7 +351,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
);
let mut sugg = None;
let mut sugg_mutref = false;
if let ty::Ref(reg, _, mutbl) = *self.cast_ty.kind() {
if let ty::Ref(reg, cast_ty, mutbl) = *self.cast_ty.kind() {
if let ty::RawPtr(TypeAndMut { ty: expr_ty, .. }) = *self.expr_ty.kind() {
if fcx
.try_coerce(
@ -366,7 +366,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
)
.is_ok()
{
sugg = Some(format!("&{}*", mutbl.prefix_str()));
sugg = Some((format!("&{}*", mutbl.prefix_str()), cast_ty == expr_ty));
}
} else if let ty::Ref(expr_reg, expr_ty, expr_mutbl) = *self.expr_ty.kind() {
if expr_mutbl == Mutability::Not
@ -400,7 +400,7 @@ impl<'a, 'tcx> CastCheck<'tcx> {
)
.is_ok()
{
sugg = Some(format!("&{}", mutbl.prefix_str()));
sugg = Some((format!("&{}", mutbl.prefix_str()), false));
}
} else if let ty::RawPtr(TypeAndMut { mutbl, .. }) = *self.cast_ty.kind() {
if fcx
@ -416,19 +416,47 @@ impl<'a, 'tcx> CastCheck<'tcx> {
)
.is_ok()
{
sugg = Some(format!("&{}", mutbl.prefix_str()));
sugg = Some((format!("&{}", mutbl.prefix_str()), false));
}
}
if sugg_mutref {
err.span_label(self.span, "invalid cast");
err.span_note(self.expr.span, "this reference is immutable");
err.span_note(self.cast_span, "trying to cast to a mutable reference type");
} else if let Some(sugg) = sugg {
} else if let Some((sugg, remove_cast)) = sugg {
err.span_label(self.span, "invalid cast");
err.span_suggestion_verbose(
self.expr.span.shrink_to_lo(),
let has_parens = fcx
.tcx
.sess
.source_map()
.span_to_snippet(self.expr.span)
.map_or(false, |snip| snip.starts_with("("));
// Very crude check to see whether the expression must be wrapped
// in parentheses for the suggestion to work (issue #89497).
// Can/should be extended in the future.
let needs_parens = !has_parens
&& match self.expr.kind {
hir::ExprKind::Cast(..) => true,
_ => false,
};
let mut suggestion = vec![(self.expr.span.shrink_to_lo(), sugg)];
if needs_parens {
suggestion[0].1 += "(";
suggestion.push((self.expr.span.shrink_to_hi(), ")".to_string()));
}
if remove_cast {
suggestion.push((
self.expr.span.shrink_to_hi().to(self.cast_span),
String::new(),
));
}
err.multipart_suggestion_verbose(
"consider borrowing the value",
sugg,
suggestion,
Applicability::MachineApplicable,
);
} else if !matches!(