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Auto merge of #77283 - estebank:if-let-sugg, r=Mark-Simulacrum

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Tweak `if let` suggestion to be more liberal with suggestion and to not ICE

Fix #77218. Fix #77238.
This commit is contained in:
bors 2020-10-26 01:53:51 +00:00
commit 16e9ed0b1c
5 changed files with 56 additions and 34 deletions
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50
compiler/rustc_typeck/src/check/expr.rs
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@ -769,34 +769,40 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
let lhs_ty = self.check_expr(&lhs);
let rhs_ty = self.check_expr(&rhs);
if self.can_coerce(lhs_ty, rhs_ty) {
if !lhs.is_syntactic_place_expr() {
// Do not suggest `if let x = y` as `==` is way more likely to be the intention.
if let hir::Node::Expr(hir::Expr {
kind: ExprKind::Match(_, _, hir::MatchSource::IfDesugar { .. }),
..
}) = self.tcx.hir().get(
self.tcx.hir().get_parent_node(self.tcx.hir().get_parent_node(expr.hir_id)),
) {
// Likely `if let` intended.
err.span_suggestion_verbose(
expr.span.shrink_to_lo(),
"you might have meant to use pattern matching",
"let ".to_string(),
Applicability::MaybeIncorrect,
);
}
let (applicability, eq) = if self.can_coerce(rhs_ty, lhs_ty) {
(Applicability::MachineApplicable, true)
} else {
(Applicability::MaybeIncorrect, false)
};
if !lhs.is_syntactic_place_expr() {
// Do not suggest `if let x = y` as `==` is way more likely to be the intention.
if let hir::Node::Expr(hir::Expr {
kind:
ExprKind::Match(
_,
_,
hir::MatchSource::IfDesugar { .. } | hir::MatchSource::WhileDesugar,
),
..
}) = self.tcx.hir().get(
self.tcx.hir().get_parent_node(self.tcx.hir().get_parent_node(expr.hir_id)),
) {
// Likely `if let` intended.
err.span_suggestion_verbose(
expr.span.shrink_to_lo(),
"you might have meant to use pattern matching",
"let ".to_string(),
applicability,
);
}
}
if eq {
err.span_suggestion_verbose(
*span,
"you might have meant to compare for equality",
"==".to_string(),
Applicability::MaybeIncorrect,
applicability,
);
} else {
// Do this to cause extra errors about the assignment.
let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
let _ = self.check_expr_coercable_to_type(&rhs, lhs_ty, Some(lhs));
}
if self.sess().if_let_suggestions.borrow().get(&expr.span).is_some() {