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Merged
merged 1 commit into from
Mar 24, 2020
Merged

[ConstraintSystem] Diagnose more cases of invalid nil use during co… #30621

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43 changes: 17 additions & 26 deletions lib/Sema/CSGen.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1155,7 +1155,18 @@ namespace {
while (parentExpr && isa<ParenExpr>(parentExpr))
parentExpr = CS.getParentExpr(parentExpr);

// In cases like `_ = nil?` AST would have `nil`
// wrapped in `BindOptionalExpr`.
if (parentExpr && isa<BindOptionalExpr>(parentExpr))
parentExpr = CS.getParentExpr(parentExpr);

if (parentExpr) {
// `_ = nil as? ...`
if (isa<ConditionalCheckedCastExpr>(parentExpr)) {
DE.diagnose(expr->getLoc(), diag::conditional_cast_from_nil);
return Type();
}

// `_ = nil!`
if (isa<ForceValueExpr>(parentExpr)) {
DE.diagnose(expr->getLoc(), diag::cannot_force_unwrap_nil_literal);
Expand All @@ -1167,13 +1178,13 @@ namespace {
DE.diagnose(expr->getLoc(), diag::unresolved_nil_literal);
return Type();
}
}

// `_ = nil`
if (auto *assignment = dyn_cast_or_null<AssignExpr>(parentExpr)) {
if (isa<DiscardAssignmentExpr>(assignment->getDest())) {
DE.diagnose(expr->getLoc(), diag::unresolved_nil_literal);
return Type();
// `_ = nil`
if (auto *assignment = dyn_cast<AssignExpr>(parentExpr)) {
if (isa<DiscardAssignmentExpr>(assignment->getDest())) {
DE.diagnose(expr->getLoc(), diag::unresolved_nil_literal);
return Type();
}
}
}

Expand Down Expand Up @@ -2982,26 +2993,6 @@ namespace {
if (!fromExpr) // Either wasn't constructed correctly or wasn't folded.
return nullptr;

std::function<Expr *(Expr *)> nilLiteralExpr = [&](Expr *expr) -> Expr * {
expr = expr->getSemanticsProvidingExpr();
if (expr->getKind() == ExprKind::NilLiteral)
return expr;

if (auto *optionalEvalExpr = dyn_cast<OptionalEvaluationExpr>(expr))
return nilLiteralExpr(optionalEvalExpr->getSubExpr());

if (auto *bindOptionalExpr = dyn_cast<BindOptionalExpr>(expr))
return nilLiteralExpr(bindOptionalExpr->getSubExpr());

return nullptr;
};

if (auto nilLiteral = nilLiteralExpr(fromExpr)) {
ctx.Diags.diagnose(nilLiteral->getLoc(),
diag::conditional_cast_from_nil);
return nullptr;
}

// Validate the resulting type.
TypeResolutionOptions options(TypeResolverContext::ExplicitCastExpr);
options |= TypeResolutionFlags::AllowUnboundGenerics;
Expand Down
2 changes: 1 addition & 1 deletion test/Constraints/casts.swift
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Expand Up @@ -221,7 +221,7 @@ func process(p: Any?) {
func compare<T>(_: T, _: T) {} // expected-note {{'compare' declared here}}
func compare<T>(_: T?, _: T?) {}

_ = nil? as? Int?? // expected-error {{nil literal cannot be the source of a conditional cast}}
_ = nil? as? Int?? // expected-error {{'nil' requires a contextual type}}

func test_tuple_casts_no_warn() {
struct Foo {}
Expand Down
7 changes: 4 additions & 3 deletions test/Constraints/optional.swift
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Expand Up @@ -439,9 +439,10 @@ func sr_12309() {
_ = (nil!) // expected-error {{'nil' literal cannot be force unwrapped}}
_ = (nil)! // expected-error {{'nil' literal cannot be force unwrapped}}
_ = ((nil))! // expected-error {{'nil' literal cannot be force unwrapped}}
_ = nil? // expected-error {{value of optional type 'Optional<_>' must be unwrapped to a value of type '_'}}
// expected-note@-1 {{coalesce using '??' to provide a default when the optional value contains 'nil'}}
// expected-note@-2 {{force-unwrap using '!' to abort execution if the optional value contains 'nil'}}
_ = nil? // expected-error {{'nil' requires a contextual type}}
_ = ((nil?)) // expected-error {{'nil' requires a contextual type}}
_ = ((nil))? // expected-error {{'nil' requires a contextual type}}
_ = ((nil)?) // expected-error {{'nil' requires a contextual type}}
_ = nil // expected-error {{'nil' requires a contextual type}}
_ = (nil) // expected-error {{'nil' requires a contextual type}}
_ = ((nil)) // expected-error {{'nil' requires a contextual type}}
Expand Down