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[Typechecker] Covariant subscript check must also take into consideration mismatched types #29828

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Merged
merged 1 commit into from
Feb 15, 2020
Merged

[Typechecker] Covariant subscript check must also take into consideration mismatched types #29828

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3 changes: 2 additions & 1 deletion lib/Sema/TypeCheckDeclOverride.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1157,7 +1157,8 @@ bool OverrideMatcher::checkOverride(ValueDecl *baseDecl,
// Otherwise, if this is a subscript, validate that covariance is ok.
// If the parent is non-mutable, it's okay to be covariant.
auto parentSubscript = cast<SubscriptDecl>(baseDecl);
if (parentSubscript->supportsMutation()) {
if (parentSubscript->supportsMutation() &&
attempt != OverrideCheckingAttempt::MismatchedTypes) {
diags.diagnose(subscript, diag::override_mutable_covariant_subscript,
declTy, baseTy);
diags.diagnose(baseDecl, diag::subscript_override_here);
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7 changes: 2 additions & 5 deletions test/attr/attr_override.swift
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Expand Up @@ -59,8 +59,7 @@ class A {
}
}

// FIXME(SR-10323): The second note is wrong; it should be "potential overridden class subscript 'subscript(_:)' here". This is a preexisting bug.
class subscript (i: String) -> String { // expected-note{{overridden declaration is here}} expected-note{{attempt to override subscript here}}
class subscript (i: String) -> String { // expected-note{{overridden declaration is here}} expected-note{{potential overridden class subscript 'subscript(_:)' here}}
get {
return "hello"
}
Expand Down Expand Up @@ -144,8 +143,7 @@ class B : A {
}
}

// FIXME(SR-10323): This error is wrong; it should be "subscript does not override any subscript from its superclass". This is a preexisting bug.
override class subscript (i: Int) -> String { // expected-error{{cannot override mutable subscript of type '(Int) -> String' with covariant type '(String) -> String'}}
override class subscript (i: Int) -> String { // expected-error{{subscript does not override any subscript from its superclass}}
get {
return "hello"
}
Expand Down Expand Up @@ -647,4 +645,3 @@ public extension SR_11740_Base where F: SR_11740_Q {
extension SR_11740_Derived where F: SR_11740_P {
public static func foo(_: A) {}
}