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Sema: Fix ConstraintSystem::getTypeOfMemberReference() for protocol typealiases #18465

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Aug 2, 2018
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Sema: Fix ConstraintSystem::getTypeOfMemberReference() for protocol typealiases #18465

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2 changes: 1 addition & 1 deletion lib/Sema/ConstraintSystem.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1268,7 +1268,7 @@ ConstraintSystem::getTypeOfMemberReference(
// protocols.
if (auto *alias = dyn_cast<TypeAliasDecl>(value)) {
if (baseObjTy->isExistentialType()) {
auto memberTy = alias->getDeclaredInterfaceType();
auto memberTy = alias->getInterfaceType();
// If we end up with a protocol typealias here, it's underlying
// type must be fully concrete.
assert(!memberTy->hasTypeParameter());
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2 changes: 1 addition & 1 deletion test/Sema/typo_correction.swift
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Expand Up @@ -119,7 +119,7 @@ protocol P { // expected-note {{'P' previously declared here}}
protocol P {} // expected-error {{invalid redeclaration of 'P'}}

func hasTypo() {
_ = P.a.a // expected-error {{value of type 'Generic' has no member 'a'}}
_ = P.a.a // expected-error {{type 'Generic' has no member 'a'}}
}

// Typo correction with AnyObject.
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16 changes: 16 additions & 0 deletions test/decl/typealias/protocol.swift
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Expand Up @@ -299,3 +299,19 @@ struct SomeConformingType : UnboundGenericAliasProto {
protocol UnboundGenericAliasProto {
typealias G = X
}

// If pre-checking cannot resolve a member type due to ambiguity,
// we go down the usual member access path. Make sure its correct
// for protocol typealiases.
protocol Amb1 {
typealias T = Int
}

protocol Amb2 {
typealias T = String
}

typealias Amb = Amb1 & Amb2

let _: Int.Type = Amb.T.self
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@AnthonyLatsis Note that this case should always be accepted -- I'm disambiguating the return type of the member access. However, I'm surprised that without the type constraint, Amb.T just picks a random result from the overload set. Maybe @xedin has ideas.

let _: String.Type = Amb.T.self