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Implement SE-0195, which introduces "Dynamic Member Lookup" Types (#14546)

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* Implement the recently accepted SE-0195 proposal, which introduces "Dynamic
Member Lookup" Types.  This is a dusted off and updated version of PR13361,
which switches from DynamicMemberLookupProtocol to @dynamicMemberLookup as
was requested by the final review decision.  This also rebases it,
updates it for other changes in the compiler, fixes a bunch of bugs, and adds support for keypaths.  

Thank you to @rudx and @DougGregor in particular for the helpful review comments and test cases!
This commit is contained in:
Chris Lattner
2018-02-16 16:19:50 -08:00
committed by GitHub
parent 3184dd8ad4
commit a0fa5d11b4
17 changed files with 845 additions and 71 deletions
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37
lib/Sema/ConstraintSystem.cpp
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@@ -1579,7 +1579,8 @@ void ConstraintSystem::resolveOverload(ConstraintLocator *locator,
case OverloadChoiceKind::DeclViaBridge:
case OverloadChoiceKind::DeclViaDynamic:
case OverloadChoiceKind::DeclViaUnwrappedOptional: {
case OverloadChoiceKind::DeclViaUnwrappedOptional:
case OverloadChoiceKind::DynamicMemberLookup: {
// Retrieve the type of a reference to the specific declaration choice.
if (auto baseTy = choice.getBaseType()) {
assert(!baseTy->hasTypeParameter());
@@ -1704,6 +1705,32 @@ void ConstraintSystem::resolveOverload(ConstraintLocator *locator,
increaseScore(SK_Unavailable);
}
if (kind == OverloadChoiceKind::DynamicMemberLookup) {
// DynamicMemberLookup results are always a (dynamicMember:T1)->T2
// subscript.
auto refFnType = refType->castTo<FunctionType>();
// If this is a dynamic member lookup, then the decl we have is for the
// subscript(dynamicMember:) member, but the type we need to return is the
// result of the subscript. Dig through it.
refType = refFnType->getResult();
// Before we drop the argument type on the floor, we need to constrain it
// to having a literal conformance to ExpressibleByStringLiteral. This
// makes the index default to String if otherwise unconstrained.
assert(refFnType->getParams().size() == 1 &&
"subscript always has one arg");
auto argType = refFnType->getParams()[0].getPlainType();
auto protoKind = KnownProtocolKind::ExpressibleByStringLiteral;
auto protocol = getTypeChecker().getProtocol(choice.getDecl()->getLoc(),
protoKind);
if (!protocol)
break;
addConstraint(ConstraintKind::LiteralConformsTo, argType,
protocol->getDeclaredType(),
locator);
}
break;
}
@@ -1755,6 +1782,7 @@ void ConstraintSystem::resolveOverload(ConstraintLocator *locator,
// Increase the score so that actual subscripts get preference.
increaseScore(SK_KeyPathSubscript);
break;
}
}
assert(!refType->hasTypeParameter() && "Cannot have a dependent type here");
@@ -1897,13 +1925,16 @@ DeclName OverloadChoice::getName() const {
case OverloadChoiceKind::DeclViaUnwrappedOptional:
return getDecl()->getFullName();
case OverloadChoiceKind::KeyPathApplication: {
case OverloadChoiceKind::KeyPathApplication:
// TODO: This should probably produce subscript(keyPath:), but we
// don't currently pre-filter subscript overload sets by argument
// keywords, so "subscript" is still the name that keypath subscripts
// are looked up by.
return DeclBaseName::createSubscript();
}
case OverloadChoiceKind::DynamicMemberLookup:
return DeclName(DynamicNameAndFRK.getPointer());
case OverloadChoiceKind::BaseType:
case OverloadChoiceKind::TupleIndex:
llvm_unreachable("no name!");