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Sema: Remove requirement/witness ranking #11244

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Jul 28, 2017
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Sema: Remove requirement/witness ranking #11244

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63 changes: 0 additions & 63 deletions lib/Sema/CSRanking.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -155,57 +155,6 @@ static bool sameOverloadChoice(const OverloadChoice &x,
llvm_unreachable("Unhandled OverloadChoiceKind in switch.");
}

/// Compare two declarations to determine whether one is a witness of the other.
static Comparison compareWitnessAndRequirement(TypeChecker &tc, DeclContext *dc,
ValueDecl *decl1,
ValueDecl *decl2) {
// We only have a witness/requirement pair if exactly one of the declarations
// comes from a protocol.
auto proto1 = dyn_cast<ProtocolDecl>(decl1->getDeclContext());
auto proto2 = dyn_cast<ProtocolDecl>(decl2->getDeclContext());
if ((bool)proto1 == (bool)proto2)
return Comparison::Unordered;

// Figure out the protocol, requirement, and potential witness.
ProtocolDecl *proto;
ValueDecl *req;
ValueDecl *potentialWitness;
if (proto1) {
proto = proto1;
req = decl1;
potentialWitness = decl2;
} else {
proto = proto2;
req = decl2;
potentialWitness = decl1;
}

// Cannot compare type declarations this way.
// FIXME: Use the same type-substitution approach as lookupMemberType.
if (isa<TypeDecl>(req))
return Comparison::Unordered;

if (!potentialWitness->getDeclContext()->isTypeContext())
return Comparison::Unordered;

// Determine whether the type of the witness's context conforms to the
// protocol.
auto owningType
= potentialWitness->getDeclContext()->getDeclaredInterfaceType();
auto conformance = tc.conformsToProtocol(owningType, proto, dc,
ConformanceCheckFlags::InExpression);
if (!conformance || conformance->isAbstract())
return Comparison::Unordered;

// If the witness and the potential witness are not the same, there's no
// ordering here.
if (conformance->getConcrete()->getWitnessDecl(req, &tc) != potentialWitness)
return Comparison::Unordered;

// We have a requirement/witness match.
return proto1? Comparison::Worse : Comparison::Better;
}

namespace {
/// Describes the relationship between the context types for two declarations.
enum class SelfTypeRelationship {
Expand Down Expand Up @@ -504,18 +453,6 @@ static bool isDeclAsSpecializedAs(TypeChecker &tc, DeclContext *dc,
return subscript2->isGeneric();
}

// A witness is always more specialized than the requirement it satisfies.
switch (compareWitnessAndRequirement(tc, dc, decl1, decl2)) {
case Comparison::Unordered:
break;

case Comparison::Better:
return true;

case Comparison::Worse:
return false;
}

// Members of protocol extensions have special overloading rules.
ProtocolDecl *inProtocolExtension1 = outerDC1
->getAsProtocolExtensionContext();
Expand Down