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[CSOptimizer] Decrease an operator argument score only if requires op… #83414

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Merged
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Aug 1, 2025
+14 −21
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[CSOptimizer] Decrease an operator argument score only if requires op… #83414

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35 changes: 14 additions & 21 deletions lib/Sema/CSOptimizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -970,8 +970,6 @@ static void determineBestChoicesInContext(

bool hasArgumentCandidates = false;
bool isOperator = isOperatorDisjunction(disjunction);
bool isNilCoalescingOperator =
isOperator && isOperatorNamed(disjunction, "??");

for (unsigned i = 0, n = argFuncType->getNumParams(); i != n; ++i) {
const auto &param = argFuncType->getParams()[i];
Expand Down Expand Up @@ -1341,17 +1339,26 @@ static void determineBestChoicesInContext(
paramType = paramType->lookThroughAllOptionalTypes(paramOptionals);

if (!candidateOptionals.empty() || !paramOptionals.empty()) {
auto requiresOptionalInjection = [&]() {
return paramOptionals.size() > candidateOptionals.size();
};

// Can match i.e. Int? to Int or T to Int?
if ((paramOptionals.empty() &&
paramType->is<GenericTypeParamType>()) ||
paramOptionals.size() >= candidateOptionals.size()) {
auto score = scoreCandidateMatch(genericSig, choice, candidateType,
paramType, options);
// Injection lowers the score slightly to comply with
// old behavior where exact matches on operator parameter
// types were always preferred.
return score > 0 && choice->isOperator() ? score.value() - 0.1
: score;

if (score > 0) {
// Injection lowers the score slightly to comply with
// old behavior where exact matches on operator parameter
// types were always preferred.
if (choice->isOperator() && requiresOptionalInjection())
return score.value() - 0.1;
}

return score;
}

// Optionality mismatch.
Expand Down Expand Up @@ -1605,20 +1612,6 @@ static void determineBestChoicesInContext(
double bestCandidateScore = 0;
llvm::BitVector mismatches(argumentCandidates[argIdx].size());

// `??` is overloaded on optionality of the second parameter,
// prevent ranking the argument candidates for this parameter
// if there are candidates that come from failable initializer
// overloads because non-optional candidates are always going
// to be better and that can skew the selection.
if (isNilCoalescingOperator && argIdx == 1) {
if (llvm::any_of(argumentCandidates[argIdx],
[](const auto &candidate) {
return candidate.fromInitializerCall &&
candidate.type->getOptionalObjectType();
}))
continue;
}

for (unsigned candidateIdx :
indices(argumentCandidates[argIdx])) {
// If one of the candidates matched exactly there is no reason
Expand Down