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Sema: Fix a fuzzer crash #85016

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Merged
merged 1 commit into from
Oct 25, 2025
+42 −14
Merged

Sema: Fix a fuzzer crash #85016

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54 changes: 41 additions & 13 deletions lib/Sema/ConstraintSystem.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2859,34 +2859,50 @@ static bool diagnoseContextualFunctionCallGenericAmbiguity(
return false;

auto contextualFix = contextualFixes.front();
if (!std::all_of(contextualFixes.begin() + 1, contextualFixes.end(),
[&contextualFix](FixInContext fix) {
return fix.second->getLocator() ==
contextualFix.second->getLocator();
}))
return false;

auto fixLocator = contextualFix.second->getLocator();

auto contextualAnchor = fixLocator->getAnchor();
auto *AE = getAsExpr<ApplyExpr>(contextualAnchor);
// All contextual failures anchored on the same function call.
if (!AE)
return false;

auto fnLocator = cs.getConstraintLocator(AE->getSemanticFn());
auto overload = contextualFix.first->getOverloadChoiceIfAvailable(fnLocator);
if (!overload)
return false;

auto applyFnType = overload->adjustedOpenedType->castTo<FunctionType>();
auto resultTypeVar = applyFnType->getResult()->getAs<TypeVariableType>();
auto getResultTypeVar = [&](FixInContext contextualFix) -> TypeVariableType * {
auto overload = contextualFix.first->getOverloadChoiceIfAvailable(fnLocator);
if (!overload)
return nullptr;

auto applyFnType = overload->adjustedOpenedType->castTo<FunctionType>();
return applyFnType->getResult()->getAs<TypeVariableType>();
};

auto resultTypeVar = getResultTypeVar(contextualFix);
if (!resultTypeVar)
return false;

auto *GP = resultTypeVar->getImpl().getGenericParameter();
if (!GP)
return false;

if (!std::all_of(contextualFixes.begin() + 1, contextualFixes.end(),
[&](FixInContext fix) {
if (fix.second->getLocator() != fixLocator)
return false;

auto resultTypeVar = getResultTypeVar(fix);

if (!resultTypeVar)
return false;

if (resultTypeVar->getImpl().getGenericParameter() != GP)
return false;

return true;
}))
return false;

auto applyLoc =
cs.getConstraintLocator(AE, {LocatorPathElt::ApplyArgument()});
auto argMatching =
Expand All @@ -2903,6 +2919,11 @@ static bool diagnoseContextualFunctionCallGenericAmbiguity(
continue;

auto argParamMatch = argMatching->second.parameterBindings[i];

// FIXME: We're just looking at the first solution's overload here,
// is that correct?
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This is fine for now, the whole method expects the first overload with an issue to be generic which is not really correct but we can refactor that separately.

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Eh, I now understand what is going on here - the expectation is that the overload is the same across solutions and only generic parameter bindings are different…

auto overload = contextualFix.first->getOverloadChoiceIfAvailable(fnLocator);
auto applyFnType = overload->adjustedOpenedType->castTo<FunctionType>();
auto param = applyFnType->getParams()[argParamMatch.front()];
auto paramFnType = param.getPlainType()->getAs<FunctionType>();
if (!paramFnType)
Expand All @@ -2922,8 +2943,15 @@ static bool diagnoseContextualFunctionCallGenericAmbiguity(
// from all the closure contextual fix/solutions and if there are more than
// one fixed type diagnose it.
swift::SmallSetVector<Type, 4> genericParamInferredTypes;
for (auto &fix : contextualFixes)
for (auto &fix : contextualFixes) {
auto resultTypeVar = getResultTypeVar(fix);
genericParamInferredTypes.insert(fix.first->getFixedType(resultTypeVar));
}

for (auto &fix : allFixes) {
auto resultTypeVar = getResultTypeVar(fix);
genericParamInferredTypes.insert(fix.first->getFixedType(resultTypeVar));
}

if (llvm::all_of(allFixes, [&](FixInContext fix) {
auto fixLocator = fix.second->getLocator();
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2 changes: 1 addition & 1 deletion ...ashers/Solution-getFixedType-98b9c4.swift → ..._fixed/Solution-getFixedType-98b9c4.swift
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
// {"kind":"typecheck","signature":"swift::constraints::Solution::getFixedType(swift::TypeVariableType*) const","signatureAssert":"Assertion failed: (knownBinding != typeBindings.end()), function getFixedType"}
// RUN: not --crash %target-swift-frontend -typecheck %s
// RUN: not %target-swift-frontend -typecheck %s
class a {
static
b {
Expand Down