Sema: Fix a fuzzer crash

This test case crashes when prepared overloads are disabled, but passes
when enabled. To avoid messing up tests if we have to turn the flag on
and off, fix the crash.

Author: slavapestov

lib/Sema/ConstraintSystem.cpp

@@ -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 =
@@ -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?
+    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)
@@ -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();

validation-test/compiler_crashers/Solution-getFixedType-98b9c4.swift renamed to validation-test/compiler_crashers_fixed/Solution-getFixedType-98b9c4.swift

@@ -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 {