Revert "[CS] Don't crash when default argument is magic literal and types don't match"

lib/Sema/CSSimplify.cpp

@@ -973,36 +973,9 @@ ConstraintSystem::TypeMatchResult constraints::matchCallArguments(
 
   for (unsigned paramIdx = 0, numParams = parameterBindings.size();
        paramIdx != numParams; ++paramIdx){
-    // If a parameter is unfulfilled, validate the default argument if it is a
-    // magic literal expression.
-    if (parameterBindings[paramIdx].empty()) {
-      if (!callee)
-        continue;
-
-      if (!callee->hasParameterList())
-        continue;
-
-      auto param = getParameterAt(callee, paramIdx);
-
-      auto defaultValueExpr = param->getDefaultValue();
-
-      if (!(defaultValueExpr &&
-            isa<MagicIdentifierLiteralExpr>(defaultValueExpr)))
-        continue;
-
-      if (defaultValueExpr->getType())
-        continue;
-
-      cs.generateConstraints(defaultValueExpr, param->getDeclContext());
-
-      auto defaultTy = cs.getType(defaultValueExpr);
-      auto paramTy = param->getType();
-      cs.addConstraint(
-          ConstraintKind::ArgumentConversion, defaultTy, paramTy,
-          locator.withPathElement(ConstraintLocator::DefaultArgument));
-
+    // Skip unfulfilled parameters. There's nothing to do for them.
+    if (parameterBindings[paramIdx].empty())
       continue;
-    }
 
     // Determine the parameter type.
     const auto &param = params[paramIdx];
@@ -2628,12 +2601,6 @@ bool ConstraintSystem::repairFailures(
     break;
   }
 
-  case ConstraintLocator::DefaultArgument: {
-    conversionsOrFixes.push_back(IgnoreDefaultArgumentTypeMismatch::create(
-        *this, lhs, rhs, getConstraintLocator(anchor, path)));
-    break;
-  }
-
   case ConstraintLocator::TypeParameterRequirement:
   case ConstraintLocator::ConditionalRequirement: {
     // If dependent members are present here it's because
@@ -7482,7 +7449,6 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyFixConstraint(
   case FixKind::SkipSameTypeRequirement:
   case FixKind::SkipSuperclassRequirement:
   case FixKind::AddMissingArguments:
-  case FixKind::DefaultArgumentTypeMismatch:
   case FixKind::SkipUnhandledConstructInFunctionBuilder:
   case FixKind::UsePropertyWrapper:
   case FixKind::UseWrappedValue: {