[CSSimplify] Increase generic argument mismatch score when matched against marker protocol

This indicates that the type doesn't have appropriate annotations
i.e. for concurrency or ownership.

(cherry picked from commit 6f967da)

Author: xedin

lib/Sema/CSSimplify.cpp

@@ -15326,14 +15326,21 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyFixConstraint(
   case FixKind::MacroMissingPound:
   case FixKind::AllowGlobalActorMismatch:
   case FixKind::AllowAssociatedValueMismatch:
-  case FixKind::GenericArgumentsMismatch:
   case FixKind::AllowConcreteTypeSpecialization:
   case FixKind::AllowFunctionSpecialization:
   case FixKind::IgnoreGenericSpecializationArityMismatch:
   case FixKind::IgnoreKeyPathSubscriptIndexMismatch:
   case FixKind::AllowMemberRefOnExistential: {
     return recordFix(fix) ? SolutionKind::Error : SolutionKind::Solved;
   }
+
+  case FixKind::GenericArgumentsMismatch: {
+    unsigned impact = 1;
+    if (type1->isMarkerExistential() || type2->isMarkerExistential())
+      ++impact;
+    return recordFix(fix, impact) ? SolutionKind::Error : SolutionKind::Solved;
+  }
+
   case FixKind::IgnoreThrownErrorMismatch: {
     return recordFix(fix, 2) ? SolutionKind::Error : SolutionKind::Solved;
   }