[Diagnostics] Extract invalid result type from overload choice

Instead of threading it through the constraint system all the way
to a diagnostic, let's extract it from overload choice instead.

Author: xedin

include/swift/Sema/CSFix.h

@@ -2314,23 +2314,19 @@ class AllowUnsupportedRuntimeCheckedCast final
 
 class AllowInvalidStaticMemberRefOnProtocolMetatype final
     : public ConstraintFix {
-  Type ResultType;
-
   AllowInvalidStaticMemberRefOnProtocolMetatype(ConstraintSystem &cs,
-                                                Type resultType,
                                                 ConstraintLocator *locator)
       : ConstraintFix(cs,
                       FixKind::AllowInvalidStaticMemberRefOnProtocolMetatype,
-                      locator),
-        ResultType(resultType) {}
+                      locator) {}
 
   public:
   std::string getName() const override {
     return "allow invalid static member reference on a protocol metatype";
   }
 
   static AllowInvalidStaticMemberRefOnProtocolMetatype *
-  create(ConstraintSystem &cs, Type resultType, ConstraintLocator *locator);
+  create(ConstraintSystem &cs, ConstraintLocator *locator);
 };
 
 } // end namespace constraints

lib/Sema/CSDiagnostics.cpp

@@ -7199,6 +7199,10 @@ bool InvalidMemberRefOnProtocolMetatype::diagnoseAsError() {
   if (!overload)
     return false;
 
+  auto resultTy = overload->openedType;
+  if (auto *fnType = resultTy->getAs<FunctionType>())
+    resultTy = fnType->getResult();
+
   auto *member = overload->choice.getDeclOrNull();
   assert(member);
 
@@ -7207,7 +7211,7 @@ bool InvalidMemberRefOnProtocolMetatype::diagnoseAsError() {
 
   emitDiagnostic(diag::type_does_not_conform_in_member_ref_on_protocol_type,
                  member->getDescriptiveKind(), member->getName(),
-                 MetatypeType::get(protocolTy), ResultType);
+                 MetatypeType::get(protocolTy), resultTy);
   emitDiagnosticAt(member, diag::decl_declared_here, member->getName());
   return true;
 }

lib/Sema/CSDiagnostics.h

@@ -2486,12 +2486,10 @@ class UnsupportedRuntimeCheckedCastFailure final
 /// `bar` can't be referenced from `P.Protocol` base because its result type
 /// `Int` doesn't conform to `Foo`.
 class InvalidMemberRefOnProtocolMetatype final : public FailureDiagnostic {
-  Type ResultType;
-
 public:
-  InvalidMemberRefOnProtocolMetatype(const Solution &solution, Type resultType,
+  InvalidMemberRefOnProtocolMetatype(const Solution &solution,
                                      ConstraintLocator *locator)
-      : FailureDiagnostic(solution, locator), ResultType(resultType) {}
+      : FailureDiagnostic(solution, locator) {}
 
   bool diagnoseAsError() override;
 };

lib/Sema/CSFix.cpp

@@ -1941,14 +1941,13 @@ bool AllowUnsupportedRuntimeCheckedCast::diagnose(const Solution &solution,
 
 bool AllowInvalidStaticMemberRefOnProtocolMetatype::diagnose(
     const Solution &solution, bool asNote) const {
-  InvalidMemberRefOnProtocolMetatype failure(solution, ResultType,
-                                             getLocator());
+  InvalidMemberRefOnProtocolMetatype failure(solution, getLocator());
   return failure.diagnose(asNote);
 }
 
 AllowInvalidStaticMemberRefOnProtocolMetatype *
 AllowInvalidStaticMemberRefOnProtocolMetatype::create(
-    ConstraintSystem &cs, Type resultType, ConstraintLocator *locator) {
+    ConstraintSystem &cs, ConstraintLocator *locator) {
   return new (cs.getAllocator())
-      AllowInvalidStaticMemberRefOnProtocolMetatype(cs, resultType, locator);
+      AllowInvalidStaticMemberRefOnProtocolMetatype(cs, locator);
 }