[CS] Clean up dynamic member overload choice checking

Add `OverloadChoice::isAnyDynamicMemberLookup`,
and use it to clean up a couple of places.

Author: hamishknight

include/swift/Sema/OverloadChoice.h

@@ -274,6 +274,12 @@ class OverloadChoice {
     return BaseAndDeclKind.getInt() == IsFallbackDeclViaUnwrappedOptional;
   }
 
+  /// Whether this choice is for any kind of dynamic member lookup.
+  bool isAnyDynamicMemberLookup() const {
+    return getKind() == OverloadChoiceKind::DynamicMemberLookup ||
+           isKeyPathDynamicMemberLookup();
+  }
+
   /// Get the name of the overload choice.
   DeclName getName() const;
 

lib/Sema/CSApply.cpp

@@ -3314,10 +3314,7 @@ namespace {
     }
 
     Type getTypeOfDynamicMemberIndex(const SelectedOverload &overload) {
-      assert(overload.choice.getKind() ==
-                 OverloadChoiceKind::DynamicMemberLookup ||
-             overload.choice.getKind() ==
-                 OverloadChoiceKind::KeyPathDynamicMemberLookup);
+      assert(overload.choice.isAnyDynamicMemberLookup());
 
       auto declTy = solution.simplifyType(overload.openedFullType);
       auto subscriptTy = declTy->castTo<FunctionType>()->getResult();
@@ -3438,8 +3435,7 @@ namespace {
         return nullptr;
       }
 
-      if (overload->choice.getKind() ==
-              OverloadChoiceKind::KeyPathDynamicMemberLookup) {
+      if (overload->choice.isKeyPathDynamicMemberLookup()) {
         return buildDynamicMemberLookupRef(
             expr, expr->getBase(), expr->getArgs()->getStartLoc(), SourceLoc(),
             *overload, memberLocator);
@@ -4803,11 +4799,7 @@ namespace {
             continue;
           }
 
-          isDynamicMember =
-              foundDecl->choice.getKind() ==
-                  OverloadChoiceKind::DynamicMemberLookup ||
-              foundDecl->choice.getKind() ==
-                  OverloadChoiceKind::KeyPathDynamicMemberLookup;
+          isDynamicMember = foundDecl->choice.isAnyDynamicMemberLookup();
 
           // If this was a @dynamicMemberLookup property, then we actually
           // form a subscript reference, so switch the kind.
@@ -5087,17 +5079,10 @@ namespace {
       // through the subscript(dynamicMember:) member, restore the
       // openedType and origComponent to its full reference as if the user
       // wrote out the subscript manually.
-      bool forDynamicLookup =
-          overload.choice.getKind() ==
-              OverloadChoiceKind::DynamicMemberLookup ||
-          overload.choice.getKind() ==
-              OverloadChoiceKind::KeyPathDynamicMemberLookup;
-
-      if (forDynamicLookup) {
+      if (overload.choice.isAnyDynamicMemberLookup()) {
         auto indexType = getTypeOfDynamicMemberIndex(overload);
         Expr *argExpr = nullptr;
-        if (overload.choice.getKind() ==
-            OverloadChoiceKind::KeyPathDynamicMemberLookup) {
+        if (overload.choice.isKeyPathDynamicMemberLookup()) {
           argExpr = buildKeyPathDynamicMemberArgExpr(
               indexType->castTo<BoundGenericType>(), componentLoc, memberLoc);
         } else {

lib/Sema/CSDiagnostics.cpp

@@ -1619,8 +1619,7 @@ bool RValueTreatedAsLValueFailure::diagnoseAsError() {
           OverloadChoiceKind::DynamicMemberLookup)
         subElementDiagID = diag::assignment_dynamic_property_has_immutable_base;
 
-      if (resolvedOverload->choice.getKind() ==
-          OverloadChoiceKind::KeyPathDynamicMemberLookup) {
+      if (resolvedOverload->choice.isKeyPathDynamicMemberLookup()) {
         if (!getType(member->getBase(), /*wantRValue=*/false)->hasLValueType())
           subElementDiagID =
               diag::assignment_dynamic_property_has_immutable_base;

lib/Sema/CSSolver.cpp

@@ -1605,8 +1605,7 @@ ConstraintSystem::filterDisjunction(
     // be attempted in-place because that would also try to operate on that
     // constraint, so instead let's keep the disjunction, but disable all
     // unviable choices.
-    if (choice->getOverloadChoice().getKind() ==
-        OverloadChoiceKind::KeyPathDynamicMemberLookup) {
+    if (choice->getOverloadChoice().isKeyPathDynamicMemberLookup()) {
       // Early simplification of the "keypath dynamic member lookup" choice
       // is impossible because it requires constraints associated with
       // subscript index expression to be present.