[AST] Avoid repeated hash lookups (NFC) (#111327)

Here I'm splitting up the existing "if" statement into two.  Mixing
hasDefinition() and insert() in one "if" condition would be extremely
confusing as hasDefinition() doesn't change anything while insert()
does.

Author: kazutakahirata

clang/lib/AST/CXXInheritance.cpp

@@ -259,12 +259,10 @@ bool CXXBasePaths::lookupInBases(ASTContext &Context,
             BaseRecord = TD->getTemplatedDecl();
         }
         if (BaseRecord) {
-          if (!BaseRecord->hasDefinition() ||
-              VisitedDependentRecords.count(BaseRecord)) {
+          if (!BaseRecord->hasDefinition())
+            BaseRecord = nullptr;
+          else if (!VisitedDependentRecords.insert(BaseRecord).second)
             BaseRecord = nullptr;
-          } else {
-            VisitedDependentRecords.insert(BaseRecord);
-          }
         }
       } else {
         BaseRecord = cast<CXXRecordDecl>(