diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -1189,7 +1189,7 @@
     S.popCodeSynthesisContext();
   }
 };
-}
+} // namespace
 
 static bool checkTupleLikeDecomposition(Sema &S,
                                         ArrayRef<BindingDecl *> Bindings,
@@ -4213,7 +4213,7 @@
   CXXRecordDecl *ClassDecl;
 };
 
-}
+} // namespace
 
 ValueDecl *Sema::tryLookupCtorInitMemberDecl(CXXRecordDecl *ClassDecl,
                                              CXXScopeSpec &SS,
@@ -5055,7 +5055,7 @@
     return false;
   }
 };
-}
+} // namespace
 
 /// Determine whether the given type is an incomplete or zero-lenfgth
 /// array type.
@@ -5994,7 +5994,7 @@
   CheckAbstractUsage(*this, D).Visit(TL, Sel);
 }
 
-}
+} // namespace
 
 /// Check for invalid uses of an abstract type in a function declaration.
 static void CheckAbstractClassUsage(AbstractUsageInfo &Info,
@@ -7386,7 +7386,7 @@
     S.popCodeSynthesisContext();
   }
 };
-}
+} // namespace
 
 static Sema::ImplicitExceptionSpecification
 ComputeDefaultedSpecialMemberExceptionSpec(
@@ -8534,7 +8534,7 @@
                                SourceRange(Loc, Loc), SourceRange(Loc, Loc));
   }
 };
-}
+} // namespace
 
 /// Perform the unqualified lookups that might be needed to form a defaulted
 /// comparison function for the given operator.
@@ -9079,7 +9079,7 @@
     return false;
   }
 };
-}
+} // namespace
 
 namespace {
 struct SpecialMemberDeletionInfo
@@ -9119,7 +9119,7 @@
 
   bool isAccessible(Subobject Subobj, CXXMethodDecl *D);
 };
-}
+} // namespace
 
 /// Is the given special member inaccessible when used on the given
 /// sub-object.
@@ -11068,7 +11068,7 @@
   Sema::SemaDiagnosticBuilder Diagnostic;
   std::string Specifiers;
 };
-}
+} // namespace
 
 /// Check the validity of a declarator that we parsed for a deduction-guide.
 /// These aren't actually declarators in the grammar, so we need to check that
@@ -11169,7 +11169,7 @@
         // This could still instantiate to the right type, unless we know it
         // names the wrong class template.
         auto *TD = SpecifiedName.getAsTemplateDecl();
-        MightInstantiateToSpecialization = !(TD && isa<ClassTemplateDecl>(TD) &&
+        MightInstantiateToSpecialization = !(isa_and_nonnull<ClassTemplateDecl>(TD) &&
                                              !TemplateMatches);
       }
     } else if (!RetTy.hasQualifiers() && RetTy->isDependentType()) {
@@ -11714,7 +11714,7 @@
   }
 };
 
-}
+} // namespace
 
 static bool TryNamespaceTypoCorrection(Sema &S, LookupResult &R, Scope *Sc,
                                        CXXScopeSpec &SS,
@@ -12190,7 +12190,7 @@
     NonTemplateTarget = TargetTD->getTemplatedDecl();
 
   UsingShadowDecl *Shadow;
-  if (NonTemplateTarget && isa<CXXConstructorDecl>(NonTemplateTarget)) {
+  if (isa_and_nonnull<CXXConstructorDecl>(NonTemplateTarget)) {
     UsingDecl *Using = cast<UsingDecl>(BUD);
     bool IsVirtualBase =
         isVirtualDirectBase(cast<CXXRecordDecl>(CurContext),
@@ -13313,7 +13313,7 @@
   void visitSubobjectCall(Subobject Subobj,
                           Sema::SpecialMemberOverloadResult SMOR);
 };
-}
+} // namespace
 
 bool SpecialMemberExceptionSpecInfo::visitBase(CXXBaseSpecifier *Base) {
   auto *RT = Base->getType()->getAs<RecordType>();
@@ -13477,7 +13477,7 @@
     return WasAlreadyBeingDeclared;
   }
 };
-}
+} // namespace
 
 void Sema::CheckImplicitSpecialMemberDeclaration(Scope *S, FunctionDecl *FD) {
   // Look up any existing declarations, but don't trigger declaration of all
@@ -16821,7 +16821,7 @@
       std::string InnerCondDescription;
       std::tie(InnerCond, InnerCondDescription) =
         findFailedBooleanCondition(Converted.get());
-      if (InnerCond && isa<ConceptSpecializationExpr>(InnerCond)) {
+      if (isa_and_nonnull<ConceptSpecializationExpr>(InnerCond)) {
         // Drill down into concept specialization expressions to see why they
         // weren't satisfied.
         Diag(AssertExpr->getBeginLoc(), diag::err_static_assert_failed)
@@ -18275,7 +18275,7 @@
       return false;
     }
   };
-}
+} // namespace
 
 bool Sema::checkThisInStaticMemberFunctionType(CXXMethodDecl *Method) {
   TypeSourceInfo *TSInfo = Method->getTypeSourceInfo();