Reapply "[Clang][Sema] Diagnose class member access expressions naming non-existent members of the current instantiation prior to instantiation in the absence of dependent base classes (llvm#84050)" (llvm#90152)

Reapplies llvm#84050, addressing a bug which cases a crash when an
expression with the type of the current instantiation is used as the
_postfix-expression_ in a class member access expression (arrow form).

Author: sdkrystian

clang-tools-extra/clangd/unittests/FindTargetTests.cpp

@@ -854,7 +854,7 @@ TEST_F(TargetDeclTest, DependentExprs) {
           }
         };
       )cpp";
-  EXPECT_DECLS("CXXDependentScopeMemberExpr", "void foo()");
+  EXPECT_DECLS("MemberExpr", "void foo()");
 
   // Similar to above but base expression involves a function call.
   Code = R"cpp(
@@ -872,7 +872,7 @@ TEST_F(TargetDeclTest, DependentExprs) {
           }
         };
       )cpp";
-  EXPECT_DECLS("CXXDependentScopeMemberExpr", "void foo()");
+  EXPECT_DECLS("MemberExpr", "void foo()");
 
   // Similar to above but uses a function pointer.
   Code = R"cpp(
@@ -891,7 +891,7 @@ TEST_F(TargetDeclTest, DependentExprs) {
           }
         };
       )cpp";
-  EXPECT_DECLS("CXXDependentScopeMemberExpr", "void foo()");
+  EXPECT_DECLS("MemberExpr", "void foo()");
 
   // Base expression involves a member access into this.
   Code = R"cpp(
@@ -962,7 +962,7 @@ TEST_F(TargetDeclTest, DependentExprs) {
           void Foo() { this->[[find]](); }
         };
   )cpp";
-  EXPECT_DECLS("CXXDependentScopeMemberExpr", "void find()");
+  EXPECT_DECLS("MemberExpr", "void find()");
 }
 
 TEST_F(TargetDeclTest, DependentTypes) {

clang-tools-extra/clangd/unittests/SemanticHighlightingTests.cpp

@@ -621,7 +621,7 @@ sizeof...($TemplateParameter[[Elements]]);
       struct $Class_def[[Foo]] {
         int $Field_decl[[Waldo]];
         void $Method_def[[bar]]() {
-          $Class[[Foo]]().$Field_dependentName[[Waldo]];
+          $Class[[Foo]]().$Field[[Waldo]];
         }
         template $Bracket[[<]]typename $TemplateParameter_def[[U]]$Bracket[[>]]
         void $Method_def[[bar1]]() {

clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/owning-memory.cpp

@@ -309,6 +309,8 @@ struct HeapArray {                                          // Ok, since destruc
 
   HeapArray(HeapArray &&other) : _data(other._data), size(other.size) { // Ok
     other._data = nullptr;                                              // Ok
+    // CHECK-NOTES: [[@LINE-1]]:5: warning: expected assignment source to be of type 'gsl::owner<>'; got 'std::nullptr_t'
+    // FIXME: This warning is emitted because an ImplicitCastExpr for the NullToPointer conversion isn't created for dependent types.
     other.size = 0;
   }
 

clang-tools-extra/test/clang-tidy/checkers/modernize/use-equals-default-copy.cpp

@@ -260,6 +260,8 @@ template <class T>
 struct Template {
   Template() = default;
   Template(const Template &Other) : Field(Other.Field) {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use '= default'
+  // CHECK-FIXES: Template(const Template &Other)  = default;
   Template &operator=(const Template &Other);
   void foo(const T &t);
   int Field;
@@ -269,8 +271,12 @@ Template<T> &Template<T>::operator=(const Template<T> &Other) {
   Field = Other.Field;
   return *this;
 }
+// CHECK-MESSAGES: :[[@LINE-4]]:27: warning: use '= default'
+// CHECK-FIXES: Template<T> &Template<T>::operator=(const Template<T> &Other) = default;
+
 Template<int> T1;
 
+
 // Dependent types.
 template <class T>
 struct DT1 {
@@ -284,6 +290,9 @@ DT1<T> &DT1<T>::operator=(const DT1<T> &Other) {
   Field = Other.Field;
   return *this;
 }
+// CHECK-MESSAGES: :[[@LINE-4]]:17: warning: use '= default'
+// CHECK-FIXES: DT1<T> &DT1<T>::operator=(const DT1<T> &Other) = default;
+
 DT1<int> Dt1;
 
 template <class T>
@@ -303,6 +312,9 @@ DT2<T> &DT2<T>::operator=(const DT2<T> &Other) {
 struct T {
   typedef int TT;
 };
+// CHECK-MESSAGES: :[[@LINE-8]]:17: warning: use '= default'
+// CHECK-FIXES: DT2<T> &DT2<T>::operator=(const DT2<T> &Other) = default;
+
 DT2<T> Dt2;
 
 // Default arguments.

clang/docs/ReleaseNotes.rst

@@ -414,6 +414,18 @@ Improvements to Clang's diagnostics
 
 - Clang now diagnoses requires expressions with explicit object parameters.
 
+- Clang now looks up members of the current instantiation in the template definition context
+  if the current instantiation has no dependent base classes.
+
+  .. code-block:: c++
+
+     template<typename T>
+     struct A {
+       int f() {
+         return this->x; // error: no member named 'x' in 'A<T>'
+       }
+     };
+
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/include/clang/Sema/Lookup.h

@@ -499,7 +499,9 @@ class LookupResult {
   /// Note that while no result was found in the current instantiation,
   /// there were dependent base classes that could not be searched.
   void setNotFoundInCurrentInstantiation() {
-    assert(ResultKind == NotFound && Decls.empty());
+    assert((ResultKind == NotFound ||
+            ResultKind == NotFoundInCurrentInstantiation) &&
+           Decls.empty());
     ResultKind = NotFoundInCurrentInstantiation;
   }
 

clang/include/clang/Sema/Sema.h

@@ -6978,12 +6978,6 @@ class Sema final : public SemaBase {
                                    SourceLocation TemplateKWLoc,
                                    UnqualifiedId &Member, Decl *ObjCImpDecl);
 
-  MemberExpr *BuildMemberExpr(
-      Expr *Base, bool IsArrow, SourceLocation OpLoc, const CXXScopeSpec *SS,
-      SourceLocation TemplateKWLoc, ValueDecl *Member, DeclAccessPair FoundDecl,
-      bool HadMultipleCandidates, const DeclarationNameInfo &MemberNameInfo,
-      QualType Ty, ExprValueKind VK, ExprObjectKind OK,
-      const TemplateArgumentListInfo *TemplateArgs = nullptr);
   MemberExpr *
   BuildMemberExpr(Expr *Base, bool IsArrow, SourceLocation OpLoc,
                   NestedNameSpecifierLoc NNS, SourceLocation TemplateKWLoc,
@@ -7472,7 +7466,7 @@ class Sema final : public SemaBase {
   bool LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
                            CXXScopeSpec &SS);
   bool LookupParsedName(LookupResult &R, Scope *S, CXXScopeSpec *SS,
-                        bool AllowBuiltinCreation = false,
+                        QualType ObjectType, bool AllowBuiltinCreation = false,
                         bool EnteringContext = false);
   ObjCProtocolDecl *LookupProtocol(
       IdentifierInfo *II, SourceLocation IdLoc,
@@ -8881,11 +8875,13 @@ class Sema final : public SemaBase {
     /// functions (but no function templates).
     FoundFunctions,
   };
-  bool LookupTemplateName(
-      LookupResult &R, Scope *S, CXXScopeSpec &SS, QualType ObjectType,
-      bool EnteringContext, bool &MemberOfUnknownSpecialization,
-      RequiredTemplateKind RequiredTemplate = SourceLocation(),
-      AssumedTemplateKind *ATK = nullptr, bool AllowTypoCorrection = true);
+
+  bool
+  LookupTemplateName(LookupResult &R, Scope *S, CXXScopeSpec &SS,
+                     QualType ObjectType, bool EnteringContext,
+                     RequiredTemplateKind RequiredTemplate = SourceLocation(),
+                     AssumedTemplateKind *ATK = nullptr,
+                     bool AllowTypoCorrection = true);
 
   TemplateNameKind isTemplateName(Scope *S, CXXScopeSpec &SS,
                                   bool hasTemplateKeyword,

clang/lib/AST/Expr.cpp

@@ -103,7 +103,7 @@ const Expr *Expr::skipRValueSubobjectAdjustments(
       }
     } else if (const auto *ME = dyn_cast<MemberExpr>(E)) {
       if (!ME->isArrow()) {
-        assert(ME->getBase()->getType()->isRecordType());
+        assert(ME->getBase()->getType()->getAsRecordDecl());
         if (const auto *Field = dyn_cast<FieldDecl>(ME->getMemberDecl())) {
           if (!Field->isBitField() && !Field->getType()->isReferenceType()) {
             E = ME->getBase();

clang/lib/Parse/ParseDecl.cpp

@@ -3026,7 +3026,7 @@ bool Parser::ParseImplicitInt(DeclSpec &DS, CXXScopeSpec *SS,
         << TokenName << TagName << getLangOpts().CPlusPlus
         << FixItHint::CreateInsertion(Tok.getLocation(), FixitTagName);
 
-      if (Actions.LookupParsedName(R, getCurScope(), SS)) {
+      if (Actions.LookupName(R, getCurScope())) {
         for (LookupResult::iterator I = R.begin(), IEnd = R.end();
              I != IEnd; ++I)
           Diag((*I)->getLocation(), diag::note_decl_hiding_tag_type)

clang/lib/Sema/HLSLExternalSemaSource.cpp

@@ -126,12 +126,15 @@ struct BuiltinTypeDeclBuilder {
 
   static DeclRefExpr *lookupBuiltinFunction(ASTContext &AST, Sema &S,
                                             StringRef Name) {
-    CXXScopeSpec SS;
     IdentifierInfo &II = AST.Idents.get(Name, tok::TokenKind::identifier);
     DeclarationNameInfo NameInfo =
         DeclarationNameInfo(DeclarationName(&II), SourceLocation());
     LookupResult R(S, NameInfo, Sema::LookupOrdinaryName);
-    S.LookupParsedName(R, S.getCurScope(), &SS, false);
+    // AllowBuiltinCreation is false but LookupDirect will create
+    // the builtin when searching the global scope anyways...
+    S.LookupName(R, S.getCurScope());
+    // FIXME: If the builtin function was user-declared in global scope,
+    // this assert *will* fail. Should this call LookupBuiltin instead?
     assert(R.isSingleResult() &&
            "Since this is a builtin it should always resolve!");
     auto *VD = cast<ValueDecl>(R.getFoundDecl());