[Clang] Fix member lookup so that we don't ignore ambiguous lookups in some cases

There are some cases during member lookup we are aggressively suppressing
diagnostics when we should just be suppressing access control diagnostic.

In this PR I add the ability to simply suppress access diagnostics while not
suppressing ambiguous lookup diagnostics.

Fixes: llvm#22413
llvm#29942
llvm#35574
llvm#27224

Differential Revision: https://reviews.llvm.org/D155387

Author: shafik

clang/docs/ReleaseNotes.rst

@@ -121,6 +121,12 @@ Bug Fixes to C++ Support
   a Unicode character whose name contains a ``-``.
   (`Fixes #64161 <https://github.com/llvm/llvm-project/issues/64161>_`)
 
+- Fix cases where we ignore ambiguous name lookup when looking up memebers.
+  (`#22413 <https://github.com/llvm/llvm-project/issues/22413>_`),
+  (`#29942 <https://github.com/llvm/llvm-project/issues/29942>_`),
+  (`#35574 <https://github.com/llvm/llvm-project/issues/35574>_`) and
+  (`#27224 <https://github.com/llvm/llvm-project/issues/27224>_`).
+
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 

clang/include/clang/Sema/Lookup.h

@@ -148,20 +148,22 @@ class LookupResult {
       : SemaPtr(&SemaRef), NameInfo(NameInfo), LookupKind(LookupKind),
         Redecl(Redecl != Sema::NotForRedeclaration),
         ExternalRedecl(Redecl == Sema::ForExternalRedeclaration),
-        Diagnose(Redecl == Sema::NotForRedeclaration) {
+        DiagnoseAccess(Redecl == Sema::NotForRedeclaration),
+        DiagnoseAmbiguous(Redecl == Sema::NotForRedeclaration) {
     configure();
   }
 
   // TODO: consider whether this constructor should be restricted to take
   // as input a const IdentifierInfo* (instead of Name),
   // forcing other cases towards the constructor taking a DNInfo.
-  LookupResult(Sema &SemaRef, DeclarationName Name,
-               SourceLocation NameLoc, Sema::LookupNameKind LookupKind,
+  LookupResult(Sema &SemaRef, DeclarationName Name, SourceLocation NameLoc,
+               Sema::LookupNameKind LookupKind,
                Sema::RedeclarationKind Redecl = Sema::NotForRedeclaration)
       : SemaPtr(&SemaRef), NameInfo(Name, NameLoc), LookupKind(LookupKind),
         Redecl(Redecl != Sema::NotForRedeclaration),
         ExternalRedecl(Redecl == Sema::ForExternalRedeclaration),
-        Diagnose(Redecl == Sema::NotForRedeclaration) {
+        DiagnoseAccess(Redecl == Sema::NotForRedeclaration),
+        DiagnoseAmbiguous(Redecl == Sema::NotForRedeclaration) {
     configure();
   }
 
@@ -192,12 +194,14 @@ class LookupResult {
         Redecl(std::move(Other.Redecl)),
         ExternalRedecl(std::move(Other.ExternalRedecl)),
         HideTags(std::move(Other.HideTags)),
-        Diagnose(std::move(Other.Diagnose)),
+        DiagnoseAccess(std::move(Other.DiagnoseAccess)),
+        DiagnoseAmbiguous(std::move(Other.DiagnoseAmbiguous)),
         AllowHidden(std::move(Other.AllowHidden)),
         Shadowed(std::move(Other.Shadowed)),
         TemplateNameLookup(std::move(Other.TemplateNameLookup)) {
     Other.Paths = nullptr;
-    Other.Diagnose = false;
+    Other.DiagnoseAccess = false;
+    Other.DiagnoseAmbiguous = false;
   }
 
   LookupResult &operator=(LookupResult &&Other) {
@@ -215,17 +219,22 @@ class LookupResult {
     Redecl = std::move(Other.Redecl);
     ExternalRedecl = std::move(Other.ExternalRedecl);
     HideTags = std::move(Other.HideTags);
-    Diagnose = std::move(Other.Diagnose);
+    DiagnoseAccess = std::move(Other.DiagnoseAccess);
+    DiagnoseAmbiguous = std::move(Other.DiagnoseAmbiguous);
     AllowHidden = std::move(Other.AllowHidden);
     Shadowed = std::move(Other.Shadowed);
     TemplateNameLookup = std::move(Other.TemplateNameLookup);
     Other.Paths = nullptr;
-    Other.Diagnose = false;
+    Other.DiagnoseAccess = false;
+    Other.DiagnoseAmbiguous = false;
     return *this;
   }
 
   ~LookupResult() {
-    if (Diagnose) diagnose();
+    if (DiagnoseAccess)
+      diagnoseAccess();
+    if (DiagnoseAmbiguous)
+      diagnoseAmbiguous();
     if (Paths) deletePaths(Paths);
   }
 
@@ -607,13 +616,20 @@ class LookupResult {
   /// Suppress the diagnostics that would normally fire because of this
   /// lookup.  This happens during (e.g.) redeclaration lookups.
   void suppressDiagnostics() {
-    Diagnose = false;
+    DiagnoseAccess = false;
+    DiagnoseAmbiguous = false;
   }
 
-  /// Determines whether this lookup is suppressing diagnostics.
-  bool isSuppressingDiagnostics() const {
-    return !Diagnose;
-  }
+  /// Suppress the diagnostics that would normally fire because of this
+  /// lookup due to access control violations.
+  void suppressAccessDiagnostics() { DiagnoseAccess = false; }
+
+  /// Determines whether this lookup is suppressing access control diagnostics.
+  bool isSuppressingAccessDiagnostics() const { return !DiagnoseAccess; }
+
+  /// Determines whether this lookup is suppressing ambiguous lookup
+  /// diagnostics.
+  bool isSuppressingAmbiguousDiagnostics() const { return !DiagnoseAmbiguous; }
 
   /// Sets a 'context' source range.
   void setContextRange(SourceRange SR) {
@@ -726,11 +742,14 @@ class LookupResult {
   }
 
 private:
-  void diagnose() {
+  void diagnoseAccess() {
+    if (isClassLookup() && getSema().getLangOpts().AccessControl)
+      getSema().CheckLookupAccess(*this);
+  }
+
+  void diagnoseAmbiguous() {
     if (isAmbiguous())
       getSema().DiagnoseAmbiguousLookup(*this);
-    else if (isClassLookup() && getSema().getLangOpts().AccessControl)
-      getSema().CheckLookupAccess(*this);
   }
 
   void setAmbiguous(AmbiguityKind AK) {
@@ -776,7 +795,8 @@ class LookupResult {
   ///   are present
   bool HideTags = true;
 
-  bool Diagnose = false;
+  bool DiagnoseAccess = false;
+  bool DiagnoseAmbiguous = false;
 
   /// True if we should allow hidden declarations to be 'visible'.
   bool AllowHidden = false;

clang/lib/Sema/SemaOverload.cpp

@@ -950,7 +950,7 @@ static bool shouldAddReversedEqEq(Sema &S, SourceLocation OpLoc,
     LookupResult Members(S, NotEqOp, OpLoc,
                          Sema::LookupNameKind::LookupMemberName);
     S.LookupQualifiedName(Members, RHSRec->getDecl());
-    Members.suppressDiagnostics();
+    Members.suppressAccessDiagnostics();
     for (NamedDecl *Op : Members)
       if (FunctionsCorrespond(S.Context, EqFD, Op->getAsFunction()))
         return false;
@@ -961,7 +961,7 @@ static bool shouldAddReversedEqEq(Sema &S, SourceLocation OpLoc,
                           Sema::LookupNameKind::LookupOperatorName);
   S.LookupName(NonMembers,
                S.getScopeForContext(EqFD->getEnclosingNamespaceContext()));
-  NonMembers.suppressDiagnostics();
+  NonMembers.suppressAccessDiagnostics();
   for (NamedDecl *Op : NonMembers) {
     auto *FD = Op->getAsFunction();
     if(auto* UD = dyn_cast<UsingShadowDecl>(Op))
@@ -7987,7 +7987,7 @@ void Sema::AddMemberOperatorCandidates(OverloadedOperatorKind Op,
 
     LookupResult Operators(*this, OpName, OpLoc, LookupOrdinaryName);
     LookupQualifiedName(Operators, T1Rec->getDecl());
-    Operators.suppressDiagnostics();
+    Operators.suppressAccessDiagnostics();
 
     for (LookupResult::iterator Oper = Operators.begin(),
                                 OperEnd = Operators.end();
@@ -14983,7 +14983,7 @@ Sema::BuildCallToObjectOfClassType(Scope *S, Expr *Obj,
   const auto *Record = Object.get()->getType()->castAs<RecordType>();
   LookupResult R(*this, OpName, LParenLoc, LookupOrdinaryName);
   LookupQualifiedName(R, Record->getDecl());
-  R.suppressDiagnostics();
+  R.suppressAccessDiagnostics();
 
   for (LookupResult::iterator Oper = R.begin(), OperEnd = R.end();
        Oper != OperEnd; ++Oper) {
@@ -15080,12 +15080,13 @@ Sema::BuildCallToObjectOfClassType(Scope *S, Expr *Obj,
     break;
   }
   case OR_Ambiguous:
-    CandidateSet.NoteCandidates(
-        PartialDiagnosticAt(Object.get()->getBeginLoc(),
-                            PDiag(diag::err_ovl_ambiguous_object_call)
-                                << Object.get()->getType()
-                                << Object.get()->getSourceRange()),
-        *this, OCD_AmbiguousCandidates, Args);
+    if (!R.isAmbiguous())
+      CandidateSet.NoteCandidates(
+          PartialDiagnosticAt(Object.get()->getBeginLoc(),
+                              PDiag(diag::err_ovl_ambiguous_object_call)
+                                  << Object.get()->getType()
+                                  << Object.get()->getSourceRange()),
+          *this, OCD_AmbiguousCandidates, Args);
     break;
 
   case OR_Deleted:
@@ -15248,7 +15249,7 @@ Sema::BuildOverloadedArrowExpr(Scope *S, Expr *Base, SourceLocation OpLoc,
 
   LookupResult R(*this, OpName, OpLoc, LookupOrdinaryName);
   LookupQualifiedName(R, Base->getType()->castAs<RecordType>()->getDecl());
-  R.suppressDiagnostics();
+  R.suppressAccessDiagnostics();
 
   for (LookupResult::iterator Oper = R.begin(), OperEnd = R.end();
        Oper != OperEnd; ++Oper) {
@@ -15289,11 +15290,12 @@ Sema::BuildOverloadedArrowExpr(Scope *S, Expr *Base, SourceLocation OpLoc,
     return ExprError();
   }
   case OR_Ambiguous:
-    CandidateSet.NoteCandidates(
-        PartialDiagnosticAt(OpLoc, PDiag(diag::err_ovl_ambiguous_oper_unary)
-                                       << "->" << Base->getType()
-                                       << Base->getSourceRange()),
-        *this, OCD_AmbiguousCandidates, Base);
+    if (!R.isAmbiguous())
+      CandidateSet.NoteCandidates(
+          PartialDiagnosticAt(OpLoc, PDiag(diag::err_ovl_ambiguous_oper_unary)
+                                         << "->" << Base->getType()
+                                         << Base->getSourceRange()),
+          *this, OCD_AmbiguousCandidates, Base);
     return ExprError();
 
   case OR_Deleted:

clang/lib/Sema/SemaTemplate.cpp

@@ -593,7 +593,7 @@ bool Sema::LookupTemplateName(LookupResult &Found,
       //     postfix-expression and does not name a class template, the name
       //     found in the class of the object expression is used, otherwise
       FoundOuter.clear();
-    } else if (!Found.isSuppressingDiagnostics()) {
+    } else if (!Found.isSuppressingAmbiguousDiagnostics()) {
       //   - if the name found is a class template, it must refer to the same
       //     entity as the one found in the class of the object expression,
       //     otherwise the program is ill-formed.

clang/test/CXX/class.derived/class.member.lookup/gh22413.cpp

@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+struct A {
+  void operator()(int); // expected-note {{member found by ambiguous name lookup}}
+  void f(int); // expected-note {{member found by ambiguous name lookup}}
+};
+struct B {
+  void operator()(); // expected-note {{member found by ambiguous name lookup}}
+  void f() {} // expected-note {{member found by ambiguous name lookup}}
+};
+
+struct C : A, B {};
+
+int f() {
+    C c;
+    c(); // expected-error {{member 'operator()' found in multiple base classes of different types}}
+    c.f(10); //expected-error {{member 'f' found in multiple base classes of different types}}
+    return 0;
+}

clang/test/CXX/class.derived/class.member.lookup/p11.cpp

@@ -0,0 +1,25 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+struct B1 {
+  void f();
+  static void f(int);
+  int i; // expected-note 2{{member found by ambiguous name lookup}}
+};
+struct B2 {
+  void f(double);
+};
+struct I1: B1 { };
+struct I2: B1 { };
+
+struct D: I1, I2, B2 {
+  using B1::f;
+  using B2::f;
+  void g() {
+    f(); // expected-error {{ambiguous conversion from derived class 'D' to base class 'B1'}}
+    f(0); // ok
+    f(0.0); // ok
+    // FIXME next line should be well-formed
+    int B1::* mpB1 = &D::i; // expected-error {{non-static member 'i' found in multiple base-class subobjects of type 'B1'}}
+    int D::* mpD = &D::i; // expected-error {{non-static member 'i' found in multiple base-class subobjects of type 'B1'}}
+  }
+};

clang/test/SemaCXX/arrow-operator.cpp

@@ -4,11 +4,13 @@ struct T {
 };
 
 struct A {
-  T* operator->(); // expected-note{{candidate function}}
+  T* operator->();
+                   // expected-note@-1 {{member found by ambiguous name lookup}}
 };
 
 struct B {
-  T* operator->(); // expected-note{{candidate function}}
+  T* operator->();
+                   // expected-note@-1 {{member found by ambiguous name lookup}}
 };
 
 struct C : A, B {
@@ -19,7 +21,8 @@ struct D : A { };
 struct E; // expected-note {{forward declaration of 'E'}}
 
 void f(C &c, D& d, E& e) {
-  c->f(); // expected-error{{use of overloaded operator '->' is ambiguous}}
+  c->f();
+          // expected-error@-1 {{member 'operator->' found in multiple base classes of different types}}
   d->f();
   e->f(); // expected-error{{incomplete definition of type}}
 }