Revert "DR2064: decltype(E) is only a dependent type if E is type-dependent, not

if E is merely instantiation-dependent."

This change leaves us unable to distinguish between different function
templates that differ in only instantiation-dependent ways, for example

template<typename T> decltype(int(T())) f();
template<typename T> decltype(int(T(0))) f();

We'll need substantially better support for types that are
instantiation-dependent but not dependent before we can go ahead with
this change.

This reverts commit e3065ce238475ec202c707f4c58d90df171626ca.

diff --git a/clang/include/clang/AST/DependenceFlags.h b/clang/include/clang/AST/DependenceFlags.h
index 8c47047..ca96b65 100644 (file)
--- a/clang/include/clang/AST/DependenceFlags.h
+++ b/clang/include/clang/AST/DependenceFlags.h
@@ -255,12 +255,6 @@ inline TypeDependence toTypeDependence(TemplateNameDependence D) {
 inline TypeDependence toTypeDependence(TemplateArgumentDependence D) {
   return Dependence(D).type();
 }
-/// Compute the dependence of a type that depends on the type of an expression,
-/// given the dependence of that expression and of its type.
-inline TypeDependence typeToTypeDependence(ExprDependence ED, TypeDependence TD) {
-  return Dependence(ED & ~ExprDependence::Value).type() |
-         (TD & TypeDependence::VariablyModified);
-}
 
 inline NestedNameSpecifierDependence
 toNestedNameSpecifierDependendence(TypeDependence D) {

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index d396f81..c482235 100644 (file)
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -5383,10 +5383,10 @@ QualType ASTContext::getDecltypeType(Expr *e, QualType UnderlyingType) const {
   DecltypeType *dt;
 
   // C++11 [temp.type]p2:
-  //   If an expression e is type-dependent, decltype(e) denotes a unique
-  //   dependent type. Two such decltype-specifiers refer to the same type only
-  //   if their expressions are equivalent (14.5.6.1).
-  if (e->isTypeDependent()) {
+  //   If an expression e involves a template parameter, decltype(e) denotes a
+  //   unique dependent type. Two such decltype-specifiers refer to the same
+  //   type only if their expressions are equivalent (14.5.6.1).
+  if (e->isInstantiationDependent()) {
     llvm::FoldingSetNodeID ID;
     DependentDecltypeType::Profile(ID, *this, e);
 

diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index e7db8e2..27aa622 100644 (file)
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -2578,11 +2578,6 @@ void CXXNameMangler::mangleType(QualType T) {
         if (!TST->isTypeAlias())
           break;
 
-      // Don't desugar instantiation-dependent decltype / typeof types. We need
-      // to mangle the expression as written.
-      if (isa<DecltypeType, TypeOfType>(T))
-        break;
-
       // FIXME: We presumably shouldn't strip off ElaboratedTypes with
       // instantation-dependent qualifiers. See
       // https://github.com/itanium-cxx-abi/cxx-abi/issues/114.
@@ -5612,11 +5607,12 @@ static bool hasMangledSubstitutionQualifiers(QualType T) {
 
 bool CXXNameMangler::mangleSubstitution(QualType T) {
   if (!hasMangledSubstitutionQualifiers(T)) {
-    if (const RecordType *RT = dyn_cast<RecordType>(T))
+    if (const RecordType *RT = T->getAs<RecordType>())
       return mangleSubstitution(RT->getDecl());
   }
 
   uintptr_t TypePtr = reinterpret_cast<uintptr_t>(T.getAsOpaquePtr());
+
   return mangleSubstitution(TypePtr);
 }
 
@@ -5775,7 +5771,7 @@ bool CXXNameMangler::mangleStandardSubstitution(const NamedDecl *ND) {
 
 void CXXNameMangler::addSubstitution(QualType T) {
   if (!hasMangledSubstitutionQualifiers(T)) {
-    if (const RecordType *RT = dyn_cast<RecordType>(T)) {
+    if (const RecordType *RT = T->getAs<RecordType>()) {
       addSubstitution(RT->getDecl());
       return;
     }

diff --git a/clang/lib/AST/Type.cpp b/clang/lib/AST/Type.cpp
index 5dec80b..034e175 100644 (file)
--- a/clang/lib/AST/Type.cpp
+++ b/clang/lib/AST/Type.cpp
@@ -125,7 +125,8 @@ ArrayType::ArrayType(TypeClass tc, QualType et, QualType can,
     //   template<int ...N> int arr[] = {N...};
     : Type(tc, can,
            et->getDependence() |
-               (sz ? toTypeDependence(sz->getDependence())
+               (sz ? toTypeDependence(
+                         turnValueToTypeDependence(sz->getDependence()))
                    : TypeDependence::None) |
                (tc == VariableArray ? TypeDependence::VariablyModified
                                     : TypeDependence::None) |
@@ -3395,8 +3396,9 @@ QualType MacroQualifiedType::getModifiedType() const {
 
 TypeOfExprType::TypeOfExprType(Expr *E, QualType can)
     : Type(TypeOfExpr, can,
-           typeToTypeDependence(E->getDependence(),
-                                E->getType()->getDependence())),
+           toTypeDependence(E->getDependence()) |
+               (E->getType()->getDependence() &
+                TypeDependence::VariablyModified)),
       TOExpr(E) {}
 
 bool TypeOfExprType::isSugared() const {
@@ -3416,12 +3418,18 @@ void DependentTypeOfExprType::Profile(llvm::FoldingSetNodeID &ID,
 }
 
 DecltypeType::DecltypeType(Expr *E, QualType underlyingType, QualType can)
+    // C++11 [temp.type]p2: "If an expression e involves a template parameter,
+    // decltype(e) denotes a unique dependent type." Hence a decltype type is
+    // type-dependent even if its expression is only instantiation-dependent.
     : Type(Decltype, can,
-           typeToTypeDependence(E->getDependence(),
-                                E->getType()->getDependence())),
+           toTypeDependence(E->getDependence()) |
+               (E->isInstantiationDependent() ? TypeDependence::Dependent
+                                              : TypeDependence::None) |
+               (E->getType()->getDependence() &
+                TypeDependence::VariablyModified)),
       E(E), UnderlyingType(underlyingType) {}
 
-bool DecltypeType::isSugared() const { return !E->isTypeDependent(); }
+bool DecltypeType::isSugared() const { return !E->isInstantiationDependent(); }
 
 QualType DecltypeType::desugar() const {
   if (isSugared())

diff --git a/clang/test/CXX/drs/dr20xx.cpp b/clang/test/CXX/drs/dr20xx.cpp
index 6e1c050..56cc116 100644 (file)
--- a/clang/test/CXX/drs/dr20xx.cpp
+++ b/clang/test/CXX/drs/dr20xx.cpp
@@ -49,18 +49,6 @@ namespace dr2026 { // dr2026: 11
   }
 }
 
-namespace dr2064 { // dr2064: 12
-#if __cplusplus >= 201103L
-  template<typename T> struct X {
-    template<typename U> struct Y {};
-  };
-  template<typename T> void f() {
-    X<decltype(sizeof(T))>::Y<int> y; // ok
-    return X<decltype(sizeof(T))>::f(); // expected-error {{no member named 'f' in 'dr2064::X<unsigned}}
-  }
-#endif
-}
-
 namespace dr2082 { // dr2082: 11
   void test1(int x, int = sizeof(x)); // ok
 #if __cplusplus >= 201103L

diff --git a/clang/test/CodeGenCXX/mangle-subst.cpp b/clang/test/CodeGenCXX/mangle-subst.cpp
index 78b1408..20f33a7 100644 (file)
--- a/clang/test/CodeGenCXX/mangle-subst.cpp
+++ b/clang/test/CodeGenCXX/mangle-subst.cpp
@@ -96,14 +96,3 @@ typename X<T>::template Y<T>::type f(typename X<T>::template Y<T>::type2) { retu
 // CHECK: @_ZN12ManglePrefix1fIiEENS_1XIT_E1YIS2_E4typeENS5_5type2E
 template int f<int>(int);
 }
-
-namespace InstantiationDependentDecltype {
-  struct a { a(char); };
-  struct b { a c(); };
-  // FIXME: This mangling is incorrect; the second decltype type should be a
-  // substitution for the first.
-  // CHECK: @_ZN30InstantiationDependentDecltype1fINS_1bEEEvDTcvNS_1aEcldtcvT__E1cEEDTcvS2_cldtcvS3__E1cEES3_S3_S2_S2_
-  // FIXME: @_ZN30InstantiationDependentDecltype1fINS_1bEEEvDTcvNS_1aEcldtcvT__E1cEES4_S3_S3_S2_S2_
-  template<typename d> void f(decltype(a(d().c())), decltype(a(d().c())), d, d, a, a);
-  void g(a a, b b) { f(a, a, b, b, a, a); }
-}

diff --git a/clang/test/Sema/invalid-bitwidth-expr.mm b/clang/test/Sema/invalid-bitwidth-expr.mm
index 8ce498f..41ca949 100644 (file)
--- a/clang/test/Sema/invalid-bitwidth-expr.mm
+++ b/clang/test/Sema/invalid-bitwidth-expr.mm
@@ -26,7 +26,6 @@ template <typename T>
 auto func() {
   // error-bit should be propagated from TemplateArgument to NestNameSpecifier.
   class Base<decltype(Foo(T()))>::type C; // expected-error {{no matching function for call to 'Foo'}}
-  // expected-error@-1 {{no class named 'type' in 'Base<bool>'}}
   return C;
 }
 struct Z {

diff --git a/clang/test/SemaCXX/coroutines.cpp b/clang/test/SemaCXX/coroutines.cpp
index d7208f9..d6c67c0 100644 (file)
--- a/clang/test/SemaCXX/coroutines.cpp
+++ b/clang/test/SemaCXX/coroutines.cpp
@@ -1179,8 +1179,8 @@ struct TestType {
   static CoroMemberTag test_static_template(const char *volatile &, unsigned) {
     auto TC = co_yield 0;
     using TCT = decltype(TC);
-    static_assert(TCT::MatchesArgs<const char *volatile &, unsigned>, "");
-    static_assert(!TCT::MatchesArgs<TestType &, const char *volatile &, unsigned>, "");
+    static_assert(TCT::template MatchesArgs<const char *volatile &, unsigned>, "");
+    static_assert(!TCT::template MatchesArgs<TestType &, const char *volatile &, unsigned>, "");
   }
 
   BadCoroMemberTag test_diagnostics() {
@@ -1263,31 +1263,31 @@ struct DepTestType {
   static CoroMemberTag test_static() {
     auto TC = co_yield 0;
     using TCT = decltype(TC);
-    static_assert(TCT::MatchesArgs<>, "");
-    static_assert(!TCT::MatchesArgs<DepTestType>, "");
-    static_assert(!TCT::MatchesArgs<DepTestType &>, "");
-    static_assert(!TCT::MatchesArgs<DepTestType *>, "");
+    static_assert(TCT::template MatchesArgs<>, "");
+    static_assert(!TCT::template MatchesArgs<DepTestType>, "");
+    static_assert(!TCT::template MatchesArgs<DepTestType &>, "");
+    static_assert(!TCT::template MatchesArgs<DepTestType *>, "");
 
     // Ensure diagnostics are actually being generated here
-    static_assert(TCT::MatchesArgs<int>, ""); // expected-error {{static_assert failed}}
+    static_assert(TCT::template MatchesArgs<int>, ""); // expected-error {{static_assert failed}}
   }
 
   static CoroMemberTag test_static(volatile void *const, char &&) {
     auto TC = co_yield 0;
     using TCT = decltype(TC);
-    static_assert(TCT::MatchesArgs<volatile void *const, char &&>, "");
+    static_assert(TCT::template MatchesArgs<volatile void *const, char &&>, "");
   }
 
   template <class Dummy>
   static CoroMemberTag test_static_template(const char *volatile &, unsigned) {
     auto TC = co_yield 0;
     using TCT = decltype(TC);
-    static_assert(TCT::MatchesArgs<const char *volatile &, unsigned>, "");
-    static_assert(!TCT::MatchesArgs<DepTestType &, const char *volatile &, unsigned>, "");
+    static_assert(TCT::template MatchesArgs<const char *volatile &, unsigned>, "");
+    static_assert(!TCT::template MatchesArgs<DepTestType &, const char *volatile &, unsigned>, "");
   }
 };
 
-template struct DepTestType<int>; // expected-note {{requested here}}
+template struct DepTestType<int>; // expected-note 2{{requested here}}
 template CoroMemberTag DepTestType<int>::test_member_template(long, const char *) const &&;
 
 template CoroMemberTag DepTestType<int>::test_static_template<void>(const char *volatile &, unsigned);

diff --git a/clang/test/SemaCXX/invalid-template-base-specifier.cpp b/clang/test/SemaCXX/invalid-template-base-specifier.cpp
index 7760140..7a1a7f8 100644 (file)
--- a/clang/test/SemaCXX/invalid-template-base-specifier.cpp
+++ b/clang/test/SemaCXX/invalid-template-base-specifier.cpp
@@ -12,11 +12,11 @@ void test() { Crash<int>(); } // expected-note {{in instantiation of template cl
 template <typename T>
 using Alias = decltype(Foo(T())); // expected-error {{no matching function for call to 'Foo'}}
 template <typename T>
-struct Crash2 : decltype(Alias<T>()) { // expected-note {{in instantiation of template type alias 'Alias' requested here}} expected-error {{base specifier must name a class}}
+struct Crash2 : decltype(Alias<T>()) { // expected-note {{in instantiation of template type alias 'Alias' requested here}}
   Crash2(){};
 };
 
-void test2() { Crash2<int>(); } // expected-note 2{{in instantiation of template class 'Crash2<int>' requested here}}
+void test2() { Crash2<int>(); } // expected-note {{in instantiation of template class 'Crash2<int>' requested here}}
 
 template <typename T>
 class Base {};

diff --git a/clang/test/SemaTemplate/dependent-expr.cpp b/clang/test/SemaTemplate/dependent-expr.cpp
index dace7e2..abdb8e9 100644 (file)
--- a/clang/test/SemaTemplate/dependent-expr.cpp
+++ b/clang/test/SemaTemplate/dependent-expr.cpp
@@ -129,12 +129,7 @@ namespace PR45083 {
   template<typename> void f() {
     decltype(({})) x; // expected-error {{incomplete type}}
   }
-  template void f<int>();
-
-  template<typename T> void f2() {
-    decltype(({T();})) x; // expected-error {{incomplete type}}
-  }
-  template void f2<void>(); // expected-note {{instantiation of}}
+  template void f<int>(); // expected-note {{instantiation of}}
 
   template<typename> auto g() {
     auto c = [](auto, int) -> decltype(({})) {};

diff --git a/clang/test/SemaTemplate/temp_arg_template_cxx1z.cpp b/clang/test/SemaTemplate/temp_arg_template_cxx1z.cpp
index b9a1c93..03ef78f 100644 (file)
--- a/clang/test/SemaTemplate/temp_arg_template_cxx1z.cpp
+++ b/clang/test/SemaTemplate/temp_arg_template_cxx1z.cpp
@@ -115,12 +115,6 @@ namespace Auto {
 
   int n;
   template<auto A, decltype(A) B = &n> struct SubstFailure;
-  TInt<SubstFailure> isf; // expected-error {{template template argument has different template parameters than its corresponding template template parameter}}
+  TInt<SubstFailure> isf; // FIXME: this should be ill-formed
   TIntPtr<SubstFailure> ipsf;
-
-  template<template<auto A, auto B, decltype(A)> typename C> struct TAutoAutoFirst {};
-  template<auto A, auto B, decltype(A)> struct AutoAutoFirst;
-  template<auto A, auto B, decltype(B)> struct AutoAutoSecond;
-  TAutoAutoFirst<AutoAutoFirst> aaf;
-  TAutoAutoFirst<AutoAutoSecond> aas; // FIXME: this should be rejected due to parameter mismatch
 }

diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html
index 9be6f12..57093c1 100755 (executable)
--- a/clang/www/cxx_dr_status.html
+++ b/clang/www/cxx_dr_status.html
@@ -12198,7 +12198,7 @@ and <I>POD class</I></td>
     <td><a href="https://wg21.link/cwg2064">2064</a></td>
     <td>CD4</td>
     <td>Conflicting specifications for dependent <I>decltype-specifier</I>s</td>
-    <td class="unreleased" align="center">Clang 12</td>
+    <td class="none" align="center">Unknown</td>
   </tr>
   <tr class="open" id="2065">
     <td><a href="https://wg21.link/cwg2065">2065</a></td>