Revert [c++20] P1327R1: Support for typeid applied to objects of polymorphic class type in constant evaluation.

This reverts r360977 (git commit f51dc8d)

llvm-svn: 360987

Author: llvm-beanz

clang/include/clang/Basic/DiagnosticASTKinds.td

@@ -12,8 +12,7 @@ let Component = "AST" in {
 def note_expr_divide_by_zero : Note<"division by zero">;
 def note_constexpr_invalid_cast : Note<
   "%select{reinterpret_cast|dynamic_cast|cast that performs the conversions of"
-  " a reinterpret_cast|cast from %1}0 is not allowed in a constant expression"
-  "%select{| in C++ standards before C++2a||}0">;
+  " a reinterpret_cast|cast from %1}0 is not allowed in a constant expression">;
 def note_constexpr_invalid_downcast : Note<
   "cannot cast object of dynamic type %0 to type %1">;
 def note_constexpr_overflow : Note<
@@ -32,13 +31,12 @@ def note_constexpr_invalid_inhctor : Note<
 def note_constexpr_no_return : Note<
   "control reached end of constexpr function">;
 def note_constexpr_virtual_call : Note<
-  "cannot evaluate call to virtual function in a constant expression "
-  "in C++ standards before C++2a">;
+  "cannot evaluate call to virtual function in a constant expression">;
 def note_constexpr_pure_virtual_call : Note<
   "pure virtual function %q0 called">;
 def note_constexpr_polymorphic_unknown_dynamic_type : Note<
-  "%select{||||virtual function called on|dynamic_cast applied to|"
-  "typeid applied to}0 object '%1' whose dynamic type is not constant">;
+  "%select{||||virtual function called on|dynamic_cast applied to}0 "
+  "object '%1' whose dynamic type is not constant">;
 def note_constexpr_dynamic_cast_to_reference_failed : Note<
   "reference dynamic_cast failed: %select{"
   "static type %1 of operand is a non-public base class of dynamic type %2|"
@@ -92,7 +90,7 @@ def note_constexpr_var_init_non_constant : Note<
   "initializer of %0 is not a constant expression">;
 def note_constexpr_typeid_polymorphic : Note<
   "typeid applied to expression of polymorphic type %0 is "
-  "not allowed in a constant expression in C++ standards before C++2a">;
+  "not allowed in a constant expression">;
 def note_constexpr_void_comparison : Note<
   "comparison between unequal pointers to void has unspecified result">;
 def note_constexpr_temporary_here : Note<"temporary created here">;
@@ -110,11 +108,11 @@ def note_constexpr_this : Note<
   "evaluation of a call to a 'constexpr' member function">;
 def note_constexpr_lifetime_ended : Note<
   "%select{read of|assignment to|increment of|decrement of|member call on|"
-  "dynamic_cast of|typeid applied to}0 "
+  "dynamic_cast of}0 "
   "%select{temporary|variable}1 whose lifetime has ended">;
 def note_constexpr_access_uninit : Note<
   "%select{read of|assignment to|increment of|decrement of|member call on|"
-  "dynamic_cast of|typeid applied to}0 "
+  "dynamic_cast of}0 "
   "object outside its lifetime is not allowed in a constant expression">;
 def note_constexpr_use_uninit_reference : Note<
   "use of reference outside its lifetime "
@@ -141,30 +139,30 @@ def note_constexpr_ltor_incomplete_type : Note<
   "read of incomplete type %0 is not allowed in a constant expression">;
 def note_constexpr_access_null : Note<
   "%select{read of|assignment to|increment of|decrement of|member call on|"
-  "dynamic_cast of|typeid applied to}0 "
+  "dynamic_cast of}0 "
   "dereferenced null pointer is not allowed in a constant expression">;
 def note_constexpr_access_past_end : Note<
   "%select{read of|assignment to|increment of|decrement of|member call on|"
-  "dynamic_cast of|typeid applied to}0 "
+  "dynamic_cast of}0 "
   "dereferenced one-past-the-end pointer is not allowed in a constant expression">;
 def note_constexpr_access_unsized_array : Note<
   "%select{read of|assignment to|increment of|decrement of|member call on|"
-  "dynamic_cast of|typeid applied to}0 "
+  "dynamic_cast of}0 "
   "element of array without known bound "
   "is not allowed in a constant expression">;
 def note_constexpr_access_inactive_union_member : Note<
   "%select{read of|assignment to|increment of|decrement of|member call on|"
-  "dynamic_cast of|typeid applied to}0 "
+  "dynamic_cast of}0 "
   "member %1 of union with %select{active member %3|no active member}2 "
   "is not allowed in a constant expression">;
 def note_constexpr_access_static_temporary : Note<
   "%select{read of|assignment to|increment of|decrement of|member call on|"
-  "dynamic_cast of|typeid applied to}0 temporary "
+  "dynamic_cast of}0 temporary "
   "is not allowed in a constant expression outside the expression that "
   "created the temporary">;
 def note_constexpr_access_unreadable_object : Note<
   "%select{read of|assignment to|increment of|decrement of|member call on|"
-  "dynamic_cast of|typeid applied to}0 object '%1' whose value is not known">;
+  "dynamic_cast of}0 object '%1' whose value is not known">;
 def note_constexpr_modify_global : Note<
   "a constant expression cannot modify an object that is visible outside "
   "that expression">;

clang/lib/AST/ExprConstant.cpp

@@ -1349,15 +1349,13 @@ enum AccessKinds {
   AK_Decrement,
   AK_MemberCall,
   AK_DynamicCast,
-  AK_TypeId,
 };
 
 static bool isModification(AccessKinds AK) {
   switch (AK) {
   case AK_Read:
   case AK_MemberCall:
   case AK_DynamicCast:
-  case AK_TypeId:
     return false;
   case AK_Assign:
   case AK_Increment:
@@ -6031,33 +6029,19 @@ LValueExprEvaluator::VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) {
 }
 
 bool LValueExprEvaluator::VisitCXXTypeidExpr(const CXXTypeidExpr *E) {
-  TypeInfoLValue TypeInfo;
-
   if (!E->isPotentiallyEvaluated()) {
+    TypeInfoLValue TypeInfo;
     if (E->isTypeOperand())
       TypeInfo = TypeInfoLValue(E->getTypeOperand(Info.Ctx).getTypePtr());
     else
       TypeInfo = TypeInfoLValue(E->getExprOperand()->getType().getTypePtr());
-  } else {
-    if (!Info.Ctx.getLangOpts().CPlusPlus2a) {
-      Info.CCEDiag(E, diag::note_constexpr_typeid_polymorphic)
-        << E->getExprOperand()->getType()
-        << E->getExprOperand()->getSourceRange();
-    }
-
-    if (!Visit(E->getExprOperand()))
-      return false;
-
-    Optional<DynamicType> DynType =
-        ComputeDynamicType(Info, E, Result, AK_TypeId);
-    if (!DynType)
-      return false;
-
-    TypeInfo =
-        TypeInfoLValue(Info.Ctx.getRecordType(DynType->Type).getTypePtr());
+    return Success(APValue::LValueBase::getTypeInfo(TypeInfo, E->getType()));
   }
 
-  return Success(APValue::LValueBase::getTypeInfo(TypeInfo, E->getType()));
+  Info.FFDiag(E, diag::note_constexpr_typeid_polymorphic)
+    << E->getExprOperand()->getType()
+    << E->getExprOperand()->getSourceRange();
+  return false;
 }
 
 bool LValueExprEvaluator::VisitCXXUuidofExpr(const CXXUuidofExpr *E) {

clang/test/SemaCXX/constant-expression-cxx2a.cpp

@@ -2,10 +2,6 @@
 
 #include "Inputs/std-compare.h"
 
-namespace std {
-  struct type_info;
-};
-
 namespace ThreeWayComparison {
   struct A {
     int n;
@@ -358,58 +354,3 @@ namespace DynamicCast {
   // expected-note@+1 {{reference dynamic_cast failed: dynamic type 'DynamicCast::G' of operand does not have a base class of type 'DynamicCast::Unrelated'}}
   constexpr int e_unrelated = (dynamic_cast<Unrelated&>((E&)g), 0); // expected-error {{}}
 }
-
-namespace TypeId {
-  struct A {
-    const std::type_info &ti = typeid(*this);
-  };
-  struct A2 : A {};
-  static_assert(&A().ti == &typeid(A));
-  static_assert(&typeid((A2())) == &typeid(A2));
-  extern A2 extern_a2;
-  static_assert(&typeid(extern_a2) == &typeid(A2));
-
-  constexpr A2 a2;
-  constexpr const A &a1 = a2;
-  static_assert(&typeid(a1) == &typeid(A));
-
-  struct B {
-    virtual void f();
-    const std::type_info &ti1 = typeid(*this);
-  };
-  struct B2 : B {
-    const std::type_info &ti2 = typeid(*this);
-  };
-  static_assert(&B2().ti1 == &typeid(B));
-  static_assert(&B2().ti2 == &typeid(B2));
-  extern B2 extern_b2;
-  // expected-note@+1 {{typeid applied to object 'extern_b2' whose dynamic type is not constant}}
-  static_assert(&typeid(extern_b2) == &typeid(B2)); // expected-error {{constant expression}}
-
-  constexpr B2 b2;
-  constexpr const B &b1 = b2;
-  static_assert(&typeid(b1) == &typeid(B2));
-
-  constexpr bool side_effects() {
-    // Not polymorphic nor a glvalue.
-    bool OK = true;
-    (void)typeid(OK = false, A2()); // expected-warning {{has no effect}}
-    if (!OK) return false;
-
-    // Not polymorphic.
-    A2 a2;
-    (void)typeid(OK = false, a2); // expected-warning {{has no effect}}
-    if (!OK) return false;
-
-    // Not a glvalue.
-    (void)typeid(OK = false, B2()); // expected-warning {{has no effect}}
-    if (!OK) return false;
-
-    // Polymorphic glvalue: operand evaluated.
-    OK = false;
-    B2 b2;
-    (void)typeid(OK = true, b2); // expected-warning {{will be evaluated}}
-    return OK;
-  }
-  static_assert(side_effects());
-}

clang/www/cxx_status.html

@@ -973,11 +973,10 @@ <h2 id="cxx20">C++2a implementation status</h2>
       </tr>
       <tr>
         <td><a href="http://wg21.link/p1327r1">P1327R1</a></td>
-        <td class="svn" align="center">SVN</td>
+        <td rowspan=2 class="none" align="center">No</td>
       </tr>
       <tr>
         <td><a href="http://wg21.link/p1330r0">P1330R0</a></td>
-        <td class="none" align="center">No</td>
       </tr>
     <tr>
       <td>Prohibit aggregates with user-declared constructors</td>