[cfe-commits] r153461 - in /cfe/trunk: include/clang/Basic/DiagnosticSemaKinds.td lib/Sema/SemaTemplateInstantiateDecl.cpp test/SemaCXX/enum-unscoped-nonexistent.cpp

[Richard Smith]

Author: rsmith
Date: Mon Mar 26 15:28:16 2012
New Revision: 153461

URL: http://llvm.org/viewvc/llvm-project?rev=153461&view=rev
Log:
Add a special-case diagnostic for one of the more obnoxious special cases of
unscoped enumeration members: an enumerator name which is visible in the
out-of-class definition of a member of a templated class might not actually
exist in the instantiation of that class, if the enumeration is also lexically
defined outside the class definition and is explicitly specialized.

Depending on the result of a CWG discussion, we may have a different resolution
for a class of problems in this area, but this fixes the immediate issue of a
crash-on-invalid / accepts-invalid (depending on +Asserts). Thanks to Johannes
Schaub for digging into the standard wording to find how this case is currently
specified to behave.

Added:
    cfe/trunk/test/SemaCXX/enum-unscoped-nonexistent.cpp
Modified:
    cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
    cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp

Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=153461&r1=153460&r2=153461&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Mon Mar 26 15:28:16 2012
@@ -3542,6 +3542,11 @@
 def note_non_instantiated_member_here : Note<
   "not-yet-instantiated member is declared here">;
 
+def err_enumerator_does_not_exist : Error<
+  "enumerator %0 does not exist in instantiation of %1">;
+def note_enum_specialized_here : Note<
+  "enum %0 was explicitly specialized here">;
+
 def err_member_redeclared : Error<"class member cannot be redeclared">;
 def err_member_name_of_class : Error<"member %0 has the same name as its class">;
 def err_member_def_undefined_record : Error<

Modified: cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp?rev=153461&r1=153460&r2=153461&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp (original)
+++ cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp Mon Mar 26 15:28:16 2012
@@ -3289,6 +3289,20 @@
           << D->getDeclName()
           << Context.getTypeDeclType(cast<CXXRecordDecl>(ParentDC));
         Diag(D->getLocation(), diag::note_non_instantiated_member_here);
+      } else if (EnumConstantDecl *ED = dyn_cast<EnumConstantDecl>(D)) {
+        // This enumeration constant was found when the template was defined,
+        // but can't be found in the instantiation. This can happen if an
+        // unscoped enumeration member is explicitly specialized.
+        EnumDecl *Enum = cast<EnumDecl>(ED->getLexicalDeclContext());
+        EnumDecl *Spec = cast<EnumDecl>(FindInstantiatedDecl(Loc, Enum,
+                                                             TemplateArgs));
+        assert(Spec->getTemplateSpecializationKind() ==
+                 TSK_ExplicitSpecialization);
+        Diag(Loc, diag::err_enumerator_does_not_exist)
+          << D->getDeclName()
+          << Context.getTypeDeclType(cast<TypeDecl>(Spec->getDeclContext()));
+        Diag(Spec->getLocation(), diag::note_enum_specialized_here)
+          << Context.getTypeDeclType(Spec);
       } else {
         // We should have found something, but didn't.
         llvm_unreachable("Unable to find instantiation of declaration!");

Added: cfe/trunk/test/SemaCXX/enum-unscoped-nonexistent.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/enum-unscoped-nonexistent.cpp?rev=153461&view=auto
==============================================================================
--- cfe/trunk/test/SemaCXX/enum-unscoped-nonexistent.cpp (added)
+++ cfe/trunk/test/SemaCXX/enum-unscoped-nonexistent.cpp Mon Mar 26 15:28:16 2012
@@ -0,0 +1,39 @@
+// RUN: %clang_cc1 -std=c++11 -verify %s
+
+struct Base {
+  static const int a = 1;
+};
+template<typename T> struct S : Base {
+  enum E : int;
+  constexpr int f();
+  constexpr int g(); // expected-note {{declared here}}
+  void h();
+};
+template<> enum S<char>::E : int {}; // expected-note {{enum 'S<char>::E' was explicitly specialized here}}
+template<> enum S<short>::E : int { b = 2 };
+template<> enum S<int>::E : int { a = 4 };
+template<typename T> enum S<T>::E : int { b = 8 };
+
+// The unqualified-id here names a member of the non-dependent base class Base
+// and not the injected enumerator name 'a' from the specialization.
+template<typename T> constexpr int S<T>::f() { return a; }
+static_assert(S<char>().f() == 1, "");
+static_assert(S<int>().f() == 1, "");
+
+// The unqualified-id here names a member of the current instantiation, which
+// bizarrely might not exist in some instantiations.
+template<typename T> constexpr int S<T>::g() { return b; } // expected-error {{enumerator 'b' does not exist in instantiation of 'S<char>'}}
+static_assert(S<char>().g() == 1, ""); // expected-note {{here}} expected-error {{not an integral constant expression}} expected-note {{undefined}}
+static_assert(S<short>().g() == 2, "");
+static_assert(S<long>().g() == 8, "");
+
+// 'b' is type-dependent, so these assertions should not fire before 'h' is
+// instantiated.
+template<typename T> void S<T>::h() {
+  char c[S<T>::b];
+  static_assert(b != 8, "");
+  static_assert(sizeof(c) != 8, "");
+}
+void f() {
+  S<short>().h(); // ok, b == 2
+}