Report enum type name instead of constant name

The reason is that
1) enumerators led to much noise in explanatory comments
(the idea is similar to cedf9d6984323a0a68847d), and
2) without this change, EnumClass::Item is reported separately
as fwd-decl use of EnumClass along with the full use
of EnumClass::Item.

Unnamed enums are an exception.

3 files changed, 38 insertions, 37 deletions

diff --git a/iwyu.cc b/iwyu.cc
index e7a2387..e3604e0 100644
--- a/iwyu.cc
+++ b/iwyu.cc
@@ -168,6 +168,8 @@ using clang::Decl;
 using clang::DeclContext;
 using clang::DeclRefExpr;
 using clang::DeducedTemplateSpecializationType;
+using clang::EnumConstantDecl;
+using clang::EnumDecl;
 using clang::EnumType;
 using clang::Expr;
 using clang::FileEntry;
@@ -1537,6 +1539,20 @@ class IwyuBaseAstVisitor : public BaseAstVisitor<Derived> {
     // Canonicalize the use location and report the use.
     used_loc = GetCanonicalUseLocation(used_loc, target_decl);
     const FileEntry* used_in = GetFileEntry(used_loc);
+
+    // Report EnumName instead of EnumName::Item.
+    // It supports for removing EnumName forward- (opaque-) declarations
+    // from output.
+    if (const auto* enum_constant_decl =
+            dyn_cast<EnumConstantDecl>(target_decl)) {
+      const auto* enum_decl =
+          cast<EnumDecl>(enum_constant_decl->getDeclContext());
+
+      // for unnamed enums, enumerator name is still preferred
+      if (enum_decl->getIdentifier())
+        target_decl = enum_decl;
+    }
+
     preprocessor_info().FileInfoFor(used_in)->ReportFullSymbolUse(
         used_loc, target_decl, use_flags, comment);
 
@@ -1676,7 +1692,7 @@ class IwyuBaseAstVisitor : public BaseAstVisitor<Derived> {
     return true;
   }
 
-  bool VisitEnumDecl(clang::EnumDecl* decl) {
+  bool VisitEnumDecl(EnumDecl* decl) {
     if (CanIgnoreCurrentASTNode())
       return true;
 
diff --git a/tests/cxx/badinc.cc b/tests/cxx/badinc.cc
index 76c73d0..d537361 100644
--- a/tests/cxx/badinc.cc
+++ b/tests/cxx/badinc.cc
@@ -293,19 +293,17 @@ struct Cc_DeclOrderStruct {
 };
 
 // IWYU: I1_Enum is...*badinc-i1.h
-// IWYU: I11 is...*badinc-i1.h
 template<class T, I1_Enum E = I11> struct Cc_TemplateStruct { };
 // IWYU: I1_Enum is...*badinc-i1.h
 // IWYU: I1_Class needs a declaration
 // IWYU: I1_Class is...*badinc-i1.h
 template<I1_Enum E> struct Cc_TemplateStruct<I1_Class, E> { I1_Class i; };
 // IWYU: I1_Class needs a declaration
-// IWYU: I12 is...*badinc-i1.h
+// IWYU: I1_Enum is...*badinc-i1.h
 template<> struct Cc_TemplateStruct<I1_Class, I12> { I1_Class* i; };
 // TODO(csilvers): I1_Class is technically forward-declarable.
 // IWYU: I1_Class is...*badinc-i1.h
 // IWYU: I1_Enum is...*badinc-i1.h
-// IWYU: I11 is...*badinc-i1.h
 template<class T = I1_Class, I1_Enum E = I11> class Cc_DeclareOnlyTemplateClass;
 
 // I2_Class has a non-explicit constructor (actually, two), so we need
@@ -342,11 +340,11 @@ const I2_Class& Cc_Function(
 // IWYU: I1_Enum is...*badinc-i1.h
 template<class T, I1_Enum E> int Cc_TemplateFunction() { return T().a(); }
 // IWYU: I1_Class needs a declaration
-// IWYU: I12 is...*badinc-i1.h
+// IWYU: I1_Enum is...*badinc-i1.h
 template<> int Cc_TemplateFunction<I1_Class, I12>() { return 3; }
 // IWYU: I1_Class needs a declaration
 // IWYU: I1_Class is...*badinc-i1.h
-// IWYU: I13 is...*badinc-i1.h
+// IWYU: I1_Enum is...*badinc-i1.h
 template<> int Cc_TemplateFunction<I1_Class, I13>() { return I1_Class().a(); }
 // IWYU: I1_Enum is...*badinc-i1.h
 template<class T, I1_Enum E> T Cc_DeclareOnlyTemplateFunction();
@@ -457,7 +455,6 @@ struct Cc_ImplicitDestructorStruct {
 // IWYU: EmptyDestructorClass is...*badinc-i1.h
 EmptyDestructorClass::~EmptyDestructorClass() { }
 // IWYU: I2_Enum is...*badinc-i2.h
-// IWYU: I22 is...*badinc-i2.h
 I2_Enum H_Class::ff_ = I22;
 // IWYU: I2_Enum is...*badinc-i2.h
 int H_Class::f(I2_Enum i2_enum) { return 1; }
@@ -557,13 +554,12 @@ Cc_Subclass cc_subclass;
 MultipleInheritanceSubclass cc_multipleinheritancesubclass;
 // IWYU: I1_Class needs a declaration
 // IWYU: I1_Class is...*badinc-i1.h
-// IWYU: I11 is...*badinc-i1.h
+// IWYU: I1_Enum is...*badinc-i1.h
 int cc_template_function_val = Cc_TemplateFunction<I1_Class, I11>();
 int cc_tricky_template_function_val =
     // IWYU: I1_Class needs a declaration
     // IWYU: kI1ConstInt is...*badinc-i1.h
-    // IWYU: I12 is...*badinc-i1.h
-    // IWYU: I13 is...*badinc-i1.h
+    // IWYU: I1_Enum is...*badinc-i1.h
     Cc_TemplateFunction<I1_Class, kI1ConstInt == 4 ? I12 : I13>();  // is I13
 // IWYU: I1_Class needs a declaration
 // IWYU: I1_Class is...*badinc-i1.h
@@ -592,7 +588,6 @@ H_Class h_class2(2);
 H_StructPtr h_structptr;
 H_TemplateClass<H_Enum> h_templateclass1(H1);
 // IWYU: I1_Enum is...*badinc-i1.h
-// IWYU: I11 is...*badinc-i1.h
 H_TemplateClass<I1_Enum> h_templateclass2(I11);
 // IWYU: I1_Struct needs a declaration
 H_TemplateStruct<I1_Struct> h_template_struct;
@@ -639,7 +634,6 @@ InlH_FunctionPtr inlh_functionptr = InlH_Function();  // badinc-inl.h
 D1_Class d1_class;       // badinc-d1.h
 D1_TemplateClass<D1_Enum> d1_templateclass1(D11);
 // IWYU: I2_Enum is...*badinc-i2.h
-// IWYU: I2_LAST is...*badinc-i2.h
 D1_TemplateClass<I2_Enum> d1_templateclass2(I2_LAST);
 // IWYU: I2_Enum is...*badinc-i2.h
 D1_TemplateClass<I2_Enum> *d1_templateclass2_ptr;
@@ -718,7 +712,6 @@ I1_Base *i1_base_ptr;
 // the I1_TemplateClass<I1_Enum> object, and once in the constructor.
 // IWYU: I1_TemplateClass is...*badinc-i1.h
 // IWYU: I1_Enum is...*badinc-i1.h
-// IWYU: I11 is...*badinc-i1.h
 I1_TemplateClass<I1_Enum> i1_templateclass(I11);
 // IWYU: I1_TemplateClass is...*badinc-i1.h
 I1_TemplateClass<int> i1_templateclass2(10);
@@ -1072,10 +1065,8 @@ int main() {
   Cc_string local_cc_string;
   H_Class local_h_class;
   // IWYU: I2_Enum is...*badinc-i2.h
-  // IWYU: I21 is...*badinc-i2.h
   D1_TemplateClass<I2_Enum> local_d1_template_class(I21);
   // IWYU: I1_Enum is...*badinc-i1.h
-  // IWYU: I11 is...*badinc-i1.h
   I1_Enum local_i1_enum = I11;
   // IWYU: I1_UnnamedStruct is...*badinc-i1.h
   I1_UnnamedStruct local_i1_unnamed_struct = {};
@@ -1102,7 +1093,7 @@ int main() {
   isascii('a');   // declared in <ctype.h> which is #included by badinc.h
   (void)(errno);  // declared in <errno.h> which is #included by badinc.h
   // Test we don't give an iwyu warning for the built-in __builtin_expect
-  // IWYU: I11 is...*badinc-i1.h
+  // IWYU: I1_Enum is...*badinc-i1.h
   if (__builtin_expect(local_i1_enum == I11, false)) (void)local_i1_enum;
 
   // IWYU: i1_int_global is...*badinc-i1.h
@@ -1367,7 +1358,7 @@ int main() {
   (*h_scoped_ptr).a();
   // IWYU: I1_Class is...*badinc-i1.h
   h_scoped_ptr->a();
-  // IWYU: I12 is...*badinc-i1.h
+  // IWYU: I1_Enum is...*badinc-i1.h
   D1Function(I12);
   // TODO(csilvers): should we be warning about I2_Struct?
   // IWYU: I1_Union is...*badinc-i1.h
@@ -1509,7 +1500,6 @@ int main() {
   std::vector<I2_Enum> local_enum_vector;
   // IWYU: I2_Enum is...*badinc-i2.h
   // IWYU: std::vector is...*<vector>
-  // IWYU: I21 is...*badinc-i2.h
   local_enum_vector.push_back(I21);
   // IWYU: std::vector is...*<vector>
   // IWYU: I2_Enum is...*badinc-i2.h
@@ -1764,26 +1754,25 @@ int main() {
 
   // Test templatized functions.
   H_TemplateFunction(1);
-  // IWYU: I11 is...*badinc-i1.h
   // IWYU: I1_Enum is...*badinc-i1.h
   H_TemplateFunction(I11);
-  // IWYU: I11 is...*badinc-i1.h
+  // IWYU: I1_Enum is...*badinc-i1.h
   H_TemplateFunction<int>(I11);
   // IWYU: I1_Class needs a declaration
   H_TemplateFunction<I1_Class*>(&i1_class);
   H_TemplateFunction(&i1_class);
-  // IWYU: I22 is...*badinc-i2.h
+  // IWYU: I2_Enum is...*badinc-i2.h
   // IWYU: I1_Enum is...*badinc-i1.h
   h_templateclass2.static_out_of_line(I22);
-  // IWYU: I22 is...*badinc-i2.h
+  // IWYU: I2_Enum is...*badinc-i2.h
   // IWYU: I1_Enum is...*badinc-i1.h
   h_templateclass2.static_inline(I22);
-  // IWYU: I22 is...*badinc-i2.h
+  // IWYU: I2_Enum is...*badinc-i2.h
   h_templateclass2.h_nested_struct.tplnested(I22);
   // TODO: I1_Enum should be reported here as a full use but isn't,
   // because we are not properly handling the dependent type FOO in
   // the nested struct.
-  // IWYU: I22 is...*badinc-i2.h
+  // IWYU: I2_Enum is...*badinc-i2.h
   h_templateclass2.h_nested_struct.static_tplnested(I22);
   // This should not cause warnings for the i2_class destructor
   h_templateclass2.uses_i2class();
@@ -1813,9 +1802,9 @@ int main() {
   I1_Class::I1_StaticClassTemplateFunction<I1_Struct*>(&i1_struct);
 
   // Test default (compiler-defined) copy constructor/operator=/operator==
-  // IWYU: I11 is...*badinc-i1.h
+  // IWYU: I1_Enum is...*badinc-i1.h
   D1_CopyClass local_d1_copy_class(D1CopyClassFn(I11));
-  // IWYU: I12 is...*badinc-i1.h
+  // IWYU: I1_Enum is...*badinc-i1.h
   local_d1_copy_class = D1CopyClassFn(I12);
   local_d1_copy_class.a();
 
@@ -1875,9 +1864,9 @@ The full include-list for tests/cxx/badinc.cc:
 #include <list>  // for list
 #include <string>  // for basic_string, operator+, string
 #include <typeinfo>  // for type_info
-#include "tests/cxx/badinc-d1.h"  // for D11, D1CopyClassFn, D1Function, D1_Class, D1_CopyClass, D1_Enum, D1_I1_Typedef, D1_StructPtr, D1_Subclass, D1_TemplateClass, D1_TemplateStructWithDefaultParam, MACRO_CALLING_I4_FUNCTION
+#include "tests/cxx/badinc-d1.h"  // for D1CopyClassFn, D1Function, D1_Class, D1_CopyClass, D1_Enum, D1_I1_Typedef, D1_StructPtr, D1_Subclass, D1_TemplateClass, D1_TemplateStructWithDefaultParam, MACRO_CALLING_I4_FUNCTION
 #include "tests/cxx/badinc-d4.h"  // for D4_ClassForOperator, operator<<
-#include "tests/cxx/badinc-i1.h"  // for EmptyDestructorClass, H_Class::H_Class_DefinedInI1, I11, I12, I13, I1_And_I2_OverloadedFunction, I1_Base, I1_Class, I1_ClassPtr, I1_Enum, I1_Function, I1_FunctionPtr, I1_I2_Class_Typedef, I1_MACRO_LOGGING_CLASS, I1_MACRO_SYMBOL_WITHOUT_VALUE, I1_MACRO_SYMBOL_WITH_VALUE, I1_MACRO_SYMBOL_WITH_VALUE0, I1_MACRO_SYMBOL_WITH_VALUE2, I1_ManyPtrStruct (ptr only), I1_MemberPtr, I1_NamespaceClass, I1_NamespaceStruct, I1_NamespaceTemplateFn, I1_OverloadedFunction, I1_PtrAndUseOnSameLine, I1_PtrDereferenceClass, I1_PtrDereferenceStatic, I1_PtrDereferenceStruct, I1_SiblingClass, I1_StaticMethod, I1_Struct, I1_Subclass, I1_SubclassesI2Class, I1_TemplateClass, I1_TemplateClassFwdDeclaredInD2 (ptr only), I1_TemplateFunction, I1_TemplateMethodOnlyClass, I1_TemplateSubclass, I1_Typedef, I1_TypedefOnly_Class, I1_Union, I1_UnnamedStruct, I1_UnusedNamespaceStruct (ptr only), I1_const_ptr, I2_OperatorDefinedInI1Class::operator<<, MACRO_CALLING_I6_FUNCTION, OperateOn, i1_GlobalFunction, i1_int, i1_int_global, i1_int_global2, i1_int_global2sub, i1_int_global3, i1_int_global3sub, i1_int_global4, i1_int_global4sub, i1_int_globalsub, i1_ns2, i1_ns4, i1_ns5, kI1ConstInt, operator==
+#include "tests/cxx/badinc-i1.h"  // for EmptyDestructorClass, H_Class::H_Class_DefinedInI1, I1_And_I2_OverloadedFunction, I1_Base, I1_Class, I1_ClassPtr, I1_Enum, I1_Function, I1_FunctionPtr, I1_I2_Class_Typedef, I1_MACRO_LOGGING_CLASS, I1_MACRO_SYMBOL_WITHOUT_VALUE, I1_MACRO_SYMBOL_WITH_VALUE, I1_MACRO_SYMBOL_WITH_VALUE0, I1_MACRO_SYMBOL_WITH_VALUE2, I1_ManyPtrStruct (ptr only), I1_MemberPtr, I1_NamespaceClass, I1_NamespaceStruct, I1_NamespaceTemplateFn, I1_OverloadedFunction, I1_PtrAndUseOnSameLine, I1_PtrDereferenceClass, I1_PtrDereferenceStatic, I1_PtrDereferenceStruct, I1_SiblingClass, I1_StaticMethod, I1_Struct, I1_Subclass, I1_SubclassesI2Class, I1_TemplateClass, I1_TemplateClassFwdDeclaredInD2 (ptr only), I1_TemplateFunction, I1_TemplateMethodOnlyClass, I1_TemplateSubclass, I1_Typedef, I1_TypedefOnly_Class, I1_Union, I1_UnnamedStruct, I1_UnusedNamespaceStruct (ptr only), I1_const_ptr, I2_OperatorDefinedInI1Class::operator<<, MACRO_CALLING_I6_FUNCTION, OperateOn, i1_GlobalFunction, i1_int, i1_int_global, i1_int_global2, i1_int_global2sub, i1_int_global3, i1_int_global3sub, i1_int_global4, i1_int_global4sub, i1_int_globalsub, i1_ns2, i1_ns4, i1_ns5, kI1ConstInt, operator==
 #include "tests/cxx/badinc2.c"
 class D2_Class;
 class D2_ForwardDeclareClass;
diff --git a/tests/cxx/badinc.h b/tests/cxx/badinc.h
index f61cc14..75cbf4d 100644
--- a/tests/cxx/badinc.h
+++ b/tests/cxx/badinc.h
@@ -126,9 +126,9 @@ class H_Class {
     if (q.empty()) return s.length();
     // IWYU: I2_Enum is...*badinc-i2.h
     switch (static_cast<I2_Enum>(a_)) {
-      // IWYU: I21 is...*badinc-i2.h
+      // IWYU: I2_Enum is...*badinc-i2.h
       case I21: return 21;
-        // IWYU: I22 is...*badinc-i2.h
+        // IWYU: I2_Enum is...*badinc-i2.h
       case I22: return 22;
       default: return errno;
     }
@@ -178,7 +178,6 @@ class H_Class {
   H_Class(const H_Class&);
 };
 // IWYU: I2_Enum is...*badinc-i2.h
-// IWYU: I21 is...*badinc-i2.h
 I2_Enum H_Class::ee_ = I21;
 
 template<typename FOO>
@@ -237,7 +236,6 @@ class H_TemplateClass {
   H_TemplateClass(const H_TemplateClass&);
 };
 // IWYU: I2_Enum is...*badinc-i2.h
-// IWYU: I21 is...*badinc-i2.h
 template<typename FOO> I2_Enum H_TemplateClass<FOO>::h_template_i2_static_ = I21;
 H_TemplateClass<int>* h_templateclass_var;
 
@@ -251,7 +249,6 @@ class H_TemplateTemplateClass {
   // TODO(csilvers): attribute this use here, not at the caller sites.
   // TODO(csilvers): IWYU: I2_TemplateClass::~I2_TemplateClass<.*> is...*badinc-i2-inl.h
   // IWYU: I2_Enum is...*badinc-i2.h
-  // IWYU: I21 is...*badinc-i2.h
   H_TemplateTemplateClass() : t(T<I2_Enum>(I21)) {}
   // IWYU: I2_Enum is...*badinc-i2.h
   T<I2_Enum> t;
@@ -313,7 +310,7 @@ H_Enum H_Function(H_Class* c) {
 // IWYU: I2_Class needs a declaration
 // IWYU: I2_Enum is...*badinc-i2.h
 I2_Enum H_Function_I(I2_Class*) {
-  // IWYU: I21 is...*badinc-i2.h
+  // IWYU: I2_Enum is...*badinc-i2.h
   return I21;
 }
 
@@ -366,7 +363,6 @@ H_Enum h_h_enum;
 I2_Class h_i2_class;
 H_TemplateClass<D3_Enum> h_d3_template_class(D31);
 // IWYU: I2_Enum is...*badinc-i2.h
-// IWYU: I22 is...*badinc-i2.h
 H_TemplateClass<I2_Enum> h_i2_template_class(I22);
 // TODO(csilvers): this should be attributed to the .h, since it comes
 // via a default template argument.
@@ -400,9 +396,9 @@ The full include-list for tests/cxx/badinc.h:
 #include <set>  // for set
 #include <string>  // for string
 #include <vector>  // for vector
-#include "tests/cxx/badinc-d3.h"  // for D31, D3_Enum
+#include "tests/cxx/badinc-d3.h"  // for D3_Enum
 #include "tests/cxx/badinc-i2-inl.h"  // for I2_Class::I2_Class, I2_Class::InlFileFn, I2_Class::InlFileStaticFn, I2_Class::InlFileTemplateFn, I2_Class::~I2_Class, I2_TemplateClass::I2_TemplateClass<FOO>, I2_TemplateClass::InlFileTemplateClassFn, I2_TemplateClass::~I2_TemplateClass<FOO>
-#include "tests/cxx/badinc-i2.h"  // for I21, I22, I2_Class, I2_Enum, I2_EnumForTypedefs, I2_MACRO, I2_Struct, I2_TemplateClass, I2_Typedef, I2_TypedefOnly_Class (ptr only), TemplateForHClassTplFn (ptr only)
+#include "tests/cxx/badinc-i2.h"  // for I2_Class, I2_Enum, I2_EnumForTypedefs, I2_MACRO, I2_Struct, I2_TemplateClass, I2_Typedef, I2_TypedefOnly_Class (ptr only), TemplateForHClassTplFn (ptr only)
 class Cc_Class;  // lines XX-XX
 // TODO(csilvers): this should change to struct Cc_Struct.
 class Cc_Struct;  // lines XX-XX