Re-land "[lldb] Fix FindDirectNestedType not working with class templates (#81666)"

This patch attempts to fix lookup in class template specialization.

The first fixed problem is that during type lookup `DeclContextGetName`
have been dropping template arguments. So when such a name was compared
against a name in `DW_AT_name`, which contains template arguments, false
mismatches have been occurring.

The second fixed problem is that LLDB's printing policy hasn't been
matching Clang's printing policy when it comes to integral non-type
template arguments. This again caused some false mismatches during type
lookup, because Clang puts e.g. `3U` in debug info for class
specializations, but LLDB has been expecting just `3`. This patch brings
printing policy in line with what Clang does.

Author: Endilll

lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp

@@ -9265,8 +9265,14 @@ ConstString TypeSystemClang::DeclContextGetName(void *opaque_decl_ctx) {
   if (opaque_decl_ctx) {
     clang::NamedDecl *named_decl =
         llvm::dyn_cast<clang::NamedDecl>((clang::DeclContext *)opaque_decl_ctx);
-    if (named_decl)
-      return ConstString(named_decl->getName());
+    if (named_decl) {
+      std::string name;
+      llvm::raw_string_ostream stream{name};
+      auto policy = GetTypePrintingPolicy();
+      policy.AlwaysIncludeTypeForTemplateArgument = true;
+      named_decl->getNameForDiagnostic(stream, policy, /*qualified=*/false);
+      return ConstString(name);
+    }
   }
   return ConstString();
 }

lldb/test/API/python_api/type/TestTypeList.py

@@ -150,6 +150,23 @@ def test(self):
         invalid_type = task_type.FindDirectNestedType(None)
         self.assertFalse(invalid_type)
 
+        # Check that FindDirectNestedType works with types from AST
+        pointer = frame0.FindVariable("pointer")
+        pointer_type = pointer.GetType()
+        self.assertTrue(pointer_type)
+        self.DebugSBType(pointer_type)
+        pointer_info_type = pointer_type.template_args[1]
+        self.assertTrue(pointer_info_type)
+        self.DebugSBType(pointer_info_type)
+
+        pointer_masks1_type = pointer_info_type.FindDirectNestedType("Masks1")
+        self.assertTrue(pointer_masks1_type)
+        self.DebugSBType(pointer_masks1_type)
+
+        pointer_masks2_type = pointer_info_type.FindDirectNestedType("Masks2")
+        self.assertTrue(pointer_masks2_type)
+        self.DebugSBType(pointer_masks2_type)
+
         # We'll now get the child member 'id' from 'task_head'.
         id = task_head.GetChildMemberWithName("id")
         self.DebugSBValue(id)

lldb/test/API/python_api/type/main.cpp

@@ -34,6 +34,14 @@ class Task {
     {}
 };
 
+template <unsigned Value> struct PointerInfo {
+  enum Masks1 { pointer_mask };
+  enum class Masks2 { pointer_mask };
+};
+
+template <unsigned Value, typename InfoType = PointerInfo<Value>>
+struct Pointer {};
+
 enum EnumType {};
 enum class ScopedEnumType {};
 enum class EnumUChar : unsigned char {};
@@ -71,5 +79,9 @@ int main (int argc, char const *argv[])
     ScopedEnumType scoped_enum_type;
     EnumUChar scoped_enum_type_uchar;
 
+    Pointer<3> pointer;
+    PointerInfo<3>::Masks1 mask1 = PointerInfo<3>::Masks1::pointer_mask;
+    PointerInfo<3>::Masks2 mask2 = PointerInfo<3>::Masks2::pointer_mask;
+
     return 0; // Break at this line
 }