[lldb] Ignore certain Clang type sugar when creating the type name

Clang has some type sugar that only serves as a way to preserve the way a user
has typed a certain type in the source code. These types are currently not
unwrapped when we query the type name for a Clang type, which means that this
type sugar actually influences what formatters are picked for a certain type.
Currently if a user decides to reference a type by doing `::GlobalDecl Var = 3;`,
the type formatter for `GlobalDecl` will not be used (as the type sugar
around the type gives it the name `::GlobalDecl`. The same goes for other ways
to spell out a type such as `auto` etc.

With this patch most of this type sugar gets stripped when the full type name is
calculated. Typedefs are not getting desugared as that seems counterproductive.
I also don't desugar atomic types as that's technically not type sugar.

Reviewed By: jarin

Differential Revision: https://reviews.llvm.org/D87481

1 files changed, 10 insertions, 0 deletions

diff --git a/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp b/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
index d80d075..ee6fc895 100644
--- a/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
+++ b/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
@@ -3639,6 +3639,16 @@ ConstString TypeSystemClang::GetTypeName(lldb::opaque_compiler_type_t type) {
 
   clang::QualType qual_type(GetQualType(type));
 
+  // Remove certain type sugar from the name. Sugar such as elaborated types
+  // or template types which only serve to improve diagnostics shouldn't
+  // act as their own types from the user's perspective (e.g., formatter
+  // shouldn't format a variable differently depending on how the ser has
+  // specified the type. '::Type' and 'Type' should behave the same).
+  // Typedefs and atomic derived types are not removed as they are actually
+  // useful for identifiying specific types.
+  qual_type = RemoveWrappingTypes(qual_type,
+                                  {clang::Type::Typedef, clang::Type::Atomic});
+
   // For a typedef just return the qualified name.
   if (const auto *typedef_type = qual_type->getAs<clang::TypedefType>()) {
     const clang::TypedefNameDecl *typedef_decl = typedef_type->getDecl();