[lldb] Add GetMangledTypeName to TypeSystem/CompilerType (#113006)

Swift types have mangled names, so there should be a way to read those
from the compiler type.

This patch upstreams these two changes from swiftlang/llvm-project
(which were added there since at least 2016).

Author: augusto2112

lldb/include/lldb/Symbol/CompilerType.h

@@ -279,6 +279,8 @@ class CompilerType {
 
   ConstString GetDisplayTypeName() const;
 
+  ConstString GetMangledTypeName() const;
+
   uint32_t
   GetTypeInfo(CompilerType *pointee_or_element_compiler_type = nullptr) const;
 

lldb/include/lldb/Symbol/TypeSystem.h

@@ -237,6 +237,10 @@ class TypeSystem : public PluginInterface,
 
   virtual ConstString GetDisplayTypeName(lldb::opaque_compiler_type_t type) = 0;
 
+  // Defaults to GetTypeName(type).  Override if your language desires
+  // specialized behavior.
+  virtual ConstString GetMangledTypeName(lldb::opaque_compiler_type_t type);
+
   virtual uint32_t
   GetTypeInfo(lldb::opaque_compiler_type_t type,
               CompilerType *pointee_or_element_compiler_type) = 0;

lldb/source/Symbol/CompilerType.cpp

@@ -540,6 +540,14 @@ ConstString CompilerType::GetDisplayTypeName() const {
   return ConstString("<invalid>");
 }
 
+ConstString CompilerType::GetMangledTypeName() const {
+  if (IsValid()) {
+    if (auto type_system_sp = GetTypeSystem())
+      return type_system_sp->GetMangledTypeName(m_type);
+  }
+  return ConstString("<invalid>");
+}
+
 uint32_t CompilerType::GetTypeInfo(
     CompilerType *pointee_or_element_compiler_type) const {
   if (IsValid())

lldb/source/Symbol/TypeSystem.cpp

@@ -157,6 +157,10 @@ bool TypeSystem::IsMeaninglessWithoutDynamicResolution(void *type) {
   return false;
 }
 
+ConstString TypeSystem::GetMangledTypeName(void *type) {
+  return GetTypeName(type, false);
+}
+
 ConstString TypeSystem::DeclGetMangledName(void *opaque_decl) {
   return ConstString();
 }