[lldb][NFC] Rename TypeSystemClangForExpressions to ScratchTypeSystemClang

We keep referring to the single object created by this class as
'scratch AST/Context/TypeSystem' so at this point we might as well rename the
class. It's also not involved at all in expression evaluation, so the
'ForExpressions' prefix is a bit misleading.

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

@@ -613,7 +613,7 @@ lldb::TypeSystemSP TypeSystemClang::CreateInstance(lldb::LanguageType language,
         "ASTContext for '" + module->GetFileSpec().GetPath() + "'";
     return std::make_shared<TypeSystemClang>(ast_name, triple);
   } else if (target && target->IsValid())
-    return std::make_shared<TypeSystemClangForExpressions>(*target, triple);
+    return std::make_shared<ScratchTypeSystemClang>(*target, triple);
   return lldb::TypeSystemSP();
 }
 
@@ -9567,8 +9567,8 @@ TypeSystemClang::DeclContextGetTypeSystemClang(const CompilerDeclContext &dc) {
   return nullptr;
 }
 
-TypeSystemClangForExpressions::TypeSystemClangForExpressions(
-    Target &target, llvm::Triple triple)
+ScratchTypeSystemClang::ScratchTypeSystemClang(Target &target,
+                                               llvm::Triple triple)
     : TypeSystemClang("scratch ASTContext", triple),
       m_target_wp(target.shared_from_this()),
       m_persistent_variables(new ClangPersistentVariables) {
@@ -9580,16 +9580,15 @@ TypeSystemClangForExpressions::TypeSystemClangForExpressions(
   SetExternalSource(proxy_ast_source);
 }
 
-void TypeSystemClangForExpressions::Finalize() {
+void ScratchTypeSystemClang::Finalize() {
   TypeSystemClang::Finalize();
   m_scratch_ast_source_up.reset();
 }
 
-UserExpression *TypeSystemClangForExpressions::GetUserExpression(
+UserExpression *ScratchTypeSystemClang::GetUserExpression(
     llvm::StringRef expr, llvm::StringRef prefix, lldb::LanguageType language,
     Expression::ResultType desired_type,
-    const EvaluateExpressionOptions &options,
-    ValueObject *ctx_obj) {
+    const EvaluateExpressionOptions &options, ValueObject *ctx_obj) {
   TargetSP target_sp = m_target_wp.lock();
   if (!target_sp)
     return nullptr;
@@ -9598,7 +9597,7 @@ UserExpression *TypeSystemClangForExpressions::GetUserExpression(
                                  desired_type, options, ctx_obj);
 }
 
-FunctionCaller *TypeSystemClangForExpressions::GetFunctionCaller(
+FunctionCaller *ScratchTypeSystemClang::GetFunctionCaller(
     const CompilerType &return_type, const Address &function_address,
     const ValueList &arg_value_list, const char *name) {
   TargetSP target_sp = m_target_wp.lock();
@@ -9614,8 +9613,8 @@ FunctionCaller *TypeSystemClangForExpressions::GetFunctionCaller(
 }
 
 std::unique_ptr<UtilityFunction>
-TypeSystemClangForExpressions::CreateUtilityFunction(std::string text,
-                                                     std::string name) {
+ScratchTypeSystemClang::CreateUtilityFunction(std::string text,
+                                              std::string name) {
   TargetSP target_sp = m_target_wp.lock();
   if (!target_sp)
     return {};
@@ -9625,6 +9624,6 @@ TypeSystemClangForExpressions::CreateUtilityFunction(std::string text,
 }
 
 PersistentExpressionState *
-TypeSystemClangForExpressions::GetPersistentExpressionState() {
+ScratchTypeSystemClang::GetPersistentExpressionState() {
   return m_persistent_variables.get();
 }

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

@@ -1122,11 +1122,11 @@ private:
 
 /// The TypeSystemClang instance used for the scratch ASTContext in a
 /// lldb::Target.
-class TypeSystemClangForExpressions : public TypeSystemClang {
+class ScratchTypeSystemClang : public TypeSystemClang {
 public:
-  TypeSystemClangForExpressions(Target &target, llvm::Triple triple);
+  ScratchTypeSystemClang(Target &target, llvm::Triple triple);
 
-  ~TypeSystemClangForExpressions() override = default;
+  ~ScratchTypeSystemClang() override = default;
 
   void Finalize() override;
 
@@ -1148,9 +1148,11 @@ public:
   PersistentExpressionState *GetPersistentExpressionState() override;
 private:
   lldb::TargetWP m_target_wp;
-  std::unique_ptr<ClangPersistentVariables>
-      m_persistent_variables; // These are the persistent variables associated
-                              // with this process for the expression parser
+  /// The persistent variables associated with this process for the expression
+  /// parser.
+  std::unique_ptr<ClangPersistentVariables> m_persistent_variables;
+  /// The ExternalASTSource that performs lookups and completes minimally
+  /// imported types.
   std::unique_ptr<ClangASTSource> m_scratch_ast_source_up;
 };