Don't destroy the scratch context in the Swift REPL after importing new dylibs.

Author: adrian-prantl

lldb/include/lldb/Target/Target.h

@@ -173,6 +173,8 @@ class TargetProperties : public Properties {
 
   bool GetUseAllCompilerFlags() const;
 
+  void SetUseAllCompilerFlags(bool b);
+
   ImportStdModule GetImportStdModule() const;
 
   bool GetEnableAutoApplyFixIts() const;

lldb/source/Plugins/ExpressionParser/Swift/SwiftREPL.cpp

@@ -146,6 +146,10 @@ lldb::REPLSP SwiftREPL::CreateInstanceFromDebugger(Status &err,
     return nullptr;
   }
 
+  // The Swift REPL can't deal with poisoning the scratch context
+  // in SwiftASTContext::ModulesDidLoad().
+  target_sp->SetUseAllCompilerFlags(false);
+
   // Limit the breakpoint to our executable module
   ModuleSP exe_module_sp(target_sp->GetExecutableModule());
   if (!exe_module_sp) {

lldb/source/Target/Target.cpp

@@ -4483,6 +4483,11 @@ bool TargetProperties::GetUseAllCompilerFlags() const {
       NULL, idx, g_target_properties[idx].default_uint_value != 0);
 }
 
+void TargetProperties::SetUseAllCompilerFlags(bool b) {
+  const uint32_t idx = ePropertyUseAllCompilerFlags;
+  m_collection_sp->SetPropertyAtIndexAsBoolean(nullptr, idx, b);
+}
+
 ImportStdModule TargetProperties::GetImportStdModule() const {
   const uint32_t idx = ePropertyImportStdModule;
   return (ImportStdModule)m_collection_sp->GetPropertyAtIndexAsEnumeration(