LazyASTScopes only matters when ASTScopes are enabled

Author: David Ungar

include/swift/Basic/LangOptions.h

@@ -259,7 +259,7 @@ namespace swift {
     bool WarnIfASTScopeLookup = false;
 
     /// Build the ASTScope tree lazily
-    bool LazyASTScopes = false;
+    bool LazyASTScopes = true;
 
     /// Whether to use the import as member inference system
     ///

include/swift/Frontend/Frontend.h

@@ -297,7 +297,6 @@ class CompilerInvocation {
   /// Called from lldb, see rdar://53971116
   void disableASTScopeLookup() {
     LangOpts.EnableASTScopeLookup = false;
-    LangOpts.LazyASTScopes = false;
   }
 
   CodeCompletionCallbacksFactory *getCodeCompletionFactory() const {

lib/Frontend/CompilerInvocation.cpp

@@ -339,8 +339,7 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
       Opts.DisableParserLookup;
   Opts.CompareToASTScopeLookup |= Args.hasArg(OPT_compare_to_astscope_lookup);
   Opts.WarnIfASTScopeLookup |= Args.hasArg(OPT_warn_if_astscope_lookup);
-  Opts.LazyASTScopes |=
-      Opts.EnableASTScopeLookup && Args.hasArg(OPT_lazy_astscopes);
+  Opts.LazyASTScopes |= Args.hasArg(OPT_lazy_astscopes);
 
   Opts.DebugConstraintSolver |= Args.hasArg(OPT_debug_constraints);
   Opts.NamedLazyMemberLoading &= !Args.hasArg(OPT_disable_named_lazy_member_loading);