[CodeCompletion] Make lookupCodeCompletionResultsFromModule() only accept

SourceFile as the decl context.

Author: rintaro

include/swift/IDE/CodeCompletion.h

@@ -33,6 +33,7 @@ class Decl;
 class DeclContext;
 class FrontendOptions;
 class ModuleDecl;
+class SourceFile;
 
 namespace ide {
 
@@ -1025,7 +1026,7 @@ void lookupCodeCompletionResultsFromModule(CodeCompletionResultSink &targetSink,
                                            const ModuleDecl *module,
                                            ArrayRef<std::string> accessPath,
                                            bool needLeadingDot,
-                                           const DeclContext *currDeclContext);
+                                           const SourceFile *SF);
 
 /// Copy code completion results from \p sourceSink to \p targetSink, possibly
 /// restricting by \p onlyTypes. Returns copied results in \p targetSink.

lib/IDE/CodeCompletion.cpp

@@ -7440,10 +7440,9 @@ swift::ide::makeCodeCompletionCallbacksFactory(
 void swift::ide::lookupCodeCompletionResultsFromModule(
     CodeCompletionResultSink &targetSink, const ModuleDecl *module,
     ArrayRef<std::string> accessPath, bool needLeadingDot,
-    const DeclContext *currDeclContext) {
-  // Consisitently use the SourceFile as the decl context, to avoid decl
-  // context specific behaviors.
-  auto *SF = currDeclContext->getParentSourceFile();
+    const SourceFile *SF) {
+  // Use the SourceFile as the decl context, to avoid decl context specific
+  // behaviors.
   CompletionLookup Lookup(targetSink, module->getASTContext(), SF);
   Lookup.lookupExternalModuleDecls(module, accessPath, needLeadingDot);
 }
@@ -7519,8 +7518,9 @@ void SimpleCachingCodeCompletionConsumer::handleResultsAndModules(
 
   // Use the current SourceFile as the DeclContext so that we can use it to
   // perform qualified lookup, and to get the correct visibility for
-  // @testable imports.
-  DeclContext *DCForModules = DC->getParentSourceFile();
+  // @testable imports. Also it cannot use 'DC' since it would apply decl
+  // context changes to cached results.
+  const SourceFile *SF = DC->getParentSourceFile();
 
   for (auto &R : requestedModules) {
     // FIXME(thread-safety): lock the whole AST context.  We might load a
@@ -7533,7 +7533,7 @@ void SimpleCachingCodeCompletionConsumer::handleResultsAndModules(
       (*V)->Sink.annotateResult = context.getAnnotateResult();
       lookupCodeCompletionResultsFromModule(
           (*V)->Sink, R.TheModule, R.Key.AccessPath,
-          R.Key.ResultsHaveLeadingDot, DCForModules);
+          R.Key.ResultsHaveLeadingDot, SF);
       context.Cache.set(R.Key, *V);
     }
     assert(V.hasValue());