[CodeCompletion] Implement completions in using declaration's specifier position

(cherry picked from commit 816ea9fda6)

include/swift/IDE/CodeCompletionResult.h

@@ -190,6 +190,7 @@ enum class CodeCompletionKeywordKind : uint8_t {
 enum class CompletionKind : uint8_t {
   None,
   Import,
+  Using,
   UnresolvedMember,
   DotExpr,
   StmtOrExpr,

include/swift/IDE/CompletionLookup.h

@@ -325,6 +325,8 @@ public:
 
   void addImportModuleNames();
 
+  void addUsingSpecifiers();
+
   SemanticContextKind getSemanticContext(const Decl *D,
                                          DeclVisibilityKind Reason,
                                          DynamicLookupInfo dynamicLookupInfo);

include/swift/Parse/IDEInspectionCallbacks.h

@@ -255,6 +255,10 @@ public:
   virtual void
   completeImportDecl(ImportPath::Builder &Path) {};
 
+  /// Complete the 'using' decl with supported specifiers.
+  virtual void
+  completeUsingDecl() {};
+
   /// Complete unresolved members after dot.
   virtual void completeUnresolvedMember(CodeCompletionExpr *E,
                                         SourceLoc DotLoc) {};

lib/IDE/CodeCompletion.cpp

@@ -283,6 +283,7 @@ public:
 
   void completePoundAvailablePlatform() override;
   void completeImportDecl(ImportPath::Builder &Path) override;
+  void completeUsingDecl() override;
   void completeUnresolvedMember(CodeCompletionExpr *E,
                                 SourceLoc DotLoc) override;
   void completeCallArg(CodeCompletionExpr *E) override;
@@ -550,6 +551,11 @@ void CodeCompletionCallbacksImpl::completeImportDecl(
   Path.pop_back();
 }
 
+void CodeCompletionCallbacksImpl::completeUsingDecl() {
+  Kind = CompletionKind::Using;
+  CurDeclContext = P.CurDeclContext;
+}
+
 void CodeCompletionCallbacksImpl::completeUnresolvedMember(CodeCompletionExpr *E,
     SourceLoc DotLoc) {
   Kind = CompletionKind::UnresolvedMember;
@@ -990,6 +996,7 @@ void CodeCompletionCallbacksImpl::addKeywords(CodeCompletionResultSink &Sink,
   case CompletionKind::AttributeBegin:
   case CompletionKind::PoundAvailablePlatform:
   case CompletionKind::Import:
+  case CompletionKind::Using:
   case CompletionKind::UnresolvedMember:
   case CompletionKind::AfterPoundExpr:
   case CompletionKind::AfterPoundDirective:
@@ -1915,7 +1922,10 @@ void CodeCompletionCallbacksImpl::doneParsing(SourceFile *SrcFile) {
       Lookup.addImportModuleNames();
     break;
   }
-
+  case CompletionKind::Using: {
+    Lookup.addUsingSpecifiers();
+    break;
+  }
   case CompletionKind::AfterPoundDirective: {
     addPoundDirectives(CompletionContext.getResultSink());
 

lib/IDE/CodeCompletionResult.cpp

@@ -315,6 +315,7 @@ ContextFreeCodeCompletionResult::getCodeCompletionDeclKind(const Decl *D) {
   case DeclKind::OpaqueType:
   case DeclKind::BuiltinTuple:
   case DeclKind::MacroExpansion:
+  case DeclKind::Using:
     llvm_unreachable("not expecting such a declaration result");
   case DeclKind::Module:
     return CodeCompletionDeclKind::Module;

lib/IDE/CompletionLookup.cpp

@@ -387,6 +387,23 @@ void CompletionLookup::addImportModuleNames() {
   }
 }
 
+void CompletionLookup::addUsingSpecifiers() {
+  for (unsigned i = 0,
+                n = static_cast<unsigned>(UsingSpecifier::LastSpecifier) + 1;
+       i != n; ++i) {
+    CodeCompletionResultBuilder Builder = makeResultBuilder(
+        CodeCompletionResultKind::Keyword, SemanticContextKind::None);
+    switch (static_cast<UsingSpecifier>(i)) {
+    case UsingSpecifier::MainActor:
+      Builder.addTextChunk("@MainActor");
+      break;
+    case UsingSpecifier::nonisolated:
+      Builder.addTextChunk("nonisolated");
+      break;
+    }
+  }
+}
+
 SemanticContextKind
 CompletionLookup::getSemanticContext(const Decl *D, DeclVisibilityKind Reason,
                                      DynamicLookupInfo dynamicLookupInfo) {

tools/SourceKit/tools/sourcekitd/bin/InProc/CodeCompletionSwiftInterop.cpp

@@ -489,6 +489,8 @@ swiftide_completion_result_get_kind(swiftide_completion_response_t _response) {
     return SWIFTIDE_COMPLETION_KIND_NONE;
   case CompletionKind::Import:
     return SWIFTIDE_COMPLETION_KIND_IMPORT;
+  case CompletionKind::Using:
+    return SWIFTIDE_COMPLETION_KIND_USING;
   case CompletionKind::UnresolvedMember:
     return SWIFTIDE_COMPLETION_KIND_UNRESOLVEDMEMBER;
   case CompletionKind::DotExpr:

tools/SourceKit/tools/sourcekitd/bin/InProc/CodeCompletionSwiftInterop.h

@@ -123,6 +123,7 @@ typedef enum swiftide_completion_kind_t: uint32_t {
   SWIFTIDE_COMPLETION_KIND_TYPEPOSSIBLEFUNCTIONPARAMBEGINNING = 42,
   SWIFTIDE_COMPLETION_KIND_TYPEATTRINHERITANCEBEGINNING = 43,
   SWIFTIDE_COMPLETION_KIND_TYPESIMPLEINVERTED = 44,
+  SWIFTIDE_COMPLETION_KIND_USING = 45,
 } swiftide_completion_kind_t;
 
 typedef enum swiftide_completion_item_kind_t: uint32_t {