[SourceKit] New request to retrieve context type information

This is a new SourceKit request which receives a position in the source
file, returns possible expected types and their members which can be
referenced by "implicit member expression" syntax.

Author: rintaro

test/SourceKit/TypeContextInfo/typecontext_basic.swift

@@ -0,0 +1,29 @@
+enum Direction {
+  case east, west
+  case vector(x: Int, y: Int)
+  case distance(Int)
+}
+struct Target : OptionSet {
+  /// Mine.
+  static let me: Target = .init(rawValue: 1 << 0)
+  /// Yours.
+  static let you: Target = .init(rawValue: 1 << 1)
+  /// Theirs.
+  static let them: Target = .init(rawValue: 1 << 2)
+  /// One for all.
+  static var all: Target {
+    return [.me, .you, .them]
+  }
+}
+
+class C {
+  func foo(x: Direction) {}
+  func foo(x: Target) {}
+}
+
+func test(obj: C) {
+  let _ = obj.foo(x: 
+}
+
+// RUN: %sourcekitd-test -req=typecontextinfo -pos=25:22 %s -- %s > %t.response
+// RUN: diff -u %s.response %t.response

test/SourceKit/TypeContextInfo/typecontext_basic.swift.response

@@ -0,0 +1,60 @@
+{
+  key.results: [
+    {
+      key.typename: "Direction",
+      key.typeusr: "$s17typecontext_basic9DirectionOD",
+      key.implicitmembers: [
+        {
+          key.name: "east",
+          key.sourcetext: "east",
+          key.description: "east"
+        },
+        {
+          key.name: "west",
+          key.sourcetext: "west",
+          key.description: "west"
+        },
+        {
+          key.name: "vector(x:y:)",
+          key.sourcetext: "vector(x: <#T##Int#>, y: <#T##Int#>)",
+          key.description: "vector(x: Int, y: Int)"
+        },
+        {
+          key.name: "distance(_:)",
+          key.sourcetext: "distance(<#T##Int#>)",
+          key.description: "distance(Int)"
+        }
+      ]
+    },
+    {
+      key.typename: "Target",
+      key.typeusr: "$s17typecontext_basic6TargetVD",
+      key.implicitmembers: [
+        {
+          key.name: "me",
+          key.sourcetext: "me",
+          key.description: "me",
+          key.doc.brief: "Mine."
+        },
+        {
+          key.name: "you",
+          key.sourcetext: "you",
+          key.description: "you",
+          key.doc.brief: "Yours."
+        },
+        {
+          key.name: "them",
+          key.sourcetext: "them",
+          key.description: "them",
+          key.doc.brief: "Theirs."
+        },
+        {
+          key.name: "all",
+          key.sourcetext: "all",
+          key.description: "all",
+          key.doc.brief: "One for all."
+        }
+      ]
+    }
+  ]
+}

tools/SourceKit/include/SourceKit/Core/LangSupport.h

@@ -510,6 +510,29 @@ class DocInfoConsumer {
   virtual bool handleDiagnostic(const DiagnosticEntryInfo &Info) = 0;
 };
 
+struct TypeContextInfoItem {
+  StringRef TypeName;
+  StringRef TypeUSR;
+
+  struct Member {
+    StringRef Name;
+    StringRef Description;
+    StringRef SourceText;
+    StringRef DocBrief;
+  };
+  ArrayRef<Member> ImplicitMembers;
+};
+
+class TypeContextInfoConsumer {
+  virtual void anchor();
+
+public:
+  virtual ~TypeContextInfoConsumer() {}
+
+  virtual void handleResult(const TypeContextInfoItem &Result) = 0;
+  virtual void failed(StringRef ErrDescription) = 0;
+};
+
 class LangSupport {
   virtual void anchor();
 
@@ -665,6 +688,11 @@ class LangSupport {
                           ArrayRef<const char *> Args,
                           DocInfoConsumer &Consumer) = 0;
 
+  virtual void getExpressionContextInfo(llvm::MemoryBuffer *inputBuf,
+                                        unsigned Offset,
+                                        ArrayRef<const char *> Args,
+                                        TypeContextInfoConsumer &Consumer) = 0;
+
   virtual void getStatistics(StatisticsReceiver) = 0;
 };
 

tools/SourceKit/lib/Core/LangSupport.cpp

@@ -19,4 +19,5 @@ void CodeCompletionConsumer::anchor() { }
 void EditorConsumer::anchor() { }
 void OptionsDictionary::anchor() {}
 void DocInfoConsumer::anchor() { }
+void TypeContextInfoConsumer::anchor() { }
 void LangSupport::anchor() { }

tools/SourceKit/lib/SwiftLang/CMakeLists.txt

@@ -8,6 +8,7 @@ add_sourcekit_library(SourceKitSwiftLang
   SwiftIndexing.cpp
   SwiftLangSupport.cpp
   SwiftSourceDocInfo.cpp
+  SwiftTypeContextInfo.cpp
   LINK_LIBS
     SourceKitCore swiftDriver swiftFrontend
     swiftDWARFImporter swiftClangImporter swiftIDE

tools/SourceKit/lib/SwiftLang/SwiftLangSupport.h

@@ -524,6 +524,10 @@ class SwiftLangSupport : public LangSupport {
   void findModuleGroups(StringRef ModuleName, ArrayRef<const char *> Args,
                std::function<void(ArrayRef<StringRef>, StringRef Error)> Receiver) override;
 
+  void getExpressionContextInfo(llvm::MemoryBuffer *inputBuf, unsigned Offset,
+                                ArrayRef<const char *> Args,
+                                TypeContextInfoConsumer &Consumer) override;
+
   void getStatistics(StatisticsReceiver) override;
 
 private: