[SourceKit] Disable labeled trailing closure support except code completion

Don't insert CodeCompletionExpr at the cursor position in
"conforming method list" or "typecontext" mode. This increase the chance
of successful type checking.

rdar://problem/63781922

Author: rintaro

include/swift/Parse/CodeCompletionCallbacks.h

@@ -198,6 +198,10 @@ class CodeCompletionCallbacks {
 
   virtual void completeCallArg(CodeCompletionExpr *E, bool isFirst) {};
 
+  virtual bool canPerformCompleteLabeledTrailingClosure() const {
+    return false;
+  }
+
   virtual void completeLabeledTrailingClosure(CodeCompletionExpr *E,
                                               bool isAtStartOfLine) {};
 

lib/IDE/CodeCompletion.cpp

@@ -1687,6 +1687,10 @@ class CodeCompletionCallbacksImpl : public CodeCompletionCallbacks {
   void completeLabeledTrailingClosure(CodeCompletionExpr *E,
                                       bool isAtStartOfLine) override;
 
+  bool canPerformCompleteLabeledTrailingClosure() const override {
+    return true;
+  }
+
   void completeReturnStmt(CodeCompletionExpr *E) override;
   void completeYieldStmt(CodeCompletionExpr *E,
                          Optional<unsigned> yieldIndex) override;

lib/Parse/ParseExpr.cpp

@@ -3213,6 +3213,13 @@ Parser::parseTrailingClosures(bool isExprBasic, SourceRange calleeRange,
       if (!Tok.is(tok::code_complete))
         break;
 
+      // If the current completion mode doesn't support trailing closure
+      // completion, leave the token here and let "postfix completion" to
+      // handle it.
+      if (CodeCompletion &&
+          !CodeCompletion->canPerformCompleteLabeledTrailingClosure())
+        break;
+
       // foo() {} <token>
       auto CCExpr = new (Context) CodeCompletionExpr(Tok.getLoc());
       if (CodeCompletion)

test/IDE/conforming-methods-afterclosure.swift

@@ -0,0 +1,27 @@
+// RUN: %target-swift-ide-test -conforming-methods -source-filename %s -code-completion-token=AFTER_TRAILINGCLOSURE -module-name MyModule -conforming-methods-expected-types 's:8MyModule7TargetPP' | %FileCheck %s -check-prefix=AFTER_TRAILINGCLOSURE
+
+public protocol TargetP {}
+struct ConcreteP: TargetP {}
+
+public struct MyStruct {
+    init(arg1: Int = 0, fn: () -> Int) {}
+
+    public func returnSomeP -> some TargetP { ConcreteP() }
+    public func returnConcreteP -> ConcreteP { ConcreteP() }
+    public func reutrnInt -> Int { 1 }
+}
+
+func test() {
+    MyStruct {
+        1
+    } #^AFTER_TRAILINGCLOSURE^#
+}
+
+//AFTER_TRAILINGCLOSURE:      -----BEGIN CONFORMING METHOD LIST-----
+//AFTER_TRAILINGCLOSURE-NEXT: - TypeName: MyStruct
+//AFTER_TRAILINGCLOSURE-NEXT: - Members:
+//AFTER_TRAILINGCLOSURE-NEXT:    - Name: returnSomeP()
+//AFTER_TRAILINGCLOSURE-NEXT:      TypeName: some TargetP
+//AFTER_TRAILINGCLOSURE-NEXT:    - Name: returnConcreteP()
+//AFTER_TRAILINGCLOSURE-NEXT:      TypeName: ConcreteP
+//AFTER_TRAILINGCLOSURE-NEXT: -----END CONFORMING METHOD LIST-----