[CodeCompletion] Enable call signature completion for unresolved member

rdar://problem/50696432
(cherry picked from commit 5b5d342)

Author: rintaro

include/swift/Parse/CodeCompletionCallbacks.h

@@ -209,7 +209,7 @@ class CodeCompletionCallbacks {
 
   virtual void completeAssignmentRHS(AssignExpr *E) {};
 
-  virtual void completeCallArg(CodeCompletionExpr *E) {};
+  virtual void completeCallArg(CodeCompletionExpr *E, bool isFirst) {};
 
   virtual void completeReturnStmt(CodeCompletionExpr *E) {};
 

lib/IDE/CodeCompletion.cpp

@@ -1381,7 +1381,7 @@ class CodeCompletionCallbacksImpl : public CodeCompletionCallbacks {
   void completeUnresolvedMember(CodeCompletionExpr *E,
                                 SourceLoc DotLoc) override;
   void completeAssignmentRHS(AssignExpr *E) override;
-  void completeCallArg(CodeCompletionExpr *E) override;
+  void completeCallArg(CodeCompletionExpr *E, bool isFirst) override;
   void completeReturnStmt(CodeCompletionExpr *E) override;
   void completeYieldStmt(CodeCompletionExpr *E,
                          Optional<unsigned> yieldIndex) override;
@@ -4636,10 +4636,26 @@ void CodeCompletionCallbacksImpl::completeAssignmentRHS(AssignExpr *E) {
   Kind = CompletionKind::AssignmentRHS;
 }
 
-void CodeCompletionCallbacksImpl::completeCallArg(CodeCompletionExpr *E) {
+void CodeCompletionCallbacksImpl::completeCallArg(CodeCompletionExpr *E,
+                                                  bool isFirst) {
   CurDeclContext = P.CurDeclContext;
   CodeCompleteTokenExpr = E;
   Kind = CompletionKind::CallArg;
+
+  ShouldCompleteCallPatternAfterParen = false;
+  if (isFirst) {
+    ShouldCompleteCallPatternAfterParen = true;
+    if (Context.LangOpts.CodeCompleteCallPatternHeuristics) {
+      // Lookahead one token to decide what kind of call completions to provide.
+      // When it appears that there is already code for the call present, just
+      // complete values and/or argument labels.  Otherwise give the entire call
+      // pattern.
+      Token next = P.peekToken();
+      if (!next.isAtStartOfLine() && !next.is(tok::eof) && !next.is(tok::r_paren)) {
+        ShouldCompleteCallPatternAfterParen = false;
+      }
+    }
+  }
 }
 
 void CodeCompletionCallbacksImpl::completeReturnStmt(CodeCompletionExpr *E) {
@@ -5344,13 +5360,32 @@ void CodeCompletionCallbacksImpl::doneParsing() {
   }
   case CompletionKind::CallArg : {
     ExprContextInfo ContextInfo(CurDeclContext, CodeCompleteTokenExpr);
-    if (!ContextInfo.getPossibleNames().empty()) {
+
+    bool shouldPerformGlobalCompletion = true;
+
+    if (ShouldCompleteCallPatternAfterParen &&
+        !ContextInfo.getPossibleCallees().empty()) {
+      Lookup.setHaveLParen(true);
+      for (auto &typeAndDecl : ContextInfo.getPossibleCallees())
+        Lookup.tryFunctionCallCompletions(typeAndDecl.first,
+                                          typeAndDecl.second);
+      Lookup.setHaveLParen(false);
+
+      shouldPerformGlobalCompletion =
+          !Lookup.FoundFunctionCalls ||
+          (Lookup.FoundFunctionCalls &&
+           Lookup.FoundFunctionsWithoutFirstKeyword);
+    } else if (!ContextInfo.getPossibleNames().empty()) {
       Lookup.addArgNameCompletionResults(ContextInfo.getPossibleNames());
-      break;
+
+      shouldPerformGlobalCompletion = !ContextInfo.getPossibleTypes().empty();
+    }
+
+    if (shouldPerformGlobalCompletion) {
+      Lookup.setExpectedTypes(ContextInfo.getPossibleTypes(),
+                              ContextInfo.isSingleExpressionBody());
+      DoPostfixExprBeginning();
     }
-    Lookup.setExpectedTypes(ContextInfo.getPossibleTypes(),
-                            ContextInfo.isSingleExpressionBody());
-    DoPostfixExprBeginning();
     break;
   }
 

lib/IDE/TypeContextInfo.cpp

@@ -39,7 +39,7 @@ class ContextInfoCallbacks : public CodeCompletionCallbacks {
   void completeForEachSequenceBeginning(CodeCompletionExpr *E) override;
   void completeCaseStmtBeginning() override;
 
-  void completeCallArg(CodeCompletionExpr *E) override;
+  void completeCallArg(CodeCompletionExpr *E, bool isFirst) override;
   void completeReturnStmt(CodeCompletionExpr *E) override;
   void completeYieldStmt(CodeCompletionExpr *E,
                          Optional<unsigned> yieldIndex) override;
@@ -61,7 +61,8 @@ void ContextInfoCallbacks::completeForEachSequenceBeginning(
   CurDeclContext = P.CurDeclContext;
   ParsedExpr = E;
 }
-void ContextInfoCallbacks::completeCallArg(CodeCompletionExpr *E) {
+void ContextInfoCallbacks::completeCallArg(CodeCompletionExpr *E,
+                                           bool isFirst) {
   CurDeclContext = P.CurDeclContext;
   ParsedExpr = E;
 }

lib/Parse/ParseExpr.cpp

@@ -3073,7 +3073,7 @@ ParserStatus Parser::parseExprList(tok leftTok, tok rightTok,
       // Handle call arguments specially because it may need argument labels.
       auto CCExpr = new (Context) CodeCompletionExpr(Tok.getLoc());
       if (CodeCompletion)
-        CodeCompletion->completeCallArg(CCExpr);
+        CodeCompletion->completeCallArg(CCExpr, PreviousLoc == leftLoc);
       consumeIf(tok::code_complete);
       SubExpr = CCExpr;
       Status.setHasCodeCompletion();