Index: include/clang/Parse/Parser.h
===================================================================
--- include/clang/Parse/Parser.h
+++ include/clang/Parse/Parser.h
@@ -214,6 +214,10 @@
   /// should not be set directly.
   bool InMessageExpression;
 
+  /// Gets set to true after calling CodeCompleteCall, it is for a hack to make
+  /// signature help working even when it is triggered inside a token.
+  bool CalledOverloadCompletion = false;
+
   /// The "depth" of the template parameters currently being parsed.
   unsigned TemplateParameterDepth;
 
Index: lib/Parse/ParseExpr.cpp
===================================================================
--- lib/Parse/ParseExpr.cpp
+++ lib/Parse/ParseExpr.cpp
@@ -1657,10 +1657,21 @@
 
       if (OpKind == tok::l_paren || !LHS.isInvalid()) {
         if (Tok.isNot(tok::r_paren)) {
-          if (ParseExpressionList(ArgExprs, CommaLocs, [&] {
-                Actions.CodeCompleteCall(getCurScope(), LHS.get(), ArgExprs);
-             })) {
+          auto Completer = [&] {
+            Actions.CodeCompleteCall(getCurScope(), LHS.get(), ArgExprs);
+            CalledOverloadCompletion = true;
+          };
+          if (ParseExpressionList(ArgExprs, CommaLocs, Completer)) {
             (void)Actions.CorrectDelayedTyposInExpr(LHS);
+            // If we got an error when parsing expression list, we don't call
+            // the CodeCompleteCall handler inside the parser. So call it here
+            // to make sure we get overload suggestions even when we are in the
+            // middle of a parameter. There is a different handling mechanism in
+            // ObjC for that type of completion, so don't call completion and
+            // let the parser do it instead.
+            if (!getLangOpts().ObjC1 && PP.isCodeCompletionReached() &&
+                !CalledOverloadCompletion)
+              Completer();
             LHS = ExprError();
           } else if (LHS.isInvalid()) {
             for (auto &E : ArgExprs)
Index: test/CodeCompletion/function-overloads-inside-param.cpp
===================================================================
--- /dev/null
+++ test/CodeCompletion/function-overloads-inside-param.cpp
@@ -0,0 +1,8 @@
+void f(int i, int j = 2, int k = 5);
+void f(float x, float y...);
+
+void test() {
+  ::f(1
+  // RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:5:8 %s -o - | FileCheck -check-prefix=CHECK-CC1 %s
+  // CHECK-CC1: f(<#int i#>{#, <#int j = 2#>{#, <#int k = 5#>#}#})
+  // CHECK-CC1: f(<#float x#>, <#float y, ...#>)
Index: test/CodeCompletion/function-overloads.cpp
===================================================================
--- /dev/null
+++ test/CodeCompletion/function-overloads.cpp
@@ -0,0 +1,8 @@
+void f(int i, int j = 2, int k = 5);
+void f(float x, float y...);
+
+void test() {
+  ::f(
+  // RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:5:7 %s -o - | FileCheck -check-prefix=CHECK-CC1 %s
+  // CHECK-CC1: f(<#int i#>{#, <#int j = 2#>{#, <#int k = 5#>#}#})
+  // CHECK-CC1: f(<#float x#>, <#float y, ...#>)