ClangCodeModel: Show only valid applicable overloads when completing

libclang is smart enough to filter the overloads according to which
arguments have already been entered, so let's make use of that.

Fixes: QTCREATORBUG-650
Change-Id: Ic2711f460c908c6fd9c8efe28c3c63a0ce2d9205
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/clangcodemodel/clangcompletioncontextanalyzer.cpp

@@ -183,11 +183,8 @@ void ClangCompletionContextAnalyzer::handleFunctionCall(int afterOperatorPositio
             const int functionNameStart = startOfFunctionCall(afterOperatorPosition);
             if (functionNameStart >= 0) {
                 m_addSnippets = functionNameStart == afterOperatorPosition;
-                // Always pass the position right after '(' to libclang because
-                // positions after the comma might be problematic if a preceding
-                // argument is invalid code.
                 setActionAndClangPosition(PassThroughToLibClangAfterLeftParen,
-                                          m_positionForProposal,
+                                          afterOperatorPosition,
                                           functionNameStart);
             } else { // e.g. "(" without any function name in front
                 m_addSnippets = true;