Starting overload selection in signature help doesn't account for discriminating arguments

*TS Template added by @mjbvz* **TypeScript Version**: 3.8.0-dev.20200201 **Search Terms** - overload --- Incorrect types sugestion with overload https://gitlab.com/kamidere-laboratory/duat/tree/testy overload is declarated in src/database/Controller.ts method create <!-- Please read our Rules of Conduct: https://opensource.microsoft.com/codeofconduct/ --> <!-- Please search existing issues to avoid creating duplicates. --> <!-- Also please test using the latest insiders build to make sure your issue has not already been fixed: https://code.visualstudio.com/insiders/ --> <!-- Use Help > Report Issue to prefill these. --> - VSCode Version: 1.41.1 - OS Version: Windows_NT x64 10.0.18362 Steps to Reproduce: 1. Write Database.create(DatabaseType.Graphite, {}) // now we get Influx overload xD 2. Change DatabaseType.Graphite to DatabaseType.Sqlite // now we get Sqlite overload :D 3. Change back to DatabaseType.Graphite // now we still get Sqlite overload :( https://youtu.be/a7FHxIItceA <!-- Launch with `code --disable-extensions` to check. --> Does this issue occur when all extensions are disabled?: Yes    ```typescript interface a { a: string; b: string; c: { a:number; b:string; } } interface b { a: string; b: string; c: { a: number; b: string; c: string[]; } } interface c { a: string; b: string; } enum d { "A" = 'a', "B" = 'b', "C" = 'c', } class testClass { constructor(arg1: d, arg2: a | b | c) { console.log(arg1, arg2) } static doSomething(arg1: d.A, arg2: a): testClass; static doSomething(arg1: d.B, arg2: b): testClass; static doSomething(arg1: d.C, arg2: c): testClass; static doSo…