parameter name hints do not recognize 3.6-style string formatting #344

Environment data

VS Code version: 1.18.1
Python Extension version: 0.8.0
Python Version: 3.6.2
OS and version: Windows 10 Professional

Actual behavior

When using 3.6 style f-strings as a parameter to a function, the parameter name hint breaks.
In this example, the Ogre3D constructor has multiple parameter names, with "mesh" being the first one. However, when using f-strings, the next parameter name ("shadows"), does not appear.

Expected behavior

The name hints honor f-strings and properly show the next parameter name after an f-string is given.
Here, using a normal string shows the next name hint as expected. The expected behavior is that replacing the first parameter "" with f"" would yield the same hint.

Steps to reproduce:

• Define a function with more than one parameter.
• Pass an f-string into the first parameter.
• Examine the name hint show the name of the 1st parameter after adding the comma

Logs

Output from Python output panel

Output from Console window (Help->Developer Tools menu)

/C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9 [Extension Host] rejected promise not handled within 1 second
t.log @ /C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9
/C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:10 spawn ctags ENOENT: Error: spawn ctags ENOENT
at exports._errnoException (util.js:1050:11)
at Process.ChildProcess._handle.onexit (internal/child_process.js:193:32)
at onErrorNT (internal/child_process.js:367:16)
at _combinedTickCallback (internal/process/next_tick.js:80:11)
at process._tickCallback (internal/process/next_tick.js:104:9)
e.onUnexpectedError @ /C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:10
/C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:10 command 'python.updateFeedbackCounter' not found: Error: command 'python.updateFeedbackCounter' not found
at t._tryExecuteCommand (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:1117373)
at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:1117212
at n.Class.define.cancel.then (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:69309)
at t.executeCommand (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:1117186)
at e.$executeCommand (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2823079)
at t.e.invoke (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2876809)
at e._invokeHandler (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2440566)
at e._receiveOneMessage (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2440256)
at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2439283
at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2441202
e.onUnexpectedError @ /C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:10
/C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9 [Extension Host] (node:4252) DeprecationWarning: os.tmpDir() is deprecated. Use os.tmpdir() instead.
t.log @ /C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9
62/C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:10 command 'python.updateFeedbackCounter' not found: Error: command 'python.updateFeedbackCounter' not found
at t._tryExecuteCommand (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:1117373)
at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:1117212
at n.Class.define.cancel.then (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:69309)
at t.executeCommand (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:1117186)
at e.$executeCommand (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2823079)
at t.e.invoke (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2876809)
at e._invokeHandler (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2440566)
at e._receiveOneMessage (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2440256)
at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2439283
at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2441202
e.onUnexpectedError @ /C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:10
/C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9 [Extension Host] ApplicationInsights:Sender Array(1)
t.log @ /C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9
153/C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:10 command 'python.updateFeedbackCounter' not found: Error: command 'python.updateFeedbackCounter' not found
at t._tryExecuteCommand (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:1117373)
at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:1117212
at n.Class.define.cancel.then (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:69309)
at t.executeCommand (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:1117186)
at e.$executeCommand (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2823079)
at t.e.invoke (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2876809)
at e._invokeHandler (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2440566)
at e._receiveOneMessage (file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2440256)
at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2439283
at file:///C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:9:2441202
e.onUnexpectedError @ /C:/Program Files/Microsoft VS Code/resources/app/out/vs/workbench/workbench.main.js:10