* Reject bad string interpolations
String interpolations with multiple comma-separate expressions or argument labels were being incorrectly accepted.
* Tweak error name to match message
* Diagnose empty interpolations more clearly
* Don’t double-diagnose parse errors
Fixes a test at Parse/recovery.swift:799 which the previous commit broke.
* Fix incorrect test RUN: line
A previous version of this test used FileCheck instead of -verify, and the run line wasn’t properly corrected to use -verify.
* Update comment
* Add more argument label tests
Ensures that we don’t get different results from an initializer that doesn’t exist or doesn’t take a String.
* Resolve the SR-7958 crasher test
We now diagnose the error and remove the label before it has an opportunity to crash.
