`#sourceLocation` should not allow string literals with string interpolation

[ahoppen]

Issue Kind

None

Source Code

#sourceLocation(file: "test\(1).swift", line: 1)

Description

No string interpolation should be allowed in the file argument of #sourceLocation.

[ahoppen]

IIRC there are multiple places in the syntax tree that should just allow a single-line string literal without interpolation. I think it would be worth creating a dedicated syntax node for those that just contains an open and close quote and a single token with the string literal’s contents. This would also disallow multi-line string literals, which would be mildly source-breaking but a good thing IMO.

[ahoppen]

Tracked in Apple’s issue tracker as rdar://111152590