[SR-13022] Support magic literals as enum case raw value

[theblixguy]

Previous ID	SR-13022
Radar	None
Original Reporter	@theblixguy
Type	Improvement

Additional Detail from JIRA

Votes	1
Component/s	Compiler
Labels	Improvement, TypeChecker
Assignee	None
Priority	Medium

md5: 89b49aa4c8519ddc9542ad6e2571af4e

relates to:

• SR-12998 Raw Value of literal String #file breaks enum with String Protocol

Issue Description:

Currently, the use of a magic literal (such as #file) as a raw value for an enum case:

enum Foo: String {
  case bar = #file
}

triggers an error: use of '#file' literal as raw value for enum case is not supported.

We should support use of a limited set of magic literals as raw values. The eligible literals would be #file, #filePath, #function, #line and #column since their raw value types can be used as the raw type for an enum:

enum FooString: String {
  case bar = #file // okay, #file is String which matches the raw type
}

enum FooInt: Int {
  case bar = #line // okay, #line is Int which matches the raw type
}

#line and #column can be easily fetched from the SourceManager, and the same with #file and #filePath I believe. #function name can be fetched by moving getMagicFunctionName from SILGen into AST (as a method on DeclContext).

[swift-ci]

Comment by Jonathan Pappas (JIRA)

This is incredible!

Would it be appropriate to allow magic literals within error and warning directives as well?

#error(#file)
#warning(#file)
#sourceLocation(file: #file, line: #line)

[theblixguy]

I think so, it makes sense to me.