[swift-evolution] ExpressibleByStringInterpolation vs. String re-evaluation vs. Regex

Jacob Bandes-Storch jtbandes at gmail.com
Sun Jul 31 00:35:52 CDT 2016

In the past, there has been some interest in refining the behavior of
ExpressibleByStringInterpolation (née StringInterpolationConvertible), for

- Ability to *restrict the types that can be used* as interpolation segments
- Ability to *distinguish the string-literal segments* from interpolation
segments whose type is String

Some prior discussions:
- "StringInterpolationConvertible and StringLiteralConvertible inheritance"
- Sub-discussion in "Allow multiple conformances to the same protocol"
- "StringInterpolationConvertible: can't distinguish between literal
components and String arguments"  https://bugs.swift.org/browse/SR-1260
/ rdar://problem/19800456&18681780
- "Proposal: Deprecate optionals in string interpolation"

About Swift 4, Chris wrote:

>  - *String re-evaluation:* String is one of the most important
> fundamental types in the language.  The standard library leads have
> numerous ideas of how to improve the programming model for it, without
> jeopardizing the goals of providing a unicode-correct-by-default model.
> Our goal is to be better at string processing than Perl!

I'd be interested in any more detail the team can provide on this. I'd like
to talk about string interpolation improvements, but it wouldn't be wise to
do so without keeping an eye towards possible regex/pattern-binding syntax,
and the String refinements that the stdlib team has in mind, if there's a
chance they would affect interpolation.


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