'Regex<Captures>' -> 'Regex<Match>'

[rxwei]

Changes Regex and result builder prototype to use Match as the generic parameter to make it consistent with the Strongly Typed Regex Captures pitch.

Introduces Tuple<n> structs in order to be able to express constraints on capture types (i.e. Match dropped first) while being able to filter out empty captures in concatenation. Tuple<n> is also needed to implement a prototype of the proposed matching semantics.

@frozen @dynamicMemberLookup
public struct Tuple{n}<_0, _1, ...> {
  public typealias Tuple = (_0, _1, ...)
  public var tuple: Tuple
  public init(_ tuple: Tuple)
  public init(_ _0: _0, _ _1: _1, ...)
  public subscript<T>(dynamicMember keyPath: WritableKeyPath<Tuple, T>) -> T { get _modify }
}

As coercion into Tuple<n> can no longer use runtime magic like native tuples do, we incorporate child capture type information into RECode's captureNil and captureArray instructions so that we will always get a concrete type when forming a nil or an empty array capture. The resulting existential tuple capture can then be opened and bitcast to a Tuple<n>.

[rxwei]

@kylemacomber This paves the way for Submatch (or Unbound, whatever it's called) :)

[rxwei]

@swift-ci please test linux

[rxwei]

@swift-ci please test linux

[milseman]

Overall LGTM.

In general, any switch to a nominal type makes sense to me. Out of curiosity, what necessitated this change? Also, do we need those generic parameters?

[milseman]

I don't recall whether modern computing tolerates no newline at the end of a file.

[rxwei]

Fixed. It's partly because I've been trying to use Windows to develop these days, trying Swift for Windows myself.

[rxwei]

buildBlocks need to determine whether a component has no captures. A component has no captures when every capture conforms to EmptyCaptureProtocol. For example, a OneOrMore quantifier's Match is a tuple of its whole match and an array of its capture. [Component.Match.Capture] conforms to EmptyCaptureProtocol when Component.Match.Capture (a Tuple{n}) conforms.

public struct OneOrMore<Component: RegexProtocol>: RegexProtocol {
  public typealias Match = Tuple2<Substring, [Component.Match.Capture]>

extension Tuple5: EmptyCaptureProtocol where _1: EmptyCaptureProtocol, _2: EmptyCaptureProtocol, _3: EmptyCaptureProtocol, _4: EmptyCaptureProtocol {}

[rxwei]

@swift-ci please test Linux

[rxwei]

This apparently affects regex literal type inference in the compiler, so I'll put up a PR on the compiler side to test against this.

[rxwei]

@swift-ci please test linux

[rxwei]

@swift-ci please test Linux