From 21f85e62063250f13afe4facf86532d2bff6f429 Mon Sep 17 00:00:00 2001
From: Richard Wei <rxwei@apple.com>
Date: Wed, 16 Feb 2022 12:55:19 -0800
Subject: [PATCH] Allow `.0` when `RegexMatch` has a non-tuple `Match`.

This is a hacky way of allowing the match result of a non-capturing regex to have a `.0` member.
---
 Sources/_StringProcessing/RegexDSL/Match.swift | 8 ++++++++
 Tests/RegexTests/RegexDSLTests.swift           | 5 +++++
 2 files changed, 13 insertions(+)

diff --git a/Sources/_StringProcessing/RegexDSL/Match.swift b/Sources/_StringProcessing/RegexDSL/Match.swift
index bf9e01f8a..4ebc99de6 100644
--- a/Sources/_StringProcessing/RegexDSL/Match.swift
+++ b/Sources/_StringProcessing/RegexDSL/Match.swift
@@ -17,6 +17,14 @@ public struct RegexMatch<Match> {
   public subscript<T>(dynamicMember keyPath: KeyPath<Match, T>) -> T {
     match[keyPath: keyPath]
   }
+
+  // Allows `.0` when `Match` is not a tuple.
+  @_disfavoredOverload
+  public subscript(
+    dynamicMember keyPath: KeyPath<(Match, _doNotUse: ()), Match>
+  ) -> Match {
+    match
+  }
 }
 
 extension RegexProtocol {
diff --git a/Tests/RegexTests/RegexDSLTests.swift b/Tests/RegexTests/RegexDSLTests.swift
index 749fd8b42..121ff2624 100644
--- a/Tests/RegexTests/RegexDSLTests.swift
+++ b/Tests/RegexTests/RegexDSLTests.swift
@@ -65,6 +65,11 @@ class RegexDSLTests: XCTestCase {
     }
   }
 
+  func testMatchResultDotZeroWithoutCapture() throws {
+    let match = try XCTUnwrap("aaa".match { oneOrMore { "a" } })
+    XCTAssertEqual(match.0, "aaa")
+  }
+
   func testAlternation() throws {
     do {
       let regex = choiceOf {