diff --git a/Package.swift b/Package.swift
index 526d1d0e1..6304cc76d 100644
--- a/Package.swift
+++ b/Package.swift
@@ -100,6 +100,13 @@ let package = Package(
                 "_RegexParser",
                 "_StringProcessing"
             ]),
+        .executableTarget(
+            name: "RegexTester",
+            dependencies: [
+                .product(name: "ArgumentParser", package: "swift-argument-parser"),
+                "_RegexParser",
+                "_StringProcessing"
+            ]),
 
         // MARK: Exercises
         .target(
diff --git a/Sources/RegexBuilder/Algorithms.swift b/Sources/RegexBuilder/Algorithms.swift
index 88916879b..f809e85f5 100644
--- a/Sources/RegexBuilder/Algorithms.swift
+++ b/Sources/RegexBuilder/Algorithms.swift
@@ -23,9 +23,9 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// - Parameter content: A closure that returns a regex to match against.
   /// - Returns: The match if there is one, or `nil` if none.
   @available(SwiftStdlib 5.7, *)
-  public func wholeMatch<R: RegexComponent>(
-    @RegexComponentBuilder of content: () -> R
-  ) -> Regex<R.RegexOutput>.Match? {
+  public func wholeMatch<Output>(
+    @RegexComponentBuilder of content: () -> some RegexComponent<Output>
+  ) -> Regex<Output>.Match? {
     wholeMatch(of: content())
   }
 
@@ -35,9 +35,9 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// - Parameter content: A closure that returns a regex to match against.
   /// - Returns: The match if there is one, or `nil` if none.
   @available(SwiftStdlib 5.7, *)
-  public func prefixMatch<R: RegexComponent>(
-    @RegexComponentBuilder of content: () -> R
-  ) -> Regex<R.RegexOutput>.Match? {
+  public func prefixMatch<Output>(
+    @RegexComponentBuilder of content: () -> some RegexComponent<Output>
+  ) -> Regex<Output>.Match? {
     prefixMatch(of: content())
   }
 
@@ -49,8 +49,8 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// - Returns: `true` if the regex returned by `content` matched anywhere in
   ///   this collection, otherwise `false`.
   @available(SwiftStdlib 5.7, *)
-  public func contains<R: RegexComponent>(
-    @RegexComponentBuilder _ content: () -> R
+  public func contains(
+    @RegexComponentBuilder _ content: () -> some RegexComponent
   ) -> Bool {
     contains(content())
   }
@@ -63,8 +63,8 @@ extension BidirectionalCollection where SubSequence == Substring {
   ///   match of if the regex returned by `content`. Returns `nil` if no match
   ///   for the regex is found.
   @available(SwiftStdlib 5.7, *)
-  public func firstRange<R: RegexComponent>(
-    @RegexComponentBuilder of content: () -> R
+  public func firstRange(
+    @RegexComponentBuilder of content: () -> some RegexComponent
   ) -> Range<Index>? {
     firstRange(of: content())
   }
@@ -78,8 +78,8 @@ extension BidirectionalCollection where SubSequence == Substring {
   ///   `content`. Returns an empty collection if no match for the regex
   ///   is found.
   @available(SwiftStdlib 5.7, *)
-  public func ranges<R: RegexComponent>(
-    @RegexComponentBuilder of content: () -> R
+  public func ranges(
+    @RegexComponentBuilder of content: () -> some RegexComponent
   ) -> [Range<Index>] {
     ranges(of: content())
   }
@@ -99,10 +99,10 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// - Returns: A collection of substrings, split from this collection's
   ///   elements.
   @available(SwiftStdlib 5.7, *)
-  public func split<R: RegexComponent>(
+  public func split(
     maxSplits: Int = Int.max,
     omittingEmptySubsequences: Bool = true,
-    @RegexComponentBuilder separator: () -> R
+    @RegexComponentBuilder separator: () -> some RegexComponent
   ) -> [SubSequence] {
     split(separator: separator(), maxSplits: maxSplits, omittingEmptySubsequences: omittingEmptySubsequences)
   }
@@ -115,8 +115,8 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// - Returns: `true` if the initial elements of this collection match
   ///   regex returned by `content`; otherwise, `false`.
   @available(SwiftStdlib 5.7, *)
-  public func starts<R: RegexComponent>(
-    @RegexComponentBuilder with content: () -> R
+  public func starts(
+    @RegexComponentBuilder with content: () -> some RegexComponent
   ) -> Bool {
     starts(with: content())
   }
@@ -132,8 +132,8 @@ extension BidirectionalCollection where SubSequence == Substring {
   ///   the start of the collection, the entire contents of this collection
   ///   are returned.
   @available(SwiftStdlib 5.7, *)
-  public func trimmingPrefix<R: RegexComponent>(
-    @RegexComponentBuilder _ content: () -> R
+  public func trimmingPrefix(
+    @RegexComponentBuilder _ content: () -> some RegexComponent
   ) -> SubSequence {
     trimmingPrefix(content())
   }
@@ -145,9 +145,9 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// - Returns: The first match for the regex created by `content` in this
   ///   collection, or `nil` if no match is found.
   @available(SwiftStdlib 5.7, *)
-  public func firstMatch<R: RegexComponent>(
-    @RegexComponentBuilder of content: () -> R
-  ) -> Regex<R.RegexOutput>.Match? {
+  public func firstMatch<Output>(
+    @RegexComponentBuilder of content: () -> some RegexComponent<Output>
+  ) -> Regex<Output>.Match? {
     firstMatch(of: content())
   }
 
@@ -159,9 +159,9 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// - Returns: A collection of matches for the regex returned by `content`.
   ///   If no matches are found, the returned collection is empty.
   @available(SwiftStdlib 5.7, *)
-  public func matches<R: RegexComponent>(
-    @RegexComponentBuilder of content: () -> R
-  ) -> [Regex<R.RegexOutput>.Match] {
+  public func matches<Output>(
+    @RegexComponentBuilder of content: () -> some RegexComponent<Output>
+  ) -> [Regex<Output>.Match] {
     matches(of: content())
   }
 }
@@ -175,8 +175,8 @@ where Self: BidirectionalCollection, SubSequence == Substring {
   /// - Parameter content: A closure that returns the regex to search for
   ///   at the start of this collection.
   @available(SwiftStdlib 5.7, *)
-  public mutating func trimPrefix<R: RegexComponent>(
-    @RegexComponentBuilder _ content: () -> R
+  public mutating func trimPrefix(
+    @RegexComponentBuilder _ content: () -> some RegexComponent
   ) {
     trimPrefix(content())
   }
@@ -196,11 +196,11 @@ where Self: BidirectionalCollection, SubSequence == Substring {
   /// - Returns: A new collection in which all matches for regex in `subrange`
   ///   are replaced by `replacement`, using `content` to create the regex.
   @available(SwiftStdlib 5.7, *)
-  public func replacing<R: RegexComponent, Replacement: Collection>(
+  public func replacing<Replacement: Collection>(
     with replacement: Replacement,
     subrange: Range<Index>,
     maxReplacements: Int = .max,
-    @RegexComponentBuilder content: () -> R
+    @RegexComponentBuilder content: () -> some RegexComponent
   ) -> Self where Replacement.Element == Element {
     replacing(content(), with: replacement, subrange: subrange, maxReplacements: maxReplacements)
   }
@@ -218,10 +218,10 @@ where Self: BidirectionalCollection, SubSequence == Substring {
   /// - Returns: A new collection in which all matches for regex in `subrange`
   ///   are replaced by `replacement`, using `content` to create the regex.
   @available(SwiftStdlib 5.7, *)
-  public func replacing<R: RegexComponent, Replacement: Collection>(
+  public func replacing<Replacement: Collection>(
     with replacement: Replacement,
     maxReplacements: Int = .max,
-    @RegexComponentBuilder content: () -> R
+    @RegexComponentBuilder content: () -> some RegexComponent
   ) -> Self where Replacement.Element == Element {
     replacing(content(), with: replacement, maxReplacements: maxReplacements)
   }
@@ -237,10 +237,10 @@ where Self: BidirectionalCollection, SubSequence == Substring {
   ///   - content: A closure that returns the collection to search for
   ///     and replace.
   @available(SwiftStdlib 5.7, *)
-  public mutating func replace<R: RegexComponent, Replacement: Collection>(
+  public mutating func replace<Replacement: Collection>(
     with replacement: Replacement,
     maxReplacements: Int = .max,
-    @RegexComponentBuilder content: () -> R
+    @RegexComponentBuilder content: () -> some RegexComponent
   ) where Replacement.Element == Element {
     replace(content(), with: replacement, maxReplacements: maxReplacements)
   }
@@ -262,11 +262,11 @@ where Self: BidirectionalCollection, SubSequence == Substring {
   ///   are replaced by the result of calling `replacement`, where regex
   ///   is the result of calling `content`.
   @available(SwiftStdlib 5.7, *)
-  public func replacing<R: RegexComponent, Replacement: Collection>(
+  public func replacing<Output, Replacement: Collection>(
     subrange: Range<Index>,
     maxReplacements: Int = .max,
-    @RegexComponentBuilder content: () -> R,
-    with replacement: (Regex<R.RegexOutput>.Match) throws -> Replacement
+    @RegexComponentBuilder content: () -> some RegexComponent<Output>,
+    with replacement: (Regex<Output>.Match) throws -> Replacement
   ) rethrows -> Self where Replacement.Element == Element {
     try replacing(content(), subrange: subrange, maxReplacements: maxReplacements, with: replacement)
   }
@@ -286,10 +286,10 @@ where Self: BidirectionalCollection, SubSequence == Substring {
   ///   are replaced by the result of calling `replacement`, where regex is
   ///   the result of calling `content`.
   @available(SwiftStdlib 5.7, *)
-  public func replacing<R: RegexComponent, Replacement: Collection>(
+  public func replacing<Output, Replacement: Collection>(
     maxReplacements: Int = .max,
-    @RegexComponentBuilder content: () -> R,
-    with replacement: (Regex<R.RegexOutput>.Match) throws -> Replacement
+    @RegexComponentBuilder content: () -> some RegexComponent<Output>,
+    with replacement: (Regex<Output>.Match) throws -> Replacement
   ) rethrows -> Self where Replacement.Element == Element {
     try replacing(content(), maxReplacements: maxReplacements, with: replacement)
   }
@@ -305,10 +305,10 @@ where Self: BidirectionalCollection, SubSequence == Substring {
   ///   - replacement: A closure that receives the full match information,
   ///     including captures, and returns a replacement collection.
   @available(SwiftStdlib 5.7, *)
-  public mutating func replace<R: RegexComponent, Replacement: Collection>(
+  public mutating func replace<Output, Replacement: Collection>(
     maxReplacements: Int = .max,
-    @RegexComponentBuilder content: () -> R,
-    with replacement: (Regex<R.RegexOutput>.Match) throws -> Replacement
+    @RegexComponentBuilder content: () -> some RegexComponent<Output>,
+    with replacement: (Regex<Output>.Match) throws -> Replacement
   ) rethrows where Replacement.Element == Element {
     try replace(content(), maxReplacements: maxReplacements, with: replacement)
   }
diff --git a/Sources/RegexTester/RegexTester.swift b/Sources/RegexTester/RegexTester.swift
new file mode 100644
index 000000000..970e47160
--- /dev/null
+++ b/Sources/RegexTester/RegexTester.swift
@@ -0,0 +1,50 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2021-2022 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+import ArgumentParser
+import _RegexParser
+import _StringProcessing
+
+@main
+@available(macOS 9999, *)
+struct RegexTester: ParsableCommand {
+  typealias MatchFunctionType = (String) throws -> Regex<AnyRegexOutput>.Match?
+
+  @Argument(help: "The regex pattern to test.")
+  var pattern: String
+  
+  @Argument(help: "One or more input strings to test against <pattern>.")
+  var inputs: [String]
+  
+  @Flag(
+    name: [.customShort("p"), .customLong("partial")],
+    help: "Allow partial matches.")
+  var allowPartialMatch: Bool = false
+  
+  mutating func run() throws {
+    print("Using pattern \(pattern.halfWidthCornerQuoted)")
+    let regex = try Regex(pattern)
+    
+    for input in inputs {
+      print("Input \(input.halfWidthCornerQuoted)")
+      
+      let matchFunc: MatchFunctionType = allowPartialMatch
+        ? regex.firstMatch(in:)
+        : regex.wholeMatch(in:)
+      
+      if let result = try matchFunc(input) {
+        print("   matched: \(result.0.halfWidthCornerQuoted)")
+      } else {
+        print("   no match")
+      }
+    }
+  }
+}
diff --git a/Sources/_StringProcessing/Algorithms/Algorithms/Contains.swift b/Sources/_StringProcessing/Algorithms/Algorithms/Contains.swift
index 020ea8208..e481597f8 100644
--- a/Sources/_StringProcessing/Algorithms/Algorithms/Contains.swift
+++ b/Sources/_StringProcessing/Algorithms/Algorithms/Contains.swift
@@ -73,7 +73,7 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// `false`.
   @_disfavoredOverload
   @available(SwiftStdlib 5.7, *)
-  public func contains<R: RegexComponent>(_ regex: R) -> Bool {
+  public func contains(_ regex: some RegexComponent) -> Bool {
     _contains(RegexConsumer(regex))
   }
 }
diff --git a/Sources/_StringProcessing/Algorithms/Algorithms/FirstRange.swift b/Sources/_StringProcessing/Algorithms/Algorithms/FirstRange.swift
index 30c2fac92..696f36eca 100644
--- a/Sources/_StringProcessing/Algorithms/Algorithms/FirstRange.swift
+++ b/Sources/_StringProcessing/Algorithms/Algorithms/FirstRange.swift
@@ -77,7 +77,7 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// Returns `nil` if `regex` is not found.
   @_disfavoredOverload
   @available(SwiftStdlib 5.7, *)
-  public func firstRange<R: RegexComponent>(of regex: R) -> Range<Index>? {
+  public func firstRange(of regex: some RegexComponent) -> Range<Index>? {
     _firstRange(of: RegexConsumer(regex))
   }
 
diff --git a/Sources/_StringProcessing/Algorithms/Algorithms/Ranges.swift b/Sources/_StringProcessing/Algorithms/Algorithms/Ranges.swift
index 578c499d1..36285d7cc 100644
--- a/Sources/_StringProcessing/Algorithms/Algorithms/Ranges.swift
+++ b/Sources/_StringProcessing/Algorithms/Algorithms/Ranges.swift
@@ -253,8 +253,8 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// `regex`. Returns an empty collection if `regex` is not found.
   @_disfavoredOverload
   @available(SwiftStdlib 5.7, *)
-  public func ranges<R: RegexComponent>(
-    of regex: R
+  public func ranges(
+    of regex: some RegexComponent
   ) -> [Range<Index>] {
     Array(_ranges(of: regex))
   }
diff --git a/Sources/_StringProcessing/Algorithms/Algorithms/Replace.swift b/Sources/_StringProcessing/Algorithms/Algorithms/Replace.swift
index 5c2bc035f..ccc0962d5 100644
--- a/Sources/_StringProcessing/Algorithms/Algorithms/Replace.swift
+++ b/Sources/_StringProcessing/Algorithms/Algorithms/Replace.swift
@@ -188,8 +188,8 @@ extension RangeReplaceableCollection where SubSequence == Substring {
   /// - Returns: A new collection in which all occurrences of subsequence
   /// matching `regex` in `subrange` are replaced by `replacement`.
   @available(SwiftStdlib 5.7, *)
-  public func replacing<R: RegexComponent, Replacement: Collection>(
-    _ regex: R,
+  public func replacing<Replacement: Collection>(
+    _ regex: some RegexComponent,
     with replacement: Replacement,
     subrange: Range<Index>,
     maxReplacements: Int = .max
@@ -212,8 +212,8 @@ extension RangeReplaceableCollection where SubSequence == Substring {
   /// matching `regex` are replaced by `replacement`.
   @_disfavoredOverload
   @available(SwiftStdlib 5.7, *)
-  public func replacing<R: RegexComponent, Replacement: Collection>(
-    _ regex: R,
+  public func replacing<Replacement: Collection>(
+    _ regex: some RegexComponent,
     with replacement: Replacement,
     maxReplacements: Int = .max
   ) -> Self where Replacement.Element == Element {
@@ -232,8 +232,8 @@ extension RangeReplaceableCollection where SubSequence == Substring {
   ///   - maxReplacements: A number specifying how many occurrences of the
   ///   sequence matching `regex` to replace. Default is `Int.max`.
   @available(SwiftStdlib 5.7, *)
-  public mutating func replace<R: RegexComponent, Replacement: Collection>(
-    _ regex: R,
+  public mutating func replace<Replacement: Collection>(
+    _ regex: some RegexComponent,
     with replacement: Replacement,
     maxReplacements: Int = .max
   ) where Replacement.Element == Element {
diff --git a/Sources/_StringProcessing/Algorithms/Algorithms/Split.swift b/Sources/_StringProcessing/Algorithms/Algorithms/Split.swift
index 16cc47c39..44364df71 100644
--- a/Sources/_StringProcessing/Algorithms/Algorithms/Split.swift
+++ b/Sources/_StringProcessing/Algorithms/Algorithms/Split.swift
@@ -426,8 +426,8 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// - Returns: A collection of substrings, split from this collection's
   ///   elements.
   @_disfavoredOverload
-  public func split<R: RegexComponent>(
-    separator: R,
+  public func split(
+    separator: some RegexComponent,
     maxSplits: Int = .max,
     omittingEmptySubsequences: Bool = true
   ) -> [SubSequence] {
diff --git a/Sources/_StringProcessing/Algorithms/Algorithms/StartsWith.swift b/Sources/_StringProcessing/Algorithms/Algorithms/StartsWith.swift
index c8aaf9126..694651f3a 100644
--- a/Sources/_StringProcessing/Algorithms/Algorithms/StartsWith.swift
+++ b/Sources/_StringProcessing/Algorithms/Algorithms/StartsWith.swift
@@ -55,7 +55,7 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// - Parameter regex: A regex to compare to this sequence.
   /// - Returns: `true` if the initial elements of the sequence matches the
   ///   beginning of `regex`; otherwise, `false`.
-  public func starts<R: RegexComponent>(with regex: R) -> Bool {
+  public func starts(with regex: some RegexComponent) -> Bool {
     _starts(with: RegexConsumer(regex))
   }
   
diff --git a/Sources/_StringProcessing/Algorithms/Algorithms/Trim.swift b/Sources/_StringProcessing/Algorithms/Algorithms/Trim.swift
index 16a3cb207..37f7513db 100644
--- a/Sources/_StringProcessing/Algorithms/Algorithms/Trim.swift
+++ b/Sources/_StringProcessing/Algorithms/Algorithms/Trim.swift
@@ -291,7 +291,7 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// `prefix` from the start.
   @_disfavoredOverload
   @available(SwiftStdlib 5.7, *)
-  public func trimmingPrefix<R: RegexComponent>(_ regex: R) -> SubSequence {
+  public func trimmingPrefix(_ regex: some RegexComponent) -> SubSequence {
     _trimmingPrefix(RegexConsumer(regex))
   }
 
@@ -313,7 +313,7 @@ extension RangeReplaceableCollection
   /// - Parameter regex: The regex to remove from this collection.
   @_disfavoredOverload
   @available(SwiftStdlib 5.7, *)
-  public mutating func trimPrefix<R: RegexComponent>(_ regex: R) {
+  public mutating func trimPrefix(_ regex: some RegexComponent) {
     _trimPrefix(RegexConsumer(regex))
   }
 
diff --git a/Sources/_StringProcessing/Algorithms/Matching/FirstMatch.swift b/Sources/_StringProcessing/Algorithms/Matching/FirstMatch.swift
index 2b6dd1704..c8c6867f4 100644
--- a/Sources/_StringProcessing/Algorithms/Matching/FirstMatch.swift
+++ b/Sources/_StringProcessing/Algorithms/Matching/FirstMatch.swift
@@ -58,9 +58,9 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// - Returns: The first match of `regex` in the collection, or `nil` if
   /// there isn't a match.
   @available(SwiftStdlib 5.7, *)
-  public func firstMatch<R: RegexComponent>(
-    of r: R
-  ) -> Regex<R.RegexOutput>.Match? {
+  public func firstMatch<Output>(
+    of r: some RegexComponent<Output>
+  ) -> Regex<Output>.Match? {
     let slice = self[...]
     return try? r.regex.firstMatch(in: slice)
   }
diff --git a/Sources/_StringProcessing/Algorithms/Matching/MatchReplace.swift b/Sources/_StringProcessing/Algorithms/Matching/MatchReplace.swift
index 38224e30f..6bc9b4d77 100644
--- a/Sources/_StringProcessing/Algorithms/Matching/MatchReplace.swift
+++ b/Sources/_StringProcessing/Algorithms/Matching/MatchReplace.swift
@@ -126,11 +126,11 @@ extension RangeReplaceableCollection where SubSequence == Substring {
   /// - Returns: A new collection in which all occurrences of subsequence
   /// matching `regex` are replaced by `replacement`.
   @available(SwiftStdlib 5.7, *)
-  public func replacing<R: RegexComponent, Replacement: Collection>(
-    _ regex: R,
+  public func replacing<Output, Replacement: Collection>(
+    _ regex: some RegexComponent<Output>,
     subrange: Range<Index>,
     maxReplacements: Int = .max,
-    with replacement: (Regex<R.RegexOutput>.Match) throws -> Replacement
+    with replacement: (Regex<Output>.Match) throws -> Replacement
   ) rethrows -> Self where Replacement.Element == Element {
 
     precondition(maxReplacements >= 0)
@@ -162,10 +162,10 @@ extension RangeReplaceableCollection where SubSequence == Substring {
   /// - Returns: A new collection in which all occurrences of subsequence
   /// matching `regex` are replaced by `replacement`.
   @available(SwiftStdlib 5.7, *)
-  public func replacing<R: RegexComponent, Replacement: Collection>(
-    _ regex: R,
+  public func replacing<Output, Replacement: Collection>(
+    _ regex: some RegexComponent<Output>,
     maxReplacements: Int = .max,
-    with replacement: (Regex<R.RegexOutput>.Match) throws -> Replacement
+    with replacement: (Regex<Output>.Match) throws -> Replacement
   ) rethrows -> Self where Replacement.Element == Element {
     try replacing(
       regex,
@@ -183,10 +183,10 @@ extension RangeReplaceableCollection where SubSequence == Substring {
   ///   - replacement: A closure that receives the full match information,
   ///   including captures, and returns a replacement collection.
   @available(SwiftStdlib 5.7, *)
-  public mutating func replace<R: RegexComponent, Replacement: Collection>(
-    _ regex: R,
+  public mutating func replace<Output, Replacement: Collection>(
+    _ regex: some RegexComponent<Output>,
     maxReplacements: Int = .max,
-    with replacement: (Regex<R.RegexOutput>.Match) throws -> Replacement
+    with replacement: (Regex<Output>.Match) throws -> Replacement
   ) rethrows where Replacement.Element == Element {
     self = try replacing(
       regex,
diff --git a/Sources/_StringProcessing/Algorithms/Matching/Matches.swift b/Sources/_StringProcessing/Algorithms/Matching/Matches.swift
index 293520735..a7cd17779 100644
--- a/Sources/_StringProcessing/Algorithms/Matching/Matches.swift
+++ b/Sources/_StringProcessing/Algorithms/Matching/Matches.swift
@@ -204,15 +204,15 @@ extension BidirectionalCollection where SubSequence == Substring {
   /// - Parameter regex: The regex to search for.
   /// - Returns: A collection of matches of `regex`.
   @available(SwiftStdlib 5.7, *)
-  public func matches<R: RegexComponent>(
-    of r: R
-  ) -> [Regex<R.RegexOutput>.Match] {
+  public func matches<Output>(
+    of r: some RegexComponent<Output>
+  ) -> [Regex<Output>.Match] {
     let slice = self[...]
     var start = self.startIndex
     let end = self.endIndex
     let regex = r.regex
 
-    var result = [Regex<R.RegexOutput>.Match]()
+    var result = [Regex<Output>.Match]()
     while start <= end {
       guard let match = try? regex._firstMatch(
         slice.base, in: start..<end
diff --git a/Sources/_StringProcessing/Regex/Core.swift b/Sources/_StringProcessing/Regex/Core.swift
index 5d2101afe..5c99e2ccd 100644
--- a/Sources/_StringProcessing/Regex/Core.swift
+++ b/Sources/_StringProcessing/Regex/Core.swift
@@ -14,7 +14,7 @@
 
 /// A type that represents a regular expression.
 @available(SwiftStdlib 5.7, *)
-public protocol RegexComponent {
+public protocol RegexComponent<RegexOutput> {
   associatedtype RegexOutput
   var regex: Regex<RegexOutput> { get }
 }