diff --git a/Package.swift b/Package.swift
index e95d98b67..25821a810 100644
--- a/Package.swift
+++ b/Package.swift
@@ -44,6 +44,7 @@ let package = Package(
             dependencies: ["_RegexParser", "_CUnicode"],
             swiftSettings: [
                 .unsafeFlags(["-enable-library-evolution"]),
+                .unsafeFlags(["-Xfrontend", "-enable-parameterized-protocol-types"])
             ]),
         .target(
             name: "RegexBuilder",
diff --git a/Sources/_StringProcessing/Regex/Core.swift b/Sources/_StringProcessing/Regex/Core.swift
index 96d0f3a68..b068054c6 100644
--- a/Sources/_StringProcessing/Regex/Core.swift
+++ b/Sources/_StringProcessing/Regex/Core.swift
@@ -13,7 +13,7 @@ import _RegexParser
 
 
 /// A type that represents a regular expression.
-public protocol RegexComponent {
+public protocol RegexComponent<Output> {
   associatedtype Output
   var regex: Regex<Output> { get }
 }
@@ -93,7 +93,6 @@ extension Regex {
   public init(node: DSLTree.Node) {
     self.program = Program(tree: .init(node, options: nil))
   }
-
 }
 
 // MARK: - Primitive regex components
diff --git a/Tests/RegexBuilderTests/RegexDSLTests.swift b/Tests/RegexBuilderTests/RegexDSLTests.swift
index 0c0bf7c8f..bde0f7e0b 100644
--- a/Tests/RegexBuilderTests/RegexDSLTests.swift
+++ b/Tests/RegexBuilderTests/RegexDSLTests.swift
@@ -624,38 +624,6 @@ class RegexDSLTests: XCTestCase {
     }
   }
 
-  func testDynamicCaptures() throws {
-    do {
-      let regex = try Regex(compiling: "aabcc.")
-      let line = "aabccd"
-      let match = try XCTUnwrap(line.wholeMatch(of: regex))
-      XCTAssertEqual(match.0, line[...])
-      let output = match.output
-      XCTAssertEqual(output[0].substring, line[...])
-    }
-    do {
-      let regex = try Regex(
-        compiling: #"([0-9A-F]+)(?:\.\.([0-9A-F]+))?\s+;\s+(\w+).*"#)
-      let line = """
-        A6F0..A6F1    ; Extend # Mn   [2] BAMUM COMBINING MARK KOQNDON..BAMUM \
-        COMBINING MARK TUKWENTIS
-        """
-      let match = try XCTUnwrap(line.wholeMatch(of: regex))
-      XCTAssertEqual(match.0, line[...])
-      let output = match.output
-      XCTAssertEqual(output[0].substring, line[...])
-      XCTAssertTrue(output[1].substring == "A6F0")
-      XCTAssertTrue(output[2].substring == "A6F1")
-      XCTAssertTrue(output[3].substring == "Extend")
-      let typedOutput = try XCTUnwrap(output.as(
-        (Substring, Substring, Substring?, Substring).self))
-      XCTAssertEqual(typedOutput.0, line[...])
-      XCTAssertTrue(typedOutput.1 == "A6F0")
-      XCTAssertTrue(typedOutput.2 == "A6F1")
-      XCTAssertTrue(typedOutput.3 == "Extend")
-    }
-  }
-
   func testBackreference() throws {
     try _testDSLCaptures(
       ("abc#41#42abcabcabc", ("abc#41#42abcabcabc", "abc", 42, "abc", nil)),
diff --git a/Tests/RegexTests/RegexAPITests.swift b/Tests/RegexTests/RegexAPITests.swift
new file mode 100644
index 000000000..d8ee89482
--- /dev/null
+++ b/Tests/RegexTests/RegexAPITests.swift
@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 XCTest
+@testable import _StringProcessing
+
+class RegexAPITests: XCTestCase {
+  func testDynamicConstruction() throws {
+    do {
+      let regex = try Regex(compiling: "aabcc.")
+      let line = "aabccd"
+      let match = try XCTUnwrap(line.wholeMatch(of: regex))
+      XCTAssertEqual(match.0, line[...])
+      let output = match.output
+      XCTAssertEqual(output[0].substring, line[...])
+    }
+    do {
+      let regex = try Regex(
+        compiling: #"([0-9A-F]+)(?:\.\.([0-9A-F]+))?\s+;\s+(\w+).*"#)
+      let line = """
+        A6F0..A6F1    ; Extend # Mn   [2] BAMUM COMBINING MARK KOQNDON..BAMUM \
+        COMBINING MARK TUKWENTIS
+        """
+      let match = try XCTUnwrap(line.wholeMatch(of: regex))
+      XCTAssertEqual(match.0, line[...])
+      let output = match.output
+      XCTAssertEqual(output[0].substring, line[...])
+      XCTAssertTrue(output[1].substring == "A6F0")
+      XCTAssertTrue(output[2].substring == "A6F1")
+      XCTAssertTrue(output[3].substring == "Extend")
+      let typedOutput = try XCTUnwrap(output.as(
+        (Substring, Substring, Substring?, Substring).self))
+      XCTAssertEqual(typedOutput.0, line[...])
+      XCTAssertTrue(typedOutput.1 == "A6F0")
+      XCTAssertTrue(typedOutput.2 == "A6F1")
+      XCTAssertTrue(typedOutput.3 == "Extend")
+    }
+  }
+
+  func testPrimaryAssociatedType() throws {
+    let originalRegex = try Regex(compiling: "aabcc.")
+    let regex = originalRegex as any RegexComponent<AnyRegexOutput>
+    let line = "aabccd"
+    let match = try XCTUnwrap(line.wholeMatch(of: regex))
+    XCTAssertEqual(match.0, line[...])
+    let output = match.output
+    XCTAssertEqual(output[0].substring, line[...])
+  }
+}