Statically enforce type equivalence for _testDSLCaptures

Author: hamishknight

Tests/RegexBuilderTests/RegexDSLTests.swift

@@ -22,7 +22,7 @@ class RegexDSLTests: XCTestCase {
     file: StaticString = #file,
     line: UInt = #line,
     @RegexComponentBuilder _ content: () -> Content
-  ) throws {
+  ) throws where Content.RegexOutput == MatchType {
     let regex = content()
     for (input, maybeExpectedCaptures) in tests {
       let maybeMatch = input.wholeMatch(of: regex)
@@ -33,13 +33,7 @@ class RegexDSLTests: XCTestCase {
           XCTFail("Unexpectedly matched", file: file, line: line)
           continue
         }
-        XCTAssertTrue(
-          type(of: regex).RegexOutput.self == MatchType.self,
-          """
-          Expected match type: \(MatchType.self)
-          Actual match type: \(type(of: regex).RegexOutput.self)
-          """)
-        let captures = try XCTUnwrap(match.output as? MatchType, file: file, line: line)
+        let captures = match.output
         XCTAssertTrue(
           equivalence(captures, expectedCaptures),
           "'\(captures)' is not equal to the expected '\(expectedCaptures)'.",