Add ~= overloads (#335)

Author: milseman

Sources/_StringProcessing/Regex/Match.swift

@@ -185,3 +185,15 @@ extension Regex {
     self.init(node: .quotedLiteral(string))
   }
 }
+
+@available(SwiftStdlib 5.7, *)
+public func ~=<Output>(regex: Regex<Output>, input: String) -> Bool {
+  guard let _ = try? regex.wholeMatch(in: input) else { return false }
+  return true
+}
+
+@available(SwiftStdlib 5.7, *)
+public func ~=<Output>(regex: Regex<Output>, input: Substring) -> Bool {
+  guard let _ = try? regex.wholeMatch(in: input) else { return false }
+  return true
+}

Tests/RegexTests/AlgorithmsTests.swift

@@ -172,4 +172,19 @@ class RegexConsumerTests: XCTestCase {
       s2.matches(of: regex).map(\.0),
       ["aa"])
   }
+
+  func testSwitches() {
+    switch "abcde" {
+    case try! Regex("a.*f"):
+      XCTFail()
+    case try! Regex("abc"):
+      XCTFail()
+
+    case try! Regex("a.*e"):
+      break // success
+
+    default:
+      XCTFail()
+    }
+  }
 }