diff --git a/Sources/DSLConverter/Main.swift b/Sources/DSLConverter/Main.swift
index 734e54b..fa2079c 100644
--- a/Sources/DSLConverter/Main.swift
+++ b/Sources/DSLConverter/Main.swift
@@ -22,7 +22,7 @@ struct Main {
 
 var standardError = FileHandle.standardError
 
-extension FileHandle : TextOutputStream {
+extension FileHandle: @retroactive TextOutputStream {
   public func write(_ string: String) {
     guard let data = string.data(using: .utf8) else { return }
     self.write(data)
diff --git a/Sources/ExpressionParser/ExpressionParser.swift b/Sources/ExpressionParser/ExpressionParser.swift
index 6ad9d48..197d3f9 100644
--- a/Sources/ExpressionParser/ExpressionParser.swift
+++ b/Sources/ExpressionParser/ExpressionParser.swift
@@ -4,6 +4,7 @@ import Foundation
 
 struct ExpressionParser {
   private(set) var tokens = [Token]()
+  private(set) var diagnostics: Diagnostics?
 
   private let pattern: String
   private let insensitive: Bool
@@ -16,8 +17,9 @@ struct ExpressionParser {
     self.insensitive = insensitive
   }
 
-  mutating func parse() throws {
-    let ast = try _RegexParser.parse(pattern, .traditional)
+  mutating func parse() {
+    let ast = _RegexParser.parseWithRecovery(pattern, .traditional)
+    diagnostics = ast.diags
     emitNode(ast.root)
   }
 
diff --git a/Sources/ExpressionParser/Main.swift b/Sources/ExpressionParser/Main.swift
index 86322b9..15dfa7c 100644
--- a/Sources/ExpressionParser/Main.swift
+++ b/Sources/ExpressionParser/Main.swift
@@ -10,10 +10,15 @@ struct Main {
         .map { String($0) }
 
       var parser = ExpressionParser(pattern: pattern, insensitive: matchingOptions.contains("i"))
-      try parser.parse()
+      parser.parse()
 
       let data = try JSONEncoder().encode(parser.tokens)
       print(String(data: data, encoding: .utf8) ?? "")
+      if let diagnostics = parser.diagnostics {
+        for diag in diagnostics.diags {
+          print("\(diag.message)", to:&standardError)
+        }
+      }
     } catch {
       print("\(error)", to:&standardError)
     }
@@ -22,7 +27,7 @@ struct Main {
 
 var standardError = FileHandle.standardError
 
-extension FileHandle : TextOutputStream {
+extension FileHandle: @retroactive TextOutputStream {
   public func write(_ string: String) {
     guard let data = string.data(using: .utf8) else { return }
     self.write(data)
diff --git a/Sources/Matcher/Main.swift b/Sources/Matcher/Main.swift
index d871c15..7c17232 100644
--- a/Sources/Matcher/Main.swift
+++ b/Sources/Matcher/Main.swift
@@ -29,7 +29,7 @@ struct Main {
 
 var standardError = FileHandle.standardError
 
-extension FileHandle : TextOutputStream {
+extension FileHandle: @retroactive TextOutputStream {
   public func write(_ string: String) {
     guard let data = string.data(using: .utf8) else { return }
     self.write(data)
diff --git a/Tests/RegexTests/DebuggerTests.swift b/Tests/RegexTests/DebuggerTests.swift
deleted file mode 100644
index 17f01f0..0000000
--- a/Tests/RegexTests/DebuggerTests.swift
+++ /dev/null
@@ -1,140 +0,0 @@
-import Foundation
-import XCTest
-@testable import Debugger
-
-class DebuggerTests: XCTestCase {
-  func testDebugPattern01() throws {
-    let pattern = #"a(b|c)"#
-    let text = "ac"
-
-    try run(pattern: pattern, text: text, matchingOptions: [])
-    let stepCount = Context.shared.stepCount
-
-    let context = Context.shared
-    for i in 1...stepCount {
-      try run(pattern: pattern, text: text, matchingOptions: [], until: i)
-      print("step: \(context.stepCount), start: \(context.start), current: \(context.current), \(text[text.index(text.startIndex, offsetBy: context.start)..<text.index(text.startIndex, offsetBy: context.current)])")
-    }
-  }
-
-  func testDebugPattern02() throws {
-    let pattern = #".*b"#
-    let text = "abcdefgh"
-
-    try run(pattern: pattern, text: text, matchingOptions: [])
-    let stepCount = Context.shared.stepCount
-
-    let context = Context.shared
-    for i in 1...stepCount {
-      try run(pattern: pattern, text: text, matchingOptions: [], until: i)
-      print("step: \(context.stepCount), start: \(context.start), current: \(context.current), \(text[text.index(text.startIndex, offsetBy: context.start)..<text.index(text.startIndex, offsetBy: context.current)])")
-    }
-  }
-
-  func testDebugPattern03() throws {
-    let pattern = #"a"#
-    let text = "a"
-
-    try run(pattern: pattern, text: text, matchingOptions: [])
-    let stepCount = Context.shared.stepCount
-    print("stepCount: \(stepCount)")
-
-    let context = Context.shared
-    for i in 1...stepCount {
-      try run(pattern: pattern, text: text, matchingOptions: [], until: i)
-      print("step: \(context.stepCount), start: \(context.start), current: \(context.current), \(text[text.index(text.startIndex, offsetBy: context.start)..<text.index(text.startIndex, offsetBy: context.current)])")
-    }
-  }
-
-  func testDebugPattern04() throws {
-    let pattern = #"a"#
-    let text = "ab"
-
-    try run(pattern: pattern, text: text, matchingOptions: [])
-    let stepCount = Context.shared.stepCount
-    print("stepCount: \(stepCount)")
-
-    let context = Context.shared
-    for i in 1...stepCount {
-      try run(pattern: pattern, text: text, matchingOptions: [], until: i)
-      print("step: \(context.stepCount), start: \(context.start), current: \(context.current), \(text[text.index(text.startIndex, offsetBy: context.start)..<text.index(text.startIndex, offsetBy: context.current)])")
-    }
-  }
-
-  func testDebugPattern05() throws {
-    let pattern = #"a"#
-    let text = "ba"
-
-    try run(pattern: pattern, text: text, matchingOptions: [])
-    let stepCount = Context.shared.stepCount
-    print("stepCount: \(stepCount)")
-
-    let context = Context.shared
-    for i in 1...stepCount {
-      try run(pattern: pattern, text: text, matchingOptions: [], until: i)
-      print("step: \(context.stepCount), start: \(context.start), current: \(context.current), \(text[text.index(text.startIndex, offsetBy: context.start)..<text.index(text.startIndex, offsetBy: context.current)])")
-    }
-  }
-
-  func testDebugPattern06() throws {
-    let pattern = #"this|that|the"#
-    let text = "The theory that the mathematician proposed about the threshold of the universe was both innovative and controversial."
-
-    try run(pattern: pattern, text: text, matchingOptions: [])
-    let stepCount = Context.shared.stepCount
-    print("stepCount: \(stepCount)")
-
-    let context = Context.shared
-    for i in 1...stepCount {
-      try run(pattern: pattern, text: text, matchingOptions: [], until: i)
-      print("step: \(context.stepCount), start: \(context.start), current: \(context.current), \(text[text.index(text.startIndex, offsetBy: context.start)..<text.index(text.startIndex, offsetBy: context.current)])")
-    }
-  }
-
-  func testDebugPattern07() throws {
-    let pattern = #"th(?:e|is|at)"#
-    let text = "The theory that the mathematician proposed about the threshold of the universe was both innovative and controversial."
-
-    try run(pattern: pattern, text: text, matchingOptions: [])
-    let stepCount = Context.shared.stepCount
-    print("stepCount: \(stepCount)")
-
-    let context = Context.shared
-    for i in 1...stepCount {
-      try run(pattern: pattern, text: text, matchingOptions: [], until: i)
-      print("step: \(context.stepCount), start: \(context.start), current: \(context.current), \(text[text.index(text.startIndex, offsetBy: context.start)..<text.index(text.startIndex, offsetBy: context.current)])")
-    }
-  }
-
-  func testDebugPattern08() throws {
-    let pattern = #"<<<<<<< HEAD"#
-    let text = """
-    <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
-    If you have questions, please
-    <<<<<<< HEAD
-    open an issue
-    =======
-    ask your question in IRC.
-    >>>>>>> branch-a
-    """
-
-    try run(pattern: pattern, text: text, matchingOptions: [])
-    let stepCount = Context.shared.stepCount
-    print("stepCount: \(stepCount)")
-
-    let context = Context.shared
-    for i in 1...stepCount {
-      try run(pattern: pattern, text: text, matchingOptions: [], until: i)
-      print("step: \(context.stepCount), start: \(context.start), current: \(context.current), \(text[text.index(text.startIndex, offsetBy: context.start)..<text.index(text.startIndex, offsetBy: context.current)])")
-    }
-  }
-
-  func run(pattern: String, text: String, matchingOptions: [String] = [], until step: Int? = nil) throws {
-    let context = Context.shared
-    context.reset()
-    context.breakPoint = step
-
-    let debugger = Debugger()
-    try debugger.run(pattern: pattern, text: text, matchingOptions: matchingOptions)
-  }
-}
diff --git a/Tests/RegexTests/ExpressionParserTests.swift b/Tests/RegexTests/ExpressionParserTests.swift
index 78ad4e2..d1b480c 100644
--- a/Tests/RegexTests/ExpressionParserTests.swift
+++ b/Tests/RegexTests/ExpressionParserTests.swift
@@ -3,185 +3,190 @@ import XCTest
 @testable import ExpressionParser
 
 class ParserTests: XCTestCase {
-  func testParseExpression() throws {
+  func testParseExpression() {
     do {
       var parser = ExpressionParser(pattern: #"a(?R)?b"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"\d+(?(?=regex)then|else(?(?=regex)then|else))(a)^(START)?\d+(?(1)END|\b)"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"^[^<>]*(((?'Open'<)[^<>]*)+((?'Close-Open'>)[^<>]*)+)*(?(Open)(?!))$"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"hello"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"gray|grey"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"gr(a|e)y"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"gr[ae]y"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"colou?r"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"rege(x(es)?|xps?)"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"go*gle"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"go+gle"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"g(oog)+le"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"z{3}"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"z{3,6}"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"z{3,}"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"[Bb]rainf\*\*k"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"\d"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"\d+"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"\d{5}(-\d{4})?"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"1\d{10}"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"[2-9]|[12]\d|3[0-6]"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"Hello\nworld"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"mi.....ft"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"\d+(\.\d\d)?"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"[^i*&2@]"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"//[^\r\n]*[\r\n]"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"^dog"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"dog$"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"^dog$"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"\w++\d\d\w+"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"<(\w+)>[^<]*</\1>"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"Hillary(?=\s+Clinton)"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"q(?!u)"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"(?<=-)\p{L}+"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"[\x41-\x45]{3}"#)
-      try parser.parse()
+      parser.parse()
       print(parser.tokens)
     }
     do {
       var parser = ExpressionParser(pattern: #"(?(?=regex)then|else)"#)
-      try parser.parse()
+      parser.parse()
+      print(parser.tokens)
+    }
+    do {
+      var parser = ExpressionParser(pattern: #"(?<word>\w+)\W+(?<-word>\w+)"#)
+      parser.parse()
       print(parser.tokens)
     }
   }