Recovery from parse error

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)

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)
   }
 

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)

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)