Add an irrefutable version of the NoSuccess extractor

NoSuccess.unapply cannot be changed due to binary compatibility.

Author: lrytz

Diff for: shared/src/main/scala/scala/util/parsing/combinator/Parsers.scala

@@ -185,6 +185,14 @@ trait Parsers {
     }
   }
 
+  /** An irrefutable version of the NoSuccess extractor, which cannot be changed due to binary compatibility. */
+  object NoSuccessE {
+    def unapply(x: NoSuccess): Some[(String, Input)] = x match {
+      case Failure(msg, next) => Some((msg, next))
+      case Error(msg, next) => Some((msg, next))
+    }
+  }
+
   /** The failure case of `ParseResult`: contains an error-message and the remaining input.
    *  Parsing will back-track when a failure occurs.
    *

Diff for: shared/src/test/scala/scala/util/parsing/combinator/PackratParsersTest.scala

@@ -28,9 +28,7 @@ class PackratParsersTest {
 
     def extractResult(r : ParseResult[Int]): Int = r match {
       case Success(a,_) => a
-      case NoSuccess(a,_) => sys.error(a)
-      case Failure(a, _) => sys.error(a)
-      case Error(a, _) => sys.error(a)
+      case NoSuccessE(a,_) => sys.error(a)
     }
     def check(expected: Int, expr: String): Unit = {
       val parseResult = head(new lexical.Scanner(expr))
@@ -84,9 +82,7 @@ class PackratParsersTest {
 
     def extractResult(r : ParseResult[Int]): Int = r match {
       case Success(a,_) => a
-      case NoSuccess(a,_) => sys.error(a)
-      case Failure(a, _) => sys.error(a)
-      case Error(a, _) => sys.error(a)
+      case NoSuccessE(a,_) => sys.error(a)
     }
     def check(expected: Int, expr: String): Unit = {
       val parseResult = head(new lexical.Scanner(expr))
@@ -109,9 +105,7 @@ class PackratParsersTest {
     val head = phrase(AnBnCn)
     def extractResult(r: ParseResult[AnBnCnResult]): AnBnCnResult = r match {
       case Success(a,_) => a
-      case NoSuccess(a,_) => sys.error(a)
-      case Failure(a, _) => sys.error(a)
-      case Error(a, _) => sys.error(a)
+      case NoSuccessE(a,_) => sys.error(a)
     }
     def threeLists(as: List[Symbol], bs: List[Symbol], cs: List[Symbol]): AnBnCnResult = {
       val as1 = as.map(_.name)
@@ -152,9 +146,7 @@ class PackratParsersTest {
 
     def extractResult(r: ParseResult[Res]): Res = r match {
       case Success(a,_) => a
-      case NoSuccess(a,_) => sys.error(a)
-      case Failure(a, _) => sys.error(a)
-      case Error(a, _) => sys.error(a)
+      case NoSuccessE(a,_) => sys.error(a)
     }
     def check(expected: Term, input: String, ctx: Ctx): Unit = {
       val parseResult = phraseTerm(new lexical.Scanner(input))