SI-8818 FreshName extractor forgives suffix

The test is corrected (inverted) and the extractor is made
more succinct.  Succinctness isn't enforced by the test,
but I checked it manually.

1 files changed, 14 insertions, 10 deletions

diff --git a/src/reflect/scala/reflect/internal/FreshNames.scala b/src/reflect/scala/reflect/internal/FreshNames.scala
index 7e9a568266..17883d12ad 100644
--- a/src/reflect/scala/reflect/internal/FreshNames.scala
+++ b/src/reflect/scala/reflect/internal/FreshNames.scala
@@ -7,6 +7,7 @@ package reflect
 package internal
 
 import scala.reflect.internal.util.FreshNameCreator
+import scala.util.matching.Regex
 
 trait FreshNames { self: Names with StdNames =>
   // SI-6879 Keeps track of counters that are supposed to be globally unique
@@ -23,17 +24,20 @@ trait FreshNames { self: Names with StdNames =>
   // Extractor that matches names which were generated by some
   // FreshNameCreator with known prefix. Extracts user-specified
   // prefix that was used as a parameter to newName by stripping
-  // global creator prefix and unique number in the end of the name.
+  // global creator prefix and unique numerical suffix.
+  // The creator prefix and numerical suffix may both be empty.
   class FreshNameExtractor(creatorPrefix: String = "") {
-    // quote prefix so that it can be used with replaceFirst
-    // which expects regExp rather than simple string
-    val quotedCreatorPrefix = java.util.regex.Pattern.quote(creatorPrefix)
-
-    def unapply(name: Name): Option[String] = {
-      val sname = name.toString
-      // name should start with creatorPrefix and end with number
-      if (!sname.startsWith(creatorPrefix) || !sname.matches("^.*\\d*$")) None
-      else Some(NameTransformer.decode(sname.replaceFirst(quotedCreatorPrefix, "").replaceAll("\\d*$", "")))
+
+    // name should start with creatorPrefix and end with number
+    val freshlyNamed = {
+      val pre = if (!creatorPrefix.isEmpty) Regex quote creatorPrefix else ""
+      s"""$pre(.*?)\\d*""".r
     }
+
+    def unapply(name: Name): Option[String] =
+      name.toString match {
+        case freshlyNamed(prefix) => Some(prefix)
+        case _                    => None
+      }
   }
 }