refactor out fresh name prefix extraction logic

1. refactor out FreshNameExtractor out of Quasiquotes cake into
   SymbolTable (can’t put it outside due to the fact that names are
   path-dependent)

2. add optional parameter to the fresh name creator to cover additional
   qq$ prefix needed for quasiquotes

3. add unit tests

1 files changed, 47 insertions, 0 deletions

diff --git a/test/junit/scala/tools/nsc/symtab/FreshNameExtractorTest.scala b/test/junit/scala/tools/nsc/symtab/FreshNameExtractorTest.scala
new file mode 100644
index 0000000000..cf09abdfff
--- /dev/null
+++ b/test/junit/scala/tools/nsc/symtab/FreshNameExtractorTest.scala
@@ -0,0 +1,47 @@
+package scala.tools.nsc
+package symtab
+
+import org.junit.Assert._
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+
+import scala.tools.testing.AssertUtil.assertThrows
+import scala.reflect.internal.util.FreshNameCreator
+
+@RunWith(classOf[JUnit4])
+class FreshNameExtractorTest {
+  object symbolTable extends SymbolTableForUnitTesting
+  import symbolTable._
+
+  val prefixes = List("foo$", "x$", "bar", "bippy$baz$")
+
+  @Test
+  def extractionPreservesPrefix =
+    ("" :: prefixes).foreach { creatorPrefix =>
+      prefixes.foreach { newPrefix =>
+        val Creator = new FreshNameCreator(creatorPrefix)
+        val Extractor = new FreshNameExtractor(creatorPrefix)
+        val Extractor(extractedPrefix) = TermName(Creator.newName(newPrefix))
+        assertEquals(newPrefix, extractedPrefix)
+      }
+    }
+
+  @Test
+  def extractionFailsOnCreatorPrefixMismatch = {
+    val Creator = new FreshNameCreator(prefixes.head)
+    val Extractor = new FreshNameExtractor(prefixes.tail.head)
+    assertThrows[MatchError] {
+      val Extractor(_) = TermName(Creator.newName("foo"))
+    }
+  }
+
+  @Test
+  def extractionsFailsIfNameDoesntEndWithNumber = {
+    val Creator = new FreshNameCreator(prefixes.head)
+    val Extractor = new FreshNameExtractor(prefixes.head)
+    assertThrows[MatchError] {
+      val Extractor(_) = TermName(Creator.newName("foo") + "bar")
+    }
+  }
+}
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