SI-7841 More robust unspecialization of names

Names like `T1$sp`, which can arise from `AnyRef` specialization,
were leading to negative length Names if they ever passed through
`unspecializedName` or `splitSpecializedName`. This code path was
touched when printing the tree of a certain AnyRef specialized
classes after specialization, such as `AbstractPartialFunction`
(which had such specialization until a few commits ago.)

This commit handles that case correctly, and generally hardens
against unexpected names, which could pop up from third party
classes.

The documentation for `splitSpecializedName` transposed the
class and method specializations. The things you discover
when you turn examples in documentation in to test cases!

In addition, we now require non-negative length and offset in
`newTermName`

1 files changed, 46 insertions, 0 deletions

diff --git a/test/junit/scala/tools/nsc/symtab/StdNamesTest.scala b/test/junit/scala/tools/nsc/symtab/StdNamesTest.scala
new file mode 100644
index 0000000000..05e69978c6
--- /dev/null
+++ b/test/junit/scala/tools/nsc/symtab/StdNamesTest.scala
@@ -0,0 +1,46 @@
+package scala.tools.nsc
+package symtab
+
+import org.junit.Assert._
+import scala.tools.testing.AssertUtil._
+import org.junit.{Ignore, Test}
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+
+@RunWith(classOf[JUnit4])
+class StdNamesTest {
+  object symbolTable extends SymbolTableForUnitTesting
+  import symbolTable._
+  import nme.{SPECIALIZED_SUFFIX, unspecializedName, splitSpecializedName}
+
+  @Test
+  def testNewTermNameInvalid(): Unit = {
+    assertThrows[IllegalArgumentException](newTermName("foo".toCharArray, 0, -1))
+    assertThrows[IllegalArgumentException](newTermName("foo".toCharArray, 0, 0))
+    assertThrows[IllegalArgumentException](newTermName("foo".toCharArray, -1, 1))
+  }
+
+  @Test
+  def testUnspecializedName(): Unit = {
+    def test(expected: Name, nme: Name) {
+      assertEquals(expected, unspecializedName(nme))
+    }
+    test(TermName("Tuple2"), TermName("Tuple2$mcII" + SPECIALIZED_SUFFIX))
+    test(TermName("foo"), TermName("foo$mIcD" + SPECIALIZED_SUFFIX))
+    test(TermName("foo"), TermName("foo$mIc" + SPECIALIZED_SUFFIX))
+    test(TermName("T1"), TermName(s"T1$SPECIALIZED_SUFFIX"))
+    test(TermName(""), SPECIALIZED_SUFFIX)
+  }
+
+  @Test
+  def testSplitSpecializedName(): Unit = {
+    def test(expected: (Name, String, String), nme: Name) {
+      assertEquals(expected, splitSpecializedName(nme))
+    }
+    test((TermName("Tuple2"), "II", ""), TermName("Tuple2$mcII" + SPECIALIZED_SUFFIX))
+    test((TermName("foo"), "D", "I"), TermName("foo$mIcD" + SPECIALIZED_SUFFIX))
+    test((TermName("foo"), "", "I"), TermName("foo$mIc" + SPECIALIZED_SUFFIX))
+    test((TermName("T1"), "", ""), TermName(s"T1$SPECIALIZED_SUFFIX"))
+    test((TermName(""), "", ""), SPECIALIZED_SUFFIX)
+  }
+}