don't try to create tags w/o scala-reflect.jar

Since recently type tags have relocated to scala-reflect.jar,
meaning that they are no longer always on library classpath.

In the compiler we do have code that generates type tags, and this code
is bound to fail if scala-reflect.jar isn't there.

I though this wouldn't be a problem, because type tag materialization
is only going to be triggered by users explicitly requesting a type tag.

That's generally true, but I overlooked a corner case. Since we provide
manifest <-> type tag compatibility, manifest lookup can sometimes trigger
tag lookup, which might result in tag synthesis, which blows up like this:
http://groups.google.com/group/scala-internals/browse_thread/thread/166ce4b71b7c46bb

This commit also ensures that type tag generation/interop doesnt sneak into the
code of the libraries that don't have scala-reflect.jar on their classpath.
For details refer to the discussion at scala-internals:
http://groups.google.com/group/scala-internals/browse_thread/thread/72f6ce3010f4d8

1 files changed, 45 insertions, 0 deletions

diff --git a/test/files/run/typetags_without_scala_reflect_typetag_lookup.scala b/test/files/run/typetags_without_scala_reflect_typetag_lookup.scala
new file mode 100644
index 0000000000..e51ecdb180
--- /dev/null
+++ b/test/files/run/typetags_without_scala_reflect_typetag_lookup.scala
@@ -0,0 +1,45 @@
+import scala.tools.partest._
+
+object Test extends DirectTest {
+  def code = ???
+
+  def library = """
+    import scala.reflect.runtime.universe._
+
+    object Library {
+      def foo[T: TypeTag] = ()
+    }
+  """
+  def compileLibrary() = {
+    val classpath = List(sys.props("partest.lib"), sys.props("partest.reflect")) mkString sys.props("path.separator")
+    compileString(newCompiler("-cp", classpath, "-d", testOutput.path))(library)
+  }
+
+  def app = """
+    object Test extends App {
+      // tries to materialize a type tag not having scala-reflect.jar on the classpath
+      // even though it's easy to materialize a type tag of Int, this line will fail
+      // because materialization involves classes from scala-reflect.jar
+      //
+      // in this test we make sure that the compiler doesn't crash
+      // but just displays several missing class file errors and an unavailable implicit message
+      Library.foo[Int]
+    }
+  """
+  def compileApp() = {
+    val classpath = List(sys.props("partest.lib"), testOutput.path) mkString sys.props("path.separator")
+    compileString(newCompiler("-cp", classpath, "-d", testOutput.path))(app)
+  }
+
+  def show(): Unit = {
+    val prevErr = System.err
+    val baos = new java.io.ByteArrayOutputStream();
+    System.setErr(new java.io.PrintStream(baos));
+    compileLibrary();
+    compileApp();
+    // we should get bad symbolic reference errors, because we're trying to call a method that can't be unpickled
+    // but we don't know the number of these errors and their order, so I just ignore them all
+    baos.toString.split("\n") filter (!_.startsWith("error: bad symbolic reference")) foreach println
+    System.setErr(prevErr)
+  }
+}
\ No newline at end of file