SI-7932 Exclude PolyTypes from Java generic signatures

In the enclosed test case, we were emitting just the result type of
`[a, b]Float` in the Java generic signature.

This resulted in a `GenericSignatureFormatError`.

This commit changes `argSig` to project such type functions to `*`
instead.

The test case shows that we still emit the class when we use
its type constructor directly as the type argument.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/Erasure.scala b/src/compiler/scala/tools/nsc/transform/Erasure.scala
index 60c1553ef3..4db74e70f2 100644
--- a/src/compiler/scala/tools/nsc/transform/Erasure.scala
+++ b/src/compiler/scala/tools/nsc/transform/Erasure.scala
@@ -238,8 +238,11 @@ abstract class Erasure extends AddInterfaces
               if (!(AnyRefTpe <:< bounds.hi)) "+" + boxedSig(bounds.hi)
               else if (!(bounds.lo <:< NullTpe)) "-" + boxedSig(bounds.lo)
               else "*"
-            } else {
-              boxedSig(tp)
+            } else tp match {
+              case PolyType(_, res) =>
+                "*" // SI-7932
+              case _ =>
+                boxedSig(tp)
             }
           def classSig = {
             val preRebound = pre.baseType(sym.owner) // #2585