Emitted classfiles do not contain type parameter information used by javac

[smarter]

class Foo[A] {
  def foo[T](x: T) = x
}

Compiled with scalac:

public class Foo<A> {
  public <T> T foo(T);
    Code:
       0: aload_1
       1: areturn

  public Foo();
    Code:
       0: aload_0
       1: invokespecial #19                 // Method java/lang/Object."<init>":()V
       4: return
}

Compiled with dotty:

public class Foo {
  public Foo();
    Code:
       0: aload_0
       1: invokespecial #9                  // Method java/lang/Object."<init>":()V
       4: return

  public java.lang.Object foo(java.lang.Object);
    Code:
       0: aload_1
       1: areturn
}

The type parameters in the bytecode are used by javac, see tests/pending/pos/java-interop/t1263 and tests/pending/pos/java-interop/t1745 for examples (these tests are currently not run with javac even though they should, this is fixed by #1289 which moves them to pending until this is fixed).

[DarkDimius]

In order to fix this bug one needs to implement getGenericSignature and getStaticForwarderGenericSignature in DottyBackendInterface.

[smarter]

Fixed by #3234