SI-7455 Drop dummy param for synthetic access constructor

Java synthesizes public constructors in private classes to
allow access from inner classes. The signature of
that synthetic constructor (known as a "access constructor")
has a dummy parameter appended to avoid overloading clashes.
javac chooses the type "Enclosing$1" for the dummy parameter
(called the "access constructor tag") which is either an
existing anonymous class or a synthesized class for this purpose.

In OpenJDK, this transformation is performed in:

  langtools/src/share/classes/com/sun/tools/javac/comp/Lower.java

(Incidentally, scalac would just emits a byte-code public
constructor in this situation, rather than a private constructor /
access constructor pair.)

Scala parses the signature of the access contructor, and drops
the $outer parameter, but retains the dummy parameter. This causes
havoc when it tries to parse the bytecode for that anonymous class;
the class file parser doesn't have the enclosing type parameters
of Vector in scope and crash ensues.

In any case, we shouldn't allow user code to see that constructor;
it should only be called from within its own compilation unit.

This commit drops the dummy parameter from access constructor
signatures in class file parsing.

1 files changed, 4 insertions, 0 deletions

diff --git a/test/files/run/t7455.check b/test/files/run/t7455.check
new file mode 100644
index 0000000000..0eb9342888
--- /dev/null
+++ b/test/files/run/t7455.check
@@ -0,0 +1,4 @@
+private[package <empty>] def <init>(x$1: String): Outer[E]
+private[package <empty>] def <init>(): Outer$PrivateInner
+private[package <empty>] def <init>(): Outer$PrivateStaticInner
+private[package <empty>] def <init>(x$2: String): Outer$PublicInner