scala/scala — pull request #1857 by retronym (2013-01-07 17:14:35+00:00)
Title: SI-6443 Widen dependent param types in uncurry

Bridge building operates on unusual method signatures:
after uncurry, so parameter lists are collapsed; but before
erasure, so dependently typed parameters are still around.

Original:

def foo(a: T)(b: a.type, c: a.U): Unit

During computeBridges:

(a: T, b: a.type, c: a.U)Unit

This signature no longer appears to override the corresponding
one in a superclass, because the types of `b` and `c` are dependent
on method parameters.

The root of the problem is uncurry, which leaves the trees in
a poor state. This commit changes uncurry to remedy this.

An example illustrates it best:

// source
def foo(a: A)(b: a.type): b.type = b

// post uncurry before this patch.
// not well typed code!
def foo(a: A, b: a.type): a.type = {

// post uncurry after this patch
def foo(a: A)(b: A): a.type = {
val b$1 = b.asInstanceOf[a.type]
b$1
}

Review by @adriaanm