Fails to decompile "x, y = y, x" or other TUPLE = TUPLE where rhs is not literal

[jpivarski]

Examples: x, y = y, x incorrectly decompiles to x = y = y and x, y = 1, z incorrectly decompiles to x = y = 1.

The fix is jpivarski@0941482 and I'll submit a pull request as soon as I can figure out how this testing framework works.

Below are tests I performed by hand. The "CORRECT" is after my correction, "INCORRECT" is original:

SOURCE             CORRECT             INCORRECT             
-----------------------------------------------------------
x = 1              x = 1               x = 1
x = 1, 2           x = (1, 2)          x = (1, 2)
x, y = 1, 2        (x, y) = (1, 2)     (x, y) = (1, 2)
x = 1, z           x = (1, z)          x = (1, z)
x, y = 1, z        (x, y) = (1, z)     x = y = 1           WRONG!
x, y = y, x        (x, y) = (y, x)     x = y = y           WRONG!
x, y, z = 1        (x, y, z) = 1       (x, y, z) = 1
x, y, z = zzz      (x, y, z) = zzz     (x, y, z) = zzz
x, y, z = 1, 2     (x, y, z) = (1, 2)  (x, y, z) = (1, 2)
x, y, z = 1, z     (x, y, z) = (1, z)  (x, y, z) = (1, z)
x = y = 1          x = y = 1           x = y = 1
x = y = 1, 2       x = y = (1, 2)      x = y = (1, 2)
x = y = 1, z       x = y = (1, z)      x = y = (1, z)
x = y = z          x = y = z           x = y = z
x = y = z = 1      x = y = z = 1       x = y = z = 1
x = y = z = 1, 2   x = y = z = (1, 2)  x = y = z = (1, 2)
x = y = z = 1, z   x = y = z = (1, z)  x = y = z = (1, z)
x, y = z = 1, z    (x, y) = z = (1, z) (x, y) = z = (1, z)

So it really was just this narrow case.

[jpivarski]

Clarification: we only see this as a bug inside of a function. I've written unit tests and will be pull-requesting shortly.