Prism accepts MultiWrite and Splat assign where Ruby rejects

[tompng]

MultiWrite or Splat assign like this

a = *b
(*) = a
*a = b

are accepted in these places in Prism, but Ruby rejects it.

+ a = *b
f b = *c
f((*) = a)
f[a = *b]
[a = *b]
a = *b = *c
* = (*) = *a
f(**a = *b)
f(*a = *b)
.. a = *b
a = *b in c
f (*)=key => (*)=value
{ key: (*)=value }
{ (*)=key => (*)=value }