non-exhaustive match failure in alias::check_for_each

[jruderman]

fn main() { for each p in 1 {} }

rt: b1ff:main:main: upcall fail 'non-exhaustive match failure', ../src/comp/middle/alias.rs:336
rt: b1ff:main: domain main @0x200b40c root task failed

The proximate cause is that in comp::middle::alias::check_for_each, "alt call.node" has only an "ast::expr_call" arm.

[marijnh]

The alias pass is expecting some earlier pass (probably the parser should forbid this) to make sure that only call expressions occur here.