ICE: `TyKind::CVarArgs` should have been handled elsewhere about rust HOT 5 OPEN

also repros with --edition=2018

or with 2015 if you remove the async :)

from rust.

Regression in nightly-2020-12-20
fetching (via remote github) commits from max(f745834, 2020-12-17) to 1f5bc17
ending github query because we found starting sha: f745834
get_commits_between returning commits, len: 9
commit[0] 2020-12-18: Auto merge of #80081 - ehuss:update-cargo, r=Mark-Simulacrum
commit[1] 2020-12-18: Auto merge of #80154 - GuillaumeGomez:str-to-symbol, r=jyn514
commit[2] 2020-12-19: Auto merge of #77035 - mibac138:fn-fat-arrow-return, r=davidtwco
commit[3] 2020-12-19: Auto merge of #79073 - davidtwco:issue-78957-const-param-attrs, r=lcnr
commit[4] 2020-12-19: Auto merge of #80180 - JohnTitor:rollup-a31s996, r=JohnTitor
commit[5] 2020-12-19: Auto merge of #80106 - jackh726:binder-refactor-part-2, r=lcnr
commit[6] 2020-12-19: Auto merge of #79342 - CDirkx:ipaddr-const, r=oli-obk
commit[7] 2020-12-19: Auto merge of #80132 - matthewjasper:revert-eval-order, r=nikomatsakis
commit[8] 2020-12-19: Auto merge of #80104 - Nadrieril:usefulness-merging, r=varkor

from rust.

This is also kinda bad because rustc does not tell you what you did wrong (theres no error shown)

mvce:

fn walk2<F: 'static>()
where
    for<'a> ...:,
{
}

fn main() {}

from rust.