HIR printing of `existential type` is broken

[oli-obk]

pub existential type ServeFut: Future<Output = ()>;

expanded with rustc --edition 2018 -Z unpretty=hir yields

pub existential type ServeFut : : Future<Output = ()>;

we should not print that extra :

[Pulkit07]

Hi, I will like to work on this issue.

[oli-obk]

awesome!

Most likely all that is required is to remove

rust/src/librustc/hir/print.rs

Line 649 in d58cb93

self.word_space(":")?;

you can check if there's a test in src/tests/ui that has a // compile-flags comment with -Z unpretty=hir in it. If there is, just add the above test line to it and run tests with ./x.py test --stage 1 src/test/ui --test-args name-of-the-test --bless.

If there is no such test, add such a test ;)

[alexreg]

I think I fixed this in one of my PRs, but not sure when it will merge, so go for it. :-)

[Pulkit07]

While adding test, I am getting following error message:

unexpected error: '8:5: 8:43: existential types are unstable [E0658]'

The existing test can be seen here: https://github.com/rust-lang/rust/pull/60694/files#diff-b122eeedc759d82eab86eafd6445ce8e

[oli-obk]

you need to add #![feature(existential_types)] to the test

[Pulkit07]

you need to add #![feature(existential_types)] to the test

Added that, many thanks!