Missing feature gate negative_impls

[P-E-P]

This feature gate is missing, even though it is required in order to compile core.

https://doc.rust-lang.org/beta/unstable-book/language-features/negative-impls.html

GCCRS shall be able to understand the following attribute and reject negative impls when it is missing.

#![feature(negative_impls)]

[badumbatish]

where should I perform rust_error() for missing feature gates, I'm not sure which file i should look into for this ?

[P-E-P]

where should I perform rust_error() for missing feature gates, I'm not sure which file i should look into for this ?

@badumbatish IIRC you should look into gcc/rust/checks/errors/rust-feature-gate.*