active toolchain
stage2 (default)
rustc 1.53.0-dev
Build command ./x.py build -i --stage 2 --keep-stage 0 --keep-stage 1 library/std
the error says:
const trait impls are experimental
see issue #67792 https://github.com/rust-lang/rust/issues/67792 for more information
add #![feature(const_trait_impl)]
to the crate attributes to enable
But in the core/lib.rs, it's already there in a long list of features
#![feature(const_fn)]
#![feature(const_fn_union)]
#![feature(const_impl_trait)]
#![feature(const_fn_floating_point_arithmetic)]
#![feature(const_fn_fn_ptr_basics)]