error[E0747]: type provided when a constant was expected
  --> $DIR/feature-gate-generic_arg_infer.rs:11:20
   |
LL |     let _x = foo::<_>([1,2]);
   |                    ^
   |
   = help: const arguments cannot yet be inferred with `_`
   = help: add `#![feature(generic_arg_infer)]` to the crate attributes to enable

error: aborting due to previous error

For more information about this error, try `rustc --explain E0747`.