error[E0109]: const arguments are not allowed on builtin type `usize`
  --> $DIR/usize-generic-argument-parent.rs:2:18
   |
LL |     let x: usize<foo>;
   |            ----- ^^^ const argument not allowed
   |            |
   |            not allowed on builtin type `usize`
   |
help: primitive type `usize` doesn't have generic parameters
   |
LL -     let x: usize<foo>;
LL +     let x: usize;
   |

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0109`.