usize() is parsed as the type usize

[bluss]

This compiles, but it seems it should not:

let x: usize() = 1;

[bluss]

@ubsan pointed out that the origin is the Trait() syntax (for the no type parameters case).

[petrochenkov]

This is syntactically correct (think about let a: Fn()), but the sanity check "parenthesized parameters may only be used with a trait" is missing for primitive types.

[strega-nil]

This is equivalent to let x: usize<> = 1.