1u32 << 1u32 doesn't work

[stepancheg]

Code:

1u32 << 1u32

results in:

tmp.rs:2:13: 2:17 error: mismatched types: expected `uint` but found `u32` (expected uint but found u32)
tmp.rs:2     1u32 << 1u32;
                     ^~~~
error: aborting due to previous error

Not sure it is a bug, at least it worked several days ago.

[brson]

Indeed, this changed as part of the removal of integer inference fallback. I believe all shifts now are int sized now in order to provide stronger type checking hints.

[stepancheg]

@brson Weird thing is that this code works:

fn foo<A : Shl<A, A>>(a: A) -> A {
    a << a
}

fn main() {
    foo(1u32);
}

[alexcrichton]

As a language item, the << operator on integral types requires a uint shift value. This helps to drive inference with the removal of the int fallback.

As a library feature, Shl specifies its type to shift by. In your first example you were invoking the language operator while in the second example you're invoking the library operator.