Unary operations on literals

[iamdefinitelyahuman]

What I did

Fixed some issues with negating constants.

The following example was failing because bounds checks caught 2**127 as an overflow before applying the -:

@public
def foo() -> int128:
    return -2**127

The following example was also failing with a clamping error:

a: constant(decimal) = 1.1

@public
def foo() -> decimal:
    return -a

How I did it

When an unary operation is applied to a constant, return the negated value without applying bounds checks on the original value.

How to verify it

Run the tests. I added some new test cases to verify that the issue is fixed.

Cute Animal Picture

[charles-cooper]

this should just be -2**127