defmacro! no longer crashes when modifying arguments

[scauligi]

Fixes #112.

[Kodiologist]

Thus we see the value of hylang/hy#2410. Ain't I smart?

The implementation looks good. In tests, I think it would be better to assert against a value produced by each macro, and use hy.eval instead of macroexpand-all.

[Kodiologist]

Actually, you don't even need hy.eval, since the tests are passing.

[scauligi]

I can make them use hy.eval; I wanted to use something that would compile at runtime, otherwise on test failure (which would be a compilation / test-collection failure) pytest can't run any tests at all.

[Kodiologist]

otherwise on test failure (which would be a compilation / test-collection failure) pytest can't run any tests at all

I know. The way tests are written in both Hy and Hyrule, this is pretty normal. Even if I'd scrupulously avoided that, Hy's regression tests tend to have a lot of other interdependencies.

[scauligi]

Fair enough!