This is no longer necessary now that `defn` always produces a `FunctionDef`.
To compensate, I've made small edits to two contrib modules and reverted a small test change.
The bug was a regression that I introduced in #1228.
I've created a new special form named `fn*` that works like the old `fn` (that is, it always creates a `FunctionDef`). Since this is intended only for internal use, like `with*`, I haven't documented it.
I was following along and noticed that it wasn't actually explained how to _use_ the object we just made. I include both the `setv` style of writing the Hy as we've been using in the rest of the docs up to this point and a more LISP-y style use of the object.
* Remove uses of `car` and `cdr` in /hy
* Remove uses of `car` and `cdr` in quote tests
* Remove `car` and `cdr` in favor of `first` and `rest`
I beefed up the documentation and tests for `first` and `rest` while I was at it.
I defined `car` and `cdr` in native_tests.cons so the tests read a bit more naturally.
* with-decorator: Allow a `setv` form as the form to be decorated
This feature is of dubious value by itself, but it's necessary to allow `defn` to create a lambda instead of a `def`.
* Make `fn` work the same as `lambda`
That is, allow it to generate a `lambda` instead of a `def` statement if the function body is just an expression.
I've removed two uses of with_decorator in hy.compiler because they'd require adding another case to HyASTCompiler.compile_decorate_expression and they have no ultimate effect, anyway.
In a few tests, I've added a meaningless statement in `fn` bodies to force generation of a `def`.
I've removed `test_fn_compiler_empty_function` rather than rewrite it because it seems like a pain to maintain and not very useful.
* Remove `lambda`, now that `fn` does the same thing
You can use them as thousands separators.
This change differs from PEP 515 in that not only does it allow commas in addition to underscores, but it's much more liberal about placement. Any number of underscores or commas can be placed anywhere, even at the start.
