* Meta: Fix hangs on calls to meta functions
This commit fixes a subtle bug whereby setting the meta of an existing
binder would cause hangs. Ultimately, this still points to an underlying
issue in our Lookup code that causes such loops, but for now this at
least fixes the hang introduced by the doc call in `core/Tuples.carp`
(see issue #842).
The primary fix seems to be related to setting the parentEnv in a case
in which we failed to do so in `Eval.hs`. Additionally, our meta setting
macros call `eval` which causes them to be evaluated *immediately after*
expansion, causing them to be evaluated in the incorrect context in the
Tuples.carp case.
Additionally:
- Refactored primitiveMetaSet and primitiveMeta to make them cleaner.
- Only set `implements` early when we're certain we won't accidentally
overwrite the interface.
- Generalize DocStub to `MetaStub` so that it may be used for forward
meta declarations of any kind.
* Macros: Don't eval meta-set! macros
Calling eval in the body of the meta-set! macros can cause them to be
evaluated before anticipated, possibly setting the meta on a binding in
the incorrect environment. An exemplary case of this issue existed in
`Tuples.carp` (also fixed in this commit) whereby the generated
defmodule for a tuple type called doc, which was evaluated *before* the
emitted module, resulting in overwrites of global name docs instead of
the expected module function.
We retain `evals` in macros that are more useful in the repl, such as
`print-doc`. If a user wants to evaluated one of the meta-set macros in
the REPL, they'll need to add a call to eval.
* Macros: Restore calls to eval
Turns out the meta-set! macros *do* require calls to eval, unlike I
reported in the previous commit. This commit restores those and replaces
the `doc` call in `Tuples.carp` with a direct `meta-set!` to ensure we
have docs for those functions.
Also fixed a small error in implements primitive.
* Primitives: Refactor i->inner in primitiveImplements
