The contract now has two major differences:
- It raises an error when it would have to wrap.
- It uses chaperones to delay errors as long as possible
In general, using `Any` as a type when exporting to untyped
code will now just work, unless the untyped code tries to
communicate values back to the typed side, in which case an
immediate error will be raised.
Much of the implementation comes from the membrane design
from [Strickland et al, OOPSLA 2012].
Added a couple of contracts and fixed some others up as well.
The two bugs were that with-contract was not imported, and that
subtype could be called with Values and Results.
Caveats:
- keyword function definitions do not define static
bindings, thus limiting optimization opportunities
- can't use `define:`, `lambda:`, etc with keywords
- error messages sometimes expose the implementation
- the optimizer skips most of the generated code for
keyword functions definitions (user-level code is
optimized)
Macros and other tools that need syntax privilege used
`(current-code-inspector)' at the module top-level to try to
capture the right code inspector at load time. It's more
consistent to instead use the enclosing module's declaration-time
inspector, and `var-ref->mod-decl-insp' provides that. The
new function works only on references to anonymous variables,
which limits access to the inspector.
The real function name is longer, of course.
