Shape information allows the linker to check the importing
module's compile-time expectation against the run-time
value of its imports. The JIT, in turn, can rely on that
checking to better inline structure-type predicates, etc.,
and to more directy call JIT-generated code across
module boundaries.
In addition to checking the "shape" of an import, the import's
JITted vs. non-JITted state must be consistent. To prevent shifts
in JIT state, the `eval-jit-enabled' parameter is now restricted
in its effect to top-level bindings.
The new parameter (and supporting environment variables and
command-line flags) can bytecode lookup to a tree other than
where a source file resides, so that sources and generated
compiled files can be kept separate. It also supports storing
bytecode files in a version-specific location (either with
the source or elsewhere).
When a module is loaded from bytecode and then the value of
`use-compiled-file-paths' changes, an attempt to load a submodule
would fail, because source isn't used if the main module is
already declared, and the bytecode code is not used according to
`use-compiled-file-paths'. Make the bytecode path stick when it
is used once, so that submodule loads succeed, and make it work
even with `namespace-module-attach'.
The module-attach part of this protocol requires a change to the
API of a module name resolver: the notification mode gets two
arguments, instead of one, where the second argument is an
environment.
Setting the environment variable causes the bytecode compiler to run
the bytecode validator (which is normally applied to input from a
bytecode file) immediately on all of the compiler's own results.
including adding some uses of `with-module-read-parameterization'
so that `read-accept-lang' is set right anyway; still, so many
many places just set `read-accept-reader' to #t that making
`read-accept-lang' #f by default looks like too big of an
incompatibility
