ShowBasisDirective
==================

A comment of the form `(*#showBasis "<file>"*)` is recognized as a directive to
save the current basis (i.e., environment) to `<file>` (in the same format as
the `-show-basis <file>` <:CompileTimeOptions: compile-time option>).  The
`<file>` is interpreted relative to the source file in which it appears.  The
comment is lexed as a distinct token and is parsed as a structure-level
declaration.  [Note that treating the directive as a top-level declaration would
prohibit using it inside a functor body, which would make the feature
significantly less useful in the context of the MLton compiler sources (with its
nearly fully functorial style).]

This feature is meant to facilitate auto-completion via
https://github.com/MatthewFluet/company-mlton[`company-mlton`] and similar
tools.
