The body must match the following module-body grammar:
|module-body||=||(require require-spec ...) ... sig-spec ...|
The resulting signature is exported as base^, where base is derived from the enclosing module’s name (i.e., its symbolic name, or its path without the directory and file suffix). If the module name ends in -sig, then base corresponds to the module name before -sig. Otherwise, the module name serves as base.
A struct form as a sig-spec is consistent with the definitions introduced by define-struct, as opposed to definitions introduced struct. (That behavior was originally a bug, but it is preserved for compatibility.)