Joseph Ferano
f585df494c
The boundary was verified by compilation and had never executed. Now it does:
three Flan functions compiled into a .so, dlopened into the test process, and
called with Forms this side laid out in raw memory.
lib/expand.ml is the image format and nothing else yet. A Form is 24 bytes,
align 8, payload at offset 8, and every case holds one member at the payload's
start -- a string and a slice are both { ptr, i64 }, so there is no third
offset anywhere in it. The tag is the case's position in the prelude's
defunion, which is why that list says it is a layout contract; a tag this file
and the prelude disagree about is named rather than read as some other case.
The case sends one Form of every one of the nine shapes through an identity
macro, so a tag nobody thought about is a failure and not a gap. Then two
arguments through a macro that reads the second, because a slice whose length
did not cross reads past its arguments and an identity macro would not notice.
Then a Form the *macro* allocated, through the prelude's form-cons, on the
loaded module's own heap: that is the direction nothing had ever tested, and
it is the one the expander spends all its time in.
Checked by breaking the last expectation before restoring it.
A parser bug this turned up, and it is the reason the previous lane's Form
work could not have been finished as written: is_type_form decides whether a
leading form is a return type or the first form of the body by asking whether
its name is a declared type, and the set it asks was collected from the file's
own declarations only. Check.program prepends the prelude to every program, so
the prelude's types are every file's types -- but nothing told the parser that.
It never mattered while the prelude's structs were only taken as parameters.
A macro is (defn m [args [Form]] Form ...), and bare Form in return position
was parsed as a body expression and reported as an unknown name, while [[Form]]
worked, because a Vec in that position is a type whatever is inside it. The
prelude's types are now part of the base set, read once.
