fix function isdef

[omlins]

fixes #172

[omlins]

@cstjean, can you review and merge this?

[cstjean]

It's on my todo list, but it may take a few more weeks, with covid... Sorry

[cstjean]

should that be a function definition?

We should probably check the docs. I'd call it function declaration, but if the docs say otherwise...

[matthias314]

The proposed function

islongdef(ex)  = @capture(ex, function (fcall_ | fcall_) body_ end)

seems to work (although I don't fully understand why). Replacing (fcall_ | fcall_) by fcall_ would lead to a syntax error both in Julia 1.9 and 1.10.0-beta1.

However, I think there is a problem with isshortdef: I've tried definitions of the form

ex1 = :( function f(x,y) x+y end )
ex2 = :( function (x,y) x+y end )
ex3 = :( f(x,y) = x+y )
ex4 = :( (x,y) -> x+y )

plus variants with argument type annotations, return type annotations and where clauses. They are all accepted by splitdef. Moreover, longdef preserves ex1 and ex2 and converts ex3 and ex4 to ex1 and ex2, respectively. shortdef preserves ex3 and ex4 and converts ex1 and ex2 to ex3 and ex4, respectively. islongdef is true for ex1 and ex2, but isshortdef is true only for ex3. I think it would make sense for isshortdef to return true also for ex4.

[cstjean]

Right - those would all be good test cases for whoever takes up the baton on this PR.

[matthias314]

I could give it a try. Do you insist on using @capture? For example, I think one could simply say

islongdef(ex) = isexpr(ex, :function)

Of course, this doesn't check whether ex is well-formed, but the version with @capture doesn't do this completely, either.

[cstjean]

As long as the tests have good coverage, I don't think we need to worry about malformed expressions. isexpr is fine.