Incorrect error message on code with (apaprently) no errors

[psilord]

Hello,

The intention of this code is to select a function and bind it to a symbol.

The shader code:

  (let ((easing-func
          (cond
            ((= easing-func-id 0)
             #'umbra.easing:bounce-in)
            ((= easing-func-id 1)
             #'umbra.easing:bounce-out)
            (t
             #'umbra.easing:bounce-in))))

     (some-other-func easing-func 1 2 3 4 5)

    .....)

results in:

    Varjo: Found an invalid attempt to make a local variable EASING-FUNC with the
type (OR (FUNCTION (FLOAT) FLOAT)
         (OR (FUNCTION (FLOAT) FLOAT) (FUNCTION (FLOAT) FLOAT)))

This usually happens due to the use of a conditions (like an 'if') where the
different branches of the conditional have different types. Due to this CEPL
can't infer a single valid type for this form and this is triggering this
issue.
[Condition of type VARJO-CONDITIONS:LET-OR]

Thank you!

[cbaggers]

Ah ok, so the error message is a bit bad here. The problem is that varjo needs to be able to resolve function calls statically and there is no way to know the value of easing-func until runtime. Of course if we had constant propagation there would be resolvable in more cases, however this would still apply sometimes.

[cbaggers]

I'll close this once I've made a better error for this case

[psilord]

What I really need, though is the ability to have an array of higher order functions and then index it in the shader. Is this concept possible in Varjo? Thank you!

[cbaggers]

Nope, the only way would involve passing around an identifier (e.g. an int) and having a switch at every call site. This would work but would have non-obvious implications on performance (think divergence) which would require folks to always debug against the glsl (as it would be too hard to predict the resulting code)

It's a bummer though as otherwise it would be a dope feature :D

[cbaggers]

Pushed a better error message for the cases when the all the branches of the or type are functions