Functions from other modules are never inlined

[rniii]

As an example, here's a function composition operator:

let (>>) f g x = f (g x)

Using it from the same file as it is defined always gets the function inlined --

let logPlusTwo = Js.log >> ((+) 2)

function logPlusTwo(param) {
  console.log(2 + param | 0);
}

But when moving the operator to something like an Utils module, the inlining never happens, which makes the output unnecessarily large. Explicitly annotating it with [@inline] also doesn't seem to do anything.

Is this a limitation with the build system working file-by-file? If so, is there any workaround?

[anmonteiro]

Is this a limitation with the build system working file-by-file? If so, is there any workaround?

Yeah, effectively. We have limited, experimental support for cross-module optimizations. Try adding this in your dune file:

({melange.,}compile_flags :standard --mel-cross-module-opt)

[anmonteiro]

I added a fairly comprehensive test for this in #1291. We could make a few improvements:

• perform compiler optimizations after inlining the cross-module function (would likely eliminate some of the calls to Curry
• store the relevant information in the .cmj even if --mel-cross-module-opt isn't passed in, such that libraries don't need to explicitly pass that flag (and optimizations can still be had in melange.emit without changing upstream libraries)