wasm build rego_type_error: undefined ref

[shm12]

Hi all. I'm facing strange behavior.
I have an example.rego file:

package play

allow {
	b := foo("bar")
	b == true
}

bar(val) = value {
	value = true
}

foo(val) = value {
	value = bar(val)
}

Now, if I run it, or build it - opa build example.rego , it's alright. But if I try to build a WASM bundle, I get:

$ opa build -t wasm -e play example.rego
error: 1 error occurred: example.rego:1: rego_type_error: undefined ref: data.play.foo
        data.play.foo
        ^^^^^^^^^^^^^
        have: (any) => boolean

Is it a bug, or is something wrong with the Rego code?

If It's only one function, like:

package play

allow {
	b := bar("bar")
	b == true
}

bar(val) = value {
	value = true
}

I don't get this error. Only where a function calls another function.

[srenatus]

Can you try the command line argument mentioned in open-policy-agent/opa#4411?

[shm12]

It worked :)

I didn't quite understand why though.
Putting here the command for people who get to here:

opa build -t wasm -e play example.rego --prune-unused