E4037

E4037#

Cannot perform action: package is not imported.

Erroneous Example#

In main/main.mbt, we try to call a function from @middle:

fn main {
  let a = @middle.return_Obj().m()
}

In middle/middle.mbt, we define a function that returns an object of a trait Obj defined in @ty:

pub fn return_Obj() -> &@ty.Obj {
  @ty.T(42)
}

In ty/ty.mbt, we define a trait Obj and a type T that implements it:

pub(all) type T Int

pub fn f(self: T) -> Unit {
  println(self._)
}

pub(open) trait Obj {
  f(Self) -> Unit
}

... but in main/moon.pkg.json there is no mention of @ty:

{
  "import": ["<PACKAGE>/middle"]
}

This gives the following error on line 2 of main/main.mbt:

Cannot call method of type &@<PACKAGE>/ty.Obj: package @<PACKAGE>/ty is not imported.

Suggestion#

Make sure that all relevant packages are imported.

In the above example, this means importing both @middle and @ty in main/moon.pkg.json:

{
  "import": ["<PACKAGE>/middle", "<PACKAGE>/ty"]
}
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