unknown_qualified_name: a qualified name does not exist in that module

A qualified reference Module.name names a module that exists but does not export name. When a close match exists the message suggests it.

A program that triggers it

mod Main do
  needs IO.Console
  fn main(_console : Cap(IO.Console)) do
    println(int_to_string(List.size([1, 2, 3])))
  end
end

The fix

Use the name the module actually exports. forge search <name> and the module’s stdlib page list what is there.

mod Main do
  needs IO.Console
  fn main(_console : Cap(IO.Console)) do
    println(int_to_string(List.length([1, 2, 3])))
  end
end

Why the rule exists

Qualified names are resolved statically; there is no dynamic lookup and no fallback to a global of the same name, so a misspelled or missing export is reported at the reference instead of failing at run time.

See also: the language reference.

See it in the error tour

• A misspelled module