import conflicts should be lazy

[orenbenkiki]

If importing two modules, Elixir immediately complains about any potential names conflict, even for names that are not used in the importing module.

I suggest that the Haskell-like behavior of defering conflict complaints to the point of actually using the ambiguous name is preferable.

That is:

defmodule Foo do
  def foo do ... end
  def baz do ... end
end

defmodule Bar do
  def bar do ... end
  def baz do ... end
end

defmodule Baz do
  import Foo
  import Bar # This triggers an error today; under the new proposal, it wouldn't.
  def valid do { foo, bar } end # This will compile cleanly
  def invalid do baz end # This will trigger a compilation error
  def workaround do { Foo.baz, Bar.baz } end # This, however, will work as expected
end

The current mechanism is too strict in that adding a function to a module can cause compilation to break in modules down the line, making the whole system more fragile (at compile time). The current workarounds (adding only or except) are "tedious" compared to simply ignoring potential-but-not-actual conflicts.

[alexrp]

Virtually every language with modules reports conflicts lazily. I was frankly quite surprised by this behavior in Elixir.

Definitely +1 for this.

[josevalim]

This makes perfect sense. We already lazily check for conflicts between local functions and imported ones. Switching import to do the same should not be an issue. I will tackle it after 0.8.0 is out.

[yrashk]

👍