Compiler warning when using a variable bound in assert_receive

[alco]

The following code causes the compiler to emit a warning:

assert_receive {:ok, num}  # line 10
assert ^num = 13           # line 11

test/exunit_export_test.exs:11: warning: variable num@1 exported from 'receive' (line 10)

Example repo with 2 tags: warning and no-warning – https://github.com/alco/ex_unit-warning-exported-var

[DefiPanda]

Interesting, I am running the latest code on master branch and didn't receive any warning when running mix test on your linked mix project.

[alco]

@jw2013 you need to check out the warning tag.

[DefiPanda]

@alco Ah, thanks so much for the clarification.

Is there any particular reason we don't use this instead:

num = 13                          # line 10
assert_receive {:ok, ^num}        # line 11

[lexmag]

It happens beyond assert_receive example with every macro + export_head before ^, e.g:

destructure([x], [3])
^x = 3

and comes from erl_lint.erl.