W0001 - Module Mismatch

Error

-module(bar).
%%      ^^^ error: Module name (bar) does not match file name (foo)

Explanation

The error message is indicating that the module name specified in the -module attribute (bar) does not match the file name of the source code file (foo.erl).

In Erlang, the module name - an atom - has to be same as the file name minus the extension .erl. This is to ensure code loading works as intended.

To fix this error, you should either change the -module directive to match the file name (i.e. -module(foo)) or rename the file to match the module name (i.e. foo.erl -> bar.erl).