L1212 - Bad deprecated attribute

Error

    -deprecated([{foo, 1}]).
%%  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: deprecated function foo/1 undefined or not exported

Explanation

This error occurs when you mark a function as deprecated using the -deprecated attribute, but the specified function doesn't exist in the module.

The deprecated attribute can only be applied to functions that are actually defined in the module.

To fix this error:

1. Ensure the function name and arity are correct
2. Verify the function exists in the module
3. Check for typos in the function name
4. Remove the deprecated attribute if the function was removed

%% Correctly deprecate an existing function
-export([foo/1]).
-deprecated([{foo, 1}]).
foo(Arg) ->
    Arg.