[kawhah]

Hmm, no. You rewrite it as

    key1 = foo/bar
    key2 = baz/bat
    a[key1] = b[key2]
    if (a[key1] == c)

I'm sure a coder who understands the context can come up with better names than key1 and key2.

edit: or better yet

    key2 = baz/bat
    normal_var = b[key2]
    if (normal_var == c)
    ...
    key1 = foo/bar
    a[key1] = normal_var

[kmoser]

While your solution splits the whole thing into smaller and arguably more easily digestible steps, you have introduced two new variables, key1 and key2, which need to be carefully scoped (if they aren't already) so they don't clash with existing variables. If your project consists of many instances of code like this, you end up with many variables which can become harder to manage.

You're also splitting what is intended to be essentially an atomic operation into multiple steps, which can be good if you want to analyze and tweak them in the future, but it's now no longer clear where the process begins and ends in relation to the code that comes before and after: you have to add more comments, or split the whole thing out into its own function.

I'm not saying your code is bad or wrong, just that there are downsides to any solution (including mine), and ultimately everybody has to pick whichever has the fewest negatives for their particular project.