Recently the --warn-return-any option was added which causes mypy to warn if returning a value with an Any type (#2854). @ddfisher pointed out the this is not very general:

Thinking out loud here: this helps catch accidental Anys in one particular circumstance, but it might be nice to have something a bit more comprehensive as well. Perhaps we should consider adding a flag which disallows use of Any-typed values except as the right hand side of an assignment with a type comment (i.e. forcing all Anys to be immediately typed).

I agree that #2854 seems too narrowly focused. I like @ddfisher's suggestion, with a few tweaks:

• Any should probably be okay as a function argument type if the argument type is Any (or object).
• Assigning an Any value to a variable with an Any / object type seems okay as well.
• Narrowing down from an Any value using isinstance or cast should be allowed.