Check that every function has an annotation [no-untyped-def]

If you use —disallow-untyped-defs, mypy requires that all functionshave annotations (either a Python 3 annotation or a type comment).

Example:

# mypy: disallow-untyped-defs
 
def inc(x):  # Error: Function is missing a type annotation  [no-untyped-def]
    return x + 1
 
def inc_ok(x: int) -> int:  # OK
    return x + 1
 
class Counter:
     # Error: Function is missing a type annotation  [no-untyped-def]
     def __init__(self):
         self.value = 0
 
class CounterOk:
     # OK: An explicit "-> None" is needed if "__init__" takes no arguments
     def __init__(self) -> None:
         self.value = 0