Stating that A is an integer isn't much of a issue but once you get a reasonably complex program and A now has a compound type made of 5 parts, it really does slow you down and it really does make you write considerably worse programs for the sake of passing a type checker.
Any commercial code will need to be unit tested so there is no time saving from finding runtime errors earlier and an any good IDE will detect the same errors and provide you with the same auto complete automatically for free without any type annotations at all. These are problems which exist solely in your head.
1 developer vs a whole team of developers. I think you need to face the facts.
There are studies comparing old dynamically types languages against statically type languages. They always show approximately 1/3 of the lines of code being used with 3x faster development times in the dynamically types languages. This isn't some new discovery.
Well even Python is strongly typed but for the sake of this we are discussing type complexity.