Mypy should warn about conditions whose value can be deduced

Feature

Mypy can warn about left and right operands of conditions its value mypy can deduce. Unfortunately, it cannot do so for conditions consisting of one operand.

Pitch

val = 1337

if val is not None:
    pass

if val is not None and True:
    pass

Mypy can hint about the pointless left hand operand in the second if. Unfortunately, it does not do so for the first if. Supporting this use case would help the programmer to simplify her code by suggesting conditions to remove.

Comienza con el diagnóstico existente de mypy para el operando izquierdo innecesario en el ejemplo and True; después, localiza la implementación y las pruebas que lo generan. Añade cobertura para el caso de un solo operando if val is not None y verifica que mypy informe de la condición eliminable sin alterar el comportamiento existente.