[Python-Dev] Please reject or postpone PEP 526 (original) (raw)

Greg Ewing greg.ewing at canterbury.ac.nz
Sun Sep 4 17:59:12 EDT 2016

On Sun, Sep 04, 2016 at 12:31:26PM +0100, Mark Shannon wrote:

As defined in PEP 526, I think that type annotations become a hindrance to type inference.

In Haskell-like languages, type annotations have no ability to influence whether types can be inferred. The compiler infers a type for everything, whether you annotate or not. The annotations serve as assertions about what the inferred types should be. If they don't match, it means the programmer has made a mistake somewhere.

I don't think it's possible for an annotation to prevent the compiler from being able to infer a type where it could have inferred one without the annotation.

-- Greg

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