On 31 August 2016 at 15:40, Guido van Rossum <[email protected]> wrote:
> On Tuesday, August 30, 2016, Nick Coghlan <[email protected]> wrote:
>> What if we included local variable annotations in func.__annotations__
>> as cells, like the entries in func.__closure__?
>>
>> We could also use that as a micro-optimisation technique: once the
>> type annotation cell is populated, CPython would just use it, rather
>> than re-evaluating the local variable type annotation expression every
>> time the function is called.
>
> But what runtime use have the annotations on locals? They are not part of
> any inspectable interface. I don't want to spend any effort on them at
> runtime. (Just the bit that they are treated as locals.)
I guess as long as they're included somewhere in the AST for the
function body, I don't mind if the translation to bytecode throws them
away - that's essentially saying that a function level type annotation
is effectively interpreted as if it was:
if False:
__annotations__[<varname>] = <annotation>
So the code generator will pick up syntax errors during normal
execution, but not runtime errors (since the expression never actually
gets evaluated).
Cheers,
Nick.
--
Nick Coghlan | [email protected] | Brisbane, Australia
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