On Jul 2, 2010, at 12:28 AM, Steven D'Aprano wrote:
> This question was inspired by something asked on #python today. Consider
> it a hypothetical, not a serious proposal.
>
> We know that many semantic errors in Python lead to runtime errors, e.g.
> 1 + "1". If an implementation rejected them at compile time, would it
> still be Python? E.g. if the keyhole optimizer raised SyntaxError (or
> some other exception) on seeing this:
>
> def f():
> return 1 + "1"
>
> instead of compiling something which can't fail to raise an exception,
> would that still be a legal Python implementation?
I'd say "no". Python has defined semantics in this situation: a TypeError is
raised.
To me, this seems akin to a keyhole optimizer arbitrarily deciding that
raise TypeError()
should cause the compiler to abort.
If this type of expression were common, it would be within the rights of, for
example, a Python JIT to generate a fast path through 'f' that wouldn't bother
to actually invoke its 'int' type's '__add__' method, since there is no
possible way for a Python program to tell the difference, since int.__add__ is
immutable.
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