Missing exceptions in PEP 3107

[Christoph Zwerschke]

Matimus wrote:
 > Christoph wrote:
 >> Maybe the following syntax would be even more intuitive:
 >>
 >> def foo(a: "a info", b: "b info") return "ret info" raise "exc info":
 >>         return "hello world"
 >
 > That seems much more intuitive and extensible. The "->" syntax has
 > always bothered me. The main issue I see with it though is that it
 > might be confusing. Consider:
 >
 > def foo(a, b) return 0:
 >
 >     return a + b
 >
 > A person reading the code might be tempted to read the annotation and
 > think that it is the body. Maybe not a huge problem, but definitely
 > something that will come up occasionally.

Yes, that's a drawback; and the same problem for a "raise" clause.

>> Well, yes, but wasn't the whole point of PEP 3107 to get rid of such
>> decorators and provide a single standard way of specifying this kind of
>> info instead?
> 
> Maybe, but I think it also does two more things: 1. creates a standard
> location for storing annotations, and 2. Keeps you from violating DRY
> (http://en.wikipedia.org/wiki/DRY).
> Using a single decorator for exception info (or even return info) does
> not violate either of the two stated benefits. The exception
> information would go into the standard annotations dictionary. The
> raises decorator does not violate DRY any more or less than it would
> if added to the language syntax.

That's a valid point, but as you already mentioned, the same applies to 
the return value. In my opinion it is desirable that either both return 
value and exceptions get a special syntax, or both must be described 
using decorators.

-- Christoph