Use duck typing instead of abc checking in pattern matching

[evhub]

Should be significantly faster.

[munael]

You still have to check. What do you mean by using duck typing here? Try to match, assuming everything is in order, and skip if an exception is raised?

That may make sense in irrefutable patterns.

[evhub]

@narfanar Instead of

if isinstance(thing, Sequence) and thing[0] == 1:
    ...

do

no_ind = object()
def try_index(obj, ind):
    try:
        return obj[ind]
    except:
        return no_ind
check_ind = try_index(thing, 0)
if check_ind is not no_ind and check_ind == 1:
    ...

though honestly I'm not sure if that's actually a good idea.

[munael]

With absolutely no data to support my claim, I'll guess this would be slower than the isinstance check.

Though as mentioned, it might make sense in places where patterns should not fail but can (that is, if they fail, the function is bound to return (with a fallback) or throw).

I'm not sure this construct even exists in Coconut though. Think something like guard let in Swift but you always throw in the handler.

It is.