On Mon, Oct 31, 2016, at 13:16, Guido van Rossum wrote:
For "everything to the right" it would seem we have some freedom: e.g. if we have "foo.bar?.baz(bletch)" is the call included? The answer is yes -- the concept we're after here is named "trailer" in the Grammar file in the source code ( https://github.com/python/cpython/blob/master/Grammar/Grammar#L119), and "primary" in the reference manual ( https://docs.python.org/3/reference/expressions.html#primaries). This means all attribute references ("x.y"), index/slice operations ("x[...]"), and calls ("x(...)").
One thing that I think I touched on in an earlier iteration of this discussion but hasn't been revisited is: what's the AST going to look like? Right now, foo.bar.baz(bletch) is Call(Attribute(Attribute(Name('foo'), 'bar'), 'baz'), [Name('bletch')])), which is identical to (foo.bar).baz(bletch) or (foo.bar.baz)(bletch). These are treated, essentially, as postfix operators, where you can parenthesize any left part of the expression and leave its meaning [and its AST] unchanged. Is the AST going to be unchanged, leading to the conclusion that the short-circuiting in (foo?.bar).baz will "reach outside of" the parentheses, and relying on the fact that wanting to do that with None is a silly thing to do in almost all cases? Or is there going to be a new kind of AST that is sequential rather than recursive in how it represents trailer/primary expressions?