On Fri, Apr 17, 2020 at 12:43 PM Benjamin Eberlei <kont...@beberlei.de> wrote:
> On Fri, Apr 17, 2020 at 6:11 PM Theodore Brown <theodor...@outlook.com> wrote:
>
> > Can you provide an example of an attribute name containing whitespace
> > that would be allowed with the shift left/right tokens but not with the
> > attribute token?
>
> This is about [whitespace] between token and attribute name, so `@:Foo`
> is allowed but `@: Foo` is not. Whereas with the hugging As, `<<Foo>>`
> and `<< Foo >>` is allowed.
Ah, that makes a lot more sense. Thanks for the clarification. I guess
allowing whitespace could also be considered a downside, since it will
lead to style guide wars about which spacing convention to use.
> This is a personal assumption here, but I would assume 95% of developers
> have never used >> or << before or for a long time and maybe 80% don't
> even know what bit shift means and how it works. I would think nobody
> needs this in attributes.
Even if bit shifts are rarely used, the fact that such syntax is valid
means there's a higher cognitive load when reading attributes to
understand whether a shift token is part of a parameter value or
delineating the start/end of an attribute declaration.
Quick, does this function have two attributes with one parameter each,
or one attribute with two parameters?
```php
<<SomeAttribute(2 * 3 + 3)>><<Foo(4 + 5 * 2)>>
function foo() {}
```
How about this one?
```php
const Foo = 2;
<<SomeAttribute(2 * (3 + 3)>>Foo, (4 + 5) * 2)>>
function foo() {}
```
Even if the syntax is technically unambiguous, reusing shift tokens as
attribute delineators results in symbol-heavy code which is harder to
quickly and correctly understand.
FWIW Hack is apparently moving away from the shift token attribute
syntax to one using `@` (see
https://github.com/facebook/hhvm/commit/3983bd2ca6b252a93d98f2bb2d7e8e89f6f004d1);
Sincerely,
Theodore
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