Tweak ItemDecorator API #12234
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Tweak ItemDecorator API #12234
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| @@ -233,12 +233,13 @@ pub fn expand_mod_items(module_: &ast::Mod, fld: &mut MacroExpander) -> ast::Mod | |||
| span: None | |||
| } | |||
| }); | |||
| let r = dec_fn(fld.cx, attr.span, attr.node.value, items); | |||
| items.push_all(dec_fn(fld.cx, attr.span, attr.node.value, *item)); | |||
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I wonder if this would be noticeably more efficient as
dec_fn(fld.cx, attr.span, attr.node.value, *item, |new| items.push(new))after modifying ItemDecorator to take a pusher: |@Item| as the last argument.
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Not sure. I think that this PR keeps roughly the same allocation patterns as before.
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Doesn't mean we have to repeat them :)
|
@huonw updated |
|
r=me if you update the commit message & pr description to match the fact it's passing in a callback, not returning the vector. |
The old method of building up a list of items and threading it through all of the decorators was unwieldy and not really scalable as non-deriving ItemDecorators become possible. The API is now that the decorator gets an immutable reference to the item it's attached to, and a callback that it can pass new items to. If we want to add syntax extensions that can modify the item they're attached to, we can add that later, but I think it'll have to be separate from ItemDecorator to avoid strange ordering issues.
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The old method of building up a list of items and threading it through all of the decorators was unwieldy and not really scalable as non-deriving ItemDecorators become possible. The API is now that the decorator gets an immutable reference to the item it's attached to, and a callback that it can pass new items to. If we want to add syntax extensions that can modify the item they're attached to, we can add that later, but I think it'll have to be separate from ItemDecorator to avoid strange ordering issues. @huonw
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The old method of building up a list of items and threading it through
all of the decorators was unwieldy and not really scalable as
non-deriving ItemDecorators become possible. The API is now that the
decorator gets an immutable reference to the item it's attached to, and
a callback that it can pass new items to. If we want to add syntax
extensions that can modify the item they're attached to, we can add that
later, but I think it'll have to be separate from ItemDecorator to avoid
strange ordering issues.
@huonw