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Expand ItemDecorator extensions in all contexts

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Now that fold_item can return multiple items, this is pretty trivial. It
also recursively expands generated items so ItemDecorators can generate
items that are tagged with ItemDecorators!

Closes #4913
This commit is contained in:
Steven Fackler 2014-02-13 22:57:43 -08:00 • committed by Alex Crichton
parent c1fac65396
commit 07ea23e15d
3 changed files with 59 additions and 53 deletions
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85
src/libsyntax/ext/expand.rs
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@ -203,52 +203,6 @@ pub fn expand_expr(e: @ast::Expr, fld: &mut MacroExpander) -> @ast::Expr {
}
}
// This is a secondary mechanism for invoking syntax extensions on items:
// "decorator" attributes, such as #[auto_encode]. These are invoked by an
// attribute prefixing an item, and are interpreted by feeding the item
// through the named attribute _as a syntax extension_ and splicing in the
// resulting item vec into place in favour of the decorator. Note that
// these do _not_ work for macro extensions, just ItemDecorator ones.
//
// NB: there is some redundancy between this and expand_item, below, and
// they might benefit from some amount of semantic and language-UI merger.
pub fn expand_mod_items(module_: &ast::Mod, fld: &mut MacroExpander) -> ast::Mod {
// Fold the contents first:
let module_ = noop_fold_mod(module_, fld);
// For each item, look through the attributes. If any of them are
// decorated with "item decorators", then use that function to transform
// the item into a new set of items.
let mut new_items = module_.items.clone();
for item in module_.items.iter() {
for attr in item.attrs.rev_iter() {
let mname = attr.name();
match fld.extsbox.find(&intern(mname.get())) {
Some(&ItemDecorator(dec_fn)) => {
fld.cx.bt_push(ExpnInfo {
call_site: attr.span,
callee: NameAndSpan {
name: mname.get().to_str(),
format: MacroAttribute,
span: None
}
});
dec_fn(fld.cx, attr.span, attr.node.value, *item,
|item| new_items.push(item));
fld.cx.bt_pop();
},
_ => {},
}
}
}
ast::Mod {
items: new_items,
..module_
}
}
// eval $e with a new exts frame:
macro_rules! with_exts_frame (
($extsboxexpr:expr,$macros_escape:expr,$e:expr) =>
@ -263,7 +217,35 @@ macro_rules! with_exts_frame (
// When we enter a module, record it, for the sake of `module!`
pub fn expand_item(it: @ast::Item, fld: &mut MacroExpander)
-> SmallVector<@ast::Item> {
match it.node {
let mut decorator_items = SmallVector::zero();
for attr in it.attrs.rev_iter() {
let mname = attr.name();
match fld.extsbox.find(&intern(mname.get())) {
Some(&ItemDecorator(dec_fn)) => {
fld.cx.bt_push(ExpnInfo {
call_site: attr.span,
callee: NameAndSpan {
name: mname.get().to_str(),
format: MacroAttribute,
span: None
}
});
// we'd ideally decorator_items.push_all(expand_item(item, fld)),
// but that double-mut-borrows fld
dec_fn(fld.cx, attr.span, attr.node.value, it,
|item| decorator_items.push(item));
fld.cx.bt_pop();
}
_ => {}
}
}
let decorator_items = decorator_items.move_iter()
.flat_map(|item| expand_item(item, fld).move_iter())
.collect();
let mut new_items = match it.node {
ast::ItemMac(..) => expand_item_mac(it, fld),
ast::ItemMod(_) | ast::ItemForeignMod(_) => {
fld.cx.mod_push(it.ident);
@ -275,7 +257,10 @@ pub fn expand_item(it: @ast::Item, fld: &mut MacroExpander)
result
},
_ => noop_fold_item(it, fld)
}
};
new_items.push_all(decorator_items);
new_items
}
// does this attribute list contain "macro_escape" ?
@ -778,10 +763,6 @@ impl<'a> Folder for MacroExpander<'a> {
expand_expr(expr, self)
}
fn fold_mod(&mut self, module: &ast::Mod) -> ast::Mod {
expand_mod_items(module, self)
}
fn fold_item(&mut self, item: @ast::Item) -> SmallVector<@ast::Item> {
expand_item(item, self)
}