Remove the Modifier and Decorator kinds of syntax extensions.

This is a [breaking-change] for syntax extension authors. The fix is to use MultiModifier or MultiDecorator, which have the same functionality but are more flexible. Users of syntax extensions are unaffected.

Author: Nick Cameron

src/librustc/plugin/registry.rs

@@ -14,7 +14,7 @@ use lint::{LintPassObject, LintId, Lint};
 use session::Session;
 
 use syntax::ext::base::{SyntaxExtension, NamedSyntaxExtension, NormalTT};
-use syntax::ext::base::{IdentTT, Decorator, Modifier, MultiModifier, MultiDecorator};
+use syntax::ext::base::{IdentTT, MultiModifier, MultiDecorator};
 use syntax::ext::base::{MacroExpanderFn, MacroRulesTT};
 use syntax::codemap::Span;
 use syntax::parse::token;
@@ -98,9 +98,7 @@ impl<'a> Registry<'a> {
             IdentTT(ext, _, allow_internal_unstable) => {
                 IdentTT(ext, Some(self.krate_span), allow_internal_unstable)
             }
-            Decorator(ext) => Decorator(ext),
             MultiDecorator(ext) => MultiDecorator(ext),
-            Modifier(ext) => Modifier(ext),
             MultiModifier(ext) => MultiModifier(ext),
             MacroRulesTT => {
                 self.sess.err("plugin tried to register a new MacroRulesTT");

src/libsyntax/ext/base.rs

@@ -31,60 +31,6 @@ use std::collections::HashMap;
 use std::rc::Rc;
 use std::default::Default;
 
-#[unstable(feature = "rustc_private")]
-#[deprecated(since = "1.0.0", reason = "replaced by MultiItemDecorator")]
-pub trait ItemDecorator {
-    fn expand(&self,
-              ecx: &mut ExtCtxt,
-              sp: Span,
-              meta_item: &ast::MetaItem,
-              item: &ast::Item,
-              push: &mut FnMut(P<ast::Item>));
-}
-
-#[allow(deprecated)]
-#[unstable(feature = "rustc_private")]
-#[deprecated(since = "1.0.0", reason = "replaced by MultiItemDecorator")]
-impl<F> ItemDecorator for F
-    where F : Fn(&mut ExtCtxt, Span, &ast::MetaItem, &ast::Item, &mut FnMut(P<ast::Item>))
-{
-    fn expand(&self,
-              ecx: &mut ExtCtxt,
-              sp: Span,
-              meta_item: &ast::MetaItem,
-              item: &ast::Item,
-              push: &mut FnMut(P<ast::Item>)) {
-        (*self)(ecx, sp, meta_item, item, push)
-    }
-}
-
-#[unstable(feature = "rustc_private")]
-#[deprecated(since = "1.0.0", reason = "replaced by MultiItemModifier")]
-pub trait ItemModifier {
-    fn expand(&self,
-              ecx: &mut ExtCtxt,
-              span: Span,
-              meta_item: &ast::MetaItem,
-              item: P<ast::Item>)
-              -> P<ast::Item>;
-}
-
-#[allow(deprecated)]
-#[unstable(feature = "rustc_private")]
-#[deprecated(since = "1.0.0", reason = "replaced by MultiItemModifier")]
-impl<F> ItemModifier for F
-    where F : Fn(&mut ExtCtxt, Span, &ast::MetaItem, P<ast::Item>) -> P<ast::Item>
-{
-
-    fn expand(&self,
-              ecx: &mut ExtCtxt,
-              span: Span,
-              meta_item: &ast::MetaItem,
-              item: P<ast::Item>)
-              -> P<ast::Item> {
-        (*self)(ecx, span, meta_item, item)
-    }
-}
 
 #[derive(Debug,Clone)]
 pub enum Annotatable {
@@ -460,26 +406,12 @@ impl MacResult for DummyResult {
 
 /// An enum representing the different kinds of syntax extensions.
 pub enum SyntaxExtension {
-    /// A syntax extension that is attached to an item and creates new items
-    /// based upon it.
-    #[unstable(feature = "rustc_private")]
-    #[deprecated(since = "1.0.0", reason = "replaced by MultiDecorator")]
-    #[allow(deprecated)]
-    Decorator(Box<ItemDecorator + 'static>),
-
     /// A syntax extension that is attached to an item and creates new items
     /// based upon it.
     ///
     /// `#[derive(...)]` is a `MultiItemDecorator`.
     MultiDecorator(Box<MultiItemDecorator + 'static>),
 
-    /// A syntax extension that is attached to an item and modifies it
-    /// in-place.
-    #[unstable(feature = "rustc_private")]
-    #[deprecated(since = "1.0.0", reason = "replaced by MultiModifier")]
-    #[allow(deprecated)]
-    Modifier(Box<ItemModifier + 'static>),
-
     /// A syntax extension that is attached to an item and modifies it
     /// in-place. More flexible version than Modifier.
     MultiModifier(Box<MultiItemModifier + 'static>),

src/libsyntax/ext/expand.rs

@@ -639,9 +639,9 @@ macro_rules! with_exts_frame {
 // When we enter a module, record it, for the sake of `module!`
 pub fn expand_item(it: P<ast::Item>, fld: &mut MacroExpander)
                    -> SmallVector<P<ast::Item>> {
-    let it = expand_item_modifiers(it, fld);
+    let it = expand_item_multi_modifier(Annotatable::Item(it), fld);
 
-    expand_annotatable(Annotatable::Item(it), fld)
+    expand_annotatable(it, fld)
         .into_iter().map(|i| i.expect_item()).collect()
 }
 
@@ -1278,11 +1278,9 @@ macro_rules! partition {
     }
 }
 
-partition!(modifiers, Modifier);
 partition!(multi_modifiers, MultiModifier);
 
 
-#[allow(deprecated)] // The `allow` is needed because the `Decorator` variant is used.
 fn expand_decorators(a: Annotatable,
                      fld: &mut MacroExpander,
                      decorator_items: &mut SmallVector<Annotatable>,
@@ -1292,33 +1290,6 @@ fn expand_decorators(a: Annotatable,
         let mname = intern(&attr.name());
         match fld.cx.syntax_env.find(&mname) {
             Some(rc) => match *rc {
-                Decorator(ref dec) => {
-                    attr::mark_used(&attr);
-
-                    fld.cx.bt_push(ExpnInfo {
-                        call_site: attr.span,
-                        callee: NameAndSpan {
-                            format: MacroAttribute(mname),
-                            span: Some(attr.span),
-                            // attributes can do whatever they like,
-                            // for now.
-                            allow_internal_unstable: true,
-                        }
-                    });
-
-                    // we'd ideally decorator_items.push_all(expand_item(item, fld)),
-                    // but that double-mut-borrows fld
-                    let mut items: SmallVector<Annotatable> = SmallVector::zero();
-                    dec.expand(fld.cx,
-                               attr.span,
-                               &attr.node.value,
-                               &a.clone().expect_item(),
-                               &mut |item| items.push(Annotatable::Item(item)));
-                    decorator_items.extend(items.into_iter()
-                        .flat_map(|ann| expand_annotatable(ann, fld).into_iter()));
-
-                    fld.cx.bt_pop();
-                }
                 MultiDecorator(ref dec) => {
                     attr::mark_used(&attr);
 
@@ -1395,58 +1366,6 @@ fn expand_item_multi_modifier(mut it: Annotatable,
     expand_item_multi_modifier(it, fld)
 }
 
-#[allow(deprecated)] // This is needed because the `ItemModifier` trait is used
-fn expand_item_modifiers(mut it: P<ast::Item>,
-                         fld: &mut MacroExpander)
-                         -> P<ast::Item> {
-    // partition the attributes into ItemModifiers and others
-    let (modifiers, other_attrs) = modifiers(&it.attrs, fld);
-
-    // update the attrs, leave everything else alone. Is this mutation really a good idea?
-    it = P(ast::Item {
-        attrs: other_attrs,
-        ..(*it).clone()
-    });
-
-    if modifiers.is_empty() {
-        let it = expand_item_multi_modifier(Annotatable::Item(it), fld);
-        return it.expect_item();
-    }
-
-    for attr in &modifiers {
-        let mname = intern(&attr.name());
-
-        match fld.cx.syntax_env.find(&mname) {
-            Some(rc) => match *rc {
-                Modifier(ref mac) => {
-                    attr::mark_used(attr);
-                    fld.cx.bt_push(ExpnInfo {
-                        call_site: attr.span,
-                        callee: NameAndSpan {
-                            format: MacroAttribute(mname),
-                            span: Some(attr.span),
-                            // attributes can do whatever they like,
-                            // for now
-                            allow_internal_unstable: true,
-                        }
-                    });
-                    it = mac.expand(fld.cx, attr.span, &*attr.node.value, it);
-                    fld.cx.bt_pop();
-                }
-                _ => unreachable!()
-            },
-            _ => unreachable!()
-        }
-    }
-
-    // Expansion may have added new ItemModifiers.
-    // It is possible, that an item modifier could expand to a multi-modifier or
-    // vice versa. In this case we will expand all modifiers before multi-modifiers,
-    // which might give an odd ordering. However, I think it is unlikely that the
-    // two kinds will be mixed, and old-style multi-modifiers are deprecated.
-    expand_item_modifiers(it, fld)
-}
-
 fn expand_impl_item(ii: P<ast::ImplItem>, fld: &mut MacroExpander)
                  -> SmallVector<P<ast::ImplItem>> {
     match ii.node {

src/test/auxiliary/macro_crate_test.rs

@@ -30,10 +30,6 @@ macro_rules! unexported_macro { () => (3) }
 pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_macro("make_a_1", expand_make_a_1);
     reg.register_macro("identity", expand_identity);
-    reg.register_syntax_extension(
-        token::intern("into_foo"),
-        // FIXME (#22405): Replace `Box::new` with `box` here when/if possible.
-        Modifier(Box::new(expand_into_foo)));
     reg.register_syntax_extension(
         token::intern("into_multi_foo"),
         // FIXME (#22405): Replace `Box::new` with `box` here when/if possible.
@@ -62,14 +58,6 @@ fn expand_identity(cx: &mut ExtCtxt, _span: Span, tts: &[TokenTree])
     MacEager::expr(quote_expr!(&mut *cx, $expr))
 }
 
-fn expand_into_foo(cx: &mut ExtCtxt, sp: Span, attr: &MetaItem, it: P<Item>)
-                   -> P<Item> {
-    P(Item {
-        attrs: it.attrs.clone(),
-        ..(*quote_item!(cx, enum Foo { Bar, Baz }).unwrap()).clone()
-    })
-}
-
 fn expand_into_foo_multi(cx: &mut ExtCtxt,
                          sp: Span,
                          attr: &MetaItem,

src/test/run-pass-fulldeps/macro-crate.rs

@@ -17,10 +17,6 @@
 #[macro_use] #[no_link]
 extern crate macro_crate_test;
 
-#[into_foo]
-#[derive(PartialEq, Clone, Debug)]
-fn foo() -> AFakeTypeThatHadBetterGoAway {}
-
 #[into_multi_foo]
 #[derive(PartialEq, Clone, Debug)]
 fn foo() -> AnotherFakeTypeThatHadBetterGoAway {}
@@ -41,9 +37,6 @@ pub fn main() {
     assert_eq!(1, make_a_1!());
     assert_eq!(2, exported_macro!());
 
-    assert_eq!(Foo::Bar, Foo::Bar);
-    test(None::<Foo>);
-
     assert_eq!(Foo2::Bar2, Foo2::Bar2);
     test(None::<Foo2>);