auto merge of #17162 : sfackler/rust/decorator-traits, r=huonw

The other extension types already worked this way and it can be useful to track some state along with the extension.

I also removed the `BasicMacroExpander` and `BasicIdentMacroExpander` since the span inside of them was never used. The expander function types now directly implement the relevant trait.

Author: bors

src/librustc/plugin/registry.rs

@@ -13,7 +13,7 @@
 use lint::{LintPassObject, LintId, Lint};
 
 use syntax::ext::base::{SyntaxExtension, NamedSyntaxExtension, NormalTT};
-use syntax::ext::base::{IdentTT, LetSyntaxTT, ItemDecorator, ItemModifier, BasicMacroExpander};
+use syntax::ext::base::{IdentTT, LetSyntaxTT, ItemDecorator, ItemModifier};
 use syntax::ext::base::{MacroExpanderFn};
 use syntax::codemap::Span;
 use syntax::parse::token;
@@ -71,15 +71,10 @@ impl Registry {
     /// Register a macro of the usual kind.
     ///
     /// This is a convenience wrapper for `register_syntax_extension`.
-    /// It builds for you a `NormalTT` with a `BasicMacroExpander`,
+    /// It builds for you a `NormalTT` that calls `expander`,
     /// and also takes care of interning the macro's name.
     pub fn register_macro(&mut self, name: &str, expander: MacroExpanderFn) {
-        self.register_syntax_extension(
-            token::intern(name),
-            NormalTT(box BasicMacroExpander {
-                expander: expander,
-                span: None,
-            }, None));
+        self.register_syntax_extension(token::intern(name), NormalTT(box expander, None));
     }
 
     /// Register a compiler lint pass.

src/libsyntax/ext/base.rs

@@ -39,15 +39,44 @@ pub struct MacroDef {
     pub ext: SyntaxExtension
 }
 
-pub type ItemDecorator =
-    fn(&mut ExtCtxt, Span, Gc<ast::MetaItem>, Gc<ast::Item>, |Gc<ast::Item>|);
+pub trait ItemDecorator {
+    fn expand(&self,
+              ecx: &mut ExtCtxt,
+              sp: Span,
+              meta_item: Gc<ast::MetaItem>,
+              item: Gc<ast::Item>,
+              push: |Gc<ast::Item>|);
+}
 
-pub type ItemModifier =
-    fn(&mut ExtCtxt, Span, Gc<ast::MetaItem>, Gc<ast::Item>) -> Gc<ast::Item>;
+impl ItemDecorator for fn(&mut ExtCtxt, Span, Gc<ast::MetaItem>, Gc<ast::Item>, |Gc<ast::Item>|) {
+    fn expand(&self,
+              ecx: &mut ExtCtxt,
+              sp: Span,
+              meta_item: Gc<ast::MetaItem>,
+              item: Gc<ast::Item>,
+              push: |Gc<ast::Item>|) {
+        (*self)(ecx, sp, meta_item, item, push)
+    }
+}
 
-pub struct BasicMacroExpander {
-    pub expander: MacroExpanderFn,
-    pub span: Option<Span>
+pub trait ItemModifier {
+    fn expand(&self,
+              ecx: &mut ExtCtxt,
+              span: Span,
+              meta_item: Gc<ast::MetaItem>,
+              item: Gc<ast::Item>)
+              -> Gc<ast::Item>;
+}
+
+impl ItemModifier for fn(&mut ExtCtxt, Span, Gc<ast::MetaItem>, Gc<ast::Item>) -> Gc<ast::Item> {
+    fn expand(&self,
+              ecx: &mut ExtCtxt,
+              span: Span,
+              meta_item: Gc<ast::MetaItem>,
+              item: Gc<ast::Item>)
+              -> Gc<ast::Item> {
+        (*self)(ecx, span, meta_item, item)
+    }
 }
 
 /// Represents a thing that maps token trees to Macro Results
@@ -60,24 +89,18 @@ pub trait TTMacroExpander {
 }
 
 pub type MacroExpanderFn =
-    fn<'cx>(ecx: &'cx mut ExtCtxt, span: codemap::Span, token_tree: &[ast::TokenTree])
-            -> Box<MacResult+'cx>;
+    fn<'cx>(&'cx mut ExtCtxt, Span, &[ast::TokenTree]) -> Box<MacResult+'cx>;
 
-impl TTMacroExpander for BasicMacroExpander {
+impl TTMacroExpander for MacroExpanderFn {
     fn expand<'cx>(&self,
                    ecx: &'cx mut ExtCtxt,
                    span: Span,
                    token_tree: &[ast::TokenTree])
                    -> Box<MacResult+'cx> {
-        (self.expander)(ecx, span, token_tree)
+        (*self)(ecx, span, token_tree)
     }
 }
 
-pub struct BasicIdentMacroExpander {
-    pub expander: IdentMacroExpanderFn,
-    pub span: Option<Span>
-}
-
 pub trait IdentMacroExpander {
     fn expand<'cx>(&self,
                    cx: &'cx mut ExtCtxt,
@@ -87,20 +110,20 @@ pub trait IdentMacroExpander {
                    -> Box<MacResult+'cx>;
 }
 
-impl IdentMacroExpander for BasicIdentMacroExpander {
+pub type IdentMacroExpanderFn =
+    fn<'cx>(&'cx mut ExtCtxt, Span, ast::Ident, Vec<ast::TokenTree>) -> Box<MacResult+'cx>;
+
+impl IdentMacroExpander for IdentMacroExpanderFn {
     fn expand<'cx>(&self,
                    cx: &'cx mut ExtCtxt,
                    sp: Span,
                    ident: ast::Ident,
                    token_tree: Vec<ast::TokenTree> )
                    -> Box<MacResult+'cx> {
-        (self.expander)(cx, sp, ident, token_tree)
+        (*self)(cx, sp, ident, token_tree)
     }
 }
 
-pub type IdentMacroExpanderFn =
-    fn<'cx>(&'cx mut ExtCtxt, Span, ast::Ident, Vec<ast::TokenTree>) -> Box<MacResult+'cx>;
-
 /// The result of a macro expansion. The return values of the various
 /// methods are spliced into the AST at the callsite of the macro (or
 /// just into the compiler's internal macro table, for `make_def`).
@@ -281,11 +304,11 @@ pub enum SyntaxExtension {
     /// based upon it.
     ///
     /// `#[deriving(...)]` is an `ItemDecorator`.
-    ItemDecorator(ItemDecorator),
+    ItemDecorator(Box<ItemDecorator + 'static>),
 
     /// A syntax extension that is attached to an item and modifies it
     /// in-place.
-    ItemModifier(ItemModifier),
+    ItemModifier(Box<ItemModifier + 'static>),
 
     /// A normal, function-like syntax extension.
     ///
@@ -329,20 +352,12 @@ impl BlockInfo {
 fn initial_syntax_expander_table() -> SyntaxEnv {
     // utility function to simplify creating NormalTT syntax extensions
     fn builtin_normal_expander(f: MacroExpanderFn) -> SyntaxExtension {
-        NormalTT(box BasicMacroExpander {
-                expander: f,
-                span: None,
-            },
-            None)
+        NormalTT(box f, None)
     }
 
     let mut syntax_expanders = SyntaxEnv::new();
     syntax_expanders.insert(intern("macro_rules"),
-                            LetSyntaxTT(box BasicIdentMacroExpander {
-                                expander: ext::tt::macro_rules::add_new_extension,
-                                span: None,
-                            },
-                            None));
+                            LetSyntaxTT(box ext::tt::macro_rules::add_new_extension, None));
     syntax_expanders.insert(intern("fmt"),
                             builtin_normal_expander(
                                 ext::fmt::expand_syntax_ext));
@@ -371,7 +386,7 @@ fn initial_syntax_expander_table() -> SyntaxEnv {
                             builtin_normal_expander(
                                     ext::log_syntax::expand_syntax_ext));
     syntax_expanders.insert(intern("deriving"),
-                            ItemDecorator(ext::deriving::expand_meta_deriving));
+                            ItemDecorator(box ext::deriving::expand_meta_deriving));
 
     // Quasi-quoting expanders
     syntax_expanders.insert(intern("quote_tokens"),

src/libsyntax/ext/expand.rs

@@ -251,7 +251,7 @@ fn expand_item(it: Gc<ast::Item>, fld: &mut MacroExpander)
 
         match fld.cx.syntax_env.find(&intern(mname.get())) {
             Some(rc) => match *rc {
-                ItemDecorator(dec_fn) => {
+                ItemDecorator(ref dec) => {
                     attr::mark_used(attr);
 
                     fld.cx.bt_push(ExpnInfo {
@@ -266,8 +266,7 @@ fn expand_item(it: Gc<ast::Item>, fld: &mut MacroExpander)
                     // we'd ideally decorator_items.push_all(expand_item(item, fld)),
                     // but that double-mut-borrows fld
                     let mut items: SmallVector<Gc<ast::Item>> = SmallVector::zero();
-                    dec_fn(fld.cx, attr.span, attr.node.value, it,
-                        |item| items.push(item));
+                    dec.expand(fld.cx, attr.span, attr.node.value, it, |item| items.push(item));
                     decorator_items.extend(items.move_iter()
                         .flat_map(|item| expand_item(item, fld).move_iter()));
 
@@ -328,7 +327,7 @@ fn expand_item_modifiers(mut it: Gc<ast::Item>, fld: &mut MacroExpander)
 
         match fld.cx.syntax_env.find(&intern(mname.get())) {
             Some(rc) => match *rc {
-                ItemModifier(dec_fn) => {
+                ItemModifier(ref mac) => {
                     attr::mark_used(attr);
                     fld.cx.bt_push(ExpnInfo {
                         call_site: attr.span,
@@ -338,7 +337,7 @@ fn expand_item_modifiers(mut it: Gc<ast::Item>, fld: &mut MacroExpander)
                             span: None,
                         }
                     });
-                    it = dec_fn(fld.cx, attr.span, attr.node.value, it);
+                    it = mac.expand(fld.cx, attr.span, attr.node.value, it);
                     fld.cx.bt_pop();
                 }
                 _ => unreachable!()

src/test/auxiliary/macro_crate_test.rs

@@ -36,7 +36,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_macro("identity", expand_identity);
     reg.register_syntax_extension(
         token::intern("into_foo"),
-        ItemModifier(expand_into_foo));
+        ItemModifier(box expand_into_foo));
 }
 
 fn expand_make_a_1(cx: &mut ExtCtxt, sp: Span, tts: &[TokenTree])