auto merge of #19703 : nikomatsakis/rust/unsafe-trait, r=acrichto

This PR allows declaring traits and impls as `unsafe`. An `unsafe` trait requires an `unsafe` impl. An `unsafe` impl does not permit unsafe code within its interior (unless that code is contained within an unsafe block or unsafe fn, as normal). The commits are standalone.

r? @alexcrichton 
cc #13231

Author: bors

src/librustc/lint/builtin.rs

@@ -1721,15 +1721,15 @@ impl LintPass for Stability {
         if self.is_internal(cx, item.span) { return }
 
         match item.node {
-            ast::ItemTrait(_, _, ref supertraits, _) => {
+            ast::ItemTrait(_, _, _, ref supertraits, _) => {
                 for t in supertraits.iter() {
                     if let ast::TraitTyParamBound(ref t) = *t {
                         let id = ty::trait_ref_to_def_id(cx.tcx, &t.trait_ref);
                         self.lint(cx, id, t.trait_ref.path.span);
                     }
                 }
             }
-            ast::ItemImpl(_, Some(ref t), _, _) => {
+            ast::ItemImpl(_, _, Some(ref t), _, _) => {
                 let id = ty::trait_ref_to_def_id(cx.tcx, t);
                 self.lint(cx, id, t.path.span);
             }

src/librustc/metadata/common.rs

@@ -255,3 +255,5 @@ pub const tag_method_ty_generics: uint = 0xa7;
 pub const tag_predicate: uint = 0xa8;
 pub const tag_predicate_space: uint = 0xa9;
 pub const tag_predicate_data: uint = 0xb0;
+
+pub const tag_unsafety: uint = 0xb1;

src/librustc/metadata/decoder.rs

@@ -361,15 +361,26 @@ fn item_to_def_like(item: rbml::Doc, did: ast::DefId, cnum: ast::CrateNum)
     }
 }
 
+fn parse_unsafety(item_doc: rbml::Doc) -> ast::Unsafety {
+    let unsafety_doc = reader::get_doc(item_doc, tag_unsafety);
+    if reader::doc_as_u8(unsafety_doc) != 0 {
+        ast::Unsafety::Unsafe
+    } else {
+        ast::Unsafety::Normal
+    }
+}
+
 pub fn get_trait_def<'tcx>(cdata: Cmd,
                            item_id: ast::NodeId,
                            tcx: &ty::ctxt<'tcx>) -> ty::TraitDef<'tcx>
 {
     let item_doc = lookup_item(item_id, cdata.data());
     let generics = doc_generics(item_doc, tcx, cdata, tag_item_generics);
     let bounds = trait_def_bounds(item_doc, tcx, cdata);
+    let unsafety = parse_unsafety(item_doc);
 
     ty::TraitDef {
+        unsafety: unsafety,
         generics: generics,
         bounds: bounds,
         trait_ref: Rc::new(item_trait_ref(item_doc, tcx, cdata))

src/librustc/metadata/encoder.rs

@@ -1205,7 +1205,7 @@ fn encode_info_for_item(ecx: &EncodeContext,
             None => {}
         }
       }
-      ast::ItemImpl(_, ref opt_trait, ref ty, ref ast_items) => {
+      ast::ItemImpl(unsafety, _, ref opt_trait, ref ty, ref ast_items) => {
         // We need to encode information about the default methods we
         // have inherited, so we drive this based on the impl structure.
         let impl_items = tcx.impl_items.borrow();
@@ -1218,6 +1218,7 @@ fn encode_info_for_item(ecx: &EncodeContext,
         encode_bounds_and_type(rbml_w, ecx, &lookup_item_type(tcx, def_id));
         encode_name(rbml_w, item.ident.name);
         encode_attributes(rbml_w, item.attrs.as_slice());
+        encode_unsafety(rbml_w, unsafety);
         match ty.node {
             ast::TyPath(ref path, _) if path.segments
                                                         .len() == 1 => {
@@ -1308,13 +1309,14 @@ fn encode_info_for_item(ecx: &EncodeContext,
             }
         }
       }
-      ast::ItemTrait(_, _, _, ref ms) => {
+      ast::ItemTrait(_, _, _, _, ref ms) => {
         add_to_index(item, rbml_w, index);
         rbml_w.start_tag(tag_items_data_item);
         encode_def_id(rbml_w, def_id);
         encode_family(rbml_w, 'I');
         encode_item_variances(rbml_w, ecx, item.id);
         let trait_def = ty::lookup_trait_def(tcx, def_id);
+        encode_unsafety(rbml_w, trait_def.unsafety);
         encode_generics(rbml_w, ecx, &trait_def.generics, tag_item_generics);
         encode_trait_ref(rbml_w, ecx, &*trait_def.trait_ref, tag_item_trait_ref);
         encode_name(rbml_w, item.ident.name);
@@ -1674,6 +1676,14 @@ fn encode_attributes(rbml_w: &mut Encoder, attrs: &[ast::Attribute]) {
     rbml_w.end_tag();
 }
 
+fn encode_unsafety(rbml_w: &mut Encoder, unsafety: ast::Unsafety) {
+    let byte: u8 = match unsafety {
+        ast::Unsafety::Normal => 0,
+        ast::Unsafety::Unsafe => 1,
+    };
+    rbml_w.wr_tagged_u8(tag_unsafety, byte);
+}
+
 fn encode_crate_deps(rbml_w: &mut Encoder, cstore: &cstore::CStore) {
     fn get_ordered_deps(cstore: &cstore::CStore) -> Vec<decoder::CrateDep> {
         // Pull the cnums and name,vers,hash out of cstore
@@ -1855,7 +1865,7 @@ struct ImplVisitor<'a, 'b:'a, 'c:'a, 'tcx:'b> {
 
 impl<'a, 'b, 'c, 'tcx, 'v> Visitor<'v> for ImplVisitor<'a, 'b, 'c, 'tcx> {
     fn visit_item(&mut self, item: &ast::Item) {
-        if let ast::ItemImpl(_, Some(ref trait_ref), _, _) = item.node {
+        if let ast::ItemImpl(_, _, Some(ref trait_ref), _, _) = item.node {
             let def_map = &self.ecx.tcx.def_map;
             let trait_def = def_map.borrow()[trait_ref.ref_id].clone();
             let def_id = trait_def.def_id();

src/librustc/metadata/tydecode.rs

@@ -549,11 +549,11 @@ fn parse_hex(st: &mut PState) -> uint {
     };
 }
 
-fn parse_fn_style(c: char) -> ast::FnStyle {
+fn parse_unsafety(c: char) -> ast::Unsafety {
     match c {
-        'u' => ast::UnsafeFn,
-        'n' => ast::NormalFn,
-        _ => panic!("parse_fn_style: bad fn_style {}", c)
+        'u' => ast::Unsafety::Unsafe,
+        'n' => ast::Unsafety::Normal,
+        _ => panic!("parse_unsafety: bad unsafety {}", c)
     }
 }
 
@@ -575,14 +575,14 @@ fn parse_onceness(c: char) -> ast::Onceness {
 
 fn parse_closure_ty<'a, 'tcx>(st: &mut PState<'a, 'tcx>,
                               conv: conv_did) -> ty::ClosureTy<'tcx> {
-    let fn_style = parse_fn_style(next(st));
+    let unsafety = parse_unsafety(next(st));
     let onceness = parse_onceness(next(st));
     let store = parse_trait_store(st, |x,y| conv(x,y));
     let bounds = parse_existential_bounds(st, |x,y| conv(x,y));
     let sig = parse_sig(st, |x,y| conv(x,y));
     let abi = parse_abi_set(st);
     ty::ClosureTy {
-        fn_style: fn_style,
+        unsafety: unsafety,
         onceness: onceness,
         store: store,
         bounds: bounds,
@@ -593,11 +593,11 @@ fn parse_closure_ty<'a, 'tcx>(st: &mut PState<'a, 'tcx>,
 
 fn parse_bare_fn_ty<'a, 'tcx>(st: &mut PState<'a, 'tcx>,
                               conv: conv_did) -> ty::BareFnTy<'tcx> {
-    let fn_style = parse_fn_style(next(st));
+    let unsafety = parse_unsafety(next(st));
     let abi = parse_abi_set(st);
     let sig = parse_sig(st, |x,y| conv(x,y));
     ty::BareFnTy {
-        fn_style: fn_style,
+        unsafety: unsafety,
         abi: abi,
         sig: sig
     }

src/librustc/metadata/tyencode.rs

@@ -313,10 +313,10 @@ fn enc_sty<'a, 'tcx>(w: &mut SeekableMemWriter, cx: &ctxt<'a, 'tcx>,
     }
 }
 
-fn enc_fn_style(w: &mut SeekableMemWriter, p: ast::FnStyle) {
+fn enc_unsafety(w: &mut SeekableMemWriter, p: ast::Unsafety) {
     match p {
-        ast::NormalFn => mywrite!(w, "n"),
-        ast::UnsafeFn => mywrite!(w, "u"),
+        ast::Unsafety::Normal => mywrite!(w, "n"),
+        ast::Unsafety::Unsafe => mywrite!(w, "u"),
     }
 }
 
@@ -335,14 +335,14 @@ fn enc_onceness(w: &mut SeekableMemWriter, o: ast::Onceness) {
 
 pub fn enc_bare_fn_ty<'a, 'tcx>(w: &mut SeekableMemWriter, cx: &ctxt<'a, 'tcx>,
                                 ft: &ty::BareFnTy<'tcx>) {
-    enc_fn_style(w, ft.fn_style);
+    enc_unsafety(w, ft.unsafety);
     enc_abi(w, ft.abi);
     enc_fn_sig(w, cx, &ft.sig);
 }
 
 pub fn enc_closure_ty<'a, 'tcx>(w: &mut SeekableMemWriter, cx: &ctxt<'a, 'tcx>,
                                 ft: &ty::ClosureTy<'tcx>) {
-    enc_fn_style(w, ft.fn_style);
+    enc_unsafety(w, ft.unsafety);
     enc_onceness(w, ft.onceness);
     enc_trait_store(w, cx, ft.store);
     enc_existential_bounds(w, cx, &ft.bounds);

src/librustc/middle/dead.rs

@@ -355,7 +355,7 @@ impl<'v> Visitor<'v> for LifeSeeder {
             ast::ItemEnum(ref enum_def, _) if allow_dead_code => {
                 self.worklist.extend(enum_def.variants.iter().map(|variant| variant.node.id));
             }
-            ast::ItemImpl(_, Some(ref _trait_ref), _, ref impl_items) => {
+            ast::ItemImpl(_, _, Some(ref _trait_ref), _, ref impl_items) => {
                 for impl_item in impl_items.iter() {
                     match *impl_item {
                         ast::MethodImplItem(ref method) => {

src/librustc/middle/effect.rs

@@ -34,8 +34,8 @@ impl Copy for UnsafeContext {}
 
 fn type_is_unsafe_function(ty: Ty) -> bool {
     match ty.sty {
-        ty::ty_bare_fn(ref f) => f.fn_style == ast::UnsafeFn,
-        ty::ty_closure(ref f) => f.fn_style == ast::UnsafeFn,
+        ty::ty_bare_fn(ref f) => f.unsafety == ast::Unsafety::Unsafe,
+        ty::ty_closure(ref f) => f.unsafety == ast::Unsafety::Unsafe,
         _ => false,
     }
 }
@@ -92,9 +92,9 @@ impl<'a, 'tcx, 'v> Visitor<'v> for EffectCheckVisitor<'a, 'tcx> {
 
         let (is_item_fn, is_unsafe_fn) = match fn_kind {
             visit::FkItemFn(_, _, fn_style, _) =>
-                (true, fn_style == ast::UnsafeFn),
+                (true, fn_style == ast::Unsafety::Unsafe),
             visit::FkMethod(_, _, method) =>
-                (true, method.pe_fn_style() == ast::UnsafeFn),
+                (true, method.pe_unsafety() == ast::Unsafety::Unsafe),
             _ => (false, false),
         };
 

src/librustc/middle/infer/coercion.rs

@@ -521,7 +521,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
             debug!("coerce_from_bare_fn(a={}, b={})",
                    a.repr(self.get_ref().infcx.tcx), b.repr(self.get_ref().infcx.tcx));
 
-            if fn_ty_a.abi != abi::Rust || fn_ty_a.fn_style != ast::NormalFn {
+            if fn_ty_a.abi != abi::Rust || fn_ty_a.unsafety != ast::Unsafety::Normal {
                 return self.subtype(a, b);
             }
 

src/librustc/middle/infer/combine.rs

@@ -51,7 +51,7 @@ use middle::ty_fold;
 use middle::ty_fold::{TypeFoldable};
 use util::ppaux::Repr;
 
-use syntax::ast::{Onceness, FnStyle};
+use syntax::ast::{Onceness, Unsafety};
 use syntax::ast;
 use syntax::abi;
 use syntax::codemap::Span;
@@ -193,12 +193,12 @@ pub trait Combine<'tcx> {
 
     fn bare_fn_tys(&self, a: &ty::BareFnTy<'tcx>,
                    b: &ty::BareFnTy<'tcx>) -> cres<'tcx, ty::BareFnTy<'tcx>> {
-        let fn_style = try!(self.fn_styles(a.fn_style, b.fn_style));
+        let unsafety = try!(self.unsafeties(a.unsafety, b.unsafety));
         let abi = try!(self.abi(a.abi, b.abi));
         let sig = try!(self.fn_sigs(&a.sig, &b.sig));
-        Ok(ty::BareFnTy {fn_style: fn_style,
-                abi: abi,
-                sig: sig})
+        Ok(ty::BareFnTy {unsafety: unsafety,
+                         abi: abi,
+                         sig: sig})
     }
 
     fn closure_tys(&self, a: &ty::ClosureTy<'tcx>,
@@ -219,13 +219,13 @@ pub trait Combine<'tcx> {
                 return Err(ty::terr_sigil_mismatch(expected_found(self, a.store, b.store)))
             }
         };
-        let fn_style = try!(self.fn_styles(a.fn_style, b.fn_style));
+        let unsafety = try!(self.unsafeties(a.unsafety, b.unsafety));
         let onceness = try!(self.oncenesses(a.onceness, b.onceness));
         let bounds = try!(self.existential_bounds(a.bounds, b.bounds));
         let sig = try!(self.fn_sigs(&a.sig, &b.sig));
         let abi = try!(self.abi(a.abi, b.abi));
         Ok(ty::ClosureTy {
-            fn_style: fn_style,
+            unsafety: unsafety,
             onceness: onceness,
             store: store,
             bounds: bounds,
@@ -240,7 +240,7 @@ pub trait Combine<'tcx> {
         self.contratys(a, b).and_then(|t| Ok(t))
     }
 
-    fn fn_styles(&self, a: FnStyle, b: FnStyle) -> cres<'tcx, FnStyle>;
+    fn unsafeties(&self, a: Unsafety, b: Unsafety) -> cres<'tcx, Unsafety>;
 
     fn abi(&self, a: abi::Abi, b: abi::Abi) -> cres<'tcx, abi::Abi> {
         if a == b {