auto merge of #13398 : nick29581/rust/unsized-enum, r=nikomatsakis

Now with proper checking of enums and allows unsized fields as the last field in a struct or variant. This PR only checks passing of unsized types and distinguishing them from sized ones. To be safe we also need to control storage.

Closes issues #12969 and #13121, supersedes #13375 (all the discussion there is valid here too).

13 files changed, 103 insertions, 22 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index a6146e0eaea..116411c9e05 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -180,8 +180,10 @@ pub enum TyParamBound {
 pub struct TyParam {
     pub ident: Ident,
     pub id: NodeId,
+    pub sized: Sized,
     pub bounds: OwnedSlice<TyParamBound>,
-    pub default: Option<P<Ty>>
+    pub default: Option<P<Ty>>,
+    pub span: Span
 }
 
 #[deriving(Clone, Eq, TotalEq, Encodable, Decodable, Hash)]
@@ -1052,6 +1054,12 @@ impl Visibility {
 }
 
 #[deriving(Clone, Eq, TotalEq, Encodable, Decodable, Hash)]
+pub enum Sized {
+    DynSize,
+    StaticSize,
+}
+
+#[deriving(Clone, Eq, TotalEq, Encodable, Decodable, Hash)]
 pub struct StructField_ {
     pub kind: StructFieldKind,
     pub id: NodeId,
@@ -1109,7 +1117,7 @@ pub enum Item_ {
     ItemTy(P<Ty>, Generics),
     ItemEnum(EnumDef, Generics),
     ItemStruct(@StructDef, Generics),
-    ItemTrait(Generics, Vec<TraitRef> , Vec<TraitMethod> ),
+    ItemTrait(Generics, Sized, Vec<TraitRef> , Vec<TraitMethod> ),
     ItemImpl(Generics,
              Option<TraitRef>, // (optional) trait this impl implements
              P<Ty>, // self
diff --git a/src/libsyntax/ast_map.rs b/src/libsyntax/ast_map.rs
index 45954800e7e..7a167237d3e 100644
--- a/src/libsyntax/ast_map.rs
+++ b/src/libsyntax/ast_map.rs
@@ -265,6 +265,31 @@ impl Map {
         }
     }
 
+    pub fn expect_struct(&self, id: NodeId) -> @StructDef {
+        match self.find(id) {
+            Some(NodeItem(i)) => {
+                match i.node {
+                    ItemStruct(struct_def, _) => struct_def,
+                    _ => fail!("struct ID bound to non-struct")
+                }
+            }
+            Some(NodeVariant(ref variant)) => {
+                match (*variant).node.kind {
+                    StructVariantKind(struct_def) => struct_def,
+                    _ => fail!("struct ID bound to enum variant that isn't struct-like"),
+                }
+            }
+            _ => fail!(format!("expected struct, found {}", self.node_to_str(id))),
+        }
+    }
+
+    pub fn expect_variant(&self, id: NodeId) -> P<Variant> {
+        match self.find(id) {
+            Some(NodeVariant(variant)) => variant,
+            _ => fail!(format!("expected variant, found {}", self.node_to_str(id))),
+        }
+    }
+
     pub fn expect_foreign_item(&self, id: NodeId) -> @ForeignItem {
         match self.find(id) {
             Some(NodeForeignItem(item)) => item,
@@ -453,7 +478,7 @@ impl<'a, F: FoldOps> Folder for Ctx<'a, F> {
                     None => {}
                 }
             }
-            ItemTrait(_, ref traits, ref methods) => {
+            ItemTrait(_, _, ref traits, ref methods) => {
                 for t in traits.iter() {
                     self.insert(t.ref_id, EntryItem(self.parent, i));
                 }
diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index 203edf6590f..e1174ea6cc4 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -66,7 +66,9 @@ pub trait AstBuilder {
     fn strip_bounds(&self, bounds: &Generics) -> Generics;
 
     fn typaram(&self,
+               span: Span,
                id: ast::Ident,
+               sized: ast::Sized,
                bounds: OwnedSlice<ast::TyParamBound>,
                default: Option<P<ast::Ty>>) -> ast::TyParam;
 
@@ -368,14 +370,18 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
     }
 
     fn typaram(&self,
+               span: Span,
                id: ast::Ident,
+               sized: ast::Sized,
                bounds: OwnedSlice<ast::TyParamBound>,
                default: Option<P<ast::Ty>>) -> ast::TyParam {
         ast::TyParam {
             ident: id,
             id: ast::DUMMY_NODE_ID,
+            sized: sized,
             bounds: bounds,
-            default: default
+            default: default,
+            span: span
         }
     }
 
diff --git a/src/libsyntax/ext/deriving/decodable.rs b/src/libsyntax/ext/deriving/decodable.rs
index 579de82c8db..35a1eb0bb83 100644
--- a/src/libsyntax/ext/deriving/decodable.rs
+++ b/src/libsyntax/ext/deriving/decodable.rs
@@ -13,6 +13,7 @@ The compiler code necessary for `#[deriving(Decodable)]`. See
 encodable.rs for more.
 */
 
+use ast;
 use ast::{MetaItem, Item, Expr, MutMutable, Ident};
 use codemap::Span;
 use ext::base::ExtCtxt;
@@ -35,10 +36,10 @@ pub fn expand_deriving_decodable(cx: &mut ExtCtxt,
         additional_bounds: Vec::new(),
         generics: LifetimeBounds {
             lifetimes: Vec::new(),
-            bounds: vec!(("__D", vec!(Path::new_(
+            bounds: vec!(("__D", ast::StaticSize, vec!(Path::new_(
                             vec!("serialize", "Decoder"), None,
                             vec!(~Literal(Path::new_local("__E"))), true))),
-                         ("__E", vec!()))
+                         ("__E", ast::StaticSize, vec!()))
         },
         methods: vec!(
             MethodDef {
diff --git a/src/libsyntax/ext/deriving/encodable.rs b/src/libsyntax/ext/deriving/encodable.rs
index 1c3edce96fb..806560f6826 100644
--- a/src/libsyntax/ext/deriving/encodable.rs
+++ b/src/libsyntax/ext/deriving/encodable.rs
@@ -82,6 +82,7 @@ would yield functions like:
 ```
 */
 
+use ast;
 use ast::{MetaItem, Item, Expr, ExprRet, MutMutable, LitNil};
 use codemap::Span;
 use ext::base::ExtCtxt;
@@ -103,10 +104,10 @@ pub fn expand_deriving_encodable(cx: &mut ExtCtxt,
         additional_bounds: Vec::new(),
         generics: LifetimeBounds {
             lifetimes: Vec::new(),
-            bounds: vec!(("__S", vec!(Path::new_(
+            bounds: vec!(("__S", ast::StaticSize, vec!(Path::new_(
                             vec!("serialize", "Encoder"), None,
                             vec!(~Literal(Path::new_local("__E"))), true))),
-                         ("__E", vec!()))
+                         ("__E", ast::StaticSize, vec!()))
         },
         methods: vec!(
             MethodDef {
diff --git a/src/libsyntax/ext/deriving/generic.rs b/src/libsyntax/ext/deriving/generic.rs
index 1d4aa08f9e3..914451fb402 100644
--- a/src/libsyntax/ext/deriving/generic.rs
+++ b/src/libsyntax/ext/deriving/generic.rs
@@ -380,7 +380,11 @@ impl<'a> TraitDef<'a> {
             // require the current trait
             bounds.push(cx.typarambound(trait_path.clone()));
 
-            cx.typaram(ty_param.ident, OwnedSlice::from_vec(bounds), None)
+            cx.typaram(self.span,
+                       ty_param.ident,
+                       ty_param.sized,
+                       OwnedSlice::from_vec(bounds),
+                       None)
         }));
         let trait_generics = Generics {
             lifetimes: lifetimes,
diff --git a/src/libsyntax/ext/deriving/hash.rs b/src/libsyntax/ext/deriving/hash.rs
index 23331dc03cb..d22027d203f 100644
--- a/src/libsyntax/ext/deriving/hash.rs
+++ b/src/libsyntax/ext/deriving/hash.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use ast;
 use ast::{MetaItem, Item, Expr, MutMutable};
 use codemap::Span;
 use ext::base::ExtCtxt;
@@ -25,7 +26,7 @@ pub fn expand_deriving_hash(cx: &mut ExtCtxt,
                     vec!(~Literal(Path::new_local("__S"))), true),
          LifetimeBounds {
              lifetimes: Vec::new(),
-             bounds: vec!(("__S", vec!(Path::new(vec!("std", "io", "Writer"))))),
+             bounds: vec!(("__S", ast::StaticSize, vec!(Path::new(vec!("std", "io", "Writer"))))),
          },
          Path::new_local("__S"))
     } else {
diff --git a/src/libsyntax/ext/deriving/rand.rs b/src/libsyntax/ext/deriving/rand.rs
index 6b824e52bb3..e81aa55d10d 100644
--- a/src/libsyntax/ext/deriving/rand.rs
+++ b/src/libsyntax/ext/deriving/rand.rs
@@ -32,7 +32,8 @@ pub fn expand_deriving_rand(cx: &mut ExtCtxt,
                 generics: LifetimeBounds {
                     lifetimes: Vec::new(),
                     bounds: vec!(("R",
-                               vec!( Path::new(vec!("rand", "Rng")) )))
+                                  ast::StaticSize,
+                                  vec!( Path::new(vec!("rand", "Rng")) )))
                 },
                 explicit_self: None,
                 args: vec!(
diff --git a/src/libsyntax/ext/deriving/ty.rs b/src/libsyntax/ext/deriving/ty.rs
index c4ca2601f60..6e3327b4039 100644
--- a/src/libsyntax/ext/deriving/ty.rs
+++ b/src/libsyntax/ext/deriving/ty.rs
@@ -186,14 +186,14 @@ impl<'a> Ty<'a> {
 }
 
 
-fn mk_ty_param(cx: &ExtCtxt, span: Span, name: &str, bounds: &[Path],
+fn mk_ty_param(cx: &ExtCtxt, span: Span, name: &str, sized: ast::Sized, bounds: &[Path],
                self_ident: Ident, self_generics: &Generics) -> ast::TyParam {
     let bounds =
         bounds.iter().map(|b| {
             let path = b.to_path(cx, span, self_ident, self_generics);
             cx.typarambound(path)
         }).collect();
-    cx.typaram(cx.ident_of(name), bounds, None)
+    cx.typaram(span, cx.ident_of(name), sized, bounds, None)
 }
 
 fn mk_generics(lifetimes: Vec<ast::Lifetime> ,  ty_params: Vec<ast::TyParam> ) -> Generics {
@@ -206,7 +206,7 @@ fn mk_generics(lifetimes: Vec<ast::Lifetime> ,  ty_params: Vec<ast::TyParam> ) -
 /// Lifetimes and bounds on type parameters
 pub struct LifetimeBounds<'a> {
     pub lifetimes: Vec<&'a str>,
-    pub bounds: Vec<(&'a str, Vec<Path<'a>>)>,
+    pub bounds: Vec<(&'a str, ast::Sized, Vec<Path<'a>>)>,
 }
 
 impl<'a> LifetimeBounds<'a> {
@@ -226,10 +226,11 @@ impl<'a> LifetimeBounds<'a> {
         }).collect();
         let ty_params = self.bounds.iter().map(|t| {
             match t {
-                &(ref name, ref bounds) => {
+                &(ref name, sized, ref bounds) => {
                     mk_ty_param(cx,
                                 span,
                                 *name,
+                                sized,
                                 bounds.as_slice(),
                                 self_ty,
                                 self_generics)
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index 73ad2664be4..04b289b9fca 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -447,8 +447,10 @@ pub fn fold_ty_param<T: Folder>(tp: &TyParam, fld: &mut T) -> TyParam {
     TyParam {
         ident: tp.ident,
         id: id,
+        sized: tp.sized,
         bounds: tp.bounds.map(|x| fold_ty_param_bound(x, fld)),
-        default: tp.default.map(|x| fld.fold_ty(x))
+        default: tp.default.map(|x| fld.fold_ty(x)),
+        span: tp.span
     }
 }
 
@@ -619,7 +621,7 @@ pub fn noop_fold_item_underscore<T: Folder>(i: &Item_, folder: &mut T) -> Item_
                      methods.iter().map(|x| folder.fold_method(*x)).collect()
             )
         }
-        ItemTrait(ref generics, ref traits, ref methods) => {
+        ItemTrait(ref generics, ref sized, ref traits, ref methods) => {
             let methods = methods.iter().map(|method| {
                 match *method {
                     Required(ref m) => Required(folder.fold_type_method(m)),
@@ -627,6 +629,7 @@ pub fn noop_fold_item_underscore<T: Folder>(i: &Item_, folder: &mut T) -> Item_
                 }
             }).collect();
             ItemTrait(fold_generics(generics, folder),
+                      *sized,
                       traits.iter().map(|p| fold_trait_ref(p, folder)).collect(),
                       methods)
         }
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 6485b5a3622..8808312bed7 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -42,6 +42,7 @@ use ast::{PatIdent, PatLit, PatRange, PatRegion, PatStruct};
 use ast::{PatTup, PatUniq, PatWild, PatWildMulti};
 use ast::{BiRem, Required};
 use ast::{RetStyle, Return, BiShl, BiShr, Stmt, StmtDecl};
+use ast::{Sized, DynSize, StaticSize};
 use ast::{StmtExpr, StmtSemi, StmtMac, StructDef, StructField};
 use ast::{StructVariantKind, BiSub};
 use ast::StrStyle;
@@ -3390,8 +3391,10 @@ impl<'a> Parser<'a> {
         return (ret_lifetime, Some(OwnedSlice::from_vec(result)));
     }
 
-    // matches typaram = IDENT optbounds ( EQ ty )?
+    // matches typaram = type? IDENT optbounds ( EQ ty )?
     fn parse_ty_param(&mut self) -> TyParam {
+        let sized = self.parse_sized();
+        let span = self.span;
         let ident = self.parse_ident();
         let (_, opt_bounds) = self.parse_optional_ty_param_bounds(false);
         // For typarams we don't care about the difference b/w "<T>" and "<T:>".
@@ -3406,8 +3409,10 @@ impl<'a> Parser<'a> {
         TyParam {
             ident: ident,
             id: ast::DUMMY_NODE_ID,
+            sized: sized,
             bounds: bounds,
-            default: default
+            default: default,
+            span: span,
         }
     }
 
@@ -3795,6 +3800,7 @@ impl<'a> Parser<'a> {
     fn parse_item_trait(&mut self) -> ItemInfo {
         let ident = self.parse_ident();
         let tps = self.parse_generics();
+        let sized = self.parse_for_sized();
 
         // Parse traits, if necessary.
         let traits;
@@ -3806,7 +3812,7 @@ impl<'a> Parser<'a> {
         }
 
         let meths = self.parse_trait_methods();
-        (ident, ItemTrait(tps, traits, meths), None)
+        (ident, ItemTrait(tps, sized, traits, meths), None)
     }
 
     // Parses two variants (with the region/type params always optional):
@@ -3997,6 +4003,23 @@ impl<'a> Parser<'a> {
         else { Inherited }
     }
 
+    fn parse_sized(&mut self) -> Sized {
+        if self.eat_keyword(keywords::Type) { DynSize }
+        else { StaticSize }
+    }
+
+    fn parse_for_sized(&mut self) -> Sized {
+        if self.eat_keyword(keywords::For) {
+            if !self.eat_keyword(keywords::Type) {
+                self.span_err(self.last_span,
+                    "expected 'type' after for in trait item");
+            }
+            DynSize
+        } else {
+            StaticSize
+        }
+    }
+
     // given a termination token and a vector of already-parsed
     // attributes (of length 0 or 1), parse all of the items in a module
     fn parse_mod_items(&mut self,
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index f4e337e2048..f768bf22ce0 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -673,10 +673,14 @@ impl<'a> State<'a> {
                 }
                 try!(self.bclose(item.span));
             }
-            ast::ItemTrait(ref generics, ref traits, ref methods) => {
+            ast::ItemTrait(ref generics, ref sized, ref traits, ref methods) => {
                 try!(self.head(visibility_qualified(item.vis, "trait")));
                 try!(self.print_ident(item.ident));
                 try!(self.print_generics(generics));
+                if *sized == ast::DynSize {
+                    try!(space(&mut self.s));
+                    try!(word(&mut self.s, "for type"));
+                }
                 if traits.len() != 0u {
                     try!(word(&mut self.s, ":"));
                     for (i, trait_) in traits.iter().enumerate() {
@@ -1910,6 +1914,9 @@ impl<'a> State<'a> {
                     } else {
                         let idx = idx - generics.lifetimes.len();
                         let param = generics.ty_params.get(idx);
+                        if param.sized == ast::DynSize {
+                            try!(s.word_space("type"));
+                        }
                         try!(s.print_ident(param.ident));
                         try!(s.print_bounds(&None, &param.bounds, false));
                         match param.default {
diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index 1f75c2e062f..e830daf8ede 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -257,7 +257,7 @@ pub fn walk_item<E: Clone, V: Visitor<E>>(visitor: &mut V, item: &Item, env: E)
                                      item.id,
                                      env)
         }
-        ItemTrait(ref generics, ref trait_paths, ref methods) => {
+        ItemTrait(ref generics, _, ref trait_paths, ref methods) => {
             visitor.visit_generics(generics, env.clone());
             for trait_path in trait_paths.iter() {
                 visitor.visit_path(&trait_path.path,