Simplify the AST representation of ty param bounds

Change ast::ty_param_bound so that all ty param bounds are represented
as traits, with no special cases for Copy/Send/Owned/Const.
typeck::collect generates the special cases.

A consequence of this is that code using the #[no_core] attribute
can't use the Copy kind/trait. Probably not a big deal?

As a side effect, any user-defined traits that happen to be called
Copy, etc. in the same module override the built-in Copy trait.

r=nmatsakis

Closes #2284

Author: catamorphism

src/libsyntax/ast.rs

@@ -123,13 +123,11 @@ const crate_node_id: node_id = 0;
 
 #[auto_serialize]
 #[auto_deserialize]
-enum ty_param_bound {
-    bound_copy,
-    bound_send,
-    bound_const,
-    bound_owned,
-    bound_trait(@Ty),
-}
+// The AST represents all type param bounds as types.
+// typeck::collect::compute_bounds matches these against
+// the "special" built-in traits (see middle::lang_items) and
+// detects Copy, Send, Owned, and Const.
+enum ty_param_bound = @Ty;
 
 #[auto_serialize]
 #[auto_deserialize]

src/libsyntax/ext/auto_serialize.rs

@@ -227,7 +227,7 @@ priv impl ext_ctxt {
         path: @ast::path,
         bounds: @~[ast::ty_param_bound]
     ) -> ast::ty_param {
-        let bound = ast::bound_trait(@{
+        let bound = ast::ty_param_bound(@{
             id: self.next_id(),
             node: ast::ty_path(path, self.next_id()),
             span: span,
@@ -366,7 +366,7 @@ fn mk_impl(
     let mut trait_tps = vec::append(
         ~[ty_param],
          do tps.map |tp| {
-            let t_bound = ast::bound_trait(@{
+            let t_bound = ast::ty_param_bound(@{
                 id: cx.next_id(),
                 node: ast::ty_path(path, cx.next_id()),
                 span: span,

src/libsyntax/fold.rs

@@ -131,10 +131,7 @@ fn fold_fn_decl(decl: ast::fn_decl, fld: ast_fold) -> ast::fn_decl {
 }
 
 fn fold_ty_param_bound(tpb: ty_param_bound, fld: ast_fold) -> ty_param_bound {
-    match tpb {
-      bound_copy | bound_send | bound_const | bound_owned => tpb,
-      bound_trait(ty) => bound_trait(fld.fold_ty(ty))
-    }
+    ty_param_bound(fld.fold_ty(*tpb))
 }
 
 fn fold_ty_param(tp: ty_param, fld: ast_fold) -> ty_param {

src/libsyntax/parse/parser.rs

@@ -24,8 +24,7 @@ use obsolete::{
 };
 use ast::{_mod, add, arg, arm, attribute,
              bind_by_ref, bind_by_implicit_ref, bind_by_value, bind_by_move,
-             bitand, bitor, bitxor, blk, blk_check_mode, bound_const,
-             bound_copy, bound_send, bound_trait, bound_owned, box, by_copy,
+             bitand, bitor, bitxor, blk, blk_check_mode, box, by_copy,
              by_move, by_ref, by_val, capture_clause,
              capture_item, cdir_dir_mod, cdir_src_mod, cdir_view_item,
              class_immutable, class_mutable,
@@ -2295,19 +2294,20 @@ impl Parser {
         return spanned(lo, hi, bloc);
     }
 
+    fn mk_ty_path(i: ident) -> @Ty {
+        @{id: self.get_id(), node: ty_path(
+            ident_to_path(copy self.last_span, i),
+            self.get_id()), span: self.last_span}
+    }
+
     fn parse_optional_ty_param_bounds() -> @~[ty_param_bound] {
         let mut bounds = ~[];
         if self.eat(token::COLON) {
             while is_ident(self.token) {
                 if is_ident(self.token) {
-                    // XXX: temporary until kinds become traits
                     let maybe_bound = match self.token {
                       token::IDENT(copy sid, _) => {
                         match *self.id_to_str(sid) {
-                          ~"Send" => Some(bound_send),
-                          ~"Copy" => Some(bound_copy),
-                          ~"Const" => Some(bound_const),
-                          ~"Owned" => Some(bound_owned),
 
                           ~"send"
                           | ~"copy"
@@ -2317,7 +2317,7 @@ impl Parser {
                                           ObsoleteLowerCaseKindBounds);
                             // Bogus value, but doesn't matter, since
                             // is an error
-                            Some(bound_send)
+                            Some(ty_param_bound(self.mk_ty_path(sid)))
                           }
 
                           _ => None
@@ -2332,11 +2332,11 @@ impl Parser {
                             bounds.push(bound);
                         }
                         None => {
-                            bounds.push(bound_trait(self.parse_ty(false)));
+                            bounds.push(ty_param_bound(self.parse_ty(false)));
                         }
                     }
                 } else {
-                    bounds.push(bound_trait(self.parse_ty(false)));
+                    bounds.push(ty_param_bound(self.parse_ty(false)));
                 }
             }
         }

src/libsyntax/print/pprust.rs

@@ -1704,17 +1704,11 @@ fn print_arg_mode(s: ps, m: ast::mode) {
 }
 
 fn print_bounds(s: ps, bounds: @~[ast::ty_param_bound]) {
-    if vec::len(*bounds) > 0u {
+    if bounds.is_not_empty() {
         word(s.s, ~":");
         for vec::each(*bounds) |bound| {
             nbsp(s);
-            match *bound {
-              ast::bound_copy => word(s.s, ~"Copy"),
-              ast::bound_send => word(s.s, ~"Send"),
-              ast::bound_const => word(s.s, ~"Const"),
-              ast::bound_owned => word(s.s, ~"Owned"),
-              ast::bound_trait(t) => print_type(s, t)
-            }
+            print_type(s, **bound);
         }
     }
 }

src/libsyntax/visit.rs

@@ -264,10 +264,7 @@ fn visit_foreign_item<E>(ni: @foreign_item, e: E, v: vt<E>) {
 
 fn visit_ty_param_bounds<E>(bounds: @~[ty_param_bound], e: E, v: vt<E>) {
     for vec::each(*bounds) |bound| {
-        match *bound {
-          bound_trait(t) => v.visit_ty(t, e, v),
-          bound_copy | bound_send | bound_const | bound_owned => ()
-        }
+        v.visit_ty(**bound, e, v)
     }
 }
 

src/rustc/middle/resolve.rs

@@ -9,9 +9,9 @@ use middle::pat_util::{pat_bindings};
 use syntax::ast::{_mod, add, arm};
 use syntax::ast::{bind_by_ref, bind_by_implicit_ref, bind_by_value};
 use syntax::ast::{bitand, bitor, bitxor};
-use syntax::ast::{blk, bound_const, bound_copy, bound_owned, bound_send};
-use syntax::ast::{bound_trait, binding_mode, capture_clause, class_ctor};
-use syntax::ast::{class_dtor, crate, crate_num, decl_item};
+use syntax::ast::{binding_mode, blk,
+                     capture_clause, class_ctor, class_dtor};
+use syntax::ast::{crate, crate_num, decl_item};
 use syntax::ast::{def, def_arg, def_binding, def_class, def_const, def_fn};
 use syntax::ast::{def_foreign_mod, def_id, def_label, def_local, def_mod};
 use syntax::ast::{def_prim_ty, def_region, def_self, def_ty, def_ty_param};
@@ -39,6 +39,7 @@ use syntax::ast::{trait_ref, tuple_variant_kind, Ty, ty_bool, ty_char};
 use syntax::ast::{ty_f, ty_f32, ty_f64, ty_float, ty_i, ty_i16, ty_i32};
 use syntax::ast::{ty_i64, ty_i8, ty_int, ty_param, ty_path, ty_str, ty_u};
 use syntax::ast::{ty_u16, ty_u32, ty_u64, ty_u8, ty_uint, type_value_ns};
+use syntax::ast::{ty_param_bound};
 use syntax::ast::{variant, view_item, view_item_export, view_item_import};
 use syntax::ast::{view_item_use, view_path_glob, view_path_list};
 use syntax::ast::{view_path_simple, visibility, anonymous, named};
@@ -3764,14 +3765,7 @@ impl Resolver {
                                visitor: ResolveVisitor) {
         for type_parameters.each |type_parameter| {
             for type_parameter.bounds.each |bound| {
-                match *bound {
-                    bound_copy | bound_send | bound_const | bound_owned => {
-                        // Nothing to do.
-                    }
-                    bound_trait(trait_type) => {
-                        self.resolve_type(trait_type, visitor);
-                    }
-                }
+                self.resolve_type(**bound, visitor);
             }
         }
     }
@@ -4088,7 +4082,7 @@ impl Resolver {
                 let mut result_def = None;
 
                 // First, check to see whether the name is a primitive type.
-                if path.idents.len() == 1u {
+                if path.idents.len() == 1 {
                     let name = path.idents.last();
 
                     match self.primitive_type_table

src/rustc/middle/typeck/collect.rs

@@ -707,28 +707,41 @@ fn ty_of_foreign_item(ccx: @crate_ctxt, it: @ast::foreign_item)
     }
 }
 
+// Translate the AST's notion of ty param bounds (which are just newtyped Tys)
+// to ty's notion of ty param bounds, which can either be user-defined traits,
+// or one of the four built-in traits (formerly known as kinds): Const, Copy,
+// Owned, and Send.
 fn compute_bounds(ccx: @crate_ctxt,
                   ast_bounds: @~[ast::ty_param_bound]) -> ty::param_bounds {
     @do vec::flat_map(*ast_bounds) |b| {
-        match *b {
-          ast::bound_send => ~[ty::bound_send],
-          ast::bound_copy => ~[ty::bound_copy],
-          ast::bound_const => ~[ty::bound_const],
-          ast::bound_owned => ~[ty::bound_owned],
-          ast::bound_trait(t) => {
-            let ity = ast_ty_to_ty(ccx, empty_rscope, t);
-            match ty::get(ity).sty {
-              ty::ty_trait(*) => {
-                ~[ty::bound_trait(ity)]
-              }
-              _ => {
+        let li = &ccx.tcx.lang_items;
+        let ity = ast_ty_to_ty(ccx, empty_rscope, **b);
+        match ty::get(ity).sty {
+            ty::ty_trait(did, _, _) => {
+                let d = Some(did);
+                if d == li.send_trait {
+                    ~[ty::bound_send]
+                }
+                else if d == li.copy_trait {
+                    ~[ty::bound_copy]
+                }
+                else if d == li.const_trait {
+                    ~[ty::bound_const]
+                }
+                else if d == li.owned_trait {
+                    ~[ty::bound_owned]
+                }
+                else {
+                    // Must be a user-defined trait
+                    ~[ty::bound_trait(ity)]
+                }
+            }
+            _ => {
                 ccx.tcx.sess.span_err(
-                    t.span, ~"type parameter bounds must be \
-                              trait types");
+                    (*b).span, ~"type parameter bounds must be \
+                                 trait types");
                 ~[]
-              }
             }
-          }
         }
     }
 }

src/test/compile-fail/tag-that-dare-not-speak-its-name.rs

@@ -5,7 +5,7 @@
 
 extern mod core;
 
-fn last<T: Copy>(v: ~[const T]) -> core::Option<T> {
+fn last<T>(v: ~[const &T]) -> core::Option<T> {
     fail;
 }
 

src/test/run-pass/issue-2284.rs

@@ -1,4 +1,3 @@
-// xfail-test
 trait Send {
     fn f();
 }