auto merge of #6457 : nikomatsakis/rust/issue-6308-closure-bounds, r=brson

Add BuiltinBounds to closure type: parse and handle subtyping,
but do not integrate with kindck etc (requires a snapshot first)

r? @brson

Author: bors

src/librustc/metadata/tydecode.rs

@@ -470,12 +470,14 @@ fn parse_closure_ty(st: @mut PState, conv: conv_did) -> ty::ClosureTy {
     let purity = parse_purity(next(st));
     let onceness = parse_onceness(next(st));
     let region = parse_region(st);
+    let bounds = parse_bounds(st, conv);
     let sig = parse_sig(st, conv);
     ty::ClosureTy {
         purity: purity,
         sigil: sigil,
         onceness: onceness,
         region: region,
+        bounds: bounds.builtin_bounds,
         sig: sig
     }
 }
@@ -540,10 +542,10 @@ pub fn parse_type_param_def_data(data: @~[u8], start: uint,
 
 fn parse_type_param_def(st: @mut PState, conv: conv_did) -> ty::TypeParameterDef {
     ty::TypeParameterDef {def_id: parse_def(st, NominalType, conv),
-                          bounds: parse_bounds(st, conv)}
+                          bounds: @parse_bounds(st, conv)}
 }
 
-fn parse_bounds(st: @mut PState, conv: conv_did) -> @ty::ParamBounds {
+fn parse_bounds(st: @mut PState, conv: conv_did) -> ty::ParamBounds {
     let mut param_bounds = ty::ParamBounds {
         builtin_bounds: ty::EmptyBuiltinBounds(),
         trait_bounds: ~[]
@@ -566,7 +568,7 @@ fn parse_bounds(st: @mut PState, conv: conv_did) -> @ty::ParamBounds {
                 param_bounds.trait_bounds.push(@parse_trait_ref(st, conv));
             }
             '.' => {
-                return @param_bounds;
+                return param_bounds;
             }
             _ => {
                 fail!("parse_bounds: bad bounds")

src/librustc/metadata/tyencode.rs

@@ -380,6 +380,9 @@ fn enc_closure_ty(w: @io::Writer, cx: @ctxt, ft: &ty::ClosureTy) {
     enc_purity(w, ft.purity);
     enc_onceness(w, ft.onceness);
     enc_region(w, cx, ft.region);
+    let bounds = ty::ParamBounds {builtin_bounds: ft.bounds,
+                                  trait_bounds: ~[]};
+    enc_bounds(w, cx, &bounds);
     enc_fn_sig(w, cx, &ft.sig);
 }
 
@@ -392,7 +395,7 @@ fn enc_fn_sig(w: @io::Writer, cx: @ctxt, fsig: &ty::FnSig) {
     enc_ty(w, cx, fsig.output);
 }
 
-fn enc_bounds(w: @io::Writer, cx: @ctxt, bs: @ty::ParamBounds) {
+fn enc_bounds(w: @io::Writer, cx: @ctxt, bs: &ty::ParamBounds) {
     for bs.builtin_bounds.each |bound| {
         match bound {
             ty::BoundOwned => w.write_char('S'),

src/librustc/middle/resolve.rs

@@ -20,6 +20,7 @@ use middle::lint::{allow, level, unused_imports};
 use middle::lint::{get_lint_level, get_lint_settings_level};
 use middle::pat_util::pat_bindings;
 
+use syntax::ast::{TyParamBound, ty_closure};
 use syntax::ast::{RegionTyParamBound, TraitTyParamBound, _mod, add, arm};
 use syntax::ast::{binding_mode, bitand, bitor, bitxor, blk};
 use syntax::ast::{bind_infer, bind_by_ref, bind_by_copy};
@@ -3732,14 +3733,20 @@ pub impl Resolver {
                                type_parameters: &OptVec<TyParam>,
                                visitor: ResolveVisitor) {
         for type_parameters.each |type_parameter| {
-            for type_parameter.bounds.each |&bound| {
-                match bound {
-                    TraitTyParamBound(tref) => {
-                        self.resolve_trait_reference(tref, visitor)
-                    }
-                    RegionTyParamBound => {}
-                }
+            for type_parameter.bounds.each |bound| {
+                self.resolve_type_parameter_bound(bound, visitor);
+            }
+        }
+    }
+
+    fn resolve_type_parameter_bound(@mut self,
+                                    type_parameter_bound: &TyParamBound,
+                                    visitor: ResolveVisitor) {
+        match *type_parameter_bound {
+            TraitTyParamBound(tref) => {
+                self.resolve_trait_reference(tref, visitor)
             }
+            RegionTyParamBound => {}
         }
     }
 
@@ -4070,6 +4077,13 @@ pub impl Resolver {
                 }
             }
 
+            ty_closure(c) => {
+                for c.bounds.each |bound| {
+                    self.resolve_type_parameter_bound(bound, visitor);
+                }
+                visit_ty(ty, (), visitor);
+            }
+
             _ => {
                 // Just resolve embedded types.
                 visit_ty(ty, (), visitor);

src/librustc/middle/trans/foreign.rs

@@ -818,6 +818,7 @@ pub fn trans_intrinsic(ccx: @CrateContext,
                 sigil: ast::BorrowedSigil,
                 onceness: ast::Many,
                 region: ty::re_bound(ty::br_anon(0)),
+                bounds: ty::EmptyBuiltinBounds(),
                 sig: FnSig {
                     bound_lifetime_names: opt_vec::Empty,
                     inputs: ~[ star_u8 ],

src/librustc/middle/trans/monomorphize.rs

@@ -330,6 +330,7 @@ pub fn normalize_for_monomorphization(tcx: ty::ctxt,
                 sigil: sigil,
                 onceness: ast::Many,
                 region: ty::re_static,
+                bounds: ty::EmptyBuiltinBounds(),
                 sig: ty::FnSig {bound_lifetime_names: opt_vec::Empty,
                                 inputs: ~[],
                                 output: ty::mk_nil()}})

src/librustc/middle/ty.rs

@@ -22,7 +22,7 @@ use middle::typeck;
 use middle;
 use util::ppaux::{note_and_explain_region, bound_region_to_str};
 use util::ppaux::{trait_store_to_str, ty_to_str, vstore_to_str};
-use util::ppaux::Repr;
+use util::ppaux::{Repr, UserString};
 use util::common::{indenter};
 use util::enum_set::{EnumSet, CLike};
 
@@ -390,7 +390,8 @@ pub struct ClosureTy {
     sigil: ast::Sigil,
     onceness: ast::Onceness,
     region: Region,
-    sig: FnSig
+    bounds: BuiltinBounds,
+    sig: FnSig,
 }
 
 /**
@@ -685,6 +686,7 @@ pub enum type_err {
     terr_int_mismatch(expected_found<IntVarValue>),
     terr_float_mismatch(expected_found<ast::float_ty>),
     terr_traits(expected_found<ast::def_id>),
+    terr_builtin_bounds(expected_found<BuiltinBounds>),
 }
 
 #[deriving(Eq, IterBytes)]
@@ -707,6 +709,15 @@ pub fn EmptyBuiltinBounds() -> BuiltinBounds {
     EnumSet::empty()
 }
 
+pub fn AllBuiltinBounds() -> BuiltinBounds {
+    let mut set = EnumSet::empty();
+    set.add(BoundCopy);
+    set.add(BoundStatic);
+    set.add(BoundOwned);
+    set.add(BoundConst);
+    set
+}
+
 impl CLike for BuiltinBound {
     pub fn to_uint(&self) -> uint {
         *self as uint
@@ -3169,6 +3180,7 @@ pub fn adjust_ty(cx: ctxt,
                                        sigil: s,
                                        onceness: ast::Many,
                                        region: r,
+                                       bounds: ty::AllBuiltinBounds(),
                                        sig: copy b.sig})
                 }
                 ref b => {
@@ -3697,6 +3709,19 @@ pub fn type_err_to_str(cx: ctxt, err: &type_err) -> ~str {
                  item_path_str(cx, values.expected),
                  item_path_str(cx, values.found))
         }
+        terr_builtin_bounds(values) => {
+            if values.expected.is_empty() {
+                fmt!("expected no bounds but found `%s`",
+                     values.found.user_string(cx))
+            } else if values.found.is_empty() {
+                fmt!("expected bounds `%s` but found no bounds",
+                     values.expected.user_string(cx))
+            } else {
+                fmt!("expected bounds `%s` but found bounds `%s`",
+                     values.expected.user_string(cx),
+                     values.found.user_string(cx))
+            }
+        }
         terr_self_substs => {
             ~"inconsistent self substitution" // XXX this is more of a bug
         }

src/librustc/middle/typeck/astconv.rs

@@ -59,6 +59,7 @@ use middle::ty;
 use middle::typeck::rscope::in_binding_rscope;
 use middle::typeck::rscope::{region_scope, RegionError};
 use middle::typeck::rscope::RegionParamNames;
+use middle::typeck::lookup_def_tcx;
 
 use syntax::abi::AbiSet;
 use syntax::{ast, ast_util};
@@ -220,7 +221,6 @@ pub fn ast_path_to_trait_ref<AC:AstConv,RS:region_scope + Copy + 'static>(
     return trait_ref;
 }
 
-
 pub fn ast_path_to_ty<AC:AstConv,RS:region_scope + Copy + 'static>(
         this: &AC,
         rscope: &RS,
@@ -377,11 +377,13 @@ pub fn ast_ty_to_ty<AC:AstConv, RS:region_scope + Copy + 'static>(
                                             bf.abis, &bf.lifetimes, &bf.decl))
       }
       ast::ty_closure(ref f) => {
+          let bounds = conv_builtin_bounds(this.tcx(), &f.bounds);
           let fn_decl = ty_of_closure(this,
                                       rscope,
                                       f.sigil,
                                       f.purity,
                                       f.onceness,
+                                      bounds,
                                       f.region,
                                       &f.decl,
                                       None,
@@ -646,17 +648,18 @@ fn ty_of_method_or_bare_fn<AC:AstConv,RS:region_scope + Copy + 'static>(
 }
 
 pub fn ty_of_closure<AC:AstConv,RS:region_scope + Copy + 'static>(
-        this: &AC,
-        rscope: &RS,
-        sigil: ast::Sigil,
-        purity: ast::purity,
-        onceness: ast::Onceness,
-        opt_lifetime: Option<@ast::Lifetime>,
-        decl: &ast::fn_decl,
-        expected_sig: Option<ty::FnSig>,
-        lifetimes: &OptVec<ast::Lifetime>,
-        span: span)
-     -> ty::ClosureTy
+    this: &AC,
+    rscope: &RS,
+    sigil: ast::Sigil,
+    purity: ast::purity,
+    onceness: ast::Onceness,
+    bounds: ty::BuiltinBounds,
+    opt_lifetime: Option<@ast::Lifetime>,
+    decl: &ast::fn_decl,
+    expected_sig: Option<ty::FnSig>,
+    lifetimes: &OptVec<ast::Lifetime>,
+    span: span)
+    -> ty::ClosureTy
 {
     // The caller should not both provide explicit bound lifetime
     // names and expected types.  Either we infer the bound lifetime
@@ -713,8 +716,69 @@ pub fn ty_of_closure<AC:AstConv,RS:region_scope + Copy + 'static>(
         sigil: sigil,
         onceness: onceness,
         region: bound_region,
+        bounds: bounds,
         sig: ty::FnSig {bound_lifetime_names: bound_lifetime_names,
                         inputs: input_tys,
                         output: output_ty}
     }
 }
+
+fn conv_builtin_bounds(tcx: ty::ctxt,
+                       ast_bounds: &OptVec<ast::TyParamBound>)
+                       -> ty::BuiltinBounds {
+    //! Converts a list of bounds from the AST into a `BuiltinBounds`
+    //! struct. Reports an error if any of the bounds that appear
+    //! in the AST refer to general traits and not the built-in traits
+    //! like `Copy` or `Owned`. Used to translate the bounds that
+    //! appear in closure and trait types, where only builtin bounds are
+    //! legal.
+
+    let mut builtin_bounds = ty::EmptyBuiltinBounds();
+    for ast_bounds.each |ast_bound| {
+        match *ast_bound {
+            ast::TraitTyParamBound(b) => {
+                match lookup_def_tcx(tcx, b.path.span, b.ref_id) {
+                    ast::def_trait(trait_did) => {
+                        if try_add_builtin_trait(tcx,
+                                                 trait_did,
+                                                 &mut builtin_bounds) {
+                            loop; // success
+                        }
+                    }
+                    _ => { }
+                }
+                tcx.sess.span_fatal(
+                    b.path.span,
+                    fmt!("only the builtin traits can be used \
+                          as closure or object bounds"));
+            }
+            ast::RegionTyParamBound => {
+                builtin_bounds.add(ty::BoundStatic);
+            }
+        }
+    }
+    builtin_bounds
+}
+
+pub fn try_add_builtin_trait(tcx: ty::ctxt,
+                             trait_def_id: ast::def_id,
+                             builtin_bounds: &mut ty::BuiltinBounds) -> bool {
+    //! Checks whether `trait_ref` refers to one of the builtin
+    //! traits, like `Copy` or `Owned`, and adds the corresponding
+    //! bound to the set `builtin_bounds` if so. Returns true if `trait_ref`
+    //! is a builtin trait.
+
+    let li = &tcx.lang_items;
+    if trait_def_id == li.owned_trait() {
+        builtin_bounds.add(ty::BoundOwned);
+        true
+    } else if trait_def_id == li.copy_trait() {
+        builtin_bounds.add(ty::BoundCopy);
+        true
+    } else if trait_def_id == li.const_trait() {
+        builtin_bounds.add(ty::BoundConst);
+        true
+    } else {
+        false
+    }
+}

src/librustc/middle/typeck/check/mod.rs

@@ -1661,19 +1661,22 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
         let (expected_sig,
              expected_purity,
              expected_sigil,
-             expected_onceness) = {
+             expected_onceness,
+             expected_bounds) = {
             match expected_sty {
                 Some(ty::ty_closure(ref cenv)) => {
                     let id = expr.id;
                     let (_, _, sig) =
                         replace_bound_regions_in_fn_sig(
                             tcx, @Nil, None, &cenv.sig,
                             |br| ty::re_bound(ty::br_cap_avoid(id, @br)));
-                    (Some(sig), cenv.purity, cenv.sigil, cenv.onceness)
+                    (Some(sig), cenv.purity, cenv.sigil,
+                     cenv.onceness, cenv.bounds)
                 }
                 _ => {
                     // Not an error! Means we're inferring the closure type
-                    (None, ast::impure_fn, ast::BorrowedSigil, ast::Many)
+                    (None, ast::impure_fn, ast::BorrowedSigil,
+                     ast::Many, ty::EmptyBuiltinBounds())
                 }
             }
         };
@@ -1687,15 +1690,16 @@ pub fn check_expr_with_unifier(fcx: @mut FnCtxt,
 
         // construct the function type
         let fn_ty = astconv::ty_of_closure(fcx,
-                                               fcx,
-                                               sigil,
-                                               purity,
-                                               expected_onceness,
-                                               None,
-                                               decl,
-                                               expected_sig,
-                                               &opt_vec::Empty,
-                                               expr.span);
+                                           fcx,
+                                           sigil,
+                                           purity,
+                                           expected_onceness,
+                                           expected_bounds,
+                                           None,
+                                           decl,
+                                           expected_sig,
+                                           &opt_vec::Empty,
+                                           expr.span);
 
         let fty_sig;
         let fty = if error_happened {
@@ -3526,6 +3530,7 @@ pub fn check_intrinsic_type(ccx: @mut CrateCtxt, it: @ast::foreign_item) {
             sigil: ast::BorrowedSigil,
             onceness: ast::Once,
             region: ty::re_bound(ty::br_anon(0)),
+            bounds: ty::EmptyBuiltinBounds(),
             sig: ty::FnSig {
                 bound_lifetime_names: opt_vec::Empty,
                 inputs: ~[ty::mk_imm_ptr(ccx.tcx, ty::mk_mach_uint(ast::ty_u8))],