librustc: Implement the unboxed closure trait hierarchy.

This makes `FnMut` require `FnOnce` and `Fn` require `FnMut`. Therefore,
this change breaks code that implements the `FnMut` and/or `Fn` traits
directly, without also implementing their dependencies. A simple
forwarding implementation that defines `FnOnce` in terms of `FnMut`
and/or `Fn` in terms of `FnMut` will suffice.

This does not affect code that simply uses the `|&:|`/`|&mut:|`/`|:|`
unboxed closure construction notation.

Part of RFC rust-lang#44; needed to implement RFC rust-lang#63.

Part of issue rust-lang#12831.

[breaking-change]

Author: pcwalton

src/libcore/ops.rs

@@ -848,15 +848,15 @@ pub trait DerefMut<Sized? Result>: Deref<Result> {
 
 /// A version of the call operator that takes an immutable receiver.
 #[lang="fn"]
-pub trait Fn<Args,Result> {
+pub trait Fn<Args,Result> : FnMut<Args,Result> {
     /// This is called when the call operator is used.
     #[rust_call_abi_hack]
     fn call(&self, args: Args) -> Result;
 }
 
 /// A version of the call operator that takes a mutable receiver.
 #[lang="fn_mut"]
-pub trait FnMut<Args,Result> {
+pub trait FnMut<Args,Result> : FnOnce<Args,Result> {
     /// This is called when the call operator is used.
     #[rust_call_abi_hack]
     fn call_mut(&mut self, args: Args) -> Result;
@@ -872,6 +872,28 @@ pub trait FnOnce<Args,Result> {
 
 macro_rules! def_fn_mut(
     ($($args:ident)*) => (
+        impl<Result$(,$args)*>
+        FnOnce<($($args,)*),Result>
+        for extern "Rust" fn($($args: $args,)*) -> Result {
+            #[rust_call_abi_hack]
+            #[allow(non_snake_case)]
+            fn call_once(self, args: ($($args,)*)) -> Result {
+                let ($($args,)*) = args;
+                self($($args,)*)
+            }
+        }
+
+        impl<Result$(,$args)*>
+        Fn<($($args,)*),Result>
+        for extern "Rust" fn($($args: $args,)*) -> Result {
+            #[rust_call_abi_hack]
+            #[allow(non_snake_case)]
+            fn call(&self, args: ($($args,)*)) -> Result {
+                let ($($args,)*) = args;
+                (*self)($($args,)*)
+            }
+        }
+
         impl<Result$(,$args)*>
         FnMut<($($args,)*),Result>
         for extern "Rust" fn($($args: $args,)*) -> Result {

src/librustc/middle/astencode.rs

@@ -1332,6 +1332,7 @@ fn encode_side_tables_for_id(ecx: &e::EncodeContext,
             rbml_w.id(id);
             rbml_w.tag(c::tag_table_val, |rbml_w| {
                 rbml_w.emit_closure_type(ecx, &unboxed_closure.closure_type);
+                rbml_w.emit_def_id(unboxed_closure.expr_id);
                 encode_unboxed_closure_kind(rbml_w, unboxed_closure.kind)
             })
         })
@@ -1750,6 +1751,7 @@ impl<'a> rbml_decoder_decoder_helpers for reader::Decoder<'a> {
                 dcx.tcx,
                 |s, a| this.convert_def_id(dcx, s, a)))
         }).unwrap();
+        let expr_id = self.read_def_id(dcx);
         let variants = [
             "FnUnboxedClosureKind",
             "FnMutUnboxedClosureKind",
@@ -1765,6 +1767,7 @@ impl<'a> rbml_decoder_decoder_helpers for reader::Decoder<'a> {
         }).unwrap();
         ty::UnboxedClosure {
             closure_type: closure_type,
+            expr_id: expr_id,
             kind: kind,
         }
     }

src/librustc/middle/borrowck/mod.rs

@@ -282,7 +282,7 @@ pub fn closure_to_block(closure_id: ast::NodeId,
         ast_map::NodeExpr(expr) => match expr.node {
             ast::ExprProc(_, ref block) |
             ast::ExprFnBlock(_, _, ref block) |
-            ast::ExprUnboxedFn(_, _, _, ref block) => { block.id }
+            ast::ExprUnboxedFn(_, _, _, _, ref block) => { block.id }
             _ => fail!("encountered non-closure id: {}", closure_id)
         },
         _ => fail!("encountered non-expr id: {}", closure_id)

src/librustc/middle/check_loop.rs

@@ -49,7 +49,7 @@ impl<'a, 'v> Visitor<'v> for CheckLoopVisitor<'a> {
             }
             ast::ExprFnBlock(_, _, ref b) |
             ast::ExprProc(_, ref b) |
-            ast::ExprUnboxedFn(_, _, _, ref b) => {
+            ast::ExprUnboxedFn(_, _, _, _, ref b) => {
                 self.with_context(Closure, |v| v.visit_block(&**b));
             }
             ast::ExprBreak(_) => self.require_loop("break", e.span),

src/librustc/middle/liveness.rs

@@ -961,7 +961,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
 
           ExprFnBlock(_, _, ref blk) |
           ExprProc(_, ref blk) |
-          ExprUnboxedFn(_, _, _, ref blk) => {
+          ExprUnboxedFn(_, _, _, _, ref blk) => {
               debug!("{} is an ExprFnBlock, ExprProc, or ExprUnboxedFn",
                      expr_to_string(expr));
 

src/librustc/middle/mem_categorization.rs

@@ -580,10 +580,21 @@ impl<'t,'tcx,TYPER:Typer<'tcx>> MemCategorizationContext<'t,TYPER> {
                       }
                   }
                   ty::ty_unboxed_closure(closure_id, _) => {
-                      let unboxed_closures = self.typer
-                                                 .unboxed_closures()
-                                                 .borrow();
-                      let kind = unboxed_closures.get(&closure_id).kind;
+                      assert!(closure_id.krate == ast::LOCAL_CRATE);
+                      let kind = match self.typer
+                                           .tcx()
+                                           .map
+                                           .expect_expr(closure_id.node)
+                                           .node {
+                        ast::ExprUnboxedFn(_, kind, _, _, _) => {
+                            ty::UnboxedClosureKind::from_ast_kind(kind)
+                        }
+                        _ => {
+                            self.typer.tcx().sess.bug("didn't find unboxed \
+                                                       fn with appropriate \
+                                                       type in AST map")
+                        }
+                      };
                       let onceness = match kind {
                           ty::FnUnboxedClosureKind |
                           ty::FnMutUnboxedClosureKind => ast::Many,

src/librustc/middle/resolve.rs

@@ -5815,7 +5815,7 @@ impl<'a> Resolver<'a> {
                                       Some(&**fn_decl), NoTypeParameters,
                                       &**block);
             }
-            ExprUnboxedFn(capture_clause, _, ref fn_decl, ref block) => {
+            ExprUnboxedFn(capture_clause, _, _, ref fn_decl, ref block) => {
                 self.capture_mode_map.borrow_mut().insert(expr.id, capture_clause);
                 self.resolve_function(ClosureRibKind(expr.id, block.id),
                                       Some(&**fn_decl), NoTypeParameters,

src/librustc/middle/traits/select.rs

@@ -32,6 +32,7 @@ use std::cell::RefCell;
 use std::collections::hashmap::HashMap;
 use std::rc::Rc;
 use syntax::ast;
+use syntax::ast_util;
 use util::ppaux::Repr;
 
 pub struct SelectionContext<'cx, 'tcx:'cx> {
@@ -543,6 +544,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
          * unboxed closure type.
          */
 
+        debug!("assemble_unboxed_candidates()");
+
         let closure_def_id = match ty::get(skol_obligation_self_ty).sty {
             ty::ty_unboxed_closure(id, _) => id,
             _ => { return Ok(()); }
@@ -564,22 +567,34 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 _ => continue,
             };
 
-            // Check to see whether the argument and return types match.
-            let closure_kind = match self.typer.unboxed_closures().borrow().find(&closure_def_id) {
-                Some(closure) => closure.kind,
-                None => {
-                    self.tcx().sess.span_bug(
-                        obligation.cause.span,
-                        format!("No entry for unboxed closure: {}",
-                                closure_def_id.repr(self.tcx())).as_slice());
-                }
-            };
+            // Check to see whether the closure could implement this trait.
+            assert!(closure_def_id.krate == ast::LOCAL_CRATE);
+            let auxiliary_closure_id =
+                match self.tcx().map.expect_expr(closure_def_id.node).node {
+                    ast::ExprUnboxedFn(_, _, ref ids, _, _) => {
+                        ast_util::local_def(
+                            kind.select_auxiliary_unboxed_closure_id(&**ids))
+                    }
+                    _ => {
+                        self.tcx().sess.span_bug(
+                            obligation.cause.span,
+                            "unboxed fn didn't map to an expr")
+                    }
+                };
+
+            debug!("assemble_unboxed_candidates(kind={})", kind);
 
-            if closure_kind != kind {
-                continue;
+            // Check to see whether the argument and return types match.
+            if !self.typer
+                    .unboxed_closures()
+                    .borrow()
+                    .contains_key(&auxiliary_closure_id) {
+                // Not compatible with this trait.
+                continue
             }
 
-            candidates.push(MatchedUnboxedClosureCandidate(closure_def_id));
+            candidates.push(MatchedUnboxedClosureCandidate(
+                    auxiliary_closure_id));
         }
 
         Ok(())
@@ -1067,7 +1082,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             }
 
             MatchedUnboxedClosureCandidate(closure_def_id) => {
-                try!(self.confirm_unboxed_closure_candidate(obligation, closure_def_id));
+                try!(self.confirm_unboxed_closure_candidate(
+                        obligation,
+                        closure_def_id));
                 Ok(Some(VtableUnboxedClosure(closure_def_id)))
             }
         }
@@ -1148,11 +1165,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         Ok(vtable_impl)
     }
 
-    fn confirm_unboxed_closure_candidate(&mut self,
-                                         obligation: &Obligation,
-                                         closure_def_id: ast::DefId)
-                                         -> Result<(),SelectionError>
-    {
+    fn confirm_unboxed_closure_candidate(
+            &mut self,
+            obligation: &Obligation,
+            closure_def_id: ast::DefId)
+            -> Result<(),SelectionError> {
         debug!("confirm_unboxed_closure_candidate({},{})",
                obligation.repr(self.tcx()),
                closure_def_id.repr(self.tcx()));