auto merge of #16122 : pcwalton/rust/lifetimes-in-unboxed-closures, r=pnkfelix

This patch primarily does two things: (1) it prevents lifetimes from
leaking out of unboxed closures; (2) it allows unboxed closure type
notation, call notation, and construction notation to construct closures
matching any of the three traits.

This breaks code that looked like:

    let mut f;
    {
        let x = &5i;
        f = |&mut:| *x + 10;
    }

Change this code to avoid having a reference escape. For example:

    {
        let x = &5i;
        let mut f; // <-- move here to avoid dangling reference
        f = |&mut:| *x + 10;
    }

I believe this is enough to consider unboxed closures essentially
implemented. Further issues (for example, higher-rank lifetimes) should
be filed as followups.

Closes #14449.

[breaking-change]

r? @pnkfelix

Author: bors

src/librustc/front/feature_gate.rs

@@ -314,7 +314,7 @@ impl<'a> Visitor<()> for Context<'a> {
 
             },
             ast::TyBox(_) => { self.gate_box(t.span); }
-            ast::TyUnboxedFn(_) => {
+            ast::TyUnboxedFn(..) => {
                 self.gate_feature("unboxed_closure_sugar",
                                   t.span,
                                   "unboxed closure trait sugar is experimental");

src/librustc/metadata/common.rs

@@ -139,7 +139,7 @@ pub enum astencode_tag { // Reserves 0x40 -- 0x5f
     tag_table_adjustments = 0x51,
     tag_table_moves_map = 0x52,
     tag_table_capture_map = 0x53,
-    tag_table_unboxed_closure_type = 0x54,
+    tag_table_unboxed_closures = 0x54,
     tag_table_upvar_borrow_map = 0x55,
     tag_table_capture_modes = 0x56,
 }
@@ -229,9 +229,11 @@ pub static tag_region_param_def_index: uint = 0x94;
 pub static tag_unboxed_closures: uint = 0x95;
 pub static tag_unboxed_closure: uint = 0x96;
 pub static tag_unboxed_closure_type: uint = 0x97;
+pub static tag_unboxed_closure_kind: uint = 0x98;
 
-pub static tag_struct_fields: uint = 0x98;
-pub static tag_struct_field: uint = 0x99;
-pub static tag_struct_field_id: uint = 0x9a;
+pub static tag_struct_fields: uint = 0x99;
+pub static tag_struct_field: uint = 0x9a;
+pub static tag_struct_field_id: uint = 0x9b;
+
+pub static tag_attribute_is_sugared_doc: uint = 0x9c;
 
-pub static tag_attribute_is_sugared_doc: uint = 0x9b;

src/librustc/metadata/encoder.rs

@@ -630,6 +630,18 @@ fn encode_visibility(rbml_w: &mut Encoder, visibility: Visibility) {
     rbml_w.end_tag();
 }
 
+fn encode_unboxed_closure_kind(rbml_w: &mut Encoder,
+                               kind: ty::UnboxedClosureKind) {
+    rbml_w.start_tag(tag_unboxed_closure_kind);
+    let ch = match kind {
+        ty::FnUnboxedClosureKind => 'f',
+        ty::FnMutUnboxedClosureKind => 'm',
+        ty::FnOnceUnboxedClosureKind => 'o',
+    };
+    rbml_w.wr_str(ch.to_string().as_slice());
+    rbml_w.end_tag();
+}
+
 fn encode_explicit_self(rbml_w: &mut Encoder,
                         explicit_self: &ty::ExplicitSelfCategory) {
     rbml_w.start_tag(tag_item_trait_method_explicit_self);
@@ -1629,17 +1641,20 @@ fn encode_unboxed_closures<'a>(
                            ecx: &'a EncodeContext,
                            rbml_w: &'a mut Encoder) {
     rbml_w.start_tag(tag_unboxed_closures);
-    for (unboxed_closure_id, unboxed_closure_type) in
-            ecx.tcx.unboxed_closure_types.borrow().iter() {
+    for (unboxed_closure_id, unboxed_closure) in ecx.tcx
+                                                    .unboxed_closures
+                                                    .borrow()
+                                                    .iter() {
         if unboxed_closure_id.krate != LOCAL_CRATE {
             continue
         }
 
         rbml_w.start_tag(tag_unboxed_closure);
         encode_def_id(rbml_w, *unboxed_closure_id);
         rbml_w.start_tag(tag_unboxed_closure_type);
-        write_closure_type(ecx, rbml_w, unboxed_closure_type);
+        write_closure_type(ecx, rbml_w, &unboxed_closure.closure_type);
         rbml_w.end_tag();
+        encode_unboxed_closure_kind(rbml_w, unboxed_closure.kind);
         rbml_w.end_tag();
     }
     rbml_w.end_tag();

src/librustc/metadata/tydecode.rs

@@ -432,7 +432,8 @@ fn parse_ty(st: &mut PState, conv: conv_did) -> ty::t {
       }
       'k' => {
           let did = parse_def(st, NominalType, |x,y| conv(x,y));
-          return ty::mk_unboxed_closure(st.tcx, did);
+          let region = parse_region(st, conv);
+          return ty::mk_unboxed_closure(st.tcx, did, region);
       }
       'e' => {
           return ty::mk_err();

src/librustc/metadata/tyencode.rs

@@ -285,8 +285,9 @@ fn enc_sty(w: &mut SeekableMemWriter, cx: &ctxt, st: &ty::sty) {
             enc_substs(w, cx, substs);
             mywrite!(w, "]");
         }
-        ty::ty_unboxed_closure(def) => {
+        ty::ty_unboxed_closure(def, region) => {
             mywrite!(w, "k{}", (cx.ds)(def));
+            enc_region(w, cx, region);
         }
         ty::ty_err => {
             mywrite!(w, "e");

src/librustc/middle/astencode.rs

@@ -689,10 +689,35 @@ pub fn encode_vtable_param_res(ecx: &e::EncodeContext,
     }).unwrap()
 }
 
+pub fn encode_unboxed_closure_kind(ebml_w: &mut Encoder,
+                                   kind: ty::UnboxedClosureKind) {
+    ebml_w.emit_enum("UnboxedClosureKind", |ebml_w| {
+        match kind {
+            ty::FnUnboxedClosureKind => {
+                ebml_w.emit_enum_variant("FnUnboxedClosureKind", 0, 3, |_| {
+                    Ok(())
+                })
+            }
+            ty::FnMutUnboxedClosureKind => {
+                ebml_w.emit_enum_variant("FnMutUnboxedClosureKind", 1, 3, |_| {
+                    Ok(())
+                })
+            }
+            ty::FnOnceUnboxedClosureKind => {
+                ebml_w.emit_enum_variant("FnOnceUnboxedClosureKind",
+                                         2,
+                                         3,
+                                         |_| {
+                    Ok(())
+                })
+            }
+        }
+    }).unwrap()
+}
 
 pub fn encode_vtable_origin(ecx: &e::EncodeContext,
-                        rbml_w: &mut Encoder,
-                        vtable_origin: &typeck::vtable_origin) {
+                            rbml_w: &mut Encoder,
+                            vtable_origin: &typeck::vtable_origin) {
     rbml_w.emit_enum("vtable_origin", |rbml_w| {
         match *vtable_origin {
           typeck::vtable_static(def_id, ref substs, ref vtable_res) => {
@@ -1210,14 +1235,15 @@ fn encode_side_tables_for_id(ecx: &e::EncodeContext,
         })
     }
 
-    for unboxed_closure_type in tcx.unboxed_closure_types
-                                   .borrow()
-                                   .find(&ast_util::local_def(id))
-                                   .iter() {
-        rbml_w.tag(c::tag_table_unboxed_closure_type, |rbml_w| {
+    for unboxed_closure in tcx.unboxed_closures
+                              .borrow()
+                              .find(&ast_util::local_def(id))
+                              .iter() {
+        rbml_w.tag(c::tag_table_unboxed_closures, |rbml_w| {
             rbml_w.id(id);
             rbml_w.tag(c::tag_table_val, |rbml_w| {
-                rbml_w.emit_closure_type(ecx, *unboxed_closure_type)
+                rbml_w.emit_closure_type(ecx, &unboxed_closure.closure_type);
+                encode_unboxed_closure_kind(rbml_w, unboxed_closure.kind)
             })
         })
     }
@@ -1244,8 +1270,8 @@ trait rbml_decoder_decoder_helpers {
                      -> ty::Polytype;
     fn read_substs(&mut self, xcx: &ExtendedDecodeContext) -> subst::Substs;
     fn read_auto_adjustment(&mut self, xcx: &ExtendedDecodeContext) -> ty::AutoAdjustment;
-    fn read_unboxed_closure_type(&mut self, xcx: &ExtendedDecodeContext)
-                                 -> ty::ClosureTy;
+    fn read_unboxed_closure(&mut self, xcx: &ExtendedDecodeContext)
+                            -> ty::UnboxedClosure;
     fn convert_def_id(&mut self,
                       xcx: &ExtendedDecodeContext,
                       source: DefIdSource,
@@ -1418,16 +1444,33 @@ impl<'a> rbml_decoder_decoder_helpers for reader::Decoder<'a> {
         }).unwrap()
     }
 
-    fn read_unboxed_closure_type(&mut self, xcx: &ExtendedDecodeContext)
-                                 -> ty::ClosureTy {
-        self.read_opaque(|this, doc| {
+    fn read_unboxed_closure(&mut self, xcx: &ExtendedDecodeContext)
+                            -> ty::UnboxedClosure {
+        let closure_type = self.read_opaque(|this, doc| {
             Ok(tydecode::parse_ty_closure_data(
                 doc.data,
                 xcx.dcx.cdata.cnum,
                 doc.start,
                 xcx.dcx.tcx,
                 |s, a| this.convert_def_id(xcx, s, a)))
-        }).unwrap()
+        }).unwrap();
+        let variants = [
+            "FnUnboxedClosureKind",
+            "FnMutUnboxedClosureKind",
+            "FnOnceUnboxedClosureKind"
+        ];
+        let kind = self.read_enum_variant(variants, |_, i| {
+            Ok(match i {
+                0 => ty::FnUnboxedClosureKind,
+                1 => ty::FnMutUnboxedClosureKind,
+                2 => ty::FnOnceUnboxedClosureKind,
+                _ => fail!("bad enum variant for ty::UnboxedClosureKind"),
+            })
+        }).unwrap();
+        ty::UnboxedClosure {
+            closure_type: closure_type,
+            kind: kind,
+        }
     }
 
     fn convert_def_id(&mut self,
@@ -1566,14 +1609,14 @@ fn decode_side_tables(xcx: &ExtendedDecodeContext,
                         let adj: ty::AutoAdjustment = val_dsr.read_auto_adjustment(xcx);
                         dcx.tcx.adjustments.borrow_mut().insert(id, adj);
                     }
-                    c::tag_table_unboxed_closure_type => {
-                        let unboxed_closure_type =
-                            val_dsr.read_unboxed_closure_type(xcx);
+                    c::tag_table_unboxed_closures => {
+                        let unboxed_closure =
+                            val_dsr.read_unboxed_closure(xcx);
                         dcx.tcx
-                           .unboxed_closure_types
+                           .unboxed_closures
                            .borrow_mut()
                            .insert(ast_util::local_def(id),
-                                   unboxed_closure_type);
+                                   unboxed_closure);
                     }
                     _ => {
                         xcx.dcx.tcx.sess.bug(

src/librustc/middle/borrowck/mod.rs

@@ -290,8 +290,9 @@ pub fn closure_to_block(closure_id: ast::NodeId,
                     tcx: &ty::ctxt) -> ast::NodeId {
     match tcx.map.get(closure_id) {
         ast_map::NodeExpr(expr) => match expr.node {
-            ast::ExprProc(_decl, block) |
-            ast::ExprFnBlock(_, _decl, block) => { block.id }
+            ast::ExprProc(_, block) |
+            ast::ExprFnBlock(_, _, block) |
+            ast::ExprUnboxedFn(_, _, _, block) => { block.id }
             _ => fail!("encountered non-closure id: {}", closure_id)
         },
         _ => fail!("encountered non-expr id: {}", closure_id)

src/librustc/middle/check_loop.rs

@@ -48,7 +48,7 @@ impl<'a> Visitor<Context> for CheckLoopVisitor<'a> {
             }
             ast::ExprFnBlock(_, _, ref b) |
             ast::ExprProc(_, ref b) |
-            ast::ExprUnboxedFn(_, _, ref b) => {
+            ast::ExprUnboxedFn(_, _, _, ref b) => {
                 self.visit_block(&**b, Closure);
             }
             ast::ExprBreak(_) => self.require_loop("break", cx, e.span),

src/librustc/middle/freevars.rs

@@ -74,7 +74,7 @@ impl<'a> Visitor<int> for CollectFreevarsVisitor<'a> {
                 self.capture_mode_map.insert(expr.id, capture_mode);
                 visit::walk_expr(self, expr, depth + 1)
             }
-            ast::ExprUnboxedFn(capture_clause, _, _) => {
+            ast::ExprUnboxedFn(capture_clause, _, _, _) => {
                 let capture_mode = match capture_clause {
                     ast::CaptureByValue => CaptureByValue,
                     ast::CaptureByRef => CaptureByRef,

src/librustc/middle/kind.rs

@@ -225,7 +225,7 @@ fn with_appropriate_checker(cx: &Context,
             b(check_for_bare)
         }
 
-        ty::ty_unboxed_closure(_) => {}
+        ty::ty_unboxed_closure(..) => {}
 
         ref s => {
             cx.tcx.sess.bug(format!("expect fn type in kind checker, not \