auto merge of #11156 : luqmana/rust/trait-object-coercion, r=pcwalton

This ports over @pcwalton's old pull that bitrotted (#5597). Fixes #10039.

r? @pcwalton / @nikomatsakis

Author: bors

src/libextra/enum_set.rs

@@ -13,7 +13,7 @@
 //! This module defines a container which uses an efficient bit mask
 //! representation to hold C-like enum variants.
 
-#[deriving(Clone, Eq, IterBytes, ToStr)]
+#[deriving(Clone, Eq, IterBytes, ToStr, Encodable, Decodable)]
 /// A specialized Set implementation to use enum types.
 pub struct EnumSet<E> {
     // We must maintain the invariant that no bits are set

src/librustc/metadata/tydecode.rs

@@ -129,6 +129,12 @@ pub fn parse_trait_ref_data(data: &[u8], crate_num: ast::CrateNum, pos: uint, tc
     parse_trait_ref(&mut st, conv)
 }
 
+pub fn parse_substs_data(data: &[u8], crate_num: ast::CrateNum, pos: uint, tcx: ty::ctxt,
+                         conv: conv_did) -> ty::substs {
+    let mut st = parse_state_from_data(data, crate_num, pos, tcx);
+    parse_substs(&mut st, conv)
+}
+
 fn parse_sigil(st: &mut PState) -> ast::Sigil {
     match next(st) {
         '@' => ast::ManagedSigil,

src/librustc/metadata/tyencode.rs

@@ -140,7 +140,7 @@ fn enc_opt<T>(w: &mut MemWriter, t: Option<T>, enc_f: |&mut MemWriter, T|) {
     }
 }
 
-fn enc_substs(w: &mut MemWriter, cx: @ctxt, substs: &ty::substs) {
+pub fn enc_substs(w: &mut MemWriter, cx: @ctxt, substs: &ty::substs) {
     enc_region_substs(w, cx, &substs.regions);
     enc_opt(w, substs.self_ty, |w, t| enc_ty(w, cx, t));
     mywrite!(w, "[");

src/librustc/middle/astencode.rs

@@ -450,15 +450,13 @@ impl tr for ast::Def {
 // ______________________________________________________________________
 // Encoding and decoding of adjustment information
 
-impl tr for ty::AutoAdjustment {
-    fn tr(&self, xcx: @ExtendedDecodeContext) -> ty::AutoAdjustment {
-        match *self {
-            ty::AutoAddEnv(r, s) => ty::AutoAddEnv(r.tr(xcx), s),
-            ty::AutoDerefRef(ref adr) => {
-                ty::AutoDerefRef(ty::AutoDerefRef {
-                    autoderefs: adr.autoderefs,
-                    autoref: adr.autoref.map(|ar| ar.tr(xcx)),
-                })
+impl tr for ty::AutoDerefRef {
+    fn tr(&self, xcx: @ExtendedDecodeContext) -> ty::AutoDerefRef {
+        ty::AutoDerefRef {
+            autoderefs: self.autoderefs,
+            autoref: match self.autoref {
+                Some(ref autoref) => Some(autoref.tr(xcx)),
+                None => None
             }
         }
     }
@@ -786,6 +784,8 @@ trait ebml_writer_helpers {
     fn emit_tpbt(&mut self,
                  ecx: &e::EncodeContext,
                  tpbt: ty::ty_param_bounds_and_ty);
+    fn emit_substs(&mut self, ecx: &e::EncodeContext, substs: &ty::substs);
+    fn emit_auto_adjustment(&mut self, ecx: &e::EncodeContext, adj: &ty::AutoAdjustment);
 }
 
 impl<'a> ebml_writer_helpers for writer::Encoder<'a> {
@@ -833,6 +833,40 @@ impl<'a> ebml_writer_helpers for writer::Encoder<'a> {
             })
         })
     }
+
+    fn emit_substs(&mut self, ecx: &e::EncodeContext, substs: &ty::substs) {
+        self.emit_opaque(|this| tyencode::enc_substs(this.writer, ecx.ty_str_ctxt(), substs))
+    }
+
+    fn emit_auto_adjustment(&mut self, ecx: &e::EncodeContext, adj: &ty::AutoAdjustment) {
+        self.emit_enum("AutoAdjustment", |this| {
+            match *adj {
+                ty::AutoAddEnv(region, sigil) => {
+                    this.emit_enum_variant("AutoAddEnv", 0, 2, |this| {
+                        this.emit_enum_variant_arg(0, |this| region.encode(this));
+                        this.emit_enum_variant_arg(1, |this| sigil.encode(this));
+                    });
+                }
+
+                ty::AutoDerefRef(ref auto_deref_ref) => {
+                    this.emit_enum_variant("AutoDerefRef", 1, 1, |this| {
+                        this.emit_enum_variant_arg(0, |this| auto_deref_ref.encode(this));
+                    });
+                }
+
+                ty::AutoObject(sigil, region, m, b, def_id, ref substs) => {
+                    this.emit_enum_variant("AutoObject", 2, 6, |this| {
+                        this.emit_enum_variant_arg(0, |this| sigil.encode(this));
+                        this.emit_enum_variant_arg(1, |this| region.encode(this));
+                        this.emit_enum_variant_arg(2, |this| m.encode(this));
+                        this.emit_enum_variant_arg(3, |this| b.encode(this));
+                        this.emit_enum_variant_arg(4, |this| def_id.encode(this));
+                        this.emit_enum_variant_arg(5, |this| this.emit_substs(ecx, substs));
+                    });
+                }
+            }
+        });
+    }
 }
 
 trait write_tag_and_id {
@@ -1023,7 +1057,7 @@ fn encode_side_tables_for_id(ecx: &e::EncodeContext,
             ebml_w.tag(c::tag_table_adjustments, |ebml_w| {
                 ebml_w.id(id);
                 ebml_w.tag(c::tag_table_val, |ebml_w| {
-                    (**adj).encode(ebml_w)
+                    ebml_w.emit_auto_adjustment(ecx, **adj);
                 })
             })
         }
@@ -1064,6 +1098,8 @@ trait ebml_decoder_decoder_helpers {
                            -> ty::TypeParameterDef;
     fn read_ty_param_bounds_and_ty(&mut self, xcx: @ExtendedDecodeContext)
                                 -> ty::ty_param_bounds_and_ty;
+    fn read_substs(&mut self, xcx: @ExtendedDecodeContext) -> ty::substs;
+    fn read_auto_adjustment(&mut self, xcx: @ExtendedDecodeContext) -> ty::AutoAdjustment;
     fn convert_def_id(&mut self,
                       xcx: @ExtendedDecodeContext,
                       source: DefIdSource,
@@ -1172,6 +1208,61 @@ impl<'a> ebml_decoder_decoder_helpers for reader::Decoder<'a> {
         })
     }
 
+    fn read_substs(&mut self, xcx: @ExtendedDecodeContext) -> ty::substs {
+        self.read_opaque(|this, doc| {
+            tydecode::parse_substs_data(doc.data,
+                                        xcx.dcx.cdata.cnum,
+                                        doc.start,
+                                        xcx.dcx.tcx,
+                                        |s, a| this.convert_def_id(xcx, s, a))
+        })
+    }
+
+    fn read_auto_adjustment(&mut self, xcx: @ExtendedDecodeContext) -> ty::AutoAdjustment {
+        self.read_enum("AutoAdjustment", |this| {
+            let variants = ["AutoAddEnv", "AutoDerefRef", "AutoObject"];
+            this.read_enum_variant(variants, |this, i| {
+                match i {
+                    0 => {
+                        let region: ty::Region =
+                            this.read_enum_variant_arg(0, |this| Decodable::decode(this));
+                        let sigil: ast::Sigil =
+                            this.read_enum_variant_arg(1, |this| Decodable::decode(this));
+
+                        ty:: AutoAddEnv(region.tr(xcx), sigil)
+                    }
+                    1 => {
+                        let auto_deref_ref: ty::AutoDerefRef =
+                            this.read_enum_variant_arg(0, |this| Decodable::decode(this));
+
+                        ty::AutoDerefRef(auto_deref_ref.tr(xcx))
+                    }
+                    2 => {
+                        let sigil: ast::Sigil =
+                            this.read_enum_variant_arg(0, |this| Decodable::decode(this));
+                        let region: Option<ty::Region> =
+                            this.read_enum_variant_arg(1, |this| Decodable::decode(this));
+                        let m: ast::Mutability =
+                            this.read_enum_variant_arg(2, |this| Decodable::decode(this));
+                        let b: ty::BuiltinBounds =
+                            this.read_enum_variant_arg(3, |this| Decodable::decode(this));
+                        let def_id: ast::DefId =
+                            this.read_enum_variant_arg(4, |this| Decodable::decode(this));
+                        let substs = this.read_enum_variant_arg(5, |this| this.read_substs(xcx));
+
+                        let region = match region {
+                            Some(r) => Some(r.tr(xcx)),
+                            None => None
+                        };
+
+                        ty::AutoObject(sigil, region, m, b, def_id.tr(xcx), substs)
+                    }
+                    _ => fail!("bad enum variant for ty::AutoAdjustment")
+                }
+            })
+        })
+    }
+
     fn convert_def_id(&mut self,
                       xcx: @ExtendedDecodeContext,
                       source: tydecode::DefIdSource,
@@ -1289,8 +1380,7 @@ fn decode_side_tables(xcx: @ExtendedDecodeContext,
                         vtable_map.get().insert(id, vtable_res);
                     }
                     c::tag_table_adjustments => {
-                        let adj: @ty::AutoAdjustment = @Decodable::decode(val_dsr);
-                        adj.tr(xcx);
+                        let adj: @ty::AutoAdjustment = @val_dsr.read_auto_adjustment(xcx);
                         let mut adjustments = dcx.tcx
                                                  .adjustments
                                                  .borrow_mut();

src/librustc/middle/borrowck/gather_loans/mod.rs

@@ -419,6 +419,10 @@ impl<'a> GatherLoanCtxt<'a> {
                     ty::AutoUnsafe(_) => {}
                 }
             }
+
+            ty::AutoObject(..) => {
+                // XXX: Handle @Trait to &Trait casts here?
+            }
         }
     }
 

src/librustc/middle/borrowck/mod.rs

@@ -490,7 +490,7 @@ impl BorrowckCtxt {
                                adj: @ty::AutoAdjustment)
                                -> mc::cmt {
         match *adj {
-            ty::AutoAddEnv(..) => {
+            ty::AutoAddEnv(..) | ty::AutoObject(..) => {
                 // no autoderefs
                 mc::cat_expr_unadjusted(self.tcx, self.method_map, expr)
             }

src/librustc/middle/kind.rs

@@ -311,14 +311,9 @@ pub fn check_expr(cx: &mut Context, e: @Expr) {
             let _ = check_durable(cx.tcx, interior_type, interior.span);
         }
         ExprCast(source, _) => {
-            check_cast_for_escaping_regions(cx, source, e);
-            match ty::get(ty::expr_ty(cx.tcx, e)).sty {
-                ty::ty_trait(_, _, _, _, bounds) => {
-                    let source_ty = ty::expr_ty(cx.tcx, source);
-                    check_trait_cast_bounds(cx, e.span, source_ty, bounds)
-                }
-                _ => { }
-            }
+            let source_ty = ty::expr_ty(cx.tcx, source);
+            let target_ty = ty::expr_ty(cx.tcx, e);
+            check_trait_cast(cx, source_ty, target_ty, source.span);
         }
         ExprRepeat(element, count_expr, _) => {
             let count = ty::eval_repeat_count(&cx.tcx, count_expr);
@@ -330,9 +325,31 @@ pub fn check_expr(cx: &mut Context, e: @Expr) {
         }
         _ => {}
     }
+
+    // Search for auto-adjustments to find trait coercions.
+    let adjustments = cx.tcx.adjustments.borrow();
+    match adjustments.get().find(&e.id) {
+        Some(&@ty::AutoObject(..)) => {
+            let source_ty = ty::expr_ty(cx.tcx, e);
+            let target_ty = ty::expr_ty_adjusted(cx.tcx, e);
+            check_trait_cast(cx, source_ty, target_ty, e.span);
+        }
+        Some(&@ty::AutoAddEnv(..)) | Some(&@ty::AutoDerefRef(..)) | None => {}
+    }
+
     visit::walk_expr(cx, e, ());
 }
 
+fn check_trait_cast(cx: &mut Context, source_ty: ty::t, target_ty: ty::t, span: Span) {
+    check_cast_for_escaping_regions(cx, source_ty, target_ty, span);
+    match ty::get(target_ty).sty {
+        ty::ty_trait(_, _, _, _, bounds) => {
+            check_trait_cast_bounds(cx, span, source_ty, bounds);
+        }
+        _ => {}
+    }
+}
+
 fn check_ty(cx: &mut Context, aty: &Ty) {
     match aty.node {
       ty_path(_, _, id) => {
@@ -510,12 +527,12 @@ pub fn check_durable(tcx: ty::ctxt, ty: ty::t, sp: Span) -> bool {
 /// FIXME(#5723)---This code should probably move into regionck.
 pub fn check_cast_for_escaping_regions(
     cx: &Context,
-    source: &Expr,
-    target: &Expr)
+    source_ty: ty::t,
+    target_ty: ty::t,
+    source_span: Span)
 {
     // Determine what type we are casting to; if it is not an trait, then no
     // worries.
-    let target_ty = ty::expr_ty(cx.tcx, target);
     match ty::get(target_ty).sty {
         ty::ty_trait(..) => {}
         _ => { return; }
@@ -545,7 +562,6 @@ pub fn check_cast_for_escaping_regions(
     // Assuming the trait instance can escape, then ensure that each parameter
     // either appears in the trait type or is sendable.
     let target_params = ty::param_tys_in_type(target_ty);
-    let source_ty = ty::expr_ty(cx.tcx, source);
     ty::walk_regions_and_ty(
         cx.tcx,
         source_ty,
@@ -555,7 +571,7 @@ pub fn check_cast_for_escaping_regions(
             //
             // if !target_regions.iter().any(|t_r| is_subregion_of(cx, *t_r, r)) {
             //     cx.tcx.sess.span_err(
-            //         source.span,
+            //         source_span,
             //         format!("source contains borrowed pointer with lifetime \
             //               not found in the target type `{}`",
             //              ty_to_str(cx.tcx, target_ty)));
@@ -570,7 +586,7 @@ pub fn check_cast_for_escaping_regions(
                     if target_params.iter().any(|x| x == &source_param) {
                         /* case (2) */
                     } else {
-                        check_durable(cx.tcx, ty, source.span); /* case (3) */
+                        check_durable(cx.tcx, ty, source_span); /* case (3) */
                     }
                 }
                 _ => {}

src/librustc/middle/mem_categorization.rs

@@ -347,6 +347,13 @@ impl mem_categorization_ctxt {
                 self.cat_expr_unadjusted(expr)
             }
 
+            Some(&@ty::AutoObject(..)) => {
+                // Implicity casts a concrete object to trait object
+                // Result is an rvalue
+                let expr_ty = ty::expr_ty_adjusted(self.tcx, expr);
+                self.cat_rvalue_node(expr, expr_ty)
+            }
+
             Some(&@ty::AutoAddEnv(..)) => {
                 // Convert a bare fn to a closure by adding NULL env.
                 // Result is an rvalue.

src/librustc/middle/trans/consts.rs

@@ -199,6 +199,9 @@ pub fn const_expr(cx: @CrateContext, e: &ast::Expr) -> (ValueRef, bool) {
             cx.sess.span_bug(e.span, format!("unexpected static function: \
                                            region {:?} sigil {:?}", *r, *s))
         }
+        Some(@ty::AutoObject(..)) => {
+            cx.sess.span_unimpl(e.span, "unimplemented const coercion to trait object");
+        }
         Some(@ty::AutoDerefRef(ref adj)) => {
             let mut ty = ety;
             let mut maybe_ptr = None;

src/librustc/middle/trans/expr.rs

@@ -139,7 +139,7 @@ use middle::trans::inline;
 use middle::trans::tvec;
 use middle::trans::type_of;
 use middle::ty::struct_fields;
-use middle::ty::{AutoBorrowObj, AutoDerefRef, AutoAddEnv, AutoUnsafe};
+use middle::ty::{AutoBorrowObj, AutoDerefRef, AutoAddEnv, AutoObject, AutoUnsafe};
 use middle::ty::{AutoPtr, AutoBorrowVec, AutoBorrowVecRef, AutoBorrowFn};
 use middle::ty;
 use util::common::indenter;
@@ -228,6 +228,23 @@ pub fn trans_to_datum(bcx: @Block, expr: &ast::Expr) -> DatumBlock {
                 }
             };
         }
+        AutoObject(ref sigil, ref region, _, _, _, _) => {
+
+            let adjusted_ty = ty::expr_ty_adjusted(bcx.tcx(), expr);
+            let scratch = scratch_datum(bcx, adjusted_ty, "__adjust", false);
+
+            let trait_store = match *sigil {
+                ast::BorrowedSigil => ty::RegionTraitStore(region.expect("expected valid region")),
+                ast::OwnedSigil => ty::UniqTraitStore,
+                ast::ManagedSigil => ty::BoxTraitStore
+            };
+
+            bcx = meth::trans_trait_cast(bcx, expr, expr.id, SaveIn(scratch.val),
+                                         trait_store, false /* no adjustments */);
+
+            datum = scratch.to_appropriate_datum(bcx);
+            datum.add_clean(bcx);
+        }
     }
     debug!("after adjustments, datum={}", datum.to_str(bcx.ccx()));
     return DatumBlock {bcx: bcx, datum: datum};
@@ -432,6 +449,10 @@ pub fn trans_into(bcx: @Block, expr: &ast::Expr, dest: Dest) -> @Block {
         };
     }
 
+    trans_into_unadjusted(bcx, expr, dest)
+}
+
+pub fn trans_into_unadjusted(bcx: @Block, expr: &ast::Expr, dest: Dest) -> @Block {
     let ty = expr_ty(bcx, expr);
 
     debug!("trans_into_unadjusted(expr={}, dest={})",
@@ -778,8 +799,8 @@ fn trans_rvalue_dps_unadjusted(bcx: @Block, expr: &ast::Expr,
         ast::ExprCast(val, _) => {
             match ty::get(node_id_type(bcx, expr.id)).sty {
                 ty::ty_trait(_, _, store, _, _) => {
-                    return meth::trans_trait_cast(bcx, val, expr.id, dest,
-                                                  store);
+                    return meth::trans_trait_cast(bcx, val, expr.id,
+                                                  dest, store, true /* adjustments */);
                 }
                 _ => {
                     bcx.tcx().sess.span_bug(expr.span,