auto merge of #17952 : jakub-/rust/remove-virtual-structs, r=eddyb

Closes #17861.

Author: bors

src/doc/reference.md

@@ -1328,23 +1328,6 @@ let c = [Cookie, Cookie, Cookie, Cookie];
 The precise memory layout of a structure is not specified. One can specify a
 particular layout using the [`repr` attribute](#ffi-attributes).
 
-By using the `struct_inherit` feature gate, structures may use single
-inheritance. A Structure may only inherit from a single other structure, called
-the _super-struct_. The inheriting structure (sub-struct) acts as if all fields
-in the super-struct were present in the sub-struct. Fields declared in a
-sub-struct must not have the same name as any field in any (transitive)
-super-struct. All fields (both declared and inherited) must be specified in any
-initializers. Inheritance between structures does not give subtyping or
-coercion. The super-struct and sub-struct must be defined in the same crate.
-The super-struct must be declared using the `virtual` keyword. For example:
-
-```{.ignore}
-virtual struct Sup { x: int }
-struct Sub : Sup { y: int }
-let s = Sub {x: 10, y: 11};
-let sx = s.x;
-```
-
 ### Enumerations
 
 An _enumeration_ is a simultaneous definition of a nominal [enumerated

src/librustc/diagnostics.rs

@@ -56,7 +56,6 @@ register_diagnostics!(
     E0038,
     E0039,
     E0040,
-    E0041,
     E0044,
     E0045,
     E0046,
@@ -123,7 +122,6 @@ register_diagnostics!(
     E0121,
     E0122,
     E0124,
-    E0126,
     E0127,
     E0128,
     E0129,
@@ -141,9 +139,6 @@ register_diagnostics!(
     E0141,
     E0152,
     E0153,
-    E0154,
-    E0155,
-    E0156,
     E0157,
     E0158,
     E0159,

src/librustc/middle/resolve.rs

@@ -54,7 +54,6 @@ use syntax::parse::token::special_idents;
 use syntax::parse::token;
 use syntax::codemap::{Span, DUMMY_SP, Pos};
 use syntax::owned_slice::OwnedSlice;
-use syntax::ptr::P;
 use syntax::visit;
 use syntax::visit::Visitor;
 
@@ -4179,7 +4178,6 @@ impl<'a> Resolver<'a> {
             ItemStruct(ref struct_def, ref generics) => {
                 self.resolve_struct(item.id,
                                     generics,
-                                    &struct_def.super_struct,
                                     struct_def.fields.as_slice());
             }
 
@@ -4505,7 +4503,6 @@ impl<'a> Resolver<'a> {
     fn resolve_struct(&mut self,
                       id: NodeId,
                       generics: &Generics,
-                      super_struct: &Option<P<Ty>>,
                       fields: &[StructField]) {
         // If applicable, create a rib for the type parameters.
         self.with_type_parameter_rib(HasTypeParameters(generics,
@@ -4517,42 +4514,6 @@ impl<'a> Resolver<'a> {
             this.resolve_type_parameters(&generics.ty_params);
             this.resolve_where_clause(&generics.where_clause);
 
-            // Resolve the super struct.
-            match *super_struct {
-                Some(ref t) => match t.node {
-                    TyPath(ref path, None, path_id) => {
-                        match this.resolve_path(id, path, TypeNS, true) {
-                            Some((DefTy(def_id, _), lp)) if this.structs.contains_key(&def_id) => {
-                                let def = DefStruct(def_id);
-                                debug!("(resolving struct) resolved `{}` to type {:?}",
-                                       token::get_ident(path.segments
-                                                            .last().unwrap()
-                                                            .identifier),
-                                       def);
-                                debug!("(resolving struct) writing resolution for `{}` (id {})",
-                                       this.path_idents_to_string(path),
-                                       path_id);
-                                this.record_def(path_id, (def, lp));
-                            }
-                            Some((DefStruct(_), _)) => {
-                                span_err!(this.session, t.span, E0154,
-                                    "super-struct is defined in a different crate");
-                            },
-                            Some(_) => {
-                                span_err!(this.session, t.span, E0155,
-                                    "super-struct is not a struct type");
-                            }
-                            None => {
-                                span_err!(this.session, t.span, E0156,
-                                    "super-struct could not be resolved");
-                            }
-                        }
-                    },
-                    _ => this.session.span_bug(t.span, "path not mapped to a TyPath")
-                },
-                None => {}
-            }
-
             // Resolve fields.
             for field in fields.iter() {
                 this.resolve_type(&*field.node.ty);

src/librustc/middle/ty.rs

@@ -24,13 +24,11 @@ use middle::mem_categorization as mc;
 use middle::resolve;
 use middle::resolve_lifetime;
 use middle::stability;
-use middle::subst::{Subst, Substs, VecPerParamSpace};
-use middle::subst;
+use middle::subst::{mod, Subst, Substs, VecPerParamSpace};
 use middle::traits;
 use middle::ty;
 use middle::typeck;
-use middle::ty_fold;
-use middle::ty_fold::{TypeFoldable,TypeFolder};
+use middle::ty_fold::{mod, TypeFoldable,TypeFolder};
 use middle;
 use util::ppaux::{note_and_explain_region, bound_region_ptr_to_string};
 use util::ppaux::{trait_store_to_string, ty_to_string};
@@ -40,10 +38,8 @@ use util::nodemap::{NodeMap, NodeSet, DefIdMap, DefIdSet, FnvHashMap};
 
 use std::cell::{Cell, RefCell};
 use std::cmp;
-use std::fmt::Show;
-use std::fmt;
+use std::fmt::{mod, Show};
 use std::hash::{Hash, sip, Writer};
-use std::iter::AdditiveIterator;
 use std::mem;
 use std::ops;
 use std::rc::Rc;
@@ -55,15 +51,11 @@ use syntax::ast::{CrateNum, DefId, FnStyle, Ident, ItemTrait, LOCAL_CRATE};
 use syntax::ast::{MutImmutable, MutMutable, Name, NamedField, NodeId};
 use syntax::ast::{Onceness, StmtExpr, StmtSemi, StructField, UnnamedField};
 use syntax::ast::{Visibility};
-use syntax::ast_util::{PostExpansionMethod, is_local, lit_is_str};
-use syntax::ast_util;
-use syntax::attr;
-use syntax::attr::AttrMetaMethods;
+use syntax::ast_util::{mod, PostExpansionMethod, is_local, lit_is_str};
+use syntax::attr::{mod, AttrMetaMethods};
 use syntax::codemap::Span;
-use syntax::parse::token;
-use syntax::parse::token::InternedString;
+use syntax::parse::token::{mod, InternedString};
 use syntax::{ast, ast_map};
-use syntax::util::small_vector::SmallVector;
 use std::collections::enum_set::{EnumSet, CLike};
 
 pub type Disr = u64;
@@ -493,7 +485,6 @@ pub struct ctxt<'tcx> {
     pub lang_items: middle::lang_items::LanguageItems,
     /// A mapping of fake provided method def_ids to the default implementation
     pub provided_method_sources: RefCell<DefIdMap<ast::DefId>>,
-    pub superstructs: RefCell<DefIdMap<Option<ast::DefId>>>,
     pub struct_fields: RefCell<DefIdMap<Rc<Vec<field_ty>>>>,
 
     /// Maps from def-id of a type or region parameter to its
@@ -1512,7 +1503,6 @@ pub fn mk_ctxt<'tcx>(s: Session,
         normalized_cache: RefCell::new(HashMap::new()),
         lang_items: lang_items,
         provided_method_sources: RefCell::new(DefIdMap::new()),
-        superstructs: RefCell::new(DefIdMap::new()),
         struct_fields: RefCell::new(DefIdMap::new()),
         destructor_for_type: RefCell::new(DefIdMap::new()),
         destructors: RefCell::new(DefIdSet::new()),
@@ -4539,53 +4529,19 @@ pub fn lookup_field_type(tcx: &ctxt,
     t.subst(tcx, substs)
 }
 
-// Lookup all ancestor structs of a struct indicated by did. That is the reflexive,
-// transitive closure of doing a single lookup in cx.superstructs.
-fn each_super_struct(cx: &ctxt, mut did: ast::DefId, f: |ast::DefId|) {
-    let superstructs = cx.superstructs.borrow();
-
-    loop {
-        f(did);
-        match superstructs.find(&did) {
-            Some(&Some(def_id)) => {
-                did = def_id;
-            },
-            Some(&None) => break,
-            None => {
-                cx.sess.bug(
-                    format!("ID not mapped to super-struct: {}",
-                            cx.map.node_to_string(did.node)).as_slice());
-            }
-        }
-    }
-}
-
 // Look up the list of field names and IDs for a given struct.
 // Fails if the id is not bound to a struct.
 pub fn lookup_struct_fields(cx: &ctxt, did: ast::DefId) -> Vec<field_ty> {
     if did.krate == ast::LOCAL_CRATE {
-        // We store the fields which are syntactically in each struct in cx. So
-        // we have to walk the inheritance chain of the struct to get all the
-        // fields (explicit and inherited) for a struct. If this is expensive
-        // we could cache the whole list of fields here.
         let struct_fields = cx.struct_fields.borrow();
-        let mut results: SmallVector<&[field_ty]> = SmallVector::zero();
-        each_super_struct(cx, did, |s| {
-            match struct_fields.find(&s) {
-                Some(fields) => results.push(fields.as_slice()),
-                _ => {
-                    cx.sess.bug(
-                        format!("ID not mapped to struct fields: {}",
-                                cx.map.node_to_string(did.node)).as_slice());
-                }
+        match struct_fields.find(&did) {
+            Some(fields) => (**fields).clone(),
+            _ => {
+                cx.sess.bug(
+                    format!("ID not mapped to struct fields: {}",
+                            cx.map.node_to_string(did.node)).as_slice());
             }
-        });
-
-        let len = results.as_slice().iter().map(|x| x.len()).sum();
-        let mut result: Vec<field_ty> = Vec::with_capacity(len);
-        result.extend(results.as_slice().iter().flat_map(|rs| rs.iter().map(|f| f.clone())));
-        assert!(result.len() == len);
-        result
+        }
     } else {
         csearch::get_struct_fields(&cx.sess.cstore, did)
     }

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

@@ -127,7 +127,6 @@ use std::rc::Rc;
 use syntax::abi;
 use syntax::ast::{ProvidedMethod, RequiredMethod, TypeTraitItem};
 use syntax::ast;
-use syntax::ast_map;
 use syntax::ast_util::{local_def, PostExpansionMethod};
 use syntax::ast_util;
 use syntax::attr;
@@ -602,69 +601,12 @@ fn check_fn<'a, 'tcx>(ccx: &'a CrateCtxt<'a, 'tcx>,
     fcx
 }
 
-fn span_for_field(tcx: &ty::ctxt, field: &ty::field_ty, struct_id: ast::DefId) -> Span {
-    assert!(field.id.krate == ast::LOCAL_CRATE);
-    let item = match tcx.map.find(struct_id.node) {
-        Some(ast_map::NodeItem(item)) => item,
-        None => fail!("node not in ast map: {}", struct_id.node),
-        _ => fail!("expected item, found {}", tcx.map.node_to_string(struct_id.node))
-    };
-
-    match item.node {
-        ast::ItemStruct(ref struct_def, _) => {
-            match struct_def.fields.iter().find(|f| match f.node.kind {
-                ast::NamedField(ident, _) => ident.name == field.name,
-                _ => false,
-            }) {
-                Some(f) => f.span,
-                None => {
-                    tcx.sess
-                       .bug(format!("Could not find field {}",
-                                    token::get_name(field.name)).as_slice())
-                }
-            }
-        },
-        _ => tcx.sess.bug("Field found outside of a struct?"),
-    }
-}
-
-// Check struct fields are uniquely named wrt parents.
-fn check_for_field_shadowing(tcx: &ty::ctxt,
-                             id: ast::DefId) {
-    let struct_fields = tcx.struct_fields.borrow();
-    let fields = struct_fields.get(&id);
-
-    let superstructs = tcx.superstructs.borrow();
-    let super_struct = superstructs.get(&id);
-    match *super_struct {
-        Some(parent_id) => {
-            let super_fields = ty::lookup_struct_fields(tcx, parent_id);
-            for f in fields.iter() {
-                match super_fields.iter().find(|sf| f.name == sf.name) {
-                    Some(prev_field) => {
-                        span_err!(tcx.sess, span_for_field(tcx, f, id), E0041,
-                            "field `{}` hides field declared in super-struct",
-                            token::get_name(f.name));
-                        span_note!(tcx.sess, span_for_field(tcx, prev_field, parent_id),
-                            "previously declared here");
-                    },
-                    None => {}
-                }
-            }
-        },
-        None => {}
-    }
-}
-
 pub fn check_struct(ccx: &CrateCtxt, id: ast::NodeId, span: Span) {
     let tcx = ccx.tcx;
 
     check_representable(tcx, span, id, "struct");
     check_instantiable(tcx, span, id);
 
-    // Check there are no overlapping fields in super-structs
-    check_for_field_shadowing(tcx, local_def(id));
-
     if ty::lookup_simd(tcx, local_def(id)) {
         check_simd(tcx, span, id);
     }

src/librustc/middle/typeck/collect.rs

@@ -1235,15 +1235,6 @@ pub fn convert(ccx: &CrateCtxt, it: &ast::Item) {
 
             tcx.tcache.borrow_mut().insert(local_def(it.id), pty.clone());
 
-            // Write the super-struct type, if it exists.
-            match struct_def.super_struct {
-                Some(ref ty) => {
-                    let supserty = ccx.to_ty(&ExplicitRscope, &**ty);
-                    write_ty_to_tcx(tcx, it.id, supserty);
-                },
-                _ => {},
-            }
-
             convert_struct(ccx, &**struct_def, pty, it.id);
         },
         ast::ItemTy(_, ref generics) => {
@@ -1295,39 +1286,6 @@ pub fn convert_struct(ccx: &CrateCtxt,
 
     tcx.struct_fields.borrow_mut().insert(local_def(id), Rc::new(field_tys));
 
-    let super_struct = match struct_def.super_struct {
-        Some(ref t) => match t.node {
-            ast::TyPath(_, _, path_id) => {
-                let def_map = tcx.def_map.borrow();
-                match def_map.find(&path_id) {
-                    Some(&def::DefStruct(def_id)) => {
-                        // FIXME(#12511) Check for cycles in the inheritance hierarchy.
-                        // Check super-struct is virtual.
-                        match tcx.map.find(def_id.node) {
-                            Some(ast_map::NodeItem(i)) => match i.node {
-                                ast::ItemStruct(ref struct_def, _) => {
-                                    if !struct_def.is_virtual {
-                                        span_err!(tcx.sess, t.span, E0126,
-                                                  "struct inheritance is only \
-                                                   allowed from virtual structs");
-                                    }
-                                },
-                                _ => {},
-                            },
-                            _ => {},
-                        }
-
-                        Some(def_id)
-                    },
-                    _ => None,
-                }
-            }
-            _ => None,
-        },
-        None => None,
-    };
-    tcx.superstructs.borrow_mut().insert(local_def(id), super_struct);
-
     let substs = mk_item_substs(ccx, &pty.generics);
     let selfty = ty::mk_struct(tcx, local_def(id), substs);
 

src/libsyntax/ast.rs

@@ -1286,10 +1286,6 @@ pub struct StructDef {
     /// ID of the constructor. This is only used for tuple- or enum-like
     /// structs.
     pub ctor_id: Option<NodeId>,
-    /// Super struct, if specified.
-    pub super_struct: Option<P<Ty>>,
-    /// True iff the struct may be inherited from.
-    pub is_virtual: bool,
 }
 
 /*