Avoid comparing fields by name when possible

Resolve them into field indices once and then use those resolutions

+ Fix rebase

src/librustc/hir/intravisit.rs

@@ -658,6 +658,7 @@ pub fn walk_pat<'v, V: Visitor<'v>>(visitor: &mut V, pattern: &'v Pat) {
         PatKind::Struct(ref qpath, ref fields, _) => {
             visitor.visit_qpath(qpath, pattern.id, pattern.span);
             for field in fields {
+                visitor.visit_id(field.node.id);
                 visitor.visit_name(field.span, field.node.name);
                 visitor.visit_pat(&field.node.pat)
             }
@@ -959,6 +960,7 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr) {
         ExprStruct(ref qpath, ref fields, ref optional_base) => {
             visitor.visit_qpath(qpath, expression.id, expression.span);
             for field in fields {
+                visitor.visit_id(field.id);
                 visitor.visit_name(field.name.span, field.name.node);
                 visitor.visit_expr(&field.expr)
             }

src/librustc/hir/lowering.rs

@@ -2100,6 +2100,7 @@ impl<'a> LoweringContext<'a> {
 
     fn lower_field(&mut self, f: &Field) -> hir::Field {
         hir::Field {
+            id: self.next_id().node_id,
             name: respan(f.ident.span, self.lower_ident(f.ident)),
             expr: P(self.lower_expr(&f.expr)),
             span: f.span,
@@ -2863,6 +2864,7 @@ impl<'a> LoweringContext<'a> {
                     .map(|f| Spanned {
                         span: f.span,
                         node: hir::FieldPat {
+                            id: self.next_id().node_id,
                             name: self.lower_ident(f.node.ident),
                             pat: self.lower_pat(&f.node.pat),
                             is_shorthand: f.node.is_shorthand,
@@ -3741,6 +3743,7 @@ impl<'a> LoweringContext<'a> {
 
     fn field(&mut self, name: Name, expr: P<hir::Expr>, span: Span) -> hir::Field {
         hir::Field {
+            id: self.next_id().node_id,
             name: Spanned { node: name, span },
             span,
             expr,

src/librustc/hir/mod.rs

@@ -827,6 +827,7 @@ impl Pat {
 /// except is_shorthand is true
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct FieldPat {
+    pub id: NodeId,
     /// The identifier for the field
     pub name: Name,
     /// The pattern the field is destructured to
@@ -1172,6 +1173,7 @@ pub struct Arm {
 
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub struct Field {
+    pub id: NodeId,
     pub name: Spanned<Name>,
     pub expr: P<Expr>,
     pub span: Span,

src/librustc/ich/impls_hir.rs

@@ -420,11 +420,23 @@ impl<'a> HashStable<StableHashingContext<'a>> for hir::Pat {
 }
 
 impl_stable_hash_for_spanned!(hir::FieldPat);
-impl_stable_hash_for!(struct hir::FieldPat {
-    name,
-    pat,
-    is_shorthand
-});
+
+impl<'a> HashStable<StableHashingContext<'a>> for hir::FieldPat {
+    fn hash_stable<W: StableHasherResult>(&self,
+                                          hcx: &mut StableHashingContext<'a>,
+                                          hasher: &mut StableHasher<W>) {
+        let hir::FieldPat {
+            id: _,
+            name,
+            ref pat,
+            is_shorthand,
+        } = *self;
+
+        name.hash_stable(hcx, hasher);
+        pat.hash_stable(hcx, hasher);
+        is_shorthand.hash_stable(hcx, hasher);
+    }
+}
 
 impl_stable_hash_for!(enum hir::BindingAnnotation {
     Unannotated,
@@ -507,12 +519,24 @@ impl_stable_hash_for!(struct hir::Arm {
     body
 });
 
-impl_stable_hash_for!(struct hir::Field {
-    name,
-    expr,
-    span,
-    is_shorthand
-});
+impl<'a> HashStable<StableHashingContext<'a>> for hir::Field {
+    fn hash_stable<W: StableHasherResult>(&self,
+                                          hcx: &mut StableHashingContext<'a>,
+                                          hasher: &mut StableHasher<W>) {
+        let hir::Field {
+            id: _,
+            name,
+            ref expr,
+            span,
+            is_shorthand,
+        } = *self;
+
+        name.hash_stable(hcx, hasher);
+        expr.hash_stable(hcx, hasher);
+        span.hash_stable(hcx, hasher);
+        is_shorthand.hash_stable(hcx, hasher);
+    }
+}
 
 impl_stable_hash_for_spanned!(ast::Name);
 

src/librustc/middle/dead.rs

@@ -13,7 +13,7 @@
 // from live codes are live, and everything else is dead.
 
 use hir::map as hir_map;
-use hir::{self, Item_, PatKind};
+use hir::{self, PatKind};
 use hir::intravisit::{self, Visitor, NestedVisitorMap};
 use hir::itemlikevisit::ItemLikeVisitor;
 
@@ -99,10 +99,11 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
         self.check_def_id(self.tables.type_dependent_defs()[id].def_id());
     }
 
-    fn handle_field_access(&mut self, lhs: &hir::Expr, name: ast::Name) {
+    fn handle_field_access(&mut self, lhs: &hir::Expr, node_id: ast::NodeId) {
         match self.tables.expr_ty_adjusted(lhs).sty {
             ty::TyAdt(def, _) => {
-                self.insert_def_id(def.non_enum_variant().field_named(name).did);
+                let index = self.tcx.field_index(node_id, self.tables);
+                self.insert_def_id(def.non_enum_variant().fields[index].did);
             }
             ty::TyTuple(..) => {}
             _ => span_bug!(lhs.span, "named field access on non-ADT"),
@@ -119,7 +120,8 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
             if let PatKind::Wild = pat.node.pat.node {
                 continue;
             }
-            self.insert_def_id(variant.field_named(pat.node.name).did);
+            let index = self.tcx.field_index(pat.node.id, self.tables);
+            self.insert_def_id(variant.fields[index].did);
         }
     }
 
@@ -182,18 +184,11 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
         self.inherited_pub_visibility = had_inherited_pub_visibility;
     }
 
-    fn mark_as_used_if_union(&mut self, did: DefId, fields: &hir::HirVec<hir::Field>) {
-        if let Some(node_id) = self.tcx.hir.as_local_node_id(did) {
-            if let Some(hir_map::NodeItem(item)) = self.tcx.hir.find(node_id) {
-                if let Item_::ItemUnion(ref variant, _) = item.node {
-                    if variant.fields().len() > 1 {
-                        for field in variant.fields() {
-                            if fields.iter().find(|x| x.name.node == field.name).is_some() {
-                                self.live_symbols.insert(field.id);
-                            }
-                        }
-                    }
-                }
+    fn mark_as_used_if_union(&mut self, adt: &ty::AdtDef, fields: &hir::HirVec<hir::Field>) {
+        if adt.is_union() && adt.non_enum_variant().fields.len() > 1 && adt.did.is_local() {
+            for field in fields {
+                let index = self.tcx.field_index(field.id, self.tables);
+                self.insert_def_id(adt.non_enum_variant().fields[index].did);
             }
         }
     }
@@ -233,14 +228,12 @@ impl<'a, 'tcx> Visitor<'tcx> for MarkSymbolVisitor<'a, 'tcx> {
             hir::ExprMethodCall(..) => {
                 self.lookup_and_handle_method(expr.hir_id);
             }
-            hir::ExprField(ref lhs, ref name) => {
-                self.handle_field_access(&lhs, name.node);
+            hir::ExprField(ref lhs, ..) => {
+                self.handle_field_access(&lhs, expr.id);
             }
             hir::ExprStruct(_, ref fields, _) => {
-                if let ty::TypeVariants::TyAdt(ref def, _) = self.tables.expr_ty(expr).sty {
-                    if def.is_union() {
-                        self.mark_as_used_if_union(def.did, fields);
-                    }
+                if let ty::TypeVariants::TyAdt(ref adt, _) = self.tables.expr_ty(expr).sty {
+                    self.mark_as_used_if_union(adt, fields);
                 }
             }
             _ => ()

src/librustc/middle/expr_use_visitor.rs

@@ -659,11 +659,15 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
         match with_cmt.ty.sty {
             ty::TyAdt(adt, substs) if adt.is_struct() => {
                 // Consume those fields of the with expression that are needed.
-                for with_field in &adt.non_enum_variant().fields {
-                    if !contains_field_named(with_field, fields) {
+                for (f_index, with_field) in adt.non_enum_variant().fields.iter().enumerate() {
+                    let is_mentioned = fields.iter().any(|f| {
+                        self.tcx().field_index(f.id, self.mc.tables) == f_index
+                    });
+                    if !is_mentioned {
                         let cmt_field = self.mc.cat_field(
                             &*with_expr,
                             with_cmt.clone(),
+                            f_index,
                             with_field.name,
                             with_field.ty(self.tcx(), substs)
                         );
@@ -687,14 +691,6 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
         // walk the with expression so that complex expressions
         // are properly handled.
         self.walk_expr(with_expr);
-
-        fn contains_field_named(field: &ty::FieldDef,
-                                fields: &[hir::Field])
-                                -> bool
-        {
-            fields.iter().any(
-                |f| f.name.node == field.name)
-        }
     }
 
     // Invoke the appropriate delegate calls for anything that gets

src/librustc/middle/mem_categorization.rs

@@ -84,6 +84,7 @@ use syntax::ast::{self, Name};
 use syntax_pos::Span;
 
 use std::fmt;
+use std::hash::{Hash, Hasher};
 use rustc_data_structures::sync::Lrc;
 use std::rc::Rc;
 use util::nodemap::ItemLocalSet;
@@ -132,9 +133,22 @@ pub enum InteriorKind {
     InteriorElement(InteriorOffsetKind),
 }
 
-// FIXME: Use actual index instead of `ast::Name` with questionable hygiene
-#[derive(Clone, Copy, PartialEq, Eq, Hash)]
-pub struct FieldIndex(pub ast::Name);
+// Contains index of a field that is actually used for loan path comparisons and
+// string representation of the field that should be used only for diagnostics.
+#[derive(Clone, Copy, Eq)]
+pub struct FieldIndex(pub usize, pub Name);
+
+impl PartialEq for FieldIndex {
+    fn eq(&self, rhs: &Self) -> bool {
+        self.0 == rhs.0
+    }
+}
+
+impl Hash for FieldIndex {
+    fn hash<H: Hasher>(&self, h: &mut H) {
+        self.0.hash(h)
+    }
+}
 
 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
 pub enum InteriorOffsetKind {
@@ -195,7 +209,7 @@ pub enum ImmutabilityBlame<'tcx> {
 }
 
 impl<'tcx> cmt_<'tcx> {
-    fn resolve_field(&self, field_name: Name) -> Option<(&'tcx ty::AdtDef, &'tcx ty::FieldDef)>
+    fn resolve_field(&self, field_index: usize) -> Option<(&'tcx ty::AdtDef, &'tcx ty::FieldDef)>
     {
         let adt_def = match self.ty.sty {
             ty::TyAdt(def, _) => def,
@@ -212,7 +226,7 @@ impl<'tcx> cmt_<'tcx> {
                 &adt_def.variants[0]
             }
         };
-        Some((adt_def, variant_def.field_named(field_name)))
+        Some((adt_def, &variant_def.fields[field_index]))
     }
 
     pub fn immutability_blame(&self) -> Option<ImmutabilityBlame<'tcx>> {
@@ -639,7 +653,8 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
                    expr.id,
                    expr,
                    base_cmt);
-            Ok(self.cat_field(expr, base_cmt, f_name.node, expr_ty))
+            let f_index = self.tcx.field_index(expr.id, self.tables);
+            Ok(self.cat_field(expr, base_cmt, f_index, f_name.node, expr_ty))
           }
 
           hir::ExprIndex(ref base, _) => {
@@ -967,14 +982,15 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
     pub fn cat_field<N:ast_node>(&self,
                                  node: &N,
                                  base_cmt: cmt<'tcx>,
+                                 f_index: usize,
                                  f_name: Name,
                                  f_ty: Ty<'tcx>)
                                  -> cmt<'tcx> {
         let ret = Rc::new(cmt_ {
             id: node.id(),
             span: node.span(),
             mutbl: base_cmt.mutbl.inherit(),
-            cat: Categorization::Interior(base_cmt, InteriorField(FieldIndex(f_name))),
+            cat: Categorization::Interior(base_cmt, InteriorField(FieldIndex(f_index, f_name))),
             ty: f_ty,
             note: NoteNone
         });
@@ -1262,7 +1278,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
 
             for (i, subpat) in subpats.iter().enumerate_and_adjust(expected_len, ddpos) {
                 let subpat_ty = self.pat_ty(&subpat)?; // see (*2)
-                let interior = InteriorField(FieldIndex(Name::intern(&i.to_string())));
+                let interior = InteriorField(FieldIndex(i, Name::intern(&i.to_string())));
                 let subcmt = self.cat_imm_interior(pat, cmt.clone(), subpat_ty, interior);
                 self.cat_pattern_(subcmt, &subpat, op)?;
             }
@@ -1285,7 +1301,8 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
 
             for fp in field_pats {
                 let field_ty = self.pat_ty(&fp.node.pat)?; // see (*2)
-                let cmt_field = self.cat_field(pat, cmt.clone(), fp.node.name, field_ty);
+                let f_index = self.tcx.field_index(fp.node.id, self.tables);
+                let cmt_field = self.cat_field(pat, cmt.clone(), f_index, fp.node.name, field_ty);
                 self.cat_pattern_(cmt_field, &fp.node.pat, op)?;
             }
           }
@@ -1302,7 +1319,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
             };
             for (i, subpat) in subpats.iter().enumerate_and_adjust(expected_len, ddpos) {
                 let subpat_ty = self.pat_ty(&subpat)?; // see (*2)
-                let interior = InteriorField(FieldIndex(Name::intern(&i.to_string())));
+                let interior = InteriorField(FieldIndex(i, Name::intern(&i.to_string())));
                 let subcmt = self.cat_imm_interior(pat, cmt.clone(), subpat_ty, interior);
                 self.cat_pattern_(subcmt, &subpat, op)?;
             }
@@ -1521,7 +1538,7 @@ pub fn ptr_sigil(ptr: PointerKind) -> &'static str {
 impl fmt::Debug for InteriorKind {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
-            InteriorField(FieldIndex(name)) => write!(f, "{}", name),
+            InteriorField(FieldIndex(_, info)) => write!(f, "{}", info),
             InteriorElement(..) => write!(f, "[]"),
         }
     }

src/librustc/ty/context.rs

@@ -346,6 +346,12 @@ pub struct TypeckTables<'tcx> {
     /// method calls, including those of overloaded operators.
     type_dependent_defs: ItemLocalMap<Def>,
 
+    /// Resolved field indices for field accesses in expressions (`S { field }`, `obj.field`)
+    /// or patterns (`S { field }`). The index is often useful by itself, but to learn more
+    /// about the field you also need definition of the variant to which the field
+    /// belongs, but it may not exist if it's a tuple field (`tuple.0`).
+    field_indices: ItemLocalMap<usize>,
+
     /// Stores the canonicalized types provided by the user. See also `UserAssertTy` statement in
     /// MIR.
     user_provided_tys: ItemLocalMap<CanonicalTy<'tcx>>,
@@ -426,6 +432,7 @@ impl<'tcx> TypeckTables<'tcx> {
         TypeckTables {
             local_id_root,
             type_dependent_defs: ItemLocalMap(),
+            field_indices: ItemLocalMap(),
             user_provided_tys: ItemLocalMap(),
             node_types: ItemLocalMap(),
             node_substs: ItemLocalMap(),
@@ -468,6 +475,20 @@ impl<'tcx> TypeckTables<'tcx> {
         }
     }
 
+    pub fn field_indices(&self) -> LocalTableInContext<usize> {
+        LocalTableInContext {
+            local_id_root: self.local_id_root,
+            data: &self.field_indices
+        }
+    }
+
+    pub fn field_indices_mut(&mut self) -> LocalTableInContextMut<usize> {
+        LocalTableInContextMut {
+            local_id_root: self.local_id_root,
+            data: &mut self.field_indices
+        }
+    }
+
     pub fn user_provided_tys(&self) -> LocalTableInContext<CanonicalTy<'tcx>> {
         LocalTableInContext {
             local_id_root: self.local_id_root,
@@ -706,6 +727,7 @@ impl<'a, 'gcx> HashStable<StableHashingContext<'a>> for TypeckTables<'gcx> {
         let ty::TypeckTables {
             local_id_root,
             ref type_dependent_defs,
+            ref field_indices,
             ref user_provided_tys,
             ref node_types,
             ref node_substs,
@@ -726,6 +748,7 @@ impl<'a, 'gcx> HashStable<StableHashingContext<'a>> for TypeckTables<'gcx> {
 
         hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
             type_dependent_defs.hash_stable(hcx, hasher);
+            field_indices.hash_stable(hcx, hasher);
             user_provided_tys.hash_stable(hcx, hasher);
             node_types.hash_stable(hcx, hasher);
             node_substs.hash_stable(hcx, hasher);