# visit.rs.html -- source
Source to the Rust file `/Users/travis/.cargo/registry/src/github.com-1ecc6299db9ec823/syn-0.11.11/src/visit.rs`.
Keywords: rust, rustlang, rust-lang

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    // Adapted from libsyntax.

    //! AST walker. Each overridden visit method has full control over what
    //! happens with its node, it can do its own traversal of the node's children,
    //! call `visit::walk_*` to apply the default traversal algorithm, or prevent
    //! deeper traversal by doing nothing.
    //!
    //! Note: it is an important invariant that the default visitor walks the body
    //! of a function in "execution order" (more concretely, reverse post-order
    //! with respect to the CFG implied by the AST), meaning that if AST node A may
    //! execute before AST node B, then A is visited first.  The borrow checker in
    //! particular relies on this property.
    //!
    //! Note: walking an AST before macro expansion is probably a bad idea. For
    //! instance, a walker looking for item names in a module will miss all of
    //! those that are created by the expansion of a macro.

    use super::*;

    /// Each method of the Visitor trait is a hook to be potentially
    /// overridden.  Each method's default implementation recursively visits
    /// the substructure of the input via the corresponding `walk` method;
    /// e.g. the `visit_mod` method by default calls `visit::walk_mod`.
    ///
    /// If you want to ensure that your code handles every variant
    /// explicitly, you need to override each method.  (And you also need
    /// to monitor future changes to `Visitor` in case a new method with a
    /// new default implementation gets introduced.)
    pub trait Visitor: Sized {
        fn visit_ident(&mut self, _ident: &Ident) {}
        fn visit_derive_input(&mut self, derive_input: &DeriveInput) {
            walk_derive_input(self, derive_input)
        }
        fn visit_ty(&mut self, ty: &Ty) {
            walk_ty(self, ty)
        }
        fn visit_generics(&mut self, generics: &Generics) {
            walk_generics(self, generics)
        }
        fn visit_ty_param_bound(&mut self, bound: &TyParamBound) {
            walk_ty_param_bound(self, bound)
        }
        fn visit_poly_trait_ref(&mut self, trait_ref: &PolyTraitRef, modifier: &TraitBoundModifier) {
            walk_poly_trait_ref(self, trait_ref, modifier)
        }
        fn visit_variant_data(&mut self, data: &VariantData, _ident: &Ident, _generics: &Generics) {
            walk_variant_data(self, data)
        }
        fn visit_field(&mut self, field: &Field) {
            walk_field(self, field)
        }
        fn visit_variant(&mut self, variant: &Variant, generics: &Generics) {
            walk_variant(self, variant, generics)
        }
        fn visit_lifetime(&mut self, _lifetime: &Lifetime) {}
        fn visit_lifetime_def(&mut self, lifetime: &LifetimeDef) {
            walk_lifetime_def(self, lifetime)
        }
        fn visit_path(&mut self, path: &Path) {
            walk_path(self, path)
        }
        fn visit_path_segment(&mut self, path_segment: &PathSegment) {
            walk_path_segment(self, path_segment)
        }
        fn visit_path_parameters(&mut self, path_parameters: &PathParameters) {
            walk_path_parameters(self, path_parameters)
        }
        fn visit_assoc_type_binding(&mut self, type_binding: &TypeBinding) {
            walk_assoc_type_binding(self, type_binding)
        }
        fn visit_attribute(&mut self, _attr: &Attribute) {}
        fn visit_fn_ret_ty(&mut self, ret_ty: &FunctionRetTy) {
            walk_fn_ret_ty(self, ret_ty)
        }
        fn visit_const_expr(&mut self, expr: &ConstExpr) {
            walk_const_expr(self, expr)
        }
        fn visit_lit(&mut self, _lit: &Lit) {}

        fn visit_mac(&mut self, mac: &Mac) {
            walk_mac(self, mac);
        }

        #[cfg(feature = "full")]
        fn visit_crate(&mut self, _crate: &Crate) {
            walk_crate(self, _crate);
        }
        #[cfg(feature = "full")]
        fn visit_item(&mut self, item: &Item) {
            walk_item(self, item);
        }
        #[cfg(feature = "full")]
        fn visit_expr(&mut self, expr: &Expr) {
            walk_expr(self, expr);
        }
        #[cfg(feature = "full")]
        fn visit_foreign_item(&mut self, foreign_item: &ForeignItem) {
            walk_foreign_item(self, foreign_item);
        }
        #[cfg(feature = "full")]
        fn visit_pat(&mut self, pat: &Pat) {
            walk_pat(self, pat);
        }
        #[cfg(feature = "full")]
        fn visit_fn_decl(&mut self, fn_decl: &FnDecl) {
            walk_fn_decl(self, fn_decl);
        }
        #[cfg(feature = "full")]
        fn visit_trait_item(&mut self, trait_item: &TraitItem) {
            walk_trait_item(self, trait_item);
        }
        #[cfg(feature = "full")]
        fn visit_impl_item(&mut self, impl_item: &ImplItem) {
            walk_impl_item(self, impl_item);
        }
        #[cfg(feature = "full")]
        fn visit_method_sig(&mut self, method_sig: &MethodSig) {
            walk_method_sig(self, method_sig);
        }
        #[cfg(feature = "full")]
        fn visit_stmt(&mut self, stmt: &Stmt) {
            walk_stmt(self, stmt);
        }
        #[cfg(feature = "full")]
        fn visit_local(&mut self, local: &Local) {
            walk_local(self, local);
        }
        #[cfg(feature = "full")]
        fn visit_view_path(&mut self, view_path: &ViewPath) {
            walk_view_path(self, view_path);
        }
    }

    macro_rules! walk_list {
        ($visitor:expr, $method:ident, $list:expr $(, $extra_args:expr)*) => {
            for elem in $list {
                $visitor.$method(elem $(, $extra_args)*)
            }
        };
    }

    pub fn walk_opt_ident<V: Visitor>(visitor: &mut V, opt_ident: &Option<Ident>) {
        if let Some(ref ident) = *opt_ident {
            visitor.visit_ident(ident);
        }
    }

    pub fn walk_lifetime_def<V: Visitor>(visitor: &mut V, lifetime_def: &LifetimeDef) {
        visitor.visit_lifetime(&lifetime_def.lifetime);
        walk_list!(visitor, visit_lifetime, &lifetime_def.bounds);
    }

    pub fn walk_poly_trait_ref<V>(visitor: &mut V, trait_ref: &PolyTraitRef, _: &TraitBoundModifier)
        where V: Visitor
    {
        walk_list!(visitor, visit_lifetime_def, &trait_ref.bound_lifetimes);
        visitor.visit_path(&trait_ref.trait_ref);
    }

    pub fn walk_derive_input<V: Visitor>(visitor: &mut V, derive_input: &DeriveInput) {
        visitor.visit_ident(&derive_input.ident);
        visitor.visit_generics(&derive_input.generics);
        match derive_input.body {
            Body::Enum(ref variants) => {
                walk_list!(visitor, visit_variant, variants, &derive_input.generics);
            }
            Body::Struct(ref variant_data) => {
                visitor.visit_variant_data(variant_data, &derive_input.ident, &derive_input.generics);
            }
        }
        walk_list!(visitor, visit_attribute, &derive_input.attrs);
    }

    pub fn walk_variant<V>(visitor: &mut V, variant: &Variant, generics: &Generics)
        where V: Visitor
    {
        visitor.visit_ident(&variant.ident);
        visitor.visit_variant_data(&variant.data, &variant.ident, generics);
        walk_list!(visitor, visit_attribute, &variant.attrs);
    }

    pub fn walk_ty<V: Visitor>(visitor: &mut V, ty: &Ty) {
        match *ty {
            Ty::Slice(ref inner) |
            Ty::Paren(ref inner) => visitor.visit_ty(inner),
            Ty::Ptr(ref mutable_type) => visitor.visit_ty(&mutable_type.ty),
            Ty::Rptr(ref opt_lifetime, ref mutable_type) => {
                walk_list!(visitor, visit_lifetime, opt_lifetime);
                visitor.visit_ty(&mutable_type.ty)
            }
            Ty::Never | Ty::Infer => {}
            Ty::Tup(ref tuple_element_types) => {
                walk_list!(visitor, visit_ty, tuple_element_types);
            }
            Ty::BareFn(ref bare_fn) => {
                walk_list!(visitor, visit_lifetime_def, &bare_fn.lifetimes);
                for argument in &bare_fn.inputs {
                    walk_opt_ident(visitor, &argument.name);
                    visitor.visit_ty(&argument.ty)
                }
                visitor.visit_fn_ret_ty(&bare_fn.output)
            }
            Ty::Path(ref maybe_qself, ref path) => {
                if let Some(ref qself) = *maybe_qself {
                    visitor.visit_ty(&qself.ty);
                }
                visitor.visit_path(path);
            }
            Ty::Array(ref inner, ref len) => {
                visitor.visit_ty(inner);
                visitor.visit_const_expr(len);
            }
            Ty::TraitObject(ref bounds) |
            Ty::ImplTrait(ref bounds) => {
                walk_list!(visitor, visit_ty_param_bound, bounds);
            }
            Ty::Mac(ref mac) => {
                visitor.visit_mac(mac);
            }
        }
    }

    pub fn walk_path<V: Visitor>(visitor: &mut V, path: &Path) {
        for segment in &path.segments {
            visitor.visit_path_segment(segment);
        }
    }

    pub fn walk_path_segment<V: Visitor>(visitor: &mut V, segment: &PathSegment) {
        visitor.visit_ident(&segment.ident);
        visitor.visit_path_parameters(&segment.parameters);
    }

    pub fn walk_path_parameters<V>(visitor: &mut V, path_parameters: &PathParameters)
        where V: Visitor
    {
        match *path_parameters {
            PathParameters::AngleBracketed(ref data) => {
                walk_list!(visitor, visit_ty, &data.types);
                walk_list!(visitor, visit_lifetime, &data.lifetimes);
                walk_list!(visitor, visit_assoc_type_binding, &data.bindings);
            }
            PathParameters::Parenthesized(ref data) => {
                walk_list!(visitor, visit_ty, &data.inputs);
                walk_list!(visitor, visit_ty, &data.output);
            }
        }
    }

    pub fn walk_assoc_type_binding<V: Visitor>(visitor: &mut V, type_binding: &TypeBinding) {
        visitor.visit_ident(&type_binding.ident);
        visitor.visit_ty(&type_binding.ty);
    }

    pub fn walk_ty_param_bound<V: Visitor>(visitor: &mut V, bound: &TyParamBound) {
        match *bound {
            TyParamBound::Trait(ref ty, ref modifier) => {
                visitor.visit_poly_trait_ref(ty, modifier);
            }
            TyParamBound::Region(ref lifetime) => {
                visitor.visit_lifetime(lifetime);
            }
        }
    }

    pub fn walk_generics<V: Visitor>(visitor: &mut V, generics: &Generics) {
        for param in &generics.ty_params {
            visitor.visit_ident(&param.ident);
            walk_list!(visitor, visit_ty_param_bound, &param.bounds);
            walk_list!(visitor, visit_ty, &param.default);
        }
        walk_list!(visitor, visit_lifetime_def, &generics.lifetimes);
        for predicate in &generics.where_clause.predicates {
            match *predicate {
                WherePredicate::BoundPredicate(WhereBoundPredicate { ref bounded_ty,
                                                                     ref bounds,
                                                                     ref bound_lifetimes,
                                                                     .. }) => {
                    visitor.visit_ty(bounded_ty);
                    walk_list!(visitor, visit_ty_param_bound, bounds);
                    walk_list!(visitor, visit_lifetime_def, bound_lifetimes);
                }
                WherePredicate::RegionPredicate(WhereRegionPredicate { ref lifetime,
                                                                       ref bounds,
                                                                       .. }) => {
                    visitor.visit_lifetime(lifetime);
                    walk_list!(visitor, visit_lifetime, bounds);
                }
                WherePredicate::EqPredicate(WhereEqPredicate { ref lhs_ty, ref rhs_ty, .. }) => {
                    visitor.visit_ty(lhs_ty);
                    visitor.visit_ty(rhs_ty);
                }
            }
        }
    }

    pub fn walk_fn_ret_ty<V: Visitor>(visitor: &mut V, ret_ty: &FunctionRetTy) {
        if let FunctionRetTy::Ty(ref output_ty) = *ret_ty {
            visitor.visit_ty(output_ty)
        }
    }

    pub fn walk_variant_data<V: Visitor>(visitor: &mut V, data: &VariantData) {
        walk_list!(visitor, visit_field, data.fields());
    }

    pub fn walk_field<V: Visitor>(visitor: &mut V, field: &Field) {
        walk_opt_ident(visitor, &field.ident);
        visitor.visit_ty(&field.ty);
        walk_list!(visitor, visit_attribute, &field.attrs);
    }

    pub fn walk_const_expr<V: Visitor>(visitor: &mut V, len: &ConstExpr) {
        match *len {
            ConstExpr::Call(ref function, ref args) => {
                visitor.visit_const_expr(function);
                walk_list!(visitor, visit_const_expr, args);
            }
            ConstExpr::Binary(_op, ref left, ref right) => {
                visitor.visit_const_expr(left);
                visitor.visit_const_expr(right);
            }
            ConstExpr::Unary(_op, ref v) => {
                visitor.visit_const_expr(v);
            }
            ConstExpr::Lit(ref lit) => {
                visitor.visit_lit(lit);
            }
            ConstExpr::Cast(ref expr, ref ty) => {
                visitor.visit_const_expr(expr);
                visitor.visit_ty(ty);
            }
            ConstExpr::Path(ref path) => {
                visitor.visit_path(path);
            }
            ConstExpr::Index(ref expr, ref index) => {
                visitor.visit_const_expr(expr);
                visitor.visit_const_expr(index);
            }
            ConstExpr::Paren(ref expr) => {
                visitor.visit_const_expr(expr);
            }
            ConstExpr::Other(ref other) => {
                #[cfg(feature = "full")]
                fn walk_other<V: Visitor>(visitor: &mut V, other: &Expr) {
                    visitor.visit_expr(other);
                }
                #[cfg(not(feature = "full"))]
                fn walk_other<V: Visitor>(_: &mut V, _: &super::constant::Other) {}
                walk_other(visitor, other);
            }
        }
    }

    pub fn walk_mac<V: Visitor>(visitor: &mut V, mac: &Mac) {
        visitor.visit_path(&mac.path);
    }

    #[cfg(feature = "full")]
    pub fn walk_crate<V: Visitor>(visitor: &mut V, _crate: &Crate) {
        walk_list!(visitor, visit_attribute, &_crate.attrs);
        walk_list!(visitor, visit_item, &_crate.items);
    }

    #[cfg(feature = "full")]
    pub fn walk_item<V: Visitor>(visitor: &mut V, item: &Item) {
        visitor.visit_ident(&item.ident);
        walk_list!(visitor, visit_attribute, &item.attrs);
        match item.node {
            ItemKind::ExternCrate(ref ident) => {
                walk_opt_ident(visitor, ident);
            }
            ItemKind::Use(ref view_path) => {
                visitor.visit_view_path(view_path);
            }
            ItemKind::Static(ref ty, _, ref expr) |
            ItemKind::Const(ref ty, ref expr) => {
                visitor.visit_ty(ty);
                visitor.visit_expr(expr);
            }
            ItemKind::Fn(ref decl, _, _, _, ref generics, ref body) => {
                visitor.visit_fn_decl(decl);
                visitor.visit_generics(generics);
                walk_list!(visitor, visit_stmt, &body.stmts);
            }
            ItemKind::Mod(ref maybe_items) => {
                if let Some(ref items) = *maybe_items {
                    walk_list!(visitor, visit_item, items);
                }
            }
            ItemKind::ForeignMod(ref foreign_mod) => {
                walk_list!(visitor, visit_foreign_item, &foreign_mod.items);
            }
            ItemKind::Ty(ref ty, ref generics) => {
                visitor.visit_ty(ty);
                visitor.visit_generics(generics);
            }
            ItemKind::Enum(ref variant, ref generics) => {
                walk_list!(visitor, visit_variant, variant, generics);
            }
            ItemKind::Struct(ref variant_data, ref generics) |
            ItemKind::Union(ref variant_data, ref generics) => {
                visitor.visit_variant_data(variant_data, &item.ident, generics);
            }
            ItemKind::Trait(_, ref generics, ref bounds, ref trait_items) => {
                visitor.visit_generics(generics);
                walk_list!(visitor, visit_ty_param_bound, bounds);
                walk_list!(visitor, visit_trait_item, trait_items);
            }
            ItemKind::DefaultImpl(_, ref path) => {
                visitor.visit_path(path);
            }
            ItemKind::Impl(_, _, ref generics, ref maybe_path, ref ty, ref impl_items) => {
                visitor.visit_generics(generics);
                if let Some(ref path) = *maybe_path {
                    visitor.visit_path(path);
                }
                visitor.visit_ty(ty);
                walk_list!(visitor, visit_impl_item, impl_items);
            }
            ItemKind::Mac(ref mac) => visitor.visit_mac(mac),
        }
    }

    #[cfg(feature = "full")]
    #[cfg_attr(feature = "cargo-clippy", allow(cyclomatic_complexity))]
    pub fn walk_expr<V: Visitor>(visitor: &mut V, expr: &Expr) {
        walk_list!(visitor, visit_attribute, &expr.attrs);
        match expr.node {
            ExprKind::InPlace(ref place, ref value) => {
                visitor.visit_expr(place);
                visitor.visit_expr(value);
            }
            ExprKind::Call(ref callee, ref args) => {
                visitor.visit_expr(callee);
                walk_list!(visitor, visit_expr, args);
            }
            ExprKind::MethodCall(ref name, ref ty_args, ref args) => {
                visitor.visit_ident(name);
                walk_list!(visitor, visit_ty, ty_args);
                walk_list!(visitor, visit_expr, args);
            }
            ExprKind::Array(ref exprs) |
            ExprKind::Tup(ref exprs) => {
                walk_list!(visitor, visit_expr, exprs);
            }
            ExprKind::Unary(_, ref operand) => {
                visitor.visit_expr(operand);
            }
            ExprKind::Lit(ref lit) => {
                visitor.visit_lit(lit);
            }
            ExprKind::Cast(ref expr, ref ty) |
            ExprKind::Type(ref expr, ref ty) => {
                visitor.visit_expr(expr);
                visitor.visit_ty(ty);
            }
            ExprKind::If(ref cond, ref cons, ref maybe_alt) => {
                visitor.visit_expr(cond);
                walk_list!(visitor, visit_stmt, &cons.stmts);
                if let Some(ref alt) = *maybe_alt {
                    visitor.visit_expr(alt);
                }
            }
            ExprKind::IfLet(ref pat, ref cond, ref cons, ref maybe_alt) => {
                visitor.visit_pat(pat);
                visitor.visit_expr(cond);
                walk_list!(visitor, visit_stmt, &cons.stmts);
                if let Some(ref alt) = *maybe_alt {
                    visitor.visit_expr(alt);
                }
            }
            ExprKind::While(ref cond, ref body, ref label) => {
                visitor.visit_expr(cond);
                walk_list!(visitor, visit_stmt, &body.stmts);
                walk_opt_ident(visitor, label);
            }
            ExprKind::WhileLet(ref pat, ref cond, ref body, ref label) => {
                visitor.visit_pat(pat);
                visitor.visit_expr(cond);
                walk_list!(visitor, visit_stmt, &body.stmts);
                walk_opt_ident(visitor, label);
            }
            ExprKind::ForLoop(ref pat, ref expr, ref body, ref label) => {
                visitor.visit_pat(pat);
                visitor.visit_expr(expr);
                walk_list!(visitor, visit_stmt, &body.stmts);
                walk_opt_ident(visitor, label);
            }
            ExprKind::Loop(ref body, ref label) => {
                walk_list!(visitor, visit_stmt, &body.stmts);
                walk_opt_ident(visitor, label);
            }
            ExprKind::Match(ref expr, ref arms) => {
                visitor.visit_expr(expr);
                for &Arm { ref attrs, ref pats, ref guard, ref body } in arms {
                    walk_list!(visitor, visit_attribute, attrs);
                    walk_list!(visitor, visit_pat, pats);
                    if let Some(ref guard) = *guard {
                        visitor.visit_expr(guard);
                    }
                    visitor.visit_expr(body);
                }
            }
            ExprKind::Closure(_, ref decl, ref expr) => {
                visitor.visit_fn_decl(decl);
                visitor.visit_expr(expr);
            }
            ExprKind::Block(_, ref block) => {
                walk_list!(visitor, visit_stmt, &block.stmts);
            }
            ExprKind::Binary(_, ref lhs, ref rhs) |
            ExprKind::Assign(ref lhs, ref rhs) |
            ExprKind::AssignOp(_, ref lhs, ref rhs) => {
                visitor.visit_expr(lhs);
                visitor.visit_expr(rhs);
            }
            ExprKind::Field(ref obj, ref field) => {
                visitor.visit_expr(obj);
                visitor.visit_ident(field);
            }
            ExprKind::TupField(ref obj, _) => {
                visitor.visit_expr(obj);
            }
            ExprKind::Index(ref obj, ref idx) => {
                visitor.visit_expr(obj);
                visitor.visit_expr(idx);
            }
            ExprKind::Range(ref maybe_start, ref maybe_end, _) => {
                if let Some(ref start) = *maybe_start {
                    visitor.visit_expr(start);
                }
                if let Some(ref end) = *maybe_end {
                    visitor.visit_expr(end);
                }
            }
            ExprKind::Path(ref maybe_qself, ref path) => {
                if let Some(ref qself) = *maybe_qself {
                    visitor.visit_ty(&qself.ty);
                }
                visitor.visit_path(path);
            }
            ExprKind::Break(ref maybe_label, ref maybe_expr) => {
                walk_opt_ident(visitor, maybe_label);
                if let Some(ref expr) = *maybe_expr {
                    visitor.visit_expr(expr);
                }
            }
            ExprKind::Continue(ref maybe_label) => {
                walk_opt_ident(visitor, maybe_label);
            }
            ExprKind::Ret(ref maybe_expr) => {
                if let Some(ref expr) = *maybe_expr {
                    visitor.visit_expr(expr);
                }
            }
            ExprKind::Mac(ref mac) => {
                visitor.visit_mac(mac);
            }
            ExprKind::Struct(ref path, ref fields, ref maybe_base) => {
                visitor.visit_path(path);
                for &FieldValue { ref ident, ref expr, .. } in fields {
                    visitor.visit_ident(ident);
                    visitor.visit_expr(expr);
                }
                if let Some(ref base) = *maybe_base {
                    visitor.visit_expr(base);
                }
            }
            ExprKind::Repeat(ref value, ref times) => {
                visitor.visit_expr(value);
                visitor.visit_expr(times);
            }
            ExprKind::Box(ref expr) |
            ExprKind::AddrOf(_, ref expr) |
            ExprKind::Paren(ref expr) |
            ExprKind::Try(ref expr) => {
                visitor.visit_expr(expr);
            }
        }
    }

    #[cfg(feature = "full")]
    pub fn walk_foreign_item<V: Visitor>(visitor: &mut V, foreign_item: &ForeignItem) {
        visitor.visit_ident(&foreign_item.ident);
        walk_list!(visitor, visit_attribute, &foreign_item.attrs);
        match foreign_item.node {
            ForeignItemKind::Fn(ref decl, ref generics) => {
                visitor.visit_fn_decl(decl);
                visitor.visit_generics(generics);
            }
            ForeignItemKind::Static(ref ty, _) => {
                visitor.visit_ty(ty);
            }
        }
    }

    #[cfg(feature = "full")]
    pub fn walk_pat<V: Visitor>(visitor: &mut V, pat: &Pat) {
        match *pat {
            Pat::Wild => {}
            Pat::Ident(_, ref ident, ref maybe_pat) => {
                visitor.visit_ident(ident);
                if let Some(ref pat) = *maybe_pat {
                    visitor.visit_pat(pat);
                }
            }
            Pat::Struct(ref path, ref field_pats, _) => {
                visitor.visit_path(path);
                for &FieldPat { ref ident, ref pat, .. } in field_pats {
                    visitor.visit_ident(ident);
                    visitor.visit_pat(pat);
                }
            }
            Pat::TupleStruct(ref path, ref pats, _) => {
                visitor.visit_path(path);
                walk_list!(visitor, visit_pat, pats);
            }
            Pat::Path(ref maybe_qself, ref path) => {
                if let Some(ref qself) = *maybe_qself {
                    visitor.visit_ty(&qself.ty);
                }
                visitor.visit_path(path);
            }
            Pat::Tuple(ref pats, _) => {
                walk_list!(visitor, visit_pat, pats);
            }
            Pat::Box(ref pat) |
            Pat::Ref(ref pat, _) => {
                visitor.visit_pat(pat);
            }
            Pat::Lit(ref expr) => {
                visitor.visit_expr(expr);
            }
            Pat::Range(ref start, ref end) => {
                visitor.visit_expr(start);
                visitor.visit_expr(end);
            }
            Pat::Slice(ref start, ref maybe_mid, ref end) => {
                walk_list!(visitor, visit_pat, start);
                if let Some(ref mid) = *maybe_mid {
                    visitor.visit_pat(mid);
                }
                walk_list!(visitor, visit_pat, end);
            }
            Pat::Mac(ref mac) => {
                visitor.visit_mac(mac);
            }
        }
    }

    #[cfg(feature = "full")]
    pub fn walk_fn_decl<V: Visitor>(visitor: &mut V, fn_decl: &FnDecl) {
        for input in &fn_decl.inputs {
            match *input {
                FnArg::SelfRef(_, _) |
                FnArg::SelfValue(_) => {}
                FnArg::Captured(ref pat, ref ty) => {
                    visitor.visit_pat(pat);
                    visitor.visit_ty(ty);
                }
                FnArg::Ignored(ref ty) => {
                    visitor.visit_ty(ty);
                }
            }
        }
        visitor.visit_fn_ret_ty(&fn_decl.output);
    }

    #[cfg(feature = "full")]
    pub fn walk_trait_item<V: Visitor>(visitor: &mut V, trait_item: &TraitItem) {
        visitor.visit_ident(&trait_item.ident);
        walk_list!(visitor, visit_attribute, &trait_item.attrs);
        match trait_item.node {
            TraitItemKind::Const(ref ty, ref maybe_expr) => {
                visitor.visit_ty(ty);
                if let Some(ref expr) = *maybe_expr {
                    visitor.visit_expr(expr);
                }
            }
            TraitItemKind::Method(ref method_sig, ref maybe_block) => {
                visitor.visit_method_sig(method_sig);
                if let Some(ref block) = *maybe_block {
                    walk_list!(visitor, visit_stmt, &block.stmts);
                }
            }
            TraitItemKind::Type(ref bounds, ref maybe_ty) => {
                walk_list!(visitor, visit_ty_param_bound, bounds);
                if let Some(ref ty) = *maybe_ty {
                    visitor.visit_ty(ty);
                }
            }
            TraitItemKind::Macro(ref mac) => {
                visitor.visit_mac(mac);
            }
        }
    }

    #[cfg(feature = "full")]
    pub fn walk_impl_item<V: Visitor>(visitor: &mut V, impl_item: &ImplItem) {
        visitor.visit_ident(&impl_item.ident);
        walk_list!(visitor, visit_attribute, &impl_item.attrs);
        match impl_item.node {
            ImplItemKind::Const(ref ty, ref expr) => {
                visitor.visit_ty(ty);
                visitor.visit_expr(expr);
            }
            ImplItemKind::Method(ref method_sig, ref block) => {
                visitor.visit_method_sig(method_sig);
                walk_list!(visitor, visit_stmt, &block.stmts);
            }
            ImplItemKind::Type(ref ty) => {
                visitor.visit_ty(ty);
            }
            ImplItemKind::Macro(ref mac) => {
                visitor.visit_mac(mac);
            }
        }
    }

    #[cfg(feature = "full")]
    pub fn walk_method_sig<V: Visitor>(visitor: &mut V, method_sig: &MethodSig) {
        visitor.visit_fn_decl(&method_sig.decl);
        visitor.visit_generics(&method_sig.generics);
    }

    #[cfg(feature = "full")]
    pub fn walk_stmt<V: Visitor>(visitor: &mut V, stmt: &Stmt) {
        match *stmt {
            Stmt::Local(ref local) => {
                visitor.visit_local(local);
            }
            Stmt::Item(ref item) => {
                visitor.visit_item(item);
            }
            Stmt::Expr(ref expr) |
            Stmt::Semi(ref expr) => {
                visitor.visit_expr(expr);
            }
            Stmt::Mac(ref details) => {
                let (ref mac, _, ref attrs) = **details;
                visitor.visit_mac(mac);
                walk_list!(visitor, visit_attribute, attrs);
            }
        }
    }

    #[cfg(feature = "full")]
    pub fn walk_local<V: Visitor>(visitor: &mut V, local: &Local) {
        visitor.visit_pat(&local.pat);
        if let Some(ref ty) = local.ty {
            visitor.visit_ty(ty);
        }
        if let Some(ref init) = local.init {
            visitor.visit_expr(init);
        }
        walk_list!(visitor, visit_attribute, &local.attrs);
    }

    #[cfg(feature = "full")]
    pub fn walk_view_path<V: Visitor>(visitor: &mut V, view_path: &ViewPath) {
        match *view_path {
            ViewPath::Simple(ref path, ref maybe_ident) => {
                visitor.visit_path(path);
                walk_opt_ident(visitor, maybe_ident);
            }
            ViewPath::Glob(ref path) => {
                visitor.visit_path(path);
            }
            ViewPath::List(ref path, ref items) => {
                visitor.visit_path(path);
                for &PathListItem { ref name, ref rename } in items {
                    visitor.visit_ident(name);
                    walk_opt_ident(visitor, rename);
                }
            }
        }
    }

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