rust/src/comp/syntax/visit.rs

import ast::*;
import option;
import option::{none, some};
import codemap::span;


// Context-passing 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 (potentially passing in different contexts to each), call
// visit::visit_* to apply the default traversal algorithm (again, it can
// override the context), or prevent deeper traversal by doing nothing.

// Our typesystem doesn't do circular types, so the visitor record can not
// hold functions that take visitors. A vt tag is used to break the cycle.
tag vt<E> { mk_vt(visitor<E>); }

type visitor<E> =
    // takes the components so that one function can be
    // generic over constr and ty_constr
    @{visit_mod: fn@(_mod, span, E, vt<E>),
      visit_view_item: fn@(@view_item, E, vt<E>),
      visit_native_item: fn@(@native_item, E, vt<E>),
      visit_item: fn@(@item, E, vt<E>),
      visit_local: fn@(@local, E, vt<E>),
      visit_block: fn@(ast::blk, E, vt<E>),
      visit_stmt: fn@(@stmt, E, vt<E>),
      visit_arm: fn@(arm, E, vt<E>),
      visit_pat: fn@(@pat, E, vt<E>),
      visit_decl: fn@(@decl, E, vt<E>),
      visit_expr: fn@(@expr, E, vt<E>),
      visit_ty: fn@(@ty, E, vt<E>),
      visit_constr: fn@(@path, span, node_id, E, vt<E>),
      visit_fn: fn@(fn_decl, [ty_param], blk, span, fn_ident, node_id,
                    E, vt<E>)};

fn default_visitor<E>() -> visitor<E> {
    ret @{visit_mod: bind visit_mod::<E>(_, _, _, _),
          visit_view_item: bind visit_view_item::<E>(_, _, _),
          visit_native_item: bind visit_native_item::<E>(_, _, _),
          visit_item: bind visit_item::<E>(_, _, _),
          visit_local: bind visit_local::<E>(_, _, _),
          visit_block: bind visit_block::<E>(_, _, _),
          visit_stmt: bind visit_stmt::<E>(_, _, _),
          visit_arm: bind visit_arm::<E>(_, _, _),
          visit_pat: bind visit_pat::<E>(_, _, _),
          visit_decl: bind visit_decl::<E>(_, _, _),
          visit_expr: bind visit_expr::<E>(_, _, _),
          visit_ty: bind skip_ty::<E>(_, _, _),
          visit_constr: bind visit_constr::<E>(_, _, _, _, _),
          visit_fn: bind visit_fn::<E>(_, _, _, _, _, _, _, _)};
}

fn visit_crate<E>(c: crate, e: E, v: vt<E>) {
    v.visit_mod(c.node.module, c.span, e, v);
}

fn visit_crate_directive<E>(cd: @crate_directive, e: E, v: vt<E>) {
    alt cd.node {
      cdir_src_mod(_, _) { }
      cdir_dir_mod(_, cdirs, _) {
        for cdir: @crate_directive in cdirs {
            visit_crate_directive(cdir, e, v);
        }
      }
      cdir_view_item(vi) { v.visit_view_item(vi, e, v); }
      cdir_syntax(_) { }
    }
}

fn visit_mod<E>(m: _mod, _sp: span, e: E, v: vt<E>) {
    for vi: @view_item in m.view_items { v.visit_view_item(vi, e, v); }
    for i: @item in m.items { v.visit_item(i, e, v); }
}

fn visit_view_item<E>(_vi: @view_item, _e: E, _v: vt<E>) { }

fn visit_local<E>(loc: @local, e: E, v: vt<E>) {
    v.visit_pat(loc.node.pat, e, v);
    v.visit_ty(loc.node.ty, e, v);
    alt loc.node.init { none. { } some(i) { v.visit_expr(i.expr, e, v); } }
}

fn visit_item<E>(i: @item, e: E, v: vt<E>) {
    alt i.node {
      item_const(t, ex) { v.visit_ty(t, e, v); v.visit_expr(ex, e, v); }
      item_fn(decl, tp, body) {
        v.visit_fn(decl, tp, body, i.span, some(i.ident), i.id, e, v);
      }
      item_mod(m) { v.visit_mod(m, i.span, e, v); }
      item_native_mod(nm) {
        for vi: @view_item in nm.view_items { v.visit_view_item(vi, e, v); }
        for ni: @native_item in nm.items { v.visit_native_item(ni, e, v); }
      }
      item_ty(t, tps) { v.visit_ty(t, e, v); visit_ty_params(tps, e, v); }
      item_res(decl, tps, body, dtor_id, _) {
        v.visit_fn(decl, tps, body, i.span, some(i.ident), dtor_id,
                   e, v);
      }
      item_tag(variants, tps) {
        visit_ty_params(tps, e, v);
        for vr: variant in variants {
            for va: variant_arg in vr.node.args { v.visit_ty(va.ty, e, v); }
        }
      }
      item_obj(ob, tps, _) {
        visit_ty_params(tps, e, v);
        for f: obj_field in ob.fields { v.visit_ty(f.ty, e, v); }
        for m: @method in ob.methods {
            v.visit_fn(m.decl, m.tps, m.body, m.span,
                       some(m.ident), m.id, e, v);
        }
      }
      item_impl(tps, ifce, ty, methods) {
        visit_ty_params(tps, e, v);
        alt ifce { some(ty) { v.visit_ty(ty, e, v); } _ {} }
        v.visit_ty(ty, e, v);
        for m in methods {
            v.visit_fn(m.decl, m.tps, m.body, m.span,
                       some(m.ident), m.id, e, v);
        }
      }
      item_iface(tps, methods) {
        visit_ty_params(tps, e, v);
        for m in methods {
            for a in m.decl.inputs { v.visit_ty(a.ty, e, v); }
            v.visit_ty(m.decl.output, e, v);
        }
      }
    }
}

fn skip_ty<E>(_t: @ty, _e: E, _v: vt<E>) {}

fn visit_ty<E>(t: @ty, e: E, v: vt<E>) {
    alt t.node {
      ty_box(mt) { v.visit_ty(mt.ty, e, v); }
      ty_uniq(mt) { v.visit_ty(mt.ty, e, v); }
      ty_vec(mt) { v.visit_ty(mt.ty, e, v); }
      ty_ptr(mt) { v.visit_ty(mt.ty, e, v); }
      ty_rec(flds) {
        for f: ty_field in flds { v.visit_ty(f.node.mt.ty, e, v); }
      }
      ty_tup(ts) { for tt in ts { v.visit_ty(tt, e, v); } }
      ty_fn(decl) {
        for a in decl.inputs { v.visit_ty(a.ty, e, v); }
        for c: @constr in decl.constraints {
            v.visit_constr(c.node.path, c.span, c.node.id, e, v);
        }
        v.visit_ty(decl.output, e, v);
      }
      ty_obj(tmeths) {
        for m: ty_method in tmeths {
            for a in m.decl.inputs { v.visit_ty(a.ty, e, v); }
            v.visit_ty(m.decl.output, e, v);
        }
      }
      ty_path(p, _) { visit_path(p, e, v); }
      ty_type. {/* no-op */ }
      ty_constr(t, cs) {
        v.visit_ty(t, e, v);
        for tc: @spanned<constr_general_<@path, node_id>> in cs {
            v.visit_constr(tc.node.path, tc.span, tc.node.id, e, v);
        }
      }
      _ {}
    }
}

fn visit_constr<E>(_operator: @path, _sp: span, _id: node_id, _e: E,
                   _v: vt<E>) {
    // default
}

fn visit_path<E>(p: @path, e: E, v: vt<E>) {
    for tp: @ty in p.node.types { v.visit_ty(tp, e, v); }
}

fn visit_pat<E>(p: @pat, e: E, v: vt<E>) {
    alt p.node {
      pat_tag(path, children) {
        visit_path(path, e, v);
        for child: @pat in children { v.visit_pat(child, e, v); }
      }
      pat_rec(fields, _) {
        for f: field_pat in fields { v.visit_pat(f.pat, e, v); }
      }
      pat_tup(elts) { for elt in elts { v.visit_pat(elt, e, v); } }
      pat_box(inner) | pat_uniq(inner) | pat_bind(_, some(inner)) {
        v.visit_pat(inner, e, v);
      }
      _ { }
    }
}

fn visit_native_item<E>(ni: @native_item, e: E, v: vt<E>) {
    alt ni.node {
      native_item_fn(fd, tps) {
        visit_ty_params(tps, e, v);
        visit_fn_decl(fd, e, v);
      }
      native_item_ty. { }
    }
}

fn visit_ty_params<E>(tps: [ty_param], e: E, v: vt<E>) {
    for tp in tps {
        for bound in *tp.bounds {
            alt bound {
              bound_iface(t) { v.visit_ty(t, e, v); }
              _ {}
            }
        }
    }
}

fn visit_fn_decl<E>(fd: fn_decl, e: E, v: vt<E>) {
    for a: arg in fd.inputs { v.visit_ty(a.ty, e, v); }
    for c: @constr in fd.constraints {
        v.visit_constr(c.node.path, c.span, c.node.id, e, v);
    }
    v.visit_ty(fd.output, e, v);
}

fn visit_fn<E>(decl: fn_decl, tp: [ty_param], body: blk, _sp: span,
               _i: fn_ident, _id: node_id, e: E, v: vt<E>) {
    visit_fn_decl(decl, e, v);
    visit_ty_params(tp, e, v);
    v.visit_block(body, e, v);
}

fn visit_block<E>(b: ast::blk, e: E, v: vt<E>) {
    for vi in b.node.view_items { v.visit_view_item(vi, e, v); }
    for s in b.node.stmts { v.visit_stmt(s, e, v); }
    visit_expr_opt(b.node.expr, e, v);
}

fn visit_stmt<E>(s: @stmt, e: E, v: vt<E>) {
    alt s.node {
      stmt_decl(d, _) { v.visit_decl(d, e, v); }
      stmt_expr(ex, _) { v.visit_expr(ex, e, v); }
    }
}

fn visit_decl<E>(d: @decl, e: E, v: vt<E>) {
    alt d.node {
      decl_local(locs) {
        for (_, loc) in locs { v.visit_local(loc, e, v); }
      }
      decl_item(it) { v.visit_item(it, e, v); }
    }
}

fn visit_expr_opt<E>(eo: option::t<@expr>, e: E, v: vt<E>) {
    alt eo { none. { } some(ex) { v.visit_expr(ex, e, v); } }
}

fn visit_exprs<E>(exprs: [@expr], e: E, v: vt<E>) {
    for ex: @expr in exprs { v.visit_expr(ex, e, v); }
}

fn visit_mac<E>(m: mac, e: E, v: vt<E>) {
    alt m.node {
      ast::mac_invoc(pth, arg, body) { visit_expr(arg, e, v); }
      ast::mac_embed_type(ty) { v.visit_ty(ty, e, v); }
      ast::mac_embed_block(blk) { v.visit_block(blk, e, v); }
      ast::mac_ellipsis. { }
    }
}

fn visit_expr<E>(ex: @expr, e: E, v: vt<E>) {
    alt ex.node {
      expr_vec(es, _) { visit_exprs(es, e, v); }
      expr_rec(flds, base) {
        for f: field in flds { v.visit_expr(f.node.expr, e, v); }
        visit_expr_opt(base, e, v);
      }
      expr_tup(elts) { for el in elts { v.visit_expr(el, e, v); } }
      expr_call(callee, args, _) {
        visit_exprs(args, e, v);
        v.visit_expr(callee, e, v);
      }
      expr_bind(callee, args) {
        v.visit_expr(callee, e, v);
        for eo: option::t<@expr> in args { visit_expr_opt(eo, e, v); }
      }
      expr_binary(_, a, b) { v.visit_expr(a, e, v); v.visit_expr(b, e, v); }
      expr_unary(_, a) { v.visit_expr(a, e, v); }
      expr_lit(_) { }
      expr_cast(x, t) { v.visit_expr(x, e, v); v.visit_ty(t, e, v); }
      expr_if(x, b, eo) {
        v.visit_expr(x, e, v);
        v.visit_block(b, e, v);
        visit_expr_opt(eo, e, v);
      }
      expr_if_check(x, b, eo) {
        v.visit_expr(x, e, v);
        v.visit_block(b, e, v);
        visit_expr_opt(eo, e, v);
      }
      expr_ternary(c, t, el) {
        v.visit_expr(c, e, v);
        v.visit_expr(t, e, v);
        v.visit_expr(el, e, v);
      }
      expr_while(x, b) { v.visit_expr(x, e, v); v.visit_block(b, e, v); }
      expr_for(dcl, x, b) {
        v.visit_local(dcl, e, v);
        v.visit_expr(x, e, v);
        v.visit_block(b, e, v);
      }
      expr_do_while(b, x) { v.visit_block(b, e, v); v.visit_expr(x, e, v); }
      expr_alt(x, arms) {
        v.visit_expr(x, e, v);
        for a: arm in arms { v.visit_arm(a, e, v); }
      }
      expr_fn(decl, body, _) {
        v.visit_fn(decl, [], body, ex.span, none, ex.id, e, v);
      }
      expr_fn_block(decl, body) {
        v.visit_fn(decl, [], body, ex.span, none, ex.id, e, v);
      }
      expr_block(b) { v.visit_block(b, e, v); }
      expr_assign(a, b) { v.visit_expr(b, e, v); v.visit_expr(a, e, v); }
      expr_copy(a) { v.visit_expr(a, e, v); }
      expr_move(a, b) { v.visit_expr(b, e, v); v.visit_expr(a, e, v); }
      expr_swap(a, b) { v.visit_expr(a, e, v); v.visit_expr(b, e, v); }
      expr_assign_op(_, a, b) {
        v.visit_expr(b, e, v);
        v.visit_expr(a, e, v);
      }
      expr_field(x, _, tys) {
        v.visit_expr(x, e, v);
        for tp in tys { v.visit_ty(tp, e, v); }
      }
      expr_index(a, b) { v.visit_expr(a, e, v); v.visit_expr(b, e, v); }
      expr_path(p) { visit_path(p, e, v); }
      expr_fail(eo) { visit_expr_opt(eo, e, v); }
      expr_break. { }
      expr_cont. { }
      expr_ret(eo) { visit_expr_opt(eo, e, v); }
      expr_be(x) { v.visit_expr(x, e, v); }
      expr_log(_, lv, x) {
        v.visit_expr(lv, e, v);
        v.visit_expr(x, e, v);
      }
      expr_check(_, x) { v.visit_expr(x, e, v); }
      expr_assert(x) { v.visit_expr(x, e, v); }
      expr_anon_obj(anon_obj) {
        alt anon_obj.fields {
          none. { }
          some(fields) {
            for f: anon_obj_field in fields {
                v.visit_ty(f.ty, e, v);
                v.visit_expr(f.expr, e, v);
            }
          }
        }
        alt anon_obj.inner_obj {
          none. { }
          some(ex) { v.visit_expr(ex, e, v); }
        }
        for m: @method in anon_obj.methods {
            v.visit_fn(m.decl, m.tps, m.body, m.span,
                       some(m.ident), m.id, e, v);
        }
      }
      expr_mac(mac) { visit_mac(mac, e, v); }
    }
}

fn visit_arm<E>(a: arm, e: E, v: vt<E>) {
    for p: @pat in a.pats { v.visit_pat(p, e, v); }
    visit_expr_opt(a.guard, e, v);
    v.visit_block(a.body, e, v);
}

// Simpler, non-context passing interface. Always walks the whole tree, simply
// calls the given functions on the nodes.

type simple_visitor =
    // takes the components so that one function can be
    // generic over constr and ty_constr
    @{visit_mod: fn@(_mod, span),
      visit_view_item: fn@(@view_item),
      visit_native_item: fn@(@native_item),
      visit_item: fn@(@item),
      visit_local: fn@(@local),
      visit_block: fn@(ast::blk),
      visit_stmt: fn@(@stmt),
      visit_arm: fn@(arm),
      visit_pat: fn@(@pat),
      visit_decl: fn@(@decl),
      visit_expr: fn@(@expr),
      visit_ty: fn@(@ty),
      visit_constr: fn@(@path, span, node_id),
      visit_fn: fn@(fn_decl, [ty_param], blk, span, fn_ident, node_id)};

fn simple_ignore_ty(_t: @ty) {}

fn default_simple_visitor() -> simple_visitor {
    ret @{visit_mod: fn(_m: _mod, _sp: span) { },
          visit_view_item: fn(_vi: @view_item) { },
          visit_native_item: fn(_ni: @native_item) { },
          visit_item: fn(_i: @item) { },
          visit_local: fn(_l: @local) { },
          visit_block: fn(_b: ast::blk) { },
          visit_stmt: fn(_s: @stmt) { },
          visit_arm: fn(_a: arm) { },
          visit_pat: fn(_p: @pat) { },
          visit_decl: fn(_d: @decl) { },
          visit_expr: fn(_e: @expr) { },
          visit_ty: simple_ignore_ty,
          visit_constr: fn(_p: @path, _sp: span, _id: node_id) { },
          visit_fn: fn(_d: fn_decl, _tps: [ty_param], _b: blk, _sp: span,
                       _ident: fn_ident, _id: node_id) { }
         };
}

fn mk_simple_visitor(v: simple_visitor) -> vt<()> {
    fn v_mod(f: fn@(_mod, span), m: _mod, sp: span, &&e: (), v: vt<()>) {
        f(m, sp);
        visit_mod(m, sp, e, v);
    }
    fn v_view_item(f: fn@(@view_item), vi: @view_item, &&e: (), v: vt<()>) {
        f(vi);
        visit_view_item(vi, e, v);
    }
    fn v_native_item(f: fn@(@native_item), ni: @native_item, &&e: (),
                     v: vt<()>) {
        f(ni);
        visit_native_item(ni, e, v);
    }
    fn v_item(f: fn@(@item), i: @item, &&e: (), v: vt<()>) {
        f(i);
        visit_item(i, e, v);
    }
    fn v_local(f: fn@(@local), l: @local, &&e: (), v: vt<()>) {
        f(l);
        visit_local(l, e, v);
    }
    fn v_block(f: fn@(ast::blk), bl: ast::blk, &&e: (), v: vt<()>) {
        f(bl);
        visit_block(bl, e, v);
    }
    fn v_stmt(f: fn@(@stmt), st: @stmt, &&e: (), v: vt<()>) {
        f(st);
        visit_stmt(st, e, v);
    }
    fn v_arm(f: fn@(arm), a: arm, &&e: (), v: vt<()>) {
        f(a);
        visit_arm(a, e, v);
    }
    fn v_pat(f: fn@(@pat), p: @pat, &&e: (), v: vt<()>) {
        f(p);
        visit_pat(p, e, v);
    }
    fn v_decl(f: fn@(@decl), d: @decl, &&e: (), v: vt<()>) {
        f(d);
        visit_decl(d, e, v);
    }
    fn v_expr(f: fn@(@expr), ex: @expr, &&e: (), v: vt<()>) {
        f(ex);
        visit_expr(ex, e, v);
    }
    fn v_ty(f: fn@(@ty), ty: @ty, &&e: (), v: vt<()>) {
        f(ty);
        visit_ty(ty, e, v);
    }
    fn v_constr(f: fn@(@path, span, node_id), pt: @path, sp: span,
                id: node_id, &&e: (), v: vt<()>) {
        f(pt, sp, id);
        visit_constr(pt, sp, id, e, v);
    }
    fn v_fn(f: fn@(fn_decl, [ty_param], blk, span, fn_ident, node_id),
            decl: fn_decl, tps: [ty_param], body: blk, sp: span,
            ident: fn_ident, id: node_id, &&e: (), v: vt<()>) {
        f(decl, tps, body, sp, ident, id);
        visit_fn(decl, tps, body, sp, ident, id, e, v);
    }
    let visit_ty = if v.visit_ty == simple_ignore_ty {
        bind skip_ty(_, _, _)
    } else {
        bind v_ty(v.visit_ty, _, _, _)
    };
    ret mk_vt(@{visit_mod: bind v_mod(v.visit_mod, _, _, _, _),
                visit_view_item: bind v_view_item(v.visit_view_item, _, _, _),
                visit_native_item:
                    bind v_native_item(v.visit_native_item, _, _, _),
                visit_item: bind v_item(v.visit_item, _, _, _),
                visit_local: bind v_local(v.visit_local, _, _, _),
                visit_block: bind v_block(v.visit_block, _, _, _),
                visit_stmt: bind v_stmt(v.visit_stmt, _, _, _),
                visit_arm: bind v_arm(v.visit_arm, _, _, _),
                visit_pat: bind v_pat(v.visit_pat, _, _, _),
                visit_decl: bind v_decl(v.visit_decl, _, _, _),
                visit_expr: bind v_expr(v.visit_expr, _, _, _),
                visit_ty: visit_ty,
                visit_constr: bind v_constr(v.visit_constr, _, _, _, _, _),
                visit_fn: bind v_fn(v.visit_fn, _, _, _, _, _, _, _, _)
               });
}

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