src/libsyntax/ast_util.rs

   1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use ast::*;
  12 use ast;
  13 use ast_util;
  14 use codemap::{span, spanned};
  15 use opt_vec;
  16 use parse::token;
  17 use visit;
  18
  19 use std::hashmap::HashMap;
  20 use std::int;
  21 use std::option;
  22 use std::cast;
  23 use std::local_data;
  24
  25 pub fn path_name_i(idents: &[ident]) -> ~str {
  26     // FIXME: Bad copies (#2543 -- same for everything else that says "bad")
  27     idents.map(|i| token::interner_get(i.name)).connect("::")
  28 }
  29
  30 pub fn path_to_ident(p: @Path) -> ident { copy *p.idents.last() }
  31
  32 pub fn local_def(id: node_id) -> def_id {
  33     ast::def_id { crate: local_crate, node: id }
  34 }
  35
  36 pub fn is_local(did: ast::def_id) -> bool { did.crate == local_crate }
  37
  38 pub fn stmt_id(s: &stmt) -> node_id {
  39     match s.node {
  40       stmt_decl(_, id) => id,
  41       stmt_expr(_, id) => id,
  42       stmt_semi(_, id) => id,
  43       stmt_mac(*) => fail!("attempted to analyze unexpanded stmt")
  44     }
  45 }
  46
  47 pub fn variant_def_ids(d: def) -> Option<(def_id, def_id)> {
  48     match d {
  49       def_variant(enum_id, var_id) => {
  50           Some((enum_id, var_id))
  51       }
  52       _ => None
  53     }
  54 }
  55
  56 pub fn def_id_of_def(d: def) -> def_id {
  57     match d {
  58       def_fn(id, _) | def_static_method(id, _, _) | def_mod(id) |
  59       def_foreign_mod(id) | def_static(id, _) |
  60       def_variant(_, id) | def_ty(id) | def_ty_param(id, _) |
  61       def_use(id) | def_struct(id) | def_trait(id) | def_method(id, _) => {
  62         id
  63       }
  64       def_arg(id, _) | def_local(id, _) | def_self(id, _) | def_self_ty(id)
  65       | def_upvar(id, _, _, _) | def_binding(id, _) | def_region(id)
  66       | def_typaram_binder(id) | def_label(id) => {
  67         local_def(id)
  68       }
  69
  70       def_prim_ty(_) => fail!()
  71     }
  72 }
  73
  74 pub fn binop_to_str(op: binop) -> ~str {
  75     match op {
  76       add => return ~"+",
  77       subtract => return ~"-",
  78       mul => return ~"*",
  79       div => return ~"/",
  80       rem => return ~"%",
  81       and => return ~"&&",
  82       or => return ~"||",
  83       bitxor => return ~"^",
  84       bitand => return ~"&",
  85       bitor => return ~"|",
  86       shl => return ~"<<",
  87       shr => return ~">>",
  88       eq => return ~"==",
  89       lt => return ~"<",
  90       le => return ~"<=",
  91       ne => return ~"!=",
  92       ge => return ~">=",
  93       gt => return ~">"
  94     }
  95 }
  96
  97 pub fn binop_to_method_name(op: binop) -> Option<~str> {
  98     match op {
  99       add => return Some(~"add"),
 100       subtract => return Some(~"sub"),
 101       mul => return Some(~"mul"),
 102       div => return Some(~"div"),
 103       rem => return Some(~"rem"),
 104       bitxor => return Some(~"bitxor"),
 105       bitand => return Some(~"bitand"),
 106       bitor => return Some(~"bitor"),
 107       shl => return Some(~"shl"),
 108       shr => return Some(~"shr"),
 109       lt => return Some(~"lt"),
 110       le => return Some(~"le"),
 111       ge => return Some(~"ge"),
 112       gt => return Some(~"gt"),
 113       eq => return Some(~"eq"),
 114       ne => return Some(~"ne"),
 115       and | or => return None
 116     }
 117 }
 118
 119 pub fn lazy_binop(b: binop) -> bool {
 120     match b {
 121       and => true,
 122       or => true,
 123       _ => false
 124     }
 125 }
 126
 127 pub fn is_shift_binop(b: binop) -> bool {
 128     match b {
 129       shl => true,
 130       shr => true,
 131       _ => false
 132     }
 133 }
 134
 135 pub fn unop_to_str(op: unop) -> ~str {
 136     match op {
 137       box(mt) => if mt == m_mutbl { ~"@mut " } else { ~"@" },
 138       uniq => ~"~",
 139       deref => ~"*",
 140       not => ~"!",
 141       neg => ~"-"
 142     }
 143 }
 144
 145 pub fn is_path(e: @expr) -> bool {
 146     return match e.node { expr_path(_) => true, _ => false };
 147 }
 148
 149 pub fn int_ty_to_str(t: int_ty) -> ~str {
 150     match t {
 151       ty_char => ~"u8", // ???
 152       ty_i => ~"",
 153       ty_i8 => ~"i8",
 154       ty_i16 => ~"i16",
 155       ty_i32 => ~"i32",
 156       ty_i64 => ~"i64"
 157     }
 158 }
 159
 160 pub fn int_ty_max(t: int_ty) -> u64 {
 161     match t {
 162       ty_i8 => 0x80u64,
 163       ty_i16 => 0x8000u64,
 164       ty_i | ty_char | ty_i32 => 0x80000000u64, // actually ni about ty_i
 165       ty_i64 => 0x8000000000000000u64
 166     }
 167 }
 168
 169 pub fn uint_ty_to_str(t: uint_ty) -> ~str {
 170     match t {
 171       ty_u => ~"u",
 172       ty_u8 => ~"u8",
 173       ty_u16 => ~"u16",
 174       ty_u32 => ~"u32",
 175       ty_u64 => ~"u64"
 176     }
 177 }
 178
 179 pub fn uint_ty_max(t: uint_ty) -> u64 {
 180     match t {
 181       ty_u8 => 0xffu64,
 182       ty_u16 => 0xffffu64,
 183       ty_u | ty_u32 => 0xffffffffu64, // actually ni about ty_u
 184       ty_u64 => 0xffffffffffffffffu64
 185     }
 186 }
 187
 188 pub fn float_ty_to_str(t: float_ty) -> ~str {
 189     match t { ty_f => ~"f", ty_f32 => ~"f32", ty_f64 => ~"f64" }
 190 }
 191
 192 pub fn is_call_expr(e: @expr) -> bool {
 193     match e.node { expr_call(*) => true, _ => false }
 194 }
 195
 196 pub fn block_from_expr(e: @expr) -> blk {
 197     let blk_ = default_block(~[], option::Some::<@expr>(e), e.id);
 198     return spanned {node: blk_, span: e.span};
 199 }
 200
 201 pub fn default_block(
 202     stmts1: ~[@stmt],
 203     expr1: Option<@expr>,
 204     id1: node_id
 205 ) -> blk_ {
 206     ast::blk_ {
 207         view_items: ~[],
 208         stmts: stmts1,
 209         expr: expr1,
 210         id: id1,
 211         rules: default_blk,
 212     }
 213 }
 214
 215 pub fn ident_to_path(s: span, i: ident) -> @Path {
 216     @ast::Path { span: s,
 217                  global: false,
 218                  idents: ~[i],
 219                  rp: None,
 220                  types: ~[] }
 221 }
 222
 223 pub fn ident_to_pat(id: node_id, s: span, i: ident) -> @pat {
 224     @ast::pat { id: id,
 225                 node: pat_ident(bind_infer, ident_to_path(s, i), None),
 226                 span: s }
 227 }
 228
 229 pub fn is_unguarded(a: &arm) -> bool {
 230     match a.guard {
 231       None => true,
 232       _    => false
 233     }
 234 }
 235
 236 pub fn unguarded_pat(a: &arm) -> Option<~[@pat]> {
 237     if is_unguarded(a) { Some(/* FIXME (#2543) */ copy a.pats) } else { None }
 238 }
 239
 240 pub fn public_methods(ms: ~[@method]) -> ~[@method] {
 241     do ms.filtered |m| {
 242         match m.vis {
 243             public => true,
 244             _   => false
 245         }
 246     }
 247 }
 248
 249 // extract a ty_method from a trait_method. if the trait_method is
 250 // a default, pull out the useful fields to make a ty_method
 251 pub fn trait_method_to_ty_method(method: &trait_method) -> ty_method {
 252     match *method {
 253         required(ref m) => copy *m,
 254         provided(ref m) => {
 255             ty_method {
 256                 ident: m.ident,
 257                 attrs: copy m.attrs,
 258                 purity: m.purity,
 259                 decl: copy m.decl,
 260                 generics: copy m.generics,
 261                 explicit_self: m.explicit_self,
 262                 id: m.id,
 263                 span: m.span,
 264             }
 265         }
 266     }
 267 }
 268
 269 pub fn split_trait_methods(trait_methods: &[trait_method])
 270     -> (~[ty_method], ~[@method]) {
 271     let mut reqd = ~[];
 272     let mut provd = ~[];
 273     for trait_methods.iter().advance |trt_method| {
 274         match *trt_method {
 275           required(ref tm) => reqd.push(copy *tm),
 276           provided(m) => provd.push(m)
 277         }
 278     };
 279     (reqd, provd)
 280 }
 281
 282 pub fn struct_field_visibility(field: ast::struct_field) -> visibility {
 283     match field.node.kind {
 284         ast::named_field(_, visibility) => visibility,
 285         ast::unnamed_field => ast::public
 286     }
 287 }
 288
 289 pub trait inlined_item_utils {
 290     fn ident(&self) -> ident;
 291     fn id(&self) -> ast::node_id;
 292     fn accept<E: Copy>(&self, e: E, v: visit::vt<E>);
 293 }
 294
 295 impl inlined_item_utils for inlined_item {
 296     fn ident(&self) -> ident {
 297         match *self {
 298             ii_item(i) => /* FIXME (#2543) */ copy i.ident,
 299             ii_foreign(i) => /* FIXME (#2543) */ copy i.ident,
 300             ii_method(_, m) => /* FIXME (#2543) */ copy m.ident,
 301         }
 302     }
 303
 304     fn id(&self) -> ast::node_id {
 305         match *self {
 306             ii_item(i) => i.id,
 307             ii_foreign(i) => i.id,
 308             ii_method(_, m) => m.id,
 309         }
 310     }
 311
 312     fn accept<E: Copy>(&self, e: E, v: visit::vt<E>) {
 313         match *self {
 314             ii_item(i) => (v.visit_item)(i, (e, v)),
 315             ii_foreign(i) => (v.visit_foreign_item)(i, (e, v)),
 316             ii_method(_, m) => visit::visit_method_helper(m, (e, v)),
 317         }
 318     }
 319 }
 320
 321 /* True if d is either a def_self, or a chain of def_upvars
 322  referring to a def_self */
 323 pub fn is_self(d: ast::def) -> bool {
 324   match d {
 325     def_self(*)           => true,
 326     def_upvar(_, d, _, _) => is_self(*d),
 327     _                     => false
 328   }
 329 }
 330
 331 /// Maps a binary operator to its precedence
 332 pub fn operator_prec(op: ast::binop) -> uint {
 333   match op {
 334       mul | div | rem   => 12u,
 335       // 'as' sits between here with 11
 336       add | subtract    => 10u,
 337       shl | shr         =>  9u,
 338       bitand            =>  8u,
 339       bitxor            =>  7u,
 340       bitor             =>  6u,
 341       lt | le | ge | gt =>  4u,
 342       eq | ne           =>  3u,
 343       and               =>  2u,
 344       or                =>  1u
 345   }
 346 }
 347
 348 /// Precedence of the `as` operator, which is a binary operator
 349 /// not appearing in the prior table.
 350 pub static as_prec: uint = 11u;
 351
 352 pub fn empty_generics() -> Generics {
 353     Generics {lifetimes: opt_vec::Empty,
 354               ty_params: opt_vec::Empty}
 355 }
 356
 357 // ______________________________________________________________________
 358 // Enumerating the IDs which appear in an AST
 359
 360 #[deriving(Encodable, Decodable)]
 361 pub struct id_range {
 362     min: node_id,
 363     max: node_id,
 364 }
 365
 366 impl id_range {
 367     pub fn max() -> id_range {
 368         id_range {
 369             min: int::max_value,
 370             max: int::min_value,
 371         }
 372     }
 373
 374     pub fn empty(&self) -> bool {
 375         self.min >= self.max
 376     }
 377
 378     pub fn add(&mut self, id: node_id) {
 379         self.min = int::min(self.min, id);
 380         self.max = int::max(self.max, id + 1);
 381     }
 382 }
 383
 384 pub fn id_visitor<T: Copy>(vfn: @fn(node_id, T)) -> visit::vt<T> {
 385     let visit_generics: @fn(&Generics, T) = |generics, t| {
 386         for generics.ty_params.iter().advance |p| {
 387             vfn(p.id, copy t);
 388         }
 389         for generics.lifetimes.iter().advance |p| {
 390             vfn(p.id, copy t);
 391         }
 392     };
 393     visit::mk_vt(@visit::Visitor {
 394         visit_mod: |m, sp, id, (t, vt)| {
 395             vfn(id, copy t);
 396             visit::visit_mod(m, sp, id, (t, vt));
 397         },
 398
 399         visit_view_item: |vi, (t, vt)| {
 400             match vi.node {
 401               view_item_extern_mod(_, _, id) => vfn(id, copy t),
 402               view_item_use(ref vps) => {
 403                   for vps.iter().advance |vp| {
 404                       match vp.node {
 405                           view_path_simple(_, _, id) => vfn(id, copy t),
 406                           view_path_glob(_, id) => vfn(id, copy t),
 407                           view_path_list(_, ref paths, id) => {
 408                               vfn(id, copy t);
 409                               for paths.iter().advance |p| {
 410                                   vfn(p.node.id, copy t);
 411                               }
 412                           }
 413                       }
 414                   }
 415               }
 416             }
 417             visit::visit_view_item(vi, (t, vt));
 418         },
 419
 420         visit_foreign_item: |ni, (t, vt)| {
 421             vfn(ni.id, copy t);
 422             visit::visit_foreign_item(ni, (t, vt));
 423         },
 424
 425         visit_item: |i, (t, vt)| {
 426             vfn(i.id, copy t);
 427             match i.node {
 428               item_enum(ref enum_definition, _) =>
 429                 for (*enum_definition).variants.iter().advance |v| { vfn(v.node.id, copy t); },
 430               _ => ()
 431             }
 432             visit::visit_item(i, (t, vt));
 433         },
 434
 435         visit_local: |l, (t, vt)| {
 436             vfn(l.node.id, copy t);
 437             visit::visit_local(l, (t, vt));
 438         },
 439         visit_block: |b, (t, vt)| {
 440             vfn(b.node.id, copy t);
 441             visit::visit_block(b, (t, vt));
 442         },
 443         visit_stmt: |s, (t, vt)| {
 444             vfn(ast_util::stmt_id(s), copy t);
 445             visit::visit_stmt(s, (t, vt));
 446         },
 447         visit_pat: |p, (t, vt)| {
 448             vfn(p.id, copy t);
 449             visit::visit_pat(p, (t, vt));
 450         },
 451
 452         visit_expr: |e, (t, vt)| {
 453             {
 454                 let r = e.get_callee_id();
 455                 for r.iter().advance |callee_id| {
 456                     vfn(*callee_id, copy t);
 457                 }
 458             }
 459             vfn(e.id, copy t);
 460             visit::visit_expr(e, (t, vt));
 461         },
 462
 463         visit_ty: |ty, (t, vt)| {
 464             match ty.node {
 465               ty_path(_, _, id) => vfn(id, copy t),
 466               _ => { /* fall through */ }
 467             }
 468             visit::visit_ty(ty, (t, vt));
 469         },
 470
 471         visit_generics: |generics, (t, vt)| {
 472             visit_generics(generics, copy t);
 473             visit::visit_generics(generics, (t, vt));
 474         },
 475
 476         visit_fn: |fk, d, a, b, id, (t, vt)| {
 477             vfn(id, copy t);
 478
 479             match *fk {
 480                 visit::fk_item_fn(_, generics, _, _) => {
 481                     visit_generics(generics, copy t);
 482                 }
 483                 visit::fk_method(_, generics, m) => {
 484                     vfn(m.self_id, copy t);
 485                     visit_generics(generics, copy t);
 486                 }
 487                 visit::fk_anon(_) |
 488                 visit::fk_fn_block => {
 489                 }
 490             }
 491
 492             for d.inputs.iter().advance |arg| {
 493                 vfn(arg.id, copy t)
 494             }
 495             visit::visit_fn(fk, d, a, b, id, (copy t, vt));
 496         },
 497
 498         visit_struct_field: |f, (t, vt)| {
 499             vfn(f.node.id, copy t);
 500             visit::visit_struct_field(f, (t, vt));
 501         },
 502
 503         .. *visit::default_visitor()
 504     })
 505 }
 506
 507 pub fn visit_ids_for_inlined_item(item: &inlined_item, vfn: @fn(node_id)) {
 508     item.accept((), id_visitor(|id, ()| vfn(id)));
 509 }
 510
 511 pub fn compute_id_range(visit_ids_fn: &fn(@fn(node_id))) -> id_range {
 512     let result = @mut id_range::max();
 513     do visit_ids_fn |id| {
 514         result.add(id);
 515     }
 516     *result
 517 }
 518
 519 pub fn compute_id_range_for_inlined_item(item: &inlined_item) -> id_range {
 520     compute_id_range(|f| visit_ids_for_inlined_item(item, f))
 521 }
 522
 523 pub fn is_item_impl(item: @ast::item) -> bool {
 524     match item.node {
 525        item_impl(*) => true,
 526        _            => false
 527     }
 528 }
 529
 530 pub fn walk_pat(pat: @pat, it: &fn(@pat) -> bool) -> bool {
 531     if !it(pat) {
 532         return false;
 533     }
 534
 535     match pat.node {
 536         pat_ident(_, _, Some(p)) => walk_pat(p, it),
 537         pat_struct(_, ref fields, _) => {
 538             fields.iter().advance(|f| walk_pat(f.pat, |p| it(p)))
 539         }
 540         pat_enum(_, Some(ref s)) | pat_tup(ref s) => {
 541             s.iter().advance(|&p| walk_pat(p, |p| it(p)))
 542         }
 543         pat_box(s) | pat_uniq(s) | pat_region(s) => {
 544             walk_pat(s, it)
 545         }
 546         pat_vec(ref before, ref slice, ref after) => {
 547             before.iter().advance(|&p| walk_pat(p, |p| it(p))) &&
 548                 slice.iter().advance(|&p| walk_pat(p, |p| it(p))) &&
 549                 after.iter().advance(|&p| walk_pat(p, |p| it(p)))
 550         }
 551         pat_wild | pat_lit(_) | pat_range(_, _) | pat_ident(_, _, _) |
 552         pat_enum(_, _) => {
 553             true
 554         }
 555     }
 556 }
 557
 558 pub trait EachViewItem {
 559     pub fn each_view_item(&self, f: @fn(&ast::view_item) -> bool) -> bool;
 560 }
 561
 562 impl EachViewItem for ast::crate {
 563     fn each_view_item(&self, f: @fn(&ast::view_item) -> bool) -> bool {
 564         let broke = @mut false;
 565         let vtor: visit::vt<()> = visit::mk_simple_visitor(@visit::SimpleVisitor {
 566             visit_view_item: |vi| { *broke = f(vi); }, ..*visit::default_simple_visitor()
 567         });
 568         visit::visit_crate(self, ((), vtor));
 569         true
 570     }
 571 }
 572
 573 pub fn view_path_id(p: &view_path) -> node_id {
 574     match p.node {
 575       view_path_simple(_, _, id) |
 576       view_path_glob(_, id) |
 577       view_path_list(_, _, id) => id
 578     }
 579 }
 580
 581 /// Returns true if the given struct def is tuple-like; i.e. that its fields
 582 /// are unnamed.
 583 pub fn struct_def_is_tuple_like(struct_def: @ast::struct_def) -> bool {
 584     struct_def.ctor_id.is_some()
 585 }
 586
 587 pub fn visibility_to_privacy(visibility: visibility) -> Privacy {
 588     match visibility {
 589         public => Public,
 590         inherited | private => Private
 591     }
 592 }
 593
 594 pub fn variant_visibility_to_privacy(visibility: visibility,
 595                                      enclosing_is_public: bool)
 596                                   -> Privacy {
 597     if enclosing_is_public {
 598         match visibility {
 599             public | inherited => Public,
 600             private => Private
 601         }
 602     } else {
 603         visibility_to_privacy(visibility)
 604     }
 605 }
 606
 607 #[deriving(Eq)]
 608 pub enum Privacy {
 609     Private,
 610     Public
 611 }
 612
 613 /// Returns true if the given pattern consists solely of an identifier
 614 /// and false otherwise.
 615 pub fn pat_is_ident(pat: @ast::pat) -> bool {
 616     match pat.node {
 617         ast::pat_ident(*) => true,
 618         _ => false,
 619     }
 620 }
 621
 622 // HYGIENE FUNCTIONS
 623
 624 /// Construct an identifier with the given name and an empty context:
 625 pub fn new_ident(name: Name) -> ident { ident {name: name, ctxt: 0}}
 626
 627 /// Extend a syntax context with a given mark
 628 pub fn new_mark(m:Mrk, tail:SyntaxContext) -> SyntaxContext {
 629     new_mark_internal(m,tail,get_sctable())
 630 }
 631
 632 // Extend a syntax context with a given mark and table
 633 // FIXME #4536 : currently pub to allow testing
 634 pub fn new_mark_internal(m:Mrk, tail:SyntaxContext,table:&mut SCTable)
 635     -> SyntaxContext {
 636     let key = (tail,m);
 637     // FIXME #5074 : can't use more natural style because we're missing
 638     // flow-sensitivity. Results in two lookups on a hash table hit.
 639     // also applies to new_rename_internal, below.
 640     // let try_lookup = table.mark_memo.find(&key);
 641     match table.mark_memo.contains_key(&key) {
 642         false => {
 643             let new_idx = idx_push(&mut table.table,Mark(m,tail));
 644             table.mark_memo.insert(key,new_idx);
 645             new_idx
 646         }
 647         true => {
 648             match table.mark_memo.find(&key) {
 649                 None => fail!(~"internal error: key disappeared 2013042901"),
 650                 Some(idxptr) => {*idxptr}
 651             }
 652         }
 653     }
 654 }
 655
 656 /// Extend a syntax context with a given rename
 657 pub fn new_rename(id:ident, to:Name, tail:SyntaxContext) -> SyntaxContext {
 658     new_rename_internal(id, to, tail, get_sctable())
 659 }
 660
 661 // Extend a syntax context with a given rename and sctable
 662 // FIXME #4536 : currently pub to allow testing
 663 pub fn new_rename_internal(id:ident, to:Name, tail:SyntaxContext, table: &mut SCTable)
 664     -> SyntaxContext {
 665     let key = (tail,id,to);
 666     // FIXME #5074
 667     //let try_lookup = table.rename_memo.find(&key);
 668     match table.rename_memo.contains_key(&key) {
 669         false => {
 670             let new_idx = idx_push(&mut table.table,Rename(id,to,tail));
 671             table.rename_memo.insert(key,new_idx);
 672             new_idx
 673         }
 674         true => {
 675             match table.rename_memo.find(&key) {
 676                 None => fail!(~"internal error: key disappeared 2013042902"),
 677                 Some(idxptr) => {*idxptr}
 678             }
 679         }
 680     }
 681 }
 682
 683 /// Make a fresh syntax context table with EmptyCtxt in slot zero
 684 /// and IllegalCtxt in slot one.
 685 // FIXME #4536 : currently pub to allow testing
 686 pub fn new_sctable_internal() -> SCTable {
 687     SCTable {
 688         table: ~[EmptyCtxt,IllegalCtxt],
 689         mark_memo: HashMap::new(),
 690         rename_memo: HashMap::new()
 691     }
 692 }
 693
 694 // fetch the SCTable from TLS, create one if it doesn't yet exist.
 695 pub fn get_sctable() -> @mut SCTable {
 696     unsafe {
 697         let sctable_key = (cast::transmute::<(uint, uint),
 698                            &fn:Copy(v: @@mut SCTable)>(
 699                                (-4 as uint, 0u)));
 700         match local_data::local_data_get(sctable_key) {
 701             None => {
 702                 let new_table = @@mut new_sctable_internal();
 703                 local_data::local_data_set(sctable_key,new_table);
 704                 *new_table
 705             },
 706             Some(intr) => *intr
 707         }
 708     }
 709 }
 710
 711 /// Add a value to the end of a vec, return its index
 712 fn idx_push<T>(vec: &mut ~[T], val: T) -> uint {
 713     vec.push(val);
 714     vec.len() - 1
 715 }
 716
 717 /// Resolve a syntax object to a name, per MTWT.
 718 pub fn resolve(id : ident) -> Name {
 719     resolve_internal(id, get_sctable())
 720 }
 721
 722 // Resolve a syntax object to a name, per MTWT.
 723 // FIXME #4536 : currently pub to allow testing
 724 pub fn resolve_internal(id : ident, table : &mut SCTable) -> Name {
 725     match table.table[id.ctxt] {
 726         EmptyCtxt => id.name,
 727         // ignore marks here:
 728         Mark(_,subctxt) => resolve_internal(ident{name:id.name, ctxt: subctxt},table),
 729         // do the rename if necessary:
 730         Rename(ident{name,ctxt},toname,subctxt) => {
 731             // this could be cached or computed eagerly:
 732             let resolvedfrom = resolve_internal(ident{name:name,ctxt:ctxt},table);
 733             let resolvedthis = resolve_internal(ident{name:id.name,ctxt:subctxt},table);
 734             if ((resolvedthis == resolvedfrom)
 735                 && (marksof(ctxt,resolvedthis,table)
 736                     == marksof(subctxt,resolvedthis,table))) {
 737                 toname
 738             } else {
 739                 resolvedthis
 740             }
 741         }
 742         IllegalCtxt() => fail!(~"expected resolvable context, got IllegalCtxt")
 743     }
 744 }
 745
 746 /// Compute the marks associated with a syntax context.
 747 // it's not clear to me whether it's better to use a [] mutable
 748 // vector or a cons-list for this.
 749 pub fn marksof(ctxt: SyntaxContext, stopname: Name, table: &SCTable) -> ~[Mrk] {
 750     let mut result = ~[];
 751     let mut loopvar = ctxt;
 752     loop {
 753         match table.table[loopvar] {
 754             EmptyCtxt => {return result;},
 755             Mark(mark,tl) => {
 756                 xorPush(&mut result,mark);
 757                 loopvar = tl;
 758             },
 759             Rename(_,name,tl) => {
 760                 // see MTWT for details on the purpose of the stopname.
 761                 // short version: it prevents duplication of effort.
 762                 if (name == stopname) {
 763                     return result;
 764                 } else {
 765                     loopvar = tl;
 766                 }
 767             }
 768             IllegalCtxt => fail!(~"expected resolvable context, got IllegalCtxt")
 769         }
 770     }
 771 }
 772
 773 /// Push a name... unless it matches the one on top, in which
 774 /// case pop and discard (so two of the same marks cancel)
 775 pub fn xorPush(marks: &mut ~[uint], mark: uint) {
 776     if ((marks.len() > 0) && (getLast(marks) == mark)) {
 777         marks.pop();
 778     } else {
 779         marks.push(mark);
 780     }
 781 }
 782
 783 // get the last element of a mutable array.
 784 // FIXME #4903: , must be a separate procedure for now.
 785 pub fn getLast(arr: &~[Mrk]) -> uint {
 786     *arr.last()
 787 }
 788
 789
 790 #[cfg(test)]
 791 mod test {
 792     use ast::*;
 793     use super::*;
 794     use std::io;
 795
 796     #[test] fn xorpush_test () {
 797         let mut s = ~[];
 798         xorPush(&mut s,14);
 799         assert_eq!(copy s,~[14]);
 800         xorPush(&mut s,14);
 801         assert_eq!(copy s,~[]);
 802         xorPush(&mut s,14);
 803         assert_eq!(copy s,~[14]);
 804         xorPush(&mut s,15);
 805         assert_eq!(copy s,~[14,15]);
 806         xorPush (&mut s,16);
 807         assert_eq!(copy s,~[14,15,16]);
 808         xorPush (&mut s,16);
 809         assert_eq!(copy s,~[14,15]);
 810         xorPush (&mut s,15);
 811         assert_eq!(copy s,~[14]);
 812     }
 813
 814     // convert a list of uints to an @[ident]
 815     // (ignores the interner completely)
 816     fn uints_to_idents (uints: &~[uint]) -> @~[ident] {
 817         @uints.map(|u| ident {name:*u, ctxt: empty_ctxt})
 818     }
 819
 820     fn id (u : uint, s: SyntaxContext) -> ident {
 821         ident{name:u, ctxt: s}
 822     }
 823
 824     // because of the SCTable, I now need a tidy way of
 825     // creating syntax objects. Sigh.
 826     #[deriving(Eq)]
 827     enum TestSC {
 828         M(Mrk),
 829         R(ident,Name)
 830     }
 831
 832     // unfold a vector of TestSC values into a SCTable,
 833     // returning the resulting index
 834     fn unfold_test_sc(tscs : ~[TestSC], tail: SyntaxContext, table : &mut SCTable)
 835         -> SyntaxContext {
 836         tscs.rev_iter().fold(tail, |tail : SyntaxContext, tsc : &TestSC|
 837                   {match *tsc {
 838                       M(mrk) => new_mark_internal(mrk,tail,table),
 839                       R(ident,name) => new_rename_internal(ident,name,tail,table)}})
 840     }
 841
 842     // gather a SyntaxContext back into a vector of TestSCs
 843     fn refold_test_sc(mut sc: SyntaxContext, table : &SCTable) -> ~[TestSC] {
 844         let mut result = ~[];
 845         loop {
 846             match table.table[sc] {
 847                 EmptyCtxt => {return result;},
 848                 Mark(mrk,tail) => {
 849                     result.push(M(mrk));
 850                     sc = tail;
 851                     loop;
 852                 },
 853                 Rename(id,name,tail) => {
 854                     result.push(R(id,name));
 855                     sc = tail;
 856                     loop;
 857                 }
 858                 IllegalCtxt => fail!("expected resolvable context, got IllegalCtxt")
 859             }
 860         }
 861     }
 862
 863     #[test] fn test_unfold_refold(){
 864         let mut t = new_sctable_internal();
 865
 866         let test_sc = ~[M(3),R(id(101,0),14),M(9)];
 867         assert_eq!(unfold_test_sc(copy test_sc,empty_ctxt,&mut t),4);
 868         assert_eq!(t.table[2],Mark(9,0));
 869         assert_eq!(t.table[3],Rename(id(101,0),14,2));
 870         assert_eq!(t.table[4],Mark(3,3));
 871         assert_eq!(refold_test_sc(4,&t),test_sc);
 872     }
 873
 874     // extend a syntax context with a sequence of marks given
 875     // in a vector. v[0] will be the outermost mark.
 876     fn unfold_marks(mrks:~[Mrk],tail:SyntaxContext,table: &mut SCTable) -> SyntaxContext {
 877         mrks.rev_iter().fold(tail, |tail:SyntaxContext, mrk:&Mrk|
 878                    {new_mark_internal(*mrk,tail,table)})
 879     }
 880
 881     #[test] fn unfold_marks_test() {
 882         let mut t = new_sctable_internal();
 883
 884         assert_eq!(unfold_marks(~[3,7],empty_ctxt,&mut t),3);
 885         assert_eq!(t.table[2],Mark(7,0));
 886         assert_eq!(t.table[3],Mark(3,2));
 887     }
 888
 889     #[test] fn test_marksof () {
 890         let stopname = 242;
 891         let name1 = 243;
 892         let mut t = new_sctable_internal();
 893         assert_eq!(marksof (empty_ctxt,stopname,&t),~[]);
 894         // FIXME #5074: ANF'd to dodge nested calls
 895         { let ans = unfold_marks(~[4,98],empty_ctxt,&mut t);
 896          assert_eq! (marksof (ans,stopname,&t),~[4,98]);}
 897         // does xoring work?
 898         { let ans = unfold_marks(~[5,5,16],empty_ctxt,&mut t);
 899          assert_eq! (marksof (ans,stopname,&t), ~[16]);}
 900         // does nested xoring work?
 901         { let ans = unfold_marks(~[5,10,10,5,16],empty_ctxt,&mut t);
 902          assert_eq! (marksof (ans, stopname,&t), ~[16]);}
 903         // rename where stop doesn't match:
 904         { let chain = ~[M(9),
 905                         R(id(name1,
 906                              new_mark_internal (4, empty_ctxt,&mut t)),
 907                           100101102),
 908                         M(14)];
 909          let ans = unfold_test_sc(chain,empty_ctxt,&mut t);
 910          assert_eq! (marksof (ans, stopname, &t), ~[9,14]);}
 911         // rename where stop does match
 912         { let name1sc = new_mark_internal(4, empty_ctxt, &mut t);
 913          let chain = ~[M(9),
 914                        R(id(name1, name1sc),
 915                          stopname),
 916                        M(14)];
 917          let ans = unfold_test_sc(chain,empty_ctxt,&mut t);
 918          assert_eq! (marksof (ans, stopname, &t), ~[9]); }
 919     }
 920
 921
 922     #[test] fn resolve_tests () {
 923         let a = 40;
 924         let mut t = new_sctable_internal();
 925         // - ctxt is MT
 926         assert_eq!(resolve_internal(id(a,empty_ctxt),&mut t),a);
 927         // - simple ignored marks
 928         { let sc = unfold_marks(~[1,2,3],empty_ctxt,&mut t);
 929          assert_eq!(resolve_internal(id(a,sc),&mut t),a);}
 930         // - orthogonal rename where names don't match
 931         { let sc = unfold_test_sc(~[R(id(50,empty_ctxt),51),M(12)],empty_ctxt,&mut t);
 932          assert_eq!(resolve_internal(id(a,sc),&mut t),a);}
 933         // - rename where names do match, but marks don't
 934         { let sc1 = new_mark_internal(1,empty_ctxt,&mut t);
 935          let sc = unfold_test_sc(~[R(id(a,sc1),50),
 936                                    M(1),
 937                                    M(2)],
 938                                  empty_ctxt,&mut t);
 939         assert_eq!(resolve_internal(id(a,sc),&mut t), a);}
 940         // - rename where names and marks match
 941         { let sc1 = unfold_test_sc(~[M(1),M(2)],empty_ctxt,&mut t);
 942          let sc = unfold_test_sc(~[R(id(a,sc1),50),M(1),M(2)],empty_ctxt,&mut t);
 943          assert_eq!(resolve_internal(id(a,sc),&mut t), 50); }
 944         // - rename where names and marks match by literal sharing
 945         { let sc1 = unfold_test_sc(~[M(1),M(2)],empty_ctxt,&mut t);
 946          let sc = unfold_test_sc(~[R(id(a,sc1),50)],sc1,&mut t);
 947          assert_eq!(resolve_internal(id(a,sc),&mut t), 50); }
 948         // - two renames of the same var.. can only happen if you use
 949         // local-expand to prevent the inner binding from being renamed
 950         // during the rename-pass caused by the first:
 951         io::println("about to run bad test");
 952         { let sc = unfold_test_sc(~[R(id(a,empty_ctxt),50),
 953                                     R(id(a,empty_ctxt),51)],
 954                                   empty_ctxt,&mut t);
 955          assert_eq!(resolve_internal(id(a,sc),&mut t), 51); }
 956         // the simplest double-rename:
 957         { let a_to_a50 = new_rename_internal(id(a,empty_ctxt),50,empty_ctxt,&mut t);
 958          let a50_to_a51 = new_rename_internal(id(a,a_to_a50),51,a_to_a50,&mut t);
 959          assert_eq!(resolve_internal(id(a,a50_to_a51),&mut t),51);
 960          // mark on the outside doesn't stop rename:
 961          let sc = new_mark_internal(9,a50_to_a51,&mut t);
 962          assert_eq!(resolve_internal(id(a,sc),&mut t),51);
 963          // but mark on the inside does:
 964          let a50_to_a51_b = unfold_test_sc(~[R(id(a,a_to_a50),51),
 965                                               M(9)],
 966                                            a_to_a50,
 967                                            &mut t);
 968          assert_eq!(resolve_internal(id(a,a50_to_a51_b),&mut t),50);}
 969     }
 970
 971     #[test] fn hashing_tests () {
 972         let mut t = new_sctable_internal();
 973         assert_eq!(new_mark_internal(12,empty_ctxt,&mut t),2);
 974         assert_eq!(new_mark_internal(13,empty_ctxt,&mut t),3);
 975         // using the same one again should result in the same index:
 976         assert_eq!(new_mark_internal(12,empty_ctxt,&mut t),2);
 977         // I'm assuming that the rename table will behave the same....
 978     }
 979
 980 }