1 // Copyright 2012-2014 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.
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.
11 //! Machinery for hygienic macros, as described in the MTWT[1] paper.
13 //! [1] Matthew Flatt, Ryan Culpepper, David Darais, and Robert Bruce Findler.
14 //! 2012. *Macros that work together: Compile-time bindings, partial expansion,
15 //! and definition contexts*. J. Funct. Program. 22, 2 (March 2012), 181-216.
16 //! DOI=10.1017/S0956796812000093 http://dx.doi.org/10.1017/S0956796812000093
18 pub use self::SyntaxContext_::*;
20 use ast::{Ident, Mrk, Name, SyntaxContext};
22 use std::cell::RefCell;
23 use std::collections::HashMap;
25 /// The SCTable contains a table of SyntaxContext_'s. It
26 /// represents a flattened tree structure, to avoid having
27 /// managed pointers everywhere (that caused an ICE).
28 /// the mark_memo and rename_memo fields are side-tables
29 /// that ensure that adding the same mark to the same context
30 /// gives you back the same context as before. This shouldn't
31 /// change the semantics--everything here is immutable--but
32 /// it should cut down on memory use *a lot*; applying a mark
33 /// to a tree containing 50 identifiers would otherwise generate
36 table: RefCell<Vec<SyntaxContext_>>,
37 mark_memo: RefCell<HashMap<(SyntaxContext,Mrk),SyntaxContext>>,
38 // The pair (Name,SyntaxContext) is actually one Ident, but it needs to be hashed and
39 // compared as pair (name, ctxt) and not as an Ident
40 rename_memo: RefCell<HashMap<(SyntaxContext,(Name,SyntaxContext),Name),SyntaxContext>>,
43 #[derive(PartialEq, RustcEncodable, RustcDecodable, Hash, Debug, Copy, Clone)]
44 pub enum SyntaxContext_ {
46 Mark (Mrk,SyntaxContext),
47 /// flattening the name and syntaxcontext into the rename...
48 /// HIDDEN INVARIANTS:
49 /// 1) the first name in a Rename node
50 /// can only be a programmer-supplied name.
51 /// 2) Every Rename node with a given Name in the
52 /// "to" slot must have the same name and context
53 /// in the "from" slot. In essence, they're all
54 /// pointers to a single "rename" event node.
55 Rename (Ident,Name,SyntaxContext),
56 /// actually, IllegalCtxt may not be necessary.
60 /// A list of ident->name renamings
61 pub type RenameList = Vec<(Ident, Name)>;
63 /// Extend a syntax context with a given mark
64 pub fn apply_mark(m: Mrk, ctxt: SyntaxContext) -> SyntaxContext {
65 with_sctable(|table| apply_mark_internal(m, ctxt, table))
68 /// Extend a syntax context with a given mark and sctable (explicit memoization)
69 fn apply_mark_internal(m: Mrk, ctxt: SyntaxContext, table: &SCTable) -> SyntaxContext {
71 *table.mark_memo.borrow_mut().entry(key).or_insert_with(|| {
72 SyntaxContext(idx_push(&mut *table.table.borrow_mut(), Mark(m, ctxt)))
76 /// Extend a syntax context with a given rename
77 pub fn apply_rename(id: Ident, to:Name,
78 ctxt: SyntaxContext) -> SyntaxContext {
79 with_sctable(|table| apply_rename_internal(id, to, ctxt, table))
82 /// Extend a syntax context with a given rename and sctable (explicit memoization)
83 fn apply_rename_internal(id: Ident,
86 table: &SCTable) -> SyntaxContext {
87 let key = (ctxt, (id.name, id.ctxt), to);
89 *table.rename_memo.borrow_mut().entry(key).or_insert_with(|| {
90 SyntaxContext(idx_push(&mut *table.table.borrow_mut(), Rename(id, to, ctxt)))
94 /// Apply a list of renamings to a context
95 // if these rename lists get long, it would make sense
96 // to consider memoizing this fold. This may come up
97 // when we add hygiene to item names.
98 pub fn apply_renames(renames: &RenameList, ctxt: SyntaxContext) -> SyntaxContext {
99 renames.iter().fold(ctxt, |ctxt, &(from, to)| {
100 apply_rename(from, to, ctxt)
104 /// Fetch the SCTable from TLS, create one if it doesn't yet exist.
105 pub fn with_sctable<T, F>(op: F) -> T where
106 F: FnOnce(&SCTable) -> T,
108 thread_local!(static SCTABLE_KEY: SCTable = new_sctable_internal());
109 SCTABLE_KEY.with(move |slot| op(slot))
112 // Make a fresh syntax context table with EmptyCtxt in slot zero
113 // and IllegalCtxt in slot one.
114 fn new_sctable_internal() -> SCTable {
116 table: RefCell::new(vec!(EmptyCtxt, IllegalCtxt)),
117 mark_memo: RefCell::new(HashMap::new()),
118 rename_memo: RefCell::new(HashMap::new()),
122 /// Print out an SCTable for debugging
123 pub fn display_sctable(table: &SCTable) {
125 for (idx,val) in table.table.borrow().iter().enumerate() {
126 error!("{:4} : {:?}",idx,val);
130 /// Clear the tables from TLD to reclaim memory.
131 pub fn clear_tables() {
132 with_sctable(|table| {
133 *table.table.borrow_mut() = Vec::new();
134 *table.mark_memo.borrow_mut() = HashMap::new();
135 *table.rename_memo.borrow_mut() = HashMap::new();
137 with_resolve_table_mut(|table| *table = HashMap::new());
140 /// Reset the tables to their initial state
141 pub fn reset_tables() {
142 with_sctable(|table| {
143 *table.table.borrow_mut() = vec!(EmptyCtxt, IllegalCtxt);
144 *table.mark_memo.borrow_mut() = HashMap::new();
145 *table.rename_memo.borrow_mut() = HashMap::new();
147 with_resolve_table_mut(|table| *table = HashMap::new());
150 /// Add a value to the end of a vec, return its index
151 fn idx_push<T>(vec: &mut Vec<T>, val: T) -> u32 {
153 (vec.len() - 1) as u32
156 /// Resolve a syntax object to a name, per MTWT.
157 pub fn resolve(id: Ident) -> Name {
158 with_sctable(|sctable| {
159 with_resolve_table_mut(|resolve_table| {
160 resolve_internal(id, sctable, resolve_table)
165 type ResolveTable = HashMap<(Name,SyntaxContext),Name>;
167 // okay, I admit, putting this in TLS is not so nice:
168 // fetch the SCTable from TLS, create one if it doesn't yet exist.
169 fn with_resolve_table_mut<T, F>(op: F) -> T where
170 F: FnOnce(&mut ResolveTable) -> T,
172 thread_local!(static RESOLVE_TABLE_KEY: RefCell<ResolveTable> = {
173 RefCell::new(HashMap::new())
176 RESOLVE_TABLE_KEY.with(move |slot| op(&mut *slot.borrow_mut()))
179 /// Resolve a syntax object to a name, per MTWT.
180 /// adding memoization to resolve 500+ seconds in resolve for librustc (!)
181 fn resolve_internal(id: Ident,
183 resolve_table: &mut ResolveTable) -> Name {
184 let key = (id.name, id.ctxt);
186 match resolve_table.get(&key) {
187 Some(&name) => return name,
192 let result = (*table.table.borrow())[id.ctxt.0 as usize];
194 EmptyCtxt => id.name,
195 // ignore marks here:
197 resolve_internal(Ident::new(id.name, subctxt),
198 table, resolve_table),
199 // do the rename if necessary:
200 Rename(Ident{name, ctxt}, toname, subctxt) => {
202 resolve_internal(Ident::new(name, ctxt),
203 table, resolve_table);
205 resolve_internal(Ident::new(id.name, subctxt),
206 table, resolve_table);
207 if (resolvedthis == resolvedfrom)
208 && (marksof_internal(ctxt, resolvedthis, table)
209 == marksof_internal(subctxt, resolvedthis, table)) {
215 IllegalCtxt => panic!("expected resolvable context, got IllegalCtxt")
218 resolve_table.insert(key, resolved);
222 /// Compute the marks associated with a syntax context.
223 pub fn marksof(ctxt: SyntaxContext, stopname: Name) -> Vec<Mrk> {
224 with_sctable(|table| marksof_internal(ctxt, stopname, table))
227 // the internal function for computing marks
228 // it's not clear to me whether it's better to use a [] mutable
229 // vector or a cons-list for this.
230 fn marksof_internal(ctxt: SyntaxContext,
232 table: &SCTable) -> Vec<Mrk> {
233 let mut result = Vec::new();
234 let mut loopvar = ctxt;
236 let table_entry = (*table.table.borrow())[loopvar.0 as usize];
242 xor_push(&mut result, mark);
245 Rename(_,name,tl) => {
246 // see MTWT for details on the purpose of the stopname.
247 // short version: it prevents duplication of effort.
248 if name == stopname {
254 IllegalCtxt => panic!("expected resolvable context, got IllegalCtxt")
259 /// Return the outer mark for a context with a mark at the outside.
260 /// FAILS when outside is not a mark.
261 pub fn outer_mark(ctxt: SyntaxContext) -> Mrk {
262 with_sctable(|sctable| {
263 match (*sctable.table.borrow())[ctxt.0 as usize] {
265 _ => panic!("can't retrieve outer mark when outside is not a mark")
270 /// Push a name... unless it matches the one on top, in which
271 /// case pop and discard (so two of the same marks cancel)
272 fn xor_push(marks: &mut Vec<Mrk>, mark: Mrk) {
273 if (!marks.is_empty()) && (*marks.last().unwrap() == mark) {
274 marks.pop().unwrap();
283 use ast::{EMPTY_CTXT, Ident, Mrk, Name, SyntaxContext};
284 use super::{resolve, xor_push, apply_mark_internal, new_sctable_internal};
285 use super::{apply_rename_internal, apply_renames, marksof_internal, resolve_internal};
286 use super::{SCTable, EmptyCtxt, Mark, Rename, IllegalCtxt};
287 use std::collections::HashMap;
291 let mut s = Vec::new();
292 xor_push(&mut s, 14);
293 assert_eq!(s.clone(), [14]);
294 xor_push(&mut s, 14);
295 assert_eq!(s.clone(), []);
296 xor_push(&mut s, 14);
297 assert_eq!(s.clone(), [14]);
298 xor_push(&mut s, 15);
299 assert_eq!(s.clone(), [14, 15]);
300 xor_push(&mut s, 16);
301 assert_eq!(s.clone(), [14, 15, 16]);
302 xor_push(&mut s, 16);
303 assert_eq!(s.clone(), [14, 15]);
304 xor_push(&mut s, 15);
305 assert_eq!(s.clone(), [14]);
308 fn id(n: u32, s: SyntaxContext) -> Ident {
309 Ident::new(Name(n), s)
312 // because of the SCTable, I now need a tidy way of
313 // creating syntax objects. Sigh.
314 #[derive(Clone, PartialEq, Debug)]
320 // unfold a vector of TestSC values into a SCTable,
321 // returning the resulting index
322 fn unfold_test_sc(tscs : Vec<TestSC> , tail: SyntaxContext, table: &SCTable)
324 tscs.iter().rev().fold(tail, |tail : SyntaxContext, tsc : &TestSC|
326 M(mrk) => apply_mark_internal(mrk,tail,table),
327 R(ident,name) => apply_rename_internal(ident,name,tail,table)}})
330 // gather a SyntaxContext back into a vector of TestSCs
331 fn refold_test_sc(mut sc: SyntaxContext, table : &SCTable) -> Vec<TestSC> {
332 let mut result = Vec::new();
334 let table = table.table.borrow();
335 match (*table)[sc.0 as usize] {
336 EmptyCtxt => {return result;},
342 Rename(id,name,tail) => {
343 result.push(R(id,name));
347 IllegalCtxt => panic!("expected resolvable context, got IllegalCtxt")
353 fn test_unfold_refold(){
354 let mut t = new_sctable_internal();
356 let test_sc = vec!(M(3),R(id(101,EMPTY_CTXT),Name(14)),M(9));
357 assert_eq!(unfold_test_sc(test_sc.clone(),EMPTY_CTXT,&mut t),SyntaxContext(4));
359 let table = t.table.borrow();
360 assert!((*table)[2] == Mark(9,EMPTY_CTXT));
361 assert!((*table)[3] == Rename(id(101,EMPTY_CTXT),Name(14),SyntaxContext(2)));
362 assert!((*table)[4] == Mark(3,SyntaxContext(3)));
364 assert_eq!(refold_test_sc(SyntaxContext(4),&t),test_sc);
367 // extend a syntax context with a sequence of marks given
368 // in a vector. v[0] will be the outermost mark.
369 fn unfold_marks(mrks: Vec<Mrk> , tail: SyntaxContext, table: &SCTable)
371 mrks.iter().rev().fold(tail, |tail:SyntaxContext, mrk:&Mrk|
372 {apply_mark_internal(*mrk,tail,table)})
375 #[test] fn unfold_marks_test() {
376 let mut t = new_sctable_internal();
378 assert_eq!(unfold_marks(vec!(3,7),EMPTY_CTXT,&mut t),SyntaxContext(3));
380 let table = t.table.borrow();
381 assert!((*table)[2] == Mark(7,EMPTY_CTXT));
382 assert!((*table)[3] == Mark(3,SyntaxContext(2)));
388 let stopname = Name(242);
389 let name1 = Name(243);
390 let mut t = new_sctable_internal();
391 assert_eq!(marksof_internal (EMPTY_CTXT,stopname,&t),Vec::new());
392 // FIXME #5074: ANF'd to dodge nested calls
393 { let ans = unfold_marks(vec!(4,98),EMPTY_CTXT,&mut t);
394 assert_eq! (marksof_internal (ans,stopname,&t), [4, 98]);}
396 { let ans = unfold_marks(vec!(5,5,16),EMPTY_CTXT,&mut t);
397 assert_eq! (marksof_internal (ans,stopname,&t), [16]);}
398 // does nested xoring work?
399 { let ans = unfold_marks(vec!(5,10,10,5,16),EMPTY_CTXT,&mut t);
400 assert_eq! (marksof_internal (ans, stopname,&t), [16]);}
401 // rename where stop doesn't match:
402 { let chain = vec!(M(9),
404 apply_mark_internal (4, EMPTY_CTXT,&mut t)),
407 let ans = unfold_test_sc(chain,EMPTY_CTXT,&mut t);
408 assert_eq! (marksof_internal (ans, stopname, &t), [9, 14]);}
409 // rename where stop does match
410 { let name1sc = apply_mark_internal(4, EMPTY_CTXT, &mut t);
411 let chain = vec!(M(9),
412 R(id(name1.0, name1sc),
415 let ans = unfold_test_sc(chain,EMPTY_CTXT,&mut t);
416 assert_eq! (marksof_internal (ans, stopname, &t), [9]); }
421 fn resolve_tests () {
423 let mut t = new_sctable_internal();
424 let mut rt = HashMap::new();
426 assert_eq!(resolve_internal(id(a,EMPTY_CTXT),&mut t, &mut rt),Name(a));
427 // - simple ignored marks
428 { let sc = unfold_marks(vec!(1,2,3),EMPTY_CTXT,&mut t);
429 assert_eq!(resolve_internal(id(a,sc),&mut t, &mut rt),Name(a));}
430 // - orthogonal rename where names don't match
431 { let sc = unfold_test_sc(vec!(R(id(50,EMPTY_CTXT),Name(51)),M(12)),EMPTY_CTXT,&mut t);
432 assert_eq!(resolve_internal(id(a,sc),&mut t, &mut rt),Name(a));}
433 // - rename where names do match, but marks don't
434 { let sc1 = apply_mark_internal(1,EMPTY_CTXT,&mut t);
435 let sc = unfold_test_sc(vec!(R(id(a,sc1),Name(50)),
439 assert_eq!(resolve_internal(id(a,sc),&mut t, &mut rt), Name(a));}
440 // - rename where names and marks match
441 { let sc1 = unfold_test_sc(vec!(M(1),M(2)),EMPTY_CTXT,&mut t);
442 let sc = unfold_test_sc(vec!(R(id(a,sc1),Name(50)),M(1),M(2)),EMPTY_CTXT,&mut t);
443 assert_eq!(resolve_internal(id(a,sc),&mut t, &mut rt), Name(50)); }
444 // - rename where names and marks match by literal sharing
445 { let sc1 = unfold_test_sc(vec!(M(1),M(2)),EMPTY_CTXT,&mut t);
446 let sc = unfold_test_sc(vec!(R(id(a,sc1),Name(50))),sc1,&mut t);
447 assert_eq!(resolve_internal(id(a,sc),&mut t, &mut rt), Name(50)); }
448 // - two renames of the same var.. can only happen if you use
449 // local-expand to prevent the inner binding from being renamed
450 // during the rename-pass caused by the first:
451 println!("about to run bad test");
452 { let sc = unfold_test_sc(vec!(R(id(a,EMPTY_CTXT),Name(50)),
453 R(id(a,EMPTY_CTXT),Name(51))),
455 assert_eq!(resolve_internal(id(a,sc),&mut t, &mut rt), Name(51)); }
456 // the simplest double-rename:
457 { let a_to_a50 = apply_rename_internal(id(a,EMPTY_CTXT),Name(50),EMPTY_CTXT,&mut t);
458 let a50_to_a51 = apply_rename_internal(id(a,a_to_a50),Name(51),a_to_a50,&mut t);
459 assert_eq!(resolve_internal(id(a,a50_to_a51),&mut t, &mut rt),Name(51));
460 // mark on the outside doesn't stop rename:
461 let sc = apply_mark_internal(9,a50_to_a51,&mut t);
462 assert_eq!(resolve_internal(id(a,sc),&mut t, &mut rt),Name(51));
463 // but mark on the inside does:
464 let a50_to_a51_b = unfold_test_sc(vec!(R(id(a,a_to_a50),Name(51)),
468 assert_eq!(resolve_internal(id(a,a50_to_a51_b),&mut t, &mut rt),Name(50));}
472 fn mtwt_resolve_test(){
474 assert_eq!(resolve(id(a,EMPTY_CTXT)),Name(a));
479 fn hashing_tests () {
480 let mut t = new_sctable_internal();
481 assert_eq!(apply_mark_internal(12,EMPTY_CTXT,&mut t),SyntaxContext(2));
482 assert_eq!(apply_mark_internal(13,EMPTY_CTXT,&mut t),SyntaxContext(3));
483 // using the same one again should result in the same index:
484 assert_eq!(apply_mark_internal(12,EMPTY_CTXT,&mut t),SyntaxContext(2));
485 // I'm assuming that the rename table will behave the same....
489 fn resolve_table_hashing_tests() {
490 let mut t = new_sctable_internal();
491 let mut rt = HashMap::new();
492 assert_eq!(rt.len(),0);
493 resolve_internal(id(30,EMPTY_CTXT),&mut t, &mut rt);
494 assert_eq!(rt.len(),1);
495 resolve_internal(id(39,EMPTY_CTXT),&mut t, &mut rt);
496 assert_eq!(rt.len(),2);
497 resolve_internal(id(30,EMPTY_CTXT),&mut t, &mut rt);
498 assert_eq!(rt.len(),2);
502 fn new_resolves_test() {
503 let renames = vec!((Ident::with_empty_ctxt(Name(23)),Name(24)),
504 (Ident::with_empty_ctxt(Name(29)),Name(29)));
505 let new_ctxt1 = apply_renames(&renames,EMPTY_CTXT);
506 assert_eq!(resolve(Ident::new(Name(23),new_ctxt1)),Name(24));
507 assert_eq!(resolve(Ident::new(Name(29),new_ctxt1)),Name(29));