rust/src/libsyntax/ext/mtwt.rs

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// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Machinery for hygienic macros, as described in the MTWT[1] paper.
//!
//! [1] Matthew Flatt, Ryan Culpepper, David Darais, and Robert Bruce Findler.
//! 2012. *Macros that work together: Compile-time bindings, partial expansion,
//! and definition contexts*. J. Funct. Program. 22, 2 (March 2012), 181-216.
//! DOI=10.1017/S0956796812000093 http://dx.doi.org/10.1017/S0956796812000093
pub use self::SyntaxContext_::*;
use ast::{Ident, Mrk, Name, SyntaxContext};
use std::cell::RefCell;
use std::collections::HashMap;
use std::collections::hash_map::Entry::{Occupied, Vacant};
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/// The SCTable contains a table of SyntaxContext_'s. It
/// represents a flattened tree structure, to avoid having
/// managed pointers everywhere (that caused an ICE).
/// the mark_memo and rename_memo fields are side-tables
/// that ensure that adding the same mark to the same context
/// gives you back the same context as before. This shouldn't
/// change the semantics--everything here is immutable--but
/// it should cut down on memory use *a lot*; applying a mark
/// to a tree containing 50 identifiers would otherwise generate
/// 50 new contexts
pub struct SCTable {
table: RefCell<Vec<SyntaxContext_>>,
mark_memo: RefCell<HashMap<(SyntaxContext,Mrk),SyntaxContext>>,
rename_memo: RefCell<HashMap<(SyntaxContext,Ident,Name),SyntaxContext>>,
}
#[deriving(PartialEq, RustcEncodable, RustcDecodable, Hash, Show, Copy)]
pub enum SyntaxContext_ {
EmptyCtxt,
Mark (Mrk,SyntaxContext),
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/// flattening the name and syntaxcontext into the rename...
/// HIDDEN INVARIANTS:
/// 1) the first name in a Rename node
/// can only be a programmer-supplied name.
/// 2) Every Rename node with a given Name in the
/// "to" slot must have the same name and context
/// in the "from" slot. In essence, they're all
/// pointers to a single "rename" event node.
Rename (Ident,Name,SyntaxContext),
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/// actually, IllegalCtxt may not be necessary.
IllegalCtxt
}
/// A list of ident->name renamings
pub type RenameList = Vec<(Ident, Name)>;
/// Extend a syntax context with a given mark
pub fn apply_mark(m: Mrk, ctxt: SyntaxContext) -> SyntaxContext {
with_sctable(|table| apply_mark_internal(m, ctxt, table))
}
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/// Extend a syntax context with a given mark and sctable (explicit memoization)
fn apply_mark_internal(m: Mrk, ctxt: SyntaxContext, table: &SCTable) -> SyntaxContext {
let key = (ctxt, m);
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* match table.mark_memo.borrow_mut().entry(key) {
Vacant(entry) => entry.set(idx_push(&mut *table.table.borrow_mut(), Mark(m, ctxt))),
Occupied(entry) => entry.into_mut(),
}
}
/// Extend a syntax context with a given rename
pub fn apply_rename(id: Ident, to:Name,
ctxt: SyntaxContext) -> SyntaxContext {
with_sctable(|table| apply_rename_internal(id, to, ctxt, table))
}
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/// Extend a syntax context with a given rename and sctable (explicit memoization)
fn apply_rename_internal(id: Ident,
to: Name,
ctxt: SyntaxContext,
table: &SCTable) -> SyntaxContext {
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let key = (ctxt, id, to);
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* match table.rename_memo.borrow_mut().entry(key) {
Vacant(entry) => entry.set(idx_push(&mut *table.table.borrow_mut(), Rename(id, to, ctxt))),
Occupied(entry) => entry.into_mut(),
}
}
/// Apply a list of renamings to a context
// if these rename lists get long, it would make sense
// to consider memoizing this fold. This may come up
// when we add hygiene to item names.
pub fn apply_renames(renames: &RenameList, ctxt: SyntaxContext) -> SyntaxContext {
renames.iter().fold(ctxt, |ctxt, &(from, to)| {
apply_rename(from, to, ctxt)
})
}
/// Fetch the SCTable from TLS, create one if it doesn't yet exist.
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pub fn with_sctable<T, F>(op: F) -> T where
F: FnOnce(&SCTable) -> T,
{
thread_local!(static SCTABLE_KEY: SCTable = new_sctable_internal());
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SCTABLE_KEY.with(move |slot| op(slot))
}
// Make a fresh syntax context table with EmptyCtxt in slot zero
// and IllegalCtxt in slot one.
fn new_sctable_internal() -> SCTable {
SCTable {
table: RefCell::new(vec!(EmptyCtxt, IllegalCtxt)),
mark_memo: RefCell::new(HashMap::new()),
rename_memo: RefCell::new(HashMap::new()),
}
}
/// Print out an SCTable for debugging
pub fn display_sctable(table: &SCTable) {
error!("SC table:");
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for (idx,val) in table.table.borrow().iter().enumerate() {
error!("{:4} : {}",idx,val);
}
}
/// Clear the tables from TLD to reclaim memory.
pub fn clear_tables() {
with_sctable(|table| {
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*table.table.borrow_mut() = Vec::new();
*table.mark_memo.borrow_mut() = HashMap::new();
*table.rename_memo.borrow_mut() = HashMap::new();
});
with_resolve_table_mut(|table| *table = HashMap::new());
}
/// Reset the tables to their initial state
pub fn reset_tables() {
with_sctable(|table| {
*table.table.borrow_mut() = vec!(EmptyCtxt, IllegalCtxt);
*table.mark_memo.borrow_mut() = HashMap::new();
*table.rename_memo.borrow_mut() = HashMap::new();
});
with_resolve_table_mut(|table| *table = HashMap::new());
}
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/// Add a value to the end of a vec, return its index
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fn idx_push<T>(vec: &mut Vec<T>, val: T) -> u32 {
vec.push(val);
(vec.len() - 1) as u32
}
/// Resolve a syntax object to a name, per MTWT.
pub fn resolve(id: Ident) -> Name {
with_sctable(|sctable| {
with_resolve_table_mut(|resolve_table| {
resolve_internal(id, sctable, resolve_table)
})
})
}
type ResolveTable = HashMap<(Name,SyntaxContext),Name>;
// okay, I admit, putting this in TLS is not so nice:
// fetch the SCTable from TLS, create one if it doesn't yet exist.
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fn with_resolve_table_mut<T, F>(op: F) -> T where
F: FnOnce(&mut ResolveTable) -> T,
{
thread_local!(static RESOLVE_TABLE_KEY: RefCell<ResolveTable> = {
RefCell::new(HashMap::new())
});
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RESOLVE_TABLE_KEY.with(move |slot| op(&mut *slot.borrow_mut()))
}
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/// Resolve a syntax object to a name, per MTWT.
/// adding memoization to resolve 500+ seconds in resolve for librustc (!)
fn resolve_internal(id: Ident,
table: &SCTable,
resolve_table: &mut ResolveTable) -> Name {
let key = (id.name, id.ctxt);
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match resolve_table.get(&key) {
Some(&name) => return name,
None => {}
}
let resolved = {
let result = (*table.table.borrow())[id.ctxt as uint];
match result {
EmptyCtxt => id.name,
// ignore marks here:
Mark(_,subctxt) =>
resolve_internal(Ident{name:id.name, ctxt: subctxt},
table, resolve_table),
// do the rename if necessary:
Rename(Ident{name, ctxt}, toname, subctxt) => {
let resolvedfrom =
resolve_internal(Ident{name:name, ctxt:ctxt},
table, resolve_table);
let resolvedthis =
resolve_internal(Ident{name:id.name, ctxt:subctxt},
table, resolve_table);
if (resolvedthis == resolvedfrom)
&& (marksof_internal(ctxt, resolvedthis, table)
== marksof_internal(subctxt, resolvedthis, table)) {
toname
} else {
resolvedthis
}
}
IllegalCtxt => panic!("expected resolvable context, got IllegalCtxt")
}
};
resolve_table.insert(key, resolved);
resolved
}
/// Compute the marks associated with a syntax context.
pub fn marksof(ctxt: SyntaxContext, stopname: Name) -> Vec<Mrk> {
with_sctable(|table| marksof_internal(ctxt, stopname, table))
}
// the internal function for computing marks
// it's not clear to me whether it's better to use a [] mutable
// vector or a cons-list for this.
fn marksof_internal(ctxt: SyntaxContext,
stopname: Name,
table: &SCTable) -> Vec<Mrk> {
let mut result = Vec::new();
let mut loopvar = ctxt;
loop {
let table_entry = (*table.table.borrow())[loopvar as uint];
match table_entry {
EmptyCtxt => {
return result;
},
Mark(mark, tl) => {
xor_push(&mut result, mark);
loopvar = tl;
},
Rename(_,name,tl) => {
// see MTWT for details on the purpose of the stopname.
// short version: it prevents duplication of effort.
if name == stopname {
return result;
} else {
loopvar = tl;
}
}
IllegalCtxt => panic!("expected resolvable context, got IllegalCtxt")
}
}
}
/// Return the outer mark for a context with a mark at the outside.
/// FAILS when outside is not a mark.
pub fn outer_mark(ctxt: SyntaxContext) -> Mrk {
with_sctable(|sctable| {
match (*sctable.table.borrow())[ctxt as uint] {
Mark(mrk, _) => mrk,
_ => panic!("can't retrieve outer mark when outside is not a mark")
}
})
}
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/// Push a name... unless it matches the one on top, in which
/// case pop and discard (so two of the same marks cancel)
fn xor_push(marks: &mut Vec<Mrk>, mark: Mrk) {
if (marks.len() > 0) && (*marks.last().unwrap() == mark) {
marks.pop().unwrap();
} else {
marks.push(mark);
}
}
#[cfg(test)]
mod tests {
use self::TestSC::*;
use ast::{EMPTY_CTXT, Ident, Mrk, Name, SyntaxContext};
use super::{resolve, xor_push, apply_mark_internal, new_sctable_internal};
use super::{apply_rename_internal, apply_renames, marksof_internal, resolve_internal};
use super::{SCTable, EmptyCtxt, Mark, Rename, IllegalCtxt};
use std::collections::HashMap;
#[test]
fn xorpush_test () {
let mut s = Vec::new();
xor_push(&mut s, 14);
assert_eq!(s.clone(), vec!(14));
xor_push(&mut s, 14);
assert_eq!(s.clone(), Vec::new());
xor_push(&mut s, 14);
assert_eq!(s.clone(), vec!(14));
xor_push(&mut s, 15);
assert_eq!(s.clone(), vec!(14, 15));
xor_push(&mut s, 16);
assert_eq!(s.clone(), vec!(14, 15, 16));
xor_push(&mut s, 16);
assert_eq!(s.clone(), vec!(14, 15));
xor_push(&mut s, 15);
assert_eq!(s.clone(), vec!(14));
}
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fn id(n: u32, s: SyntaxContext) -> Ident {
Ident {name: Name(n), ctxt: s}
}
// because of the SCTable, I now need a tidy way of
// creating syntax objects. Sigh.
#[deriving(Clone, PartialEq, Show)]
enum TestSC {
M(Mrk),
R(Ident,Name)
}
// unfold a vector of TestSC values into a SCTable,
// returning the resulting index
fn unfold_test_sc(tscs : Vec<TestSC> , tail: SyntaxContext, table: &SCTable)
-> SyntaxContext {
tscs.iter().rev().fold(tail, |tail : SyntaxContext, tsc : &TestSC|
{match *tsc {
M(mrk) => apply_mark_internal(mrk,tail,table),
R(ident,name) => apply_rename_internal(ident,name,tail,table)}})
}
// gather a SyntaxContext back into a vector of TestSCs
fn refold_test_sc(mut sc: SyntaxContext, table : &SCTable) -> Vec<TestSC> {
let mut result = Vec::new();
loop {
let table = table.table.borrow();
match (*table)[sc as uint] {
EmptyCtxt => {return result;},
Mark(mrk,tail) => {
result.push(M(mrk));
sc = tail;
continue;
},
Rename(id,name,tail) => {
result.push(R(id,name));
sc = tail;
continue;
}
IllegalCtxt => panic!("expected resolvable context, got IllegalCtxt")
}
}
}
#[test]
fn test_unfold_refold(){
let mut t = new_sctable_internal();
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let test_sc = vec!(M(3),R(id(101,0),Name(14)),M(9));
assert_eq!(unfold_test_sc(test_sc.clone(),EMPTY_CTXT,&mut t),4);
{
let table = t.table.borrow();
assert!((*table)[2] == Mark(9,0));
assert!((*table)[3] == Rename(id(101,0),Name(14),2));
assert!((*table)[4] == Mark(3,3));
}
assert_eq!(refold_test_sc(4,&t),test_sc);
}
// extend a syntax context with a sequence of marks given
// in a vector. v[0] will be the outermost mark.
fn unfold_marks(mrks: Vec<Mrk> , tail: SyntaxContext, table: &SCTable)
-> SyntaxContext {
mrks.iter().rev().fold(tail, |tail:SyntaxContext, mrk:&Mrk|
{apply_mark_internal(*mrk,tail,table)})
}
#[test] fn unfold_marks_test() {
let mut t = new_sctable_internal();
assert_eq!(unfold_marks(vec!(3,7),EMPTY_CTXT,&mut t),3);
{
let table = t.table.borrow();
assert!((*table)[2] == Mark(7,0));
assert!((*table)[3] == Mark(3,2));
}
}
#[test]
fn test_marksof () {
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let stopname = Name(242);
let name1 = Name(243);
let mut t = new_sctable_internal();
assert_eq!(marksof_internal (EMPTY_CTXT,stopname,&t),Vec::new());
// FIXME #5074: ANF'd to dodge nested calls
{ let ans = unfold_marks(vec!(4,98),EMPTY_CTXT,&mut t);
assert_eq! (marksof_internal (ans,stopname,&t),vec!(4,98));}
// does xoring work?
{ let ans = unfold_marks(vec!(5,5,16),EMPTY_CTXT,&mut t);
assert_eq! (marksof_internal (ans,stopname,&t), vec!(16));}
// does nested xoring work?
{ let ans = unfold_marks(vec!(5,10,10,5,16),EMPTY_CTXT,&mut t);
assert_eq! (marksof_internal (ans, stopname,&t), vec!(16));}
// rename where stop doesn't match:
{ let chain = vec!(M(9),
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R(id(name1.uint() as u32,
apply_mark_internal (4, EMPTY_CTXT,&mut t)),
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Name(100101102)),
M(14));
let ans = unfold_test_sc(chain,EMPTY_CTXT,&mut t);
assert_eq! (marksof_internal (ans, stopname, &t), vec!(9,14));}
// rename where stop does match
{ let name1sc = apply_mark_internal(4, EMPTY_CTXT, &mut t);
let chain = vec!(M(9),
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R(id(name1.uint() as u32, name1sc),
stopname),
M(14));
let ans = unfold_test_sc(chain,EMPTY_CTXT,&mut t);
assert_eq! (marksof_internal (ans, stopname, &t), vec!(9)); }
}
#[test]
fn resolve_tests () {
let a = 40;
let mut t = new_sctable_internal();
let mut rt = HashMap::new();
// - ctxt is MT
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assert_eq!(resolve_internal(id(a,EMPTY_CTXT),&mut t, &mut rt),Name(a));
// - simple ignored marks
{ let sc = unfold_marks(vec!(1,2,3),EMPTY_CTXT,&mut t);
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assert_eq!(resolve_internal(id(a,sc),&mut t, &mut rt),Name(a));}
// - orthogonal rename where names don't match
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{ let sc = unfold_test_sc(vec!(R(id(50,EMPTY_CTXT),Name(51)),M(12)),EMPTY_CTXT,&mut t);
assert_eq!(resolve_internal(id(a,sc),&mut t, &mut rt),Name(a));}
// - rename where names do match, but marks don't
{ let sc1 = apply_mark_internal(1,EMPTY_CTXT,&mut t);
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let sc = unfold_test_sc(vec!(R(id(a,sc1),Name(50)),
M(1),
M(2)),
EMPTY_CTXT,&mut t);
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assert_eq!(resolve_internal(id(a,sc),&mut t, &mut rt), Name(a));}
// - rename where names and marks match
{ let sc1 = unfold_test_sc(vec!(M(1),M(2)),EMPTY_CTXT,&mut t);
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let sc = unfold_test_sc(vec!(R(id(a,sc1),Name(50)),M(1),M(2)),EMPTY_CTXT,&mut t);
assert_eq!(resolve_internal(id(a,sc),&mut t, &mut rt), Name(50)); }
// - rename where names and marks match by literal sharing
{ let sc1 = unfold_test_sc(vec!(M(1),M(2)),EMPTY_CTXT,&mut t);
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let sc = unfold_test_sc(vec!(R(id(a,sc1),Name(50))),sc1,&mut t);
assert_eq!(resolve_internal(id(a,sc),&mut t, &mut rt), Name(50)); }
// - two renames of the same var.. can only happen if you use
// local-expand to prevent the inner binding from being renamed
// during the rename-pass caused by the first:
println!("about to run bad test");
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{ let sc = unfold_test_sc(vec!(R(id(a,EMPTY_CTXT),Name(50)),
R(id(a,EMPTY_CTXT),Name(51))),
EMPTY_CTXT,&mut t);
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assert_eq!(resolve_internal(id(a,sc),&mut t, &mut rt), Name(51)); }
// the simplest double-rename:
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{ let a_to_a50 = apply_rename_internal(id(a,EMPTY_CTXT),Name(50),EMPTY_CTXT,&mut t);
let a50_to_a51 = apply_rename_internal(id(a,a_to_a50),Name(51),a_to_a50,&mut t);
assert_eq!(resolve_internal(id(a,a50_to_a51),&mut t, &mut rt),Name(51));
// mark on the outside doesn't stop rename:
let sc = apply_mark_internal(9,a50_to_a51,&mut t);
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assert_eq!(resolve_internal(id(a,sc),&mut t, &mut rt),Name(51));
// but mark on the inside does:
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let a50_to_a51_b = unfold_test_sc(vec!(R(id(a,a_to_a50),Name(51)),
M(9)),
a_to_a50,
&mut t);
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assert_eq!(resolve_internal(id(a,a50_to_a51_b),&mut t, &mut rt),Name(50));}
}
#[test]
fn mtwt_resolve_test(){
let a = 40;
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assert_eq!(resolve(id(a,EMPTY_CTXT)),Name(a));
}
#[test]
fn hashing_tests () {
let mut t = new_sctable_internal();
assert_eq!(apply_mark_internal(12,EMPTY_CTXT,&mut t),2);
assert_eq!(apply_mark_internal(13,EMPTY_CTXT,&mut t),3);
// using the same one again should result in the same index:
assert_eq!(apply_mark_internal(12,EMPTY_CTXT,&mut t),2);
// I'm assuming that the rename table will behave the same....
}
#[test]
fn resolve_table_hashing_tests() {
let mut t = new_sctable_internal();
let mut rt = HashMap::new();
assert_eq!(rt.len(),0);
resolve_internal(id(30,EMPTY_CTXT),&mut t, &mut rt);
assert_eq!(rt.len(),1);
resolve_internal(id(39,EMPTY_CTXT),&mut t, &mut rt);
assert_eq!(rt.len(),2);
resolve_internal(id(30,EMPTY_CTXT),&mut t, &mut rt);
assert_eq!(rt.len(),2);
}
#[test]
fn new_resolves_test() {
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let renames = vec!((Ident{name:Name(23),ctxt:EMPTY_CTXT},Name(24)),
(Ident{name:Name(29),ctxt:EMPTY_CTXT},Name(29)));
let new_ctxt1 = apply_renames(&renames,EMPTY_CTXT);
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assert_eq!(resolve(Ident{name:Name(23),ctxt:new_ctxt1}),Name(24));
assert_eq!(resolve(Ident{name:Name(29),ctxt:new_ctxt1}),Name(29));
}
}