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Rewrite SyntaxEnv
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I'd really like to be able to do something like

struct MapChain<'next, K, V> {
    info: BlockInfo,
    map: HashMap<K, V>,
    next: Option<&'next mut MapChain<'next, K, V>
}

but I can't get the lifetimes to work out.
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@sfackler
sfackler committed Dec 31, 2013
1 parent 1502b11 commit b74613b
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Showing 2 changed files with 129 additions and 247 deletions.
266 changes: 88 additions & 178 deletions src/libsyntax/ext/base.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -156,57 +156,48 @@ pub enum SyntaxExtension {
// The SyntaxEnv is the environment that's threaded through the expansion
// of macros. It contains bindings for macros, and also a special binding
// for " block" (not a legal identifier) that maps to a BlockInfo
pub type SyntaxEnv = @mut MapChain<Name, Transformer>;

// Transformer : the codomain of SyntaxEnvs

pub enum Transformer {
// this identifier maps to a syntax extension or macro
SE(SyntaxExtension),
// blockinfo : this is ... well, it's simpler than threading
// another whole data stack-structured data structure through
// expansion. Basically, there's an invariant that every
// map must contain a binding for " block".
BlockInfo(BlockInfo)
}
pub type SyntaxEnv = MapChain<Name, SyntaxExtension>;

pub struct BlockInfo {
// should macros escape from this scope?
macros_escape : bool,
// what are the pending renames?
pending_renames : @mut RenameList
pending_renames : RenameList
}

impl BlockInfo {
pub fn new() -> BlockInfo {
BlockInfo {
macros_escape: false,
pending_renames: ~[]
}
}
}

// a list of ident->name renamings
type RenameList = ~[(ast::Ident,Name)];
pub type RenameList = ~[(ast::Ident,Name)];

// The base map of methods for expanding syntax extension
// AST nodes into full ASTs
pub fn syntax_expander_table() -> SyntaxEnv {
// utility function to simplify creating NormalTT syntax extensions
fn builtin_normal_tt_no_ctxt(f: SyntaxExpanderTTFunNoCtxt)
-> @Transformer {
@SE(NormalTT(@SyntaxExpanderTT{
-> SyntaxExtension {
NormalTT(@SyntaxExpanderTT{
expander: SyntaxExpanderTTExpanderWithoutContext(f),
span: None,
} as @SyntaxExpanderTTTrait,
None))
None)
}

let mut syntax_expanders = HashMap::new();
// NB identifier starts with space, and can't conflict with legal idents
syntax_expanders.insert(intern(&" block"),
@BlockInfo(BlockInfo{
macros_escape : false,
pending_renames : @mut ~[]
}));
let mut syntax_expanders = MapChain::new();
syntax_expanders.insert(intern(&"macro_rules"),
@SE(IdentTT(@SyntaxExpanderTTItem {
IdentTT(@SyntaxExpanderTTItem {
expander: SyntaxExpanderTTItemExpanderWithContext(
ext::tt::macro_rules::add_new_extension),
span: None,
} as @SyntaxExpanderTTItemTrait,
None)));
None));
syntax_expanders.insert(intern(&"fmt"),
builtin_normal_tt_no_ctxt(
ext::fmt::expand_syntax_ext));
Expand All @@ -232,8 +223,7 @@ pub fn syntax_expander_table() -> SyntaxEnv {
builtin_normal_tt_no_ctxt(
ext::log_syntax::expand_syntax_ext));
syntax_expanders.insert(intern(&"deriving"),
@SE(ItemDecorator(
ext::deriving::expand_meta_deriving)));
ItemDecorator(ext::deriving::expand_meta_deriving));

// Quasi-quoting expanders
syntax_expanders.insert(intern(&"quote_tokens"),
Expand Down Expand Up @@ -288,7 +278,7 @@ pub fn syntax_expander_table() -> SyntaxEnv {
syntax_expanders.insert(intern(&"trace_macros"),
builtin_normal_tt_no_ctxt(
ext::trace_macros::expand_trace_macros));
MapChain::new(~syntax_expanders)
syntax_expanders
}

// One of these is made during expansion and incrementally updated as we go;
Expand All @@ -299,11 +289,6 @@ pub struct ExtCtxt {
cfg: ast::CrateConfig,
backtrace: Option<@ExpnInfo>,

// These two @mut's should really not be here,
// but the self types for CtxtRepr are all wrong
// and there are bugs in the code for object
// types that make this hard to get right at the
// moment. - nmatsakis
mod_path: ~[ast::Ident],
trace_mac: bool
}
Expand All @@ -325,7 +310,7 @@ impl ExtCtxt {
match e.node {
ast::ExprMac(..) => {
let mut expander = expand::MacroExpander {
extsbox: @mut syntax_expander_table(),
extsbox: syntax_expander_table(),
cx: self,
};
e = expand::expand_expr(e, &mut expander);
Expand Down Expand Up @@ -460,11 +445,7 @@ pub fn get_exprs_from_tts(cx: &ExtCtxt,
// we want to implement the notion of a transformation
// environment.

// This environment maps Names to Transformers.
// Initially, this includes macro definitions and
// block directives.


// This environment maps Names to SyntaxExtensions.

// Actually, the following implementation is parameterized
// by both key and value types.
Expand All @@ -479,169 +460,98 @@ pub fn get_exprs_from_tts(cx: &ExtCtxt,
// able to refer to a macro that was added to an enclosing
// scope lexically later than the deeper scope.

// Note on choice of representation: I've been pushed to
// use a top-level managed pointer by some difficulties
// with pushing and popping functionally, and the ownership
// issues. As a result, the values returned by the table
// also need to be managed; the &'a ... type that Maps
// return won't work for things that need to get outside
// of that managed pointer. The easiest way to do this
// is just to insist that the values in the tables are
// managed to begin with.

// a transformer env is either a base map or a map on top
// of another chain.
pub enum MapChain<K,V> {
BaseMapChain(~HashMap<K,@V>),
ConsMapChain(~HashMap<K,@V>,@mut MapChain<K,V>)
// Only generic to make it easy to test
struct MapChainFrame<K, V> {
info: BlockInfo,
map: HashMap<K, V>,
}

// Only generic to make it easy to test
pub struct MapChain<K, V> {
priv chain: ~[MapChainFrame<K, V>],
}

// get the map from an env frame
impl <K: Eq + Hash + IterBytes + 'static, V: 'static> MapChain<K,V>{
// Constructor. I don't think we need a zero-arg one.
pub fn new(init: ~HashMap<K,@V>) -> @mut MapChain<K,V> {
@mut BaseMapChain(init)
impl<K: Hash+Eq, V> MapChain<K, V> {
pub fn new() -> MapChain<K, V> {
let mut map = MapChain { chain: ~[] };
map.push_frame();
map
}

// add a new frame to the environment (functionally)
pub fn push_frame (@mut self) -> @mut MapChain<K,V> {
@mut ConsMapChain(~HashMap::new() ,self)
pub fn push_frame(&mut self) {
self.chain.push(MapChainFrame {
info: BlockInfo::new(),
map: HashMap::new(),
});
}

// no need for pop, it'll just be functional.

// utility fn...

// ugh: can't get this to compile with mut because of the
// lack of flow sensitivity.
pub fn get_map<'a>(&'a self) -> &'a HashMap<K,@V> {
match *self {
BaseMapChain (~ref map) => map,
ConsMapChain (~ref map,_) => map
}
pub fn pop_frame(&mut self) {
assert!(self.chain.len() > 1, "too many pops on MapChain!");
self.chain.pop();
}

// traits just don't work anywhere...?
//impl Map<Name,SyntaxExtension> for MapChain {

pub fn contains_key (&self, key: &K) -> bool {
match *self {
BaseMapChain (ref map) => map.contains_key(key),
ConsMapChain (ref map,ref rest) =>
(map.contains_key(key)
|| rest.contains_key(key))
fn find_escape_frame<'a>(&'a mut self) -> &'a mut MapChainFrame<K, V> {
for (i, frame) in self.chain.mut_iter().enumerate().invert() {
if !frame.info.macros_escape || i == 0 {
return frame
}
}
}
// should each_key and each_value operate on shadowed
// names? I think not.
// delaying implementing this....
pub fn each_key (&self, _f: |&K| -> bool) {
fail!("unimplemented 2013-02-15T10:01");
}

pub fn each_value (&self, _f: |&V| -> bool) {
fail!("unimplemented 2013-02-15T10:02");
unreachable!()
}

// Returns a copy of the value that the name maps to.
// Goes down the chain 'til it finds one (or bottom out).
pub fn find (&self, key: &K) -> Option<@V> {
match self.get_map().find (key) {
Some(ref v) => Some(**v),
None => match *self {
BaseMapChain (_) => None,
ConsMapChain (_,ref rest) => rest.find(key)
pub fn find<'a>(&'a self, k: &K) -> Option<&'a V> {
for frame in self.chain.iter().invert() {
match frame.map.find(k) {
Some(v) => return Some(v),
None => {}
}
}
None
}

pub fn find_in_topmost_frame(&self, key: &K) -> Option<@V> {
let map = match *self {
BaseMapChain(ref map) => map,
ConsMapChain(ref map,_) => map
};
// strip one layer of indirection off the pointer.
map.find(key).map(|r| {*r})
}

// insert the binding into the top-level map
pub fn insert (&mut self, key: K, ext: @V) -> bool {
// can't abstract over get_map because of flow sensitivity...
match *self {
BaseMapChain (~ref mut map) => map.insert(key, ext),
ConsMapChain (~ref mut map,_) => map.insert(key,ext)
}
pub fn insert(&mut self, k: K, v: V) {
self.find_escape_frame().map.insert(k, v);
}
// insert the binding into the topmost frame for which the binding
// associated with 'n' exists and satisfies pred
// ... there are definitely some opportunities for abstraction
// here that I'm ignoring. (e.g., manufacturing a predicate on
// the maps in the chain, and using an abstract "find".
pub fn insert_into_frame(&mut self,
key: K,
ext: @V,
n: K,
pred: |&@V| -> bool) {
match *self {
BaseMapChain (~ref mut map) => {
if satisfies_pred(map,&n,pred) {
map.insert(key,ext);
} else {
fail!("expected map chain containing satisfying frame")
}
},
ConsMapChain (~ref mut map, rest) => {
if satisfies_pred(map,&n,|v|pred(v)) {
map.insert(key,ext);
} else {
rest.insert_into_frame(key,ext,n,pred)
}
}
}
}
}

// returns true if the binding for 'n' satisfies 'pred' in 'map'
fn satisfies_pred<K:Eq + Hash + IterBytes,
V>(
map: &mut HashMap<K,V>,
n: &K,
pred: |&V| -> bool)
-> bool {
match map.find(n) {
Some(ref v) => (pred(*v)),
None => false
pub fn info<'a>(&'a mut self) -> &'a mut BlockInfo {
&mut self.chain[self.chain.len()-1].info
}
}

#[cfg(test)]
mod test {
use super::MapChain;
use std::hashmap::HashMap;

#[test]
fn testenv() {
let mut a = HashMap::new();
a.insert (@"abc",@15);
let m = MapChain::new(~a);
m.insert (@"def",@16);
assert_eq!(m.find(&@"abc"),Some(@15));
assert_eq!(m.find(&@"def"),Some(@16));
assert_eq!(*(m.find(&@"abc").unwrap()),15);
assert_eq!(*(m.find(&@"def").unwrap()),16);
let n = m.push_frame();
// old bindings are still present:
assert_eq!(*(n.find(&@"abc").unwrap()),15);
assert_eq!(*(n.find(&@"def").unwrap()),16);
n.insert (@"def",@17);
// n shows the new binding
assert_eq!(*(n.find(&@"abc").unwrap()),15);
assert_eq!(*(n.find(&@"def").unwrap()),17);
// ... but m still has the old ones
assert_eq!(m.find(&@"abc"),Some(@15));
assert_eq!(m.find(&@"def"),Some(@16));
assert_eq!(*(m.find(&@"abc").unwrap()),15);
assert_eq!(*(m.find(&@"def").unwrap()),16);
let mut m = MapChain::new();
let (a,b,c,d) = ("a", "b", "c", "d");
m.insert(1, a);
assert_eq!(Some(&a), m.find(&1));

m.push_frame();
m.info().macros_escape = true;
m.insert(2, b);
assert_eq!(Some(&a), m.find(&1));
assert_eq!(Some(&b), m.find(&2));
m.pop_frame();

assert_eq!(Some(&a), m.find(&1));
assert_eq!(Some(&b), m.find(&2));

m.push_frame();
m.push_frame();
m.info().macros_escape = true;
m.insert(3, c);
assert_eq!(Some(&c), m.find(&3));
m.pop_frame();
assert_eq!(Some(&c), m.find(&3));
m.pop_frame();
assert_eq!(None, m.find(&3));

m.push_frame();
m.insert(4, d);
m.pop_frame();
assert_eq!(None, m.find(&4));
}
}
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1 comment on commit b74613b

@pcwalton
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r+

Yes, I reviewed this earlier but I didn't give the stamp I guess. This looks good.

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