Refactor `SyntaxEnv`.

4 files changed, 119 insertions, 126 deletions

diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index 769a5af0262..fe2806891b8 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -24,6 +24,7 @@ use parse::parser;
 use parse::token;
 use parse::token::{InternedString, intern, str_to_ident};
 use ptr::P;
+use std_inject;
 use util::small_vector::SmallVector;
 use util::lev_distance::find_best_match_for_name;
 use fold::Folder;
@@ -463,19 +464,6 @@ pub enum SyntaxExtension {
 
 pub type NamedSyntaxExtension = (Name, SyntaxExtension);
 
-pub struct BlockInfo {
-    /// Should macros escape from this scope?
-    pub macros_escape: bool,
-}
-
-impl BlockInfo {
-    pub fn new() -> BlockInfo {
-        BlockInfo {
-            macros_escape: false,
-        }
-    }
-}
-
 /// The base map of methods for expanding syntax extension
 /// AST nodes into full ASTs
 fn initial_syntax_expander_table<'feat>(ecfg: &expand::ExpansionConfig<'feat>)
@@ -586,15 +574,11 @@ pub struct ExtCtxt<'a> {
     pub crate_root: Option<&'static str>,
     pub loader: &'a mut MacroLoader,
 
-    pub mod_path: Vec<ast::Ident> ,
     pub exported_macros: Vec<ast::MacroDef>,
 
     pub syntax_env: SyntaxEnv,
     pub derive_modes: HashMap<InternedString, Box<MultiItemModifier>>,
     pub recursion_count: usize,
-
-    pub directory: PathBuf,
-    pub in_block: bool,
 }
 
 impl<'a> ExtCtxt<'a> {
@@ -602,22 +586,17 @@ impl<'a> ExtCtxt<'a> {
                ecfg: expand::ExpansionConfig<'a>,
                loader: &'a mut MacroLoader)
                -> ExtCtxt<'a> {
-        let env = initial_syntax_expander_table(&ecfg);
         ExtCtxt {
+            syntax_env: initial_syntax_expander_table(&ecfg),
             parse_sess: parse_sess,
             cfg: cfg,
             backtrace: NO_EXPANSION,
-            mod_path: Vec::new(),
             ecfg: ecfg,
             crate_root: None,
             exported_macros: Vec::new(),
             loader: loader,
-            syntax_env: env,
             derive_modes: HashMap::new(),
             recursion_count: 0,
-
-            directory: PathBuf::new(),
-            in_block: false,
         }
     }
 
@@ -666,14 +645,6 @@ impl<'a> ExtCtxt<'a> {
         last_macro.expect("missing expansion backtrace")
     }
 
-    pub fn mod_push(&mut self, i: ast::Ident) { self.mod_path.push(i); }
-    pub fn mod_pop(&mut self) { self.mod_path.pop().unwrap(); }
-    pub fn mod_path(&self) -> Vec<ast::Ident> {
-        let mut v = Vec::new();
-        v.push(token::str_to_ident(&self.ecfg.crate_name));
-        v.extend(self.mod_path.iter().cloned());
-        return v;
-    }
     pub fn bt_push(&mut self, ei: ExpnInfo) {
         self.recursion_count += 1;
         if self.recursion_count > self.ecfg.recursion_limit {
@@ -818,6 +789,30 @@ impl<'a> ExtCtxt<'a> {
             }
         }
     }
+
+    pub fn initialize(&mut self, user_exts: Vec<NamedSyntaxExtension>, krate: &ast::Crate) {
+        if std_inject::no_core(&krate) {
+            self.crate_root = None;
+        } else if std_inject::no_std(&krate) {
+            self.crate_root = Some("core");
+        } else {
+            self.crate_root = Some("std");
+        }
+
+        // User extensions must be added before expander.load_macros is called,
+        // so that macros from external crates shadow user defined extensions.
+        for (name, extension) in user_exts {
+            self.syntax_env.insert(name, extension);
+        }
+
+        self.syntax_env.current_module = Module(0);
+        let mut paths = ModulePaths {
+            mod_path: vec![token::str_to_ident(&self.ecfg.crate_name)],
+            directory: PathBuf::from(self.parse_sess.codemap().span_to_filename(krate.span)),
+        };
+        paths.directory.pop();
+        self.syntax_env.module_data[0].paths = Rc::new(paths);
+    }
 }
 
 /// Extract a string literal from the macro expanded version of `expr`,
@@ -904,79 +899,103 @@ pub fn get_exprs_from_tts(cx: &mut ExtCtxt,
 ///
 /// This environment maps Names to SyntaxExtensions.
 pub struct SyntaxEnv {
-    chain: Vec<MapChainFrame>,
+    module_data: Vec<ModuleData>,
+    current_module: Module,
+
     /// All bang-style macro/extension names
     /// encountered so far; to be used for diagnostics in resolve
     pub names: HashSet<Name>,
 }
 
-// impl question: how to implement it? Initially, the
-// env will contain only macros, so it might be painful
-// to add an empty frame for every context. Let's just
-// get it working, first....
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub struct Module(u32);
 
-// NB! the mutability of the underlying maps means that
-// if expansion is out-of-order, a deeper scope may be
-// able to refer to a macro that was added to an enclosing
-// scope lexically later than the deeper scope.
+struct ModuleData {
+    parent: Module,
+    paths: Rc<ModulePaths>,
+    macros: HashMap<Name, Rc<SyntaxExtension>>,
+    macros_escape: bool,
+    in_block: bool,
+}
 
-struct MapChainFrame {
-    info: BlockInfo,
-    map: HashMap<Name, Rc<SyntaxExtension>>,
+#[derive(Clone)]
+pub struct ModulePaths {
+    pub mod_path: Vec<ast::Ident>,
+    pub directory: PathBuf,
 }
 
 impl SyntaxEnv {
     fn new() -> SyntaxEnv {
-        let mut map = SyntaxEnv { chain: Vec::new() , names: HashSet::new()};
-        map.push_frame();
-        map
+        let mut env = SyntaxEnv {
+            current_module: Module(0),
+            module_data: Vec::new(),
+            names: HashSet::new(),
+        };
+        let paths = Rc::new(ModulePaths { mod_path: Vec::new(), directory: PathBuf::new() });
+        env.add_module(false, false, paths);
+        env
     }
 
-    pub fn push_frame(&mut self) {
-        self.chain.push(MapChainFrame {
-            info: BlockInfo::new(),
-            map: HashMap::new(),
-        });
+    fn data(&self, module: Module) -> &ModuleData {
+        &self.module_data[module.0 as usize]
     }
 
-    pub fn pop_frame(&mut self) {
-        assert!(self.chain.len() > 1, "too many pops on MapChain!");
-        self.chain.pop();
+    pub fn set_current_module(&mut self, module: Module) -> Module {
+        ::std::mem::replace(&mut self.current_module, module)
     }
 
-    fn find_escape_frame(&mut self) -> &mut MapChainFrame {
-        for (i, frame) in self.chain.iter_mut().enumerate().rev() {
-            if !frame.info.macros_escape || i == 0 {
-                return frame
-            }
-        }
-        unreachable!()
+    pub fn paths(&self) -> Rc<ModulePaths> {
+        self.data(self.current_module).paths.clone()
+    }
+
+    pub fn in_block(&self) -> bool {
+        self.data(self.current_module).in_block
     }
 
-    pub fn find(&self, k: Name) -> Option<Rc<SyntaxExtension>> {
-        for frame in self.chain.iter().rev() {
-            if let Some(v) = frame.map.get(&k) {
-                return Some(v.clone());
+    pub fn add_module(&mut self, macros_escape: bool, in_block: bool, paths: Rc<ModulePaths>)
+                      -> Module {
+        let data = ModuleData {
+            parent: self.current_module,
+            paths: paths,
+            macros: HashMap::new(),
+            macros_escape: macros_escape,
+            in_block: in_block,
+        };
+
+        self.module_data.push(data);
+        Module(self.module_data.len() as u32 - 1)
+    }
+
+    pub fn find(&self, name: Name) -> Option<Rc<SyntaxExtension>> {
+        let mut module = self.current_module;
+        let mut module_data;
+        loop {
+            module_data = self.data(module);
+            if let Some(ext) = module_data.macros.get(&name) {
+                return Some(ext.clone());
             }
+            if module == module_data.parent {
+                return None;
+            }
+            module = module_data.parent;
         }
-        None
     }
 
-    pub fn insert(&mut self, k: Name, v: SyntaxExtension) {
-        if let NormalTT(..) = v {
-            self.names.insert(k);
+    pub fn insert(&mut self, name: Name, ext: SyntaxExtension) {
+        if let NormalTT(..) = ext {
+            self.names.insert(name);
         }
-        self.find_escape_frame().map.insert(k, Rc::new(v));
-    }
 
-    pub fn info(&mut self) -> &mut BlockInfo {
-        let last_chain_index = self.chain.len() - 1;
-        &mut self.chain[last_chain_index].info
+        let mut module = self.current_module;
+        while self.data(module).macros_escape {
+            module = self.data(module).parent;
+        }
+        self.module_data[module.0 as usize].macros.insert(name, Rc::new(ext));
     }
 
     pub fn is_crate_root(&mut self) -> bool {
         // The first frame is pushed in `SyntaxEnv::new()` and the second frame is
         // pushed when folding the crate root pseudo-module (c.f. noop_fold_crate).
-        self.chain.len() <= 2
+        self.current_module.0 <= 1
     }
 }
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index d3f8618aace..a713196032c 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -26,9 +26,9 @@ use tokenstream::TokenTree;
 use util::small_vector::SmallVector;
 use visit;
 use visit::Visitor;
-use std_inject;
 
 use std::path::PathBuf;
+use std::rc::Rc;
 
 macro_rules! expansions {
     ($($kind:ident: $ty:ty, $kind_name:expr, .$make:ident,
@@ -467,24 +467,9 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         }
         false
     }
-
-    fn with_exts_frame<T, F: FnOnce(&mut Self) -> T>(&mut self, macros_escape: bool, f: F) -> T {
-        self.cx.syntax_env.push_frame();
-        self.cx.syntax_env.info().macros_escape = macros_escape;
-        let result = f(self);
-        self.cx.syntax_env.pop_frame();
-        result
-    }
 }
 
 impl<'a, 'b> Folder for MacroExpander<'a, 'b> {
-    fn fold_crate(&mut self, c: Crate) -> Crate {
-        let mut directory = PathBuf::from(self.cx.parse_sess.codemap().span_to_filename(c.span));
-        directory.pop();
-        self.cx.directory = directory;
-        noop_fold_crate(c, self)
-    }
-
     fn fold_expr(&mut self, expr: P<ast::Expr>) -> P<ast::Expr> {
         let expr = expr.unwrap();
         if let ast::ExprKind::Mac(mac) = expr.node {
@@ -542,9 +527,12 @@ impl<'a, 'b> Folder for MacroExpander<'a, 'b> {
     }
 
     fn fold_block(&mut self, block: P<Block>) -> P<Block> {
-        let was_in_block = ::std::mem::replace(&mut self.cx.in_block, true);
-        let result = self.with_exts_frame(false, |this| noop_fold_block(block, this));
-        self.cx.in_block = was_in_block;
+        let paths = self.cx.syntax_env.paths();
+        let module = self.cx.syntax_env.add_module(false, true, paths);
+        let orig_module = self.cx.syntax_env.set_current_module(module);
+
+        let result = noop_fold_block(block, self);
+        self.cx.syntax_env.set_current_module(orig_module);
         result
     }
 
@@ -578,26 +566,27 @@ impl<'a, 'b> Folder for MacroExpander<'a, 'b> {
                 })
             }
             ast::ItemKind::Mod(ast::Mod { inner, .. }) => {
-                self.cx.mod_push(item.ident);
-                let macro_use = self.contains_macro_use(&item.attrs);
-
-                let directory = self.cx.directory.clone();
+                let mut paths = (*self.cx.syntax_env.paths()).clone();
+                paths.mod_path.push(item.ident);
                 if item.span.contains(inner) {
-                    self.cx.directory.push(&*{
+                    paths.directory.push(&*{
                         ::attr::first_attr_value_str_by_name(&item.attrs, "path")
                             .unwrap_or(item.ident.name.as_str())
                     });
                 } else {
-                    self.cx.directory = match inner {
+                    paths.directory = match inner {
                         syntax_pos::DUMMY_SP => PathBuf::new(),
                         _ => PathBuf::from(self.cx.parse_sess.codemap().span_to_filename(inner)),
                     };
-                    self.cx.directory.pop();
+                    paths.directory.pop();
                 }
-                let result = self.with_exts_frame(macro_use, |this| noop_fold_item(item, this));
-                self.cx.directory = directory;
 
-                self.cx.mod_pop();
+                let macro_use = self.contains_macro_use(&item.attrs);
+                let in_block = self.cx.syntax_env.in_block();
+                let module = self.cx.syntax_env.add_module(macro_use, in_block, Rc::new(paths));
+                let module = self.cx.syntax_env.set_current_module(module);
+                let result = noop_fold_item(item, self);
+                self.cx.syntax_env.set_current_module(module);
                 result
             },
             _ => noop_fold_item(item, self),
@@ -744,19 +733,7 @@ pub fn expand_crate(cx: &mut ExtCtxt,
 pub fn expand_crate_with_expander(expander: &mut MacroExpander,
                                   user_exts: Vec<NamedSyntaxExtension>,
                                   mut c: Crate) -> Crate {
-    if std_inject::no_core(&c) {
-        expander.cx.crate_root = None;
-    } else if std_inject::no_std(&c) {
-        expander.cx.crate_root = Some("core");
-    } else {
-        expander.cx.crate_root = Some("std");
-    }
-
-    // User extensions must be added before expander.load_macros is called,
-    // so that macros from external crates shadow user defined extensions.
-    for (name, extension) in user_exts {
-        expander.cx.syntax_env.insert(name, extension);
-    }
+    expander.cx.initialize(user_exts, &c);
 
     let items = Expansion::Items(SmallVector::many(c.module.items));
     let configured = items.fold_with(&mut expander.strip_unconfigured());
@@ -765,12 +742,11 @@ pub fn expand_crate_with_expander(expander: &mut MacroExpander,
 
     let err_count = expander.cx.parse_sess.span_diagnostic.err_count();
     let mut ret = expander.fold_crate(c);
-    ret.exported_macros = expander.cx.exported_macros.clone();
-
     if expander.cx.parse_sess.span_diagnostic.err_count() > err_count {
         expander.cx.parse_sess.span_diagnostic.abort_if_errors();
     }
 
+    ret.exported_macros = expander.cx.exported_macros.clone();
     ret
 }
 
diff --git a/src/libsyntax/ext/source_util.rs b/src/libsyntax/ext/source_util.rs
index 97cb09991ec..105b2261117 100644
--- a/src/libsyntax/ext/source_util.rs
+++ b/src/libsyntax/ext/source_util.rs
@@ -74,11 +74,9 @@ pub fn expand_stringify(cx: &mut ExtCtxt, sp: Span, tts: &[tokenstream::TokenTre
 pub fn expand_mod(cx: &mut ExtCtxt, sp: Span, tts: &[tokenstream::TokenTree])
                   -> Box<base::MacResult+'static> {
     base::check_zero_tts(cx, sp, tts, "module_path!");
-    let string = cx.mod_path()
-                   .iter()
-                   .map(|x| x.to_string())
-                   .collect::<Vec<String>>()
-                   .join("::");
+    let paths = cx.syntax_env.paths();
+    let string = paths.mod_path.iter().map(|x| x.to_string()).collect::<Vec<String>>().join("::");
+
     base::MacEager::expr(cx.expr_str(
             sp,
             token::intern_and_get_ident(&string[..])))
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index a4be84dfbf0..ed80ec9cbc4 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -211,8 +211,8 @@ fn generic_extension<'cx>(cx: &'cx ExtCtxt,
                                            imported_from,
                                            rhs);
                 let mut p = Parser::new(cx.parse_sess(), cx.cfg(), Box::new(trncbr));
-                p.directory = cx.directory.clone();
-                p.restrictions = match cx.in_block {
+                p.directory = cx.syntax_env.paths().directory.clone();
+                p.restrictions = match cx.syntax_env.in_block() {
                     true => Restrictions::NO_NONINLINE_MOD,
                     false => Restrictions::empty(),
                 };