syntax: use an index in CodeMap instead of Gc for ExpnInfo.

src/grammar/verify.rs

@@ -211,7 +211,7 @@ fn parse_antlr_token(s: &str, tokens: &HashMap<String, Token>) -> TokenAndSpan {
     let sp = syntax::codemap::Span {
         lo: syntax::codemap::BytePos(from_str::<u32>(start).unwrap() - offset),
         hi: syntax::codemap::BytePos(from_str::<u32>(end).unwrap() + 1),
-        expn_info: None
+        expn_id: syntax::codemap::NO_EXPANSION
     };
 
     TokenAndSpan {

src/librustc/lint/builtin.rs

@@ -42,7 +42,7 @@ use syntax::abi;
 use syntax::ast_map;
 use syntax::attr::AttrMetaMethods;
 use syntax::attr;
-use syntax::codemap::Span;
+use syntax::codemap::{Span, NO_EXPANSION};
 use syntax::parse::token;
 use syntax::{ast, ast_util, visit};
 use syntax::ptr::P;
@@ -1492,7 +1492,7 @@ impl LintPass for Stability {
 
     fn check_expr(&mut self, cx: &Context, e: &ast::Expr) {
         // if the expression was produced by a macro expansion,
-        if e.span.expn_info.is_some() { return }
+        if e.span.expn_id != NO_EXPANSION { return }
 
         let id = match e.node {
             ast::ExprPath(..) | ast::ExprStruct(..) => {

src/librustc/middle/astencode.rs

@@ -2035,7 +2035,7 @@ impl fake_ext_ctxt for parse::ParseSess {
         codemap::Span {
             lo: codemap::BytePos(0),
             hi: codemap::BytePos(0),
-            expn_info: None
+            expn_id: codemap::NO_EXPANSION
         }
     }
     fn ident_of(&self, st: &str) -> ast::Ident {

src/librustc/middle/liveness.rs

@@ -1520,11 +1520,12 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
                     sp, "not all control paths return a value");
                 if ends_with_stmt {
                     let last_stmt = body.stmts.last().unwrap();
-                    let original_span = original_sp(last_stmt.span, sp);
+                    let original_span = original_sp(self.ir.tcx.sess.codemap(),
+                                                    last_stmt.span, sp);
                     let span_semicolon = Span {
                         lo: original_span.hi - BytePos(1),
                         hi: original_span.hi,
-                        expn_info: original_span.expn_info
+                        expn_id: original_span.expn_id
                     };
                     self.ir.tcx.sess.span_note(
                         span_semicolon, "consider removing this semicolon:");

src/librustc/middle/save/mod.rs

@@ -71,7 +71,7 @@ fn escape(s: String) -> String {
 
 // If the expression is a macro expansion or other generated code, run screaming and don't index.
 fn generated_code(span: Span) -> bool {
-    span.expn_info.is_some() || span  == DUMMY_SP
+    span.expn_id != NO_EXPANSION || span  == DUMMY_SP
 }
 
 struct DxrVisitor<'l, 'tcx: 'l> {

src/librustc/middle/save/span_utils.rs

@@ -57,7 +57,7 @@ impl<'a> SpanUtils<'a> {
                 Some(Span {
                     lo: base + self.sess.codemap().lookup_byte_offset(sub.lo).pos,
                     hi: base + self.sess.codemap().lookup_byte_offset(sub.hi).pos,
-                    expn_info: None,
+                    expn_id: NO_EXPANSION,
                 })
             }
         }

src/libsyntax/ast.rs

@@ -1363,7 +1363,7 @@ mod test {
                 inner: Span {
                     lo: BytePos(11),
                     hi: BytePos(19),
-                    expn_info: None,
+                    expn_id: NO_EXPANSION,
                 },
                 view_items: Vec::new(),
                 items: Vec::new(),
@@ -1373,7 +1373,7 @@ mod test {
             span: Span {
                 lo: BytePos(10),
                 hi: BytePos(20),
-                expn_info: None,
+                expn_id: NO_EXPANSION,
             },
             exported_macros: Vec::new(),
         };

src/libsyntax/codemap.rs

@@ -25,7 +25,6 @@ source code snippets, etc.
 
 use serialize::{Encodable, Decodable, Encoder, Decoder};
 use std::cell::RefCell;
-use std::gc::Gc;
 use std::rc::Rc;
 
 pub trait Pos {
@@ -93,10 +92,10 @@ pub struct Span {
     pub hi: BytePos,
     /// Information about where the macro came from, if this piece of
     /// code was created by a macro expansion.
-    pub expn_info: Option<Gc<ExpnInfo>>
+    pub expn_id: ExpnId
 }
 
-pub static DUMMY_SP: Span = Span { lo: BytePos(0), hi: BytePos(0), expn_info: None };
+pub static DUMMY_SP: Span = Span { lo: BytePos(0), hi: BytePos(0), expn_id: NO_EXPANSION };
 
 #[deriving(Clone, PartialEq, Eq, Encodable, Decodable, Hash, Show)]
 pub struct Spanned<T> {
@@ -140,17 +139,19 @@ pub fn dummy_spanned<T>(t: T) -> Spanned<T> {
 
 /* assuming that we're not in macro expansion */
 pub fn mk_sp(lo: BytePos, hi: BytePos) -> Span {
-    Span {lo: lo, hi: hi, expn_info: None}
+    Span {lo: lo, hi: hi, expn_id: NO_EXPANSION}
 }
 
 /// Return the span itself if it doesn't come from a macro expansion,
 /// otherwise return the call site span up to the `enclosing_sp` by
 /// following the `expn_info` chain.
-pub fn original_sp(sp: Span, enclosing_sp: Span) -> Span {
-    match (sp.expn_info, enclosing_sp.expn_info) {
+pub fn original_sp(cm: &CodeMap, sp: Span, enclosing_sp: Span) -> Span {
+    let call_site1 = cm.with_expn_info(sp.expn_id, |ei| ei.map(|ei| ei.call_site));
+    let call_site2 = cm.with_expn_info(enclosing_sp.expn_id, |ei| ei.map(|ei| ei.call_site));
+    match (call_site1, call_site2) {
         (None, _) => sp,
-        (Some(expn1), Some(expn2)) if expn1.call_site == expn2.call_site => sp,
-        (Some(expn1), _) => original_sp(expn1.call_site, enclosing_sp),
+        (Some(call_site1), Some(call_site2)) if call_site1 == call_site2 => sp,
+        (Some(call_site1), _) => original_sp(cm, call_site1, enclosing_sp),
     }
 }
 
@@ -222,6 +223,11 @@ pub struct ExpnInfo {
     pub callee: NameAndSpan
 }
 
+#[deriving(PartialEq, Eq, Clone, Show, Hash)]
+pub struct ExpnId(u32);
+
+pub static NO_EXPANSION: ExpnId = ExpnId(-1);
+
 pub type FileName = String;
 
 pub struct FileLines {
@@ -299,13 +305,15 @@ impl FileMap {
 }
 
 pub struct CodeMap {
-    pub files: RefCell<Vec<Rc<FileMap>>>
+    pub files: RefCell<Vec<Rc<FileMap>>>,
+    expansions: RefCell<Vec<ExpnInfo>>
 }
 
 impl CodeMap {
     pub fn new() -> CodeMap {
         CodeMap {
             files: RefCell::new(Vec::new()),
+            expansions: RefCell::new(Vec::new()),
         }
     }
 
@@ -527,6 +535,19 @@ impl CodeMap {
             col: chpos - linechpos
         }
     }
+
+    pub fn record_expansion(&self, expn_info: ExpnInfo) -> ExpnId {
+        let mut expansions = self.expansions.borrow_mut();
+        expansions.push(expn_info);
+        ExpnId(expansions.len().to_u32().expect("too many ExpnInfo's!") - 1)
+    }
+
+    pub fn with_expn_info<T>(&self, id: ExpnId, f: |Option<&ExpnInfo>| -> T) -> T {
+        match id {
+            NO_EXPANSION => f(None),
+            ExpnId(i) => f(Some(&(*self.expansions.borrow())[i as uint]))
+        }
+    }
 }
 
 #[cfg(test)]
@@ -665,7 +686,7 @@ mod test {
     fn t7() {
         // Test span_to_lines for a span ending at the end of filemap
         let cm = init_code_map();
-        let span = Span {lo: BytePos(12), hi: BytePos(23), expn_info: None};
+        let span = Span {lo: BytePos(12), hi: BytePos(23), expn_id: NO_EXPANSION};
         let file_lines = cm.span_to_lines(span);
 
         assert_eq!(file_lines.file.name, "blork.rs".to_string());
@@ -677,7 +698,7 @@ mod test {
     fn t8() {
         // Test span_to_snippet for a span ending at the end of filemap
         let cm = init_code_map();
-        let span = Span {lo: BytePos(12), hi: BytePos(23), expn_info: None};
+        let span = Span {lo: BytePos(12), hi: BytePos(23), expn_id: NO_EXPANSION};
         let snippet = cm.span_to_snippet(span);
 
         assert_eq!(snippet, Some("second line".to_string()));
@@ -687,7 +708,7 @@ mod test {
     fn t9() {
         // Test span_to_str for a span ending at the end of filemap
         let cm = init_code_map();
-        let span = Span {lo: BytePos(12), hi: BytePos(23), expn_info: None};
+        let span = Span {lo: BytePos(12), hi: BytePos(23), expn_id: NO_EXPANSION};
         let sstr =  cm.span_to_string(span);
 
         assert_eq!(sstr, "blork.rs:2:1: 2:12".to_string());

src/libsyntax/diagnostic.rs

@@ -389,7 +389,7 @@ fn emit(dst: &mut EmitterWriter, cm: &codemap::CodeMap, rsp: RenderSpan,
         // we want to tell compiletest/runtest to look at the last line of the
         // span (since `custom_highlight_lines` displays an arrow to the end of
         // the span)
-        let span_end = Span { lo: sp.hi, hi: sp.hi, expn_info: sp.expn_info};
+        let span_end = Span { lo: sp.hi, hi: sp.hi, expn_id: sp.expn_id};
         let ses = cm.span_to_string(span_end);
         try!(print_diagnostic(dst, ses.as_slice(), lvl, msg, code));
         if rsp.is_full_span() {
@@ -523,24 +523,24 @@ fn print_macro_backtrace(w: &mut EmitterWriter,
                          cm: &codemap::CodeMap,
                          sp: Span)
                          -> io::IoResult<()> {
-    for ei in sp.expn_info.iter() {
-        let ss = ei.callee
-                   .span
-                   .as_ref()
-                   .map_or("".to_string(), |span| cm.span_to_string(*span));
-        let (pre, post) = match ei.callee.format {
-            codemap::MacroAttribute => ("#[", "]"),
-            codemap::MacroBang => ("", "!")
-        };
-        try!(print_diagnostic(w, ss.as_slice(), Note,
-                              format!("in expansion of {}{}{}", pre,
-                                      ei.callee.name,
-                                      post).as_slice(), None));
-        let ss = cm.span_to_string(ei.call_site);
-        try!(print_diagnostic(w, ss.as_slice(), Note, "expansion site", None));
-        try!(print_macro_backtrace(w, cm, ei.call_site));
-    }
-    Ok(())
+    let cs = try!(cm.with_expn_info(sp.expn_id, |expn_info| match expn_info {
+        Some(ei) => {
+            let ss = ei.callee.span.map_or(String::new(), |span| cm.span_to_string(span));
+            let (pre, post) = match ei.callee.format {
+                codemap::MacroAttribute => ("#[", "]"),
+                codemap::MacroBang => ("", "!")
+            };
+            try!(print_diagnostic(w, ss.as_slice(), Note,
+                                  format!("in expansion of {}{}{}", pre,
+                                          ei.callee.name,
+                                          post).as_slice(), None));
+            let ss = cm.span_to_string(ei.call_site);
+            try!(print_diagnostic(w, ss.as_slice(), Note, "expansion site", None));
+            Ok(Some(ei.call_site))
+        }
+        None => Ok(None)
+    }));
+    cs.map_or(Ok(()), |call_site| print_macro_backtrace(w, cm, call_site))
 }
 
 pub fn expect<T>(diag: &SpanHandler, opt: Option<T>, msg: || -> String) -> T {

src/libsyntax/ext/base.rs

@@ -11,7 +11,7 @@
 use ast;
 use ast::Name;
 use codemap;
-use codemap::{CodeMap, Span, ExpnInfo};
+use codemap::{CodeMap, Span, ExpnId, ExpnInfo, NO_EXPANSION};
 use ext;
 use ext::expand;
 use parse;
@@ -24,7 +24,6 @@ use ext::mtwt;
 use fold::Folder;
 
 use std::collections::HashMap;
-use std::gc::{Gc, GC};
 use std::rc::Rc;
 
 // new-style macro! tt code:
@@ -457,7 +456,7 @@ fn initial_syntax_expander_table() -> SyntaxEnv {
 pub struct ExtCtxt<'a> {
     pub parse_sess: &'a parse::ParseSess,
     pub cfg: ast::CrateConfig,
-    pub backtrace: Option<Gc<ExpnInfo>>,
+    pub backtrace: ExpnId,
     pub ecfg: expand::ExpansionConfig,
 
     pub mod_path: Vec<ast::Ident> ,
@@ -473,7 +472,7 @@ impl<'a> ExtCtxt<'a> {
         ExtCtxt {
             parse_sess: parse_sess,
             cfg: cfg,
-            backtrace: None,
+            backtrace: NO_EXPANSION,
             mod_path: Vec::new(),
             ecfg: ecfg,
             trace_mac: false,
@@ -501,13 +500,49 @@ impl<'a> ExtCtxt<'a> {
     pub fn parse_sess(&self) -> &'a parse::ParseSess { self.parse_sess }
     pub fn cfg(&self) -> ast::CrateConfig { self.cfg.clone() }
     pub fn call_site(&self) -> Span {
-        match self.backtrace {
+        self.codemap().with_expn_info(self.backtrace, |ei| match ei {
             Some(expn_info) => expn_info.call_site,
             None => self.bug("missing top span")
-        }
+        })
     }
     pub fn print_backtrace(&self) { }
-    pub fn backtrace(&self) -> Option<Gc<ExpnInfo>> { self.backtrace }
+    pub fn backtrace(&self) -> ExpnId { self.backtrace }
+    pub fn original_span(&self) -> Span {
+        let mut expn_id = self.backtrace;
+        let mut call_site = None;
+        loop {
+            match self.codemap().with_expn_info(expn_id, |ei| ei.map(|ei| ei.call_site)) {
+                None => break,
+                Some(cs) => {
+                    call_site = Some(cs);
+                    expn_id = cs.expn_id;
+                }
+            }
+        }
+        call_site.expect("missing expansion backtrace")
+    }
+    pub fn original_span_in_file(&self) -> Span {
+        let mut expn_id = self.backtrace;
+        let mut call_site = None;
+        loop {
+            let expn_info = self.codemap().with_expn_info(expn_id, |ei| {
+                ei.map(|ei| (ei.call_site, ei.callee.name.as_slice() == "include"))
+            });
+            match expn_info {
+                None => break,
+                Some((cs, is_include)) => {
+                    if is_include {
+                        // Don't recurse into file using "include!".
+                        break;
+                    }
+                    call_site = Some(cs);
+                    expn_id = cs.expn_id;
+                }
+            }
+        }
+        call_site.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> {
@@ -516,22 +551,22 @@ impl<'a> ExtCtxt<'a> {
         v.extend(self.mod_path.iter().map(|a| *a));
         return v;
     }
-    pub fn bt_push(&mut self, ei: codemap::ExpnInfo) {
-        match ei {
-            ExpnInfo {call_site: cs, callee: ref callee} => {
-                self.backtrace =
-                    Some(box(GC) ExpnInfo {
-                        call_site: Span {lo: cs.lo, hi: cs.hi,
-                                         expn_info: self.backtrace.clone()},
-                        callee: (*callee).clone()
-                    });
-            }
-        }
+    pub fn bt_push(&mut self, ei: ExpnInfo) {
+        let mut call_site = ei.call_site;
+        call_site.expn_id = self.backtrace;
+        self.backtrace = self.codemap().record_expansion(ExpnInfo {
+            call_site: call_site,
+            callee: ei.callee
+        });
     }
     pub fn bt_pop(&mut self) {
         match self.backtrace {
-            Some(expn_info) => self.backtrace = expn_info.call_site.expn_info,
-            _ => self.bug("tried to pop without a push")
+            NO_EXPANSION => self.bug("tried to pop without a push"),
+            expn_id => {
+                self.backtrace = self.codemap().with_expn_info(expn_id, |expn_info| {
+                    expn_info.map_or(NO_EXPANSION, |ei| ei.call_site.expn_id)
+                });
+            }
         }
     }
     /// Emit `msg` attached to `sp`, and stop compilation immediately.