diff --git a/src/libfuzzer/fuzzer.rs b/src/libfuzzer/fuzzer.rs
index a4968382cf478..86e45179cb033 100644
--- a/src/libfuzzer/fuzzer.rs
+++ b/src/libfuzzer/fuzzer.rs
@@ -225,7 +225,7 @@ fn as_str(f: fn@(+x: io::Writer)) -> ~str {
     io::with_str_writer(f)
 }
 
-fn check_variants_of_ast(crate: ast::crate, codemap: codemap::CodeMap,
+fn check_variants_of_ast(crate: ast::crate, codemap: @codemap::CodeMap,
                          filename: &Path, cx: context) {
     let stolen = steal(crate, cx.mode);
     let extra_exprs = vec::filter(common_exprs(),
@@ -239,7 +239,7 @@ fn check_variants_of_ast(crate: ast::crate, codemap: codemap::CodeMap,
 
 fn check_variants_T<T: Copy>(
   crate: ast::crate,
-  codemap: codemap::CodeMap,
+  codemap: @codemap::CodeMap,
   filename: &Path,
   thing_label: ~str,
   things: ~[T],
diff --git a/src/librustc/driver/driver.rs b/src/librustc/driver/driver.rs
index 934a02d6dd3e3..4879ae30699a1 100644
--- a/src/librustc/driver/driver.rs
+++ b/src/librustc/driver/driver.rs
@@ -354,7 +354,7 @@ fn pretty_print_input(sess: Session, cfg: ast::crate_cfg, input: input,
       ppm_expanded | ppm_normal => pprust::no_ann()
     };
     let is_expanded = upto != cu_parse;
-    let src = codemap::get_filemap(sess.codemap, source_name(input)).src;
+    let src = sess.codemap.get_filemap(source_name(input)).src;
     do io::with_str_reader(*src) |rdr| {
         pprust::print_crate(sess.codemap, sess.parse_sess.interner,
                             sess.span_diagnostic, crate,
@@ -574,7 +574,7 @@ fn build_session_options(binary: ~str,
 
 fn build_session(sopts: @session::options,
                  demitter: diagnostic::emitter) -> Session {
-    let codemap = codemap::new_codemap();
+    let codemap = @codemap::CodeMap::new();
     let diagnostic_handler =
         diagnostic::mk_handler(Some(demitter));
     let span_diagnostic_handler =
@@ -583,7 +583,7 @@ fn build_session(sopts: @session::options,
 }
 
 fn build_session_(sopts: @session::options,
-                  cm: codemap::CodeMap,
+                  cm: @codemap::CodeMap,
                   demitter: diagnostic::emitter,
                   span_diagnostic_handler: diagnostic::span_handler)
                -> Session {
diff --git a/src/librustc/driver/session.rs b/src/librustc/driver/session.rs
index ed73bcb6d7259..d2a277e82fbd5 100644
--- a/src/librustc/driver/session.rs
+++ b/src/librustc/driver/session.rs
@@ -131,7 +131,7 @@ type Session_ = {targ_cfg: @config,
                  opts: @options,
                  cstore: metadata::cstore::CStore,
                  parse_sess: parse_sess,
-                 codemap: codemap::CodeMap,
+                 codemap: @codemap::CodeMap,
                  // For a library crate, this is always none
                  mut main_fn: Option<(node_id, codemap::span)>,
                  span_diagnostic: diagnostic::span_handler,
diff --git a/src/librustc/metadata/encoder.rs b/src/librustc/metadata/encoder.rs
index 07fc637a04933..5aed12dba9594 100644
--- a/src/librustc/metadata/encoder.rs
+++ b/src/librustc/metadata/encoder.rs
@@ -557,7 +557,7 @@ fn encode_info_for_item(ecx: @encode_ctxt, ebml_w: ebml::Serializer,
     let add_to_index = |copy ebml_w| add_to_index_(item, ebml_w, index);
 
     debug!("encoding info for item at %s",
-           syntax::codemap::span_to_str(item.span, ecx.tcx.sess.codemap));
+           ecx.tcx.sess.codemap.span_to_str(item.span));
 
     match item.node {
       item_const(_, _) => {
diff --git a/src/librustc/middle/liveness.rs b/src/librustc/middle/liveness.rs
index ec7c2ffc6f1da..ed9549cedd7e6 100644
--- a/src/librustc/middle/liveness.rs
+++ b/src/librustc/middle/liveness.rs
@@ -97,7 +97,7 @@ use std::map::HashMap;
 use syntax::{visit, ast_util};
 use syntax::print::pprust::{expr_to_str, block_to_str};
 use visit::vt;
-use syntax::codemap::{span, span_to_str};
+use syntax::codemap::span;
 use syntax::ast::*;
 use io::WriterUtil;
 use capture::{cap_move, cap_drop, cap_copy, cap_ref};
@@ -170,9 +170,9 @@ impl LiveNodeKind : cmp::Eq {
 fn live_node_kind_to_str(lnk: LiveNodeKind, cx: ty::ctxt) -> ~str {
     let cm = cx.sess.codemap;
     match lnk {
-        FreeVarNode(s) => fmt!("Free var node [%s]", span_to_str(s, cm)),
-        ExprNode(s)    => fmt!("Expr node [%s]", span_to_str(s, cm)),
-        VarDefNode(s)  => fmt!("Var def node [%s]", span_to_str(s, cm)),
+        FreeVarNode(s) => fmt!("Free var node [%s]", cm.span_to_str(s)),
+        ExprNode(s)    => fmt!("Expr node [%s]", cm.span_to_str(s)),
+        VarDefNode(s)  => fmt!("Var def node [%s]", cm.span_to_str(s)),
         ExitNode       => ~"Exit node"
     }
 }
diff --git a/src/librustc/middle/trans/base.rs b/src/librustc/middle/trans/base.rs
index f509c15ab5f8d..4941885cafb54 100644
--- a/src/librustc/middle/trans/base.rs
+++ b/src/librustc/middle/trans/base.rs
@@ -919,7 +919,7 @@ fn trans_trace(bcx: block, sp_opt: Option<span>, trace_str: ~str) {
     let {V_filename, V_line} = match sp_opt {
       Some(sp) => {
         let sess = bcx.sess();
-        let loc = codemap::lookup_char_pos(sess.parse_sess.cm, sp.lo);
+        let loc = sess.parse_sess.cm.lookup_char_pos(sp.lo);
         {V_filename: C_cstr(bcx.ccx(), loc.file.name),
          V_line: loc.line as int}
       }
diff --git a/src/librustc/middle/trans/build.rs b/src/librustc/middle/trans/build.rs
index f7690b7bc9300..f980990517495 100644
--- a/src/librustc/middle/trans/build.rs
+++ b/src/librustc/middle/trans/build.rs
@@ -645,7 +645,7 @@ fn _UndefReturn(cx: block, Fn: ValueRef) -> ValueRef {
 fn add_span_comment(bcx: block, sp: span, text: ~str) {
     let ccx = bcx.ccx();
     if !ccx.sess.no_asm_comments() {
-        let s = text + ~" (" + codemap::span_to_str(sp, ccx.sess.codemap)
+        let s = text + ~" (" + ccx.sess.codemap.span_to_str(sp)
             + ~")";
         log(debug, s);
         add_comment(bcx, s);
diff --git a/src/librustc/middle/trans/controlflow.rs b/src/librustc/middle/trans/controlflow.rs
index 59a733433bf22..0c09b02bb07b1 100644
--- a/src/librustc/middle/trans/controlflow.rs
+++ b/src/librustc/middle/trans/controlflow.rs
@@ -339,7 +339,7 @@ fn trans_fail_value(bcx: block, sp_opt: Option<span>, V_fail_str: ValueRef)
     let {V_filename, V_line} = match sp_opt {
       Some(sp) => {
         let sess = bcx.sess();
-        let loc = codemap::lookup_char_pos(sess.parse_sess.cm, sp.lo);
+        let loc = sess.parse_sess.cm.lookup_char_pos(sp.lo);
         {V_filename: C_cstr(bcx.ccx(), loc.file.name),
          V_line: loc.line as int}
       }
@@ -361,7 +361,7 @@ fn trans_fail_bounds_check(bcx: block, sp: span,
     let _icx = bcx.insn_ctxt("trans_fail_bounds_check");
     let ccx = bcx.ccx();
 
-    let loc = codemap::lookup_char_pos(bcx.sess().parse_sess.cm, sp.lo);
+    let loc = bcx.sess().parse_sess.cm.lookup_char_pos(sp.lo);
     let line = C_int(ccx, loc.line as int);
     let filename_cstr = C_cstr(bcx.ccx(), loc.file.name);
     let filename = PointerCast(bcx, filename_cstr, T_ptr(T_i8()));
diff --git a/src/librustc/middle/trans/debuginfo.rs b/src/librustc/middle/trans/debuginfo.rs
index fd18aaaf58ec6..d4d1c8d3b2ecd 100644
--- a/src/librustc/middle/trans/debuginfo.rs
+++ b/src/librustc/middle/trans/debuginfo.rs
@@ -8,7 +8,7 @@ use trans::build::B;
 use middle::ty;
 use syntax::{ast, codemap, ast_util, ast_map};
 use syntax::parse::token::ident_interner;
-use codemap::span;
+use codemap::{span, CharPos};
 use ast::Ty;
 use pat_util::*;
 use util::ppaux::ty_to_str;
@@ -112,7 +112,7 @@ type compile_unit_md = {name: ~str};
 type subprogram_md = {id: ast::node_id};
 type local_var_md = {id: ast::node_id};
 type tydesc_md = {hash: uint};
-type block_md = {start: codemap::loc, end: codemap::loc};
+type block_md = {start: codemap::Loc, end: codemap::Loc};
 type argument_md = {id: ast::node_id};
 type retval_md = {id: ast::node_id};
 
@@ -229,8 +229,8 @@ fn create_file(cx: @crate_ctxt, full_path: ~str) -> @metadata<file_md> {
     return mdval;
 }
 
-fn line_from_span(cm: codemap::CodeMap, sp: span) -> uint {
-    codemap::lookup_char_pos(cm, sp.lo).line
+fn line_from_span(cm: @codemap::CodeMap, sp: span) -> uint {
+    cm.lookup_char_pos(sp.lo).line
 }
 
 fn create_block(cx: block) -> @metadata<block_md> {
@@ -244,9 +244,9 @@ fn create_block(cx: block) -> @metadata<block_md> {
     }
     let sp = cx.node_info.get().span;
 
-    let start = codemap::lookup_char_pos(cx.sess().codemap, sp.lo);
+    let start = cx.sess().codemap.lookup_char_pos(sp.lo);
     let fname = start.file.name;
-    let end = codemap::lookup_char_pos(cx.sess().codemap, sp.hi);
+    let end = cx.sess().codemap.lookup_char_pos(sp.hi);
     let tg = LexicalBlockTag;
     /*alt cached_metadata::<@metadata<block_md>>(
         cache, tg,
@@ -266,8 +266,8 @@ fn create_block(cx: block) -> @metadata<block_md> {
     };
     let lldata = ~[lltag(tg),
                   parent,
-                  lli32(start.line as int),
-                  lli32(start.col as int),
+                  lli32(start.line.to_int()),
+                  lli32(start.col.to_int()),
                   file_node.node,
                   lli32(unique_id)
                  ];
@@ -597,7 +597,7 @@ fn create_ty(_cx: @crate_ctxt, _t: ty::t, _ty: @ast::Ty)
 }
 
 fn filename_from_span(cx: @crate_ctxt, sp: codemap::span) -> ~str {
-    codemap::lookup_char_pos(cx.sess.codemap, sp.lo).file.name
+    cx.sess.codemap.lookup_char_pos(sp.lo).file.name
 }
 
 fn create_var(type_tag: int, context: ValueRef, name: ~str, file: ValueRef,
@@ -629,8 +629,7 @@ fn create_local_var(bcx: block, local: @ast::local)
       // FIXME this should be handled (#2533)
       _ => fail ~"no single variable name for local"
     };
-    let loc = codemap::lookup_char_pos(cx.sess.codemap,
-                                       local.span.lo);
+    let loc = cx.sess.codemap.lookup_char_pos(local.span.lo);
     let ty = node_id_type(bcx, local.node.id);
     let tymd = create_ty(cx, ty, local.node.ty);
     let filemd = create_file(cx, loc.file.name);
@@ -674,8 +673,7 @@ fn create_arg(bcx: block, arg: ast::arg, sp: span)
       option::None => ()
     }
 
-    let loc = codemap::lookup_char_pos(cx.sess.codemap,
-                                       sp.lo);
+    let loc = cx.sess.codemap.lookup_char_pos(sp.lo);
     let ty = node_id_type(bcx, arg.id);
     let tymd = create_ty(cx, ty, arg.ty);
     let filemd = create_file(cx, loc.file.name);
@@ -714,9 +712,9 @@ fn update_source_pos(cx: block, s: span) {
     }
     let cm = cx.sess().codemap;
     let blockmd = create_block(cx);
-    let loc = codemap::lookup_char_pos(cm, s.lo);
-    let scopedata = ~[lli32(loc.line as int),
-                     lli32(loc.col as int),
+    let loc = cm.lookup_char_pos(s.lo);
+    let scopedata = ~[lli32(loc.line.to_int()),
+                     lli32(loc.col.to_int()),
                      blockmd.node,
                      llnull()];
     let dbgscope = llmdnode(scopedata);
@@ -731,7 +729,7 @@ fn create_function(fcx: fn_ctxt) -> @metadata<subprogram_md> {
     log(debug, fcx.id);
 
     let sp = fcx.span.get();
-    log(debug, codemap::span_to_str(sp, cx.sess.codemap));
+    log(debug, cx.sess.codemap.span_to_str(sp));
 
     let (ident, ret_ty, id) = match cx.tcx.items.get(fcx.id) {
       ast_map::node_item(item, _) => {
@@ -773,8 +771,7 @@ fn create_function(fcx: fn_ctxt) -> @metadata<subprogram_md> {
       option::None => ()
     }
 
-    let loc = codemap::lookup_char_pos(cx.sess.codemap,
-                                       sp.lo);
+    let loc = cx.sess.codemap.lookup_char_pos(sp.lo);
     let file_node = create_file(cx, loc.file.name).node;
     let ty_node = if cx.sess.opts.extra_debuginfo {
         match ret_ty.node {
diff --git a/src/librustc/middle/typeck/infer/region_inference.rs b/src/librustc/middle/typeck/infer/region_inference.rs
index bdc764a8d0b09..652d99779d312 100644
--- a/src/librustc/middle/typeck/infer/region_inference.rs
+++ b/src/librustc/middle/typeck/infer/region_inference.rs
@@ -507,7 +507,7 @@ impl RegionVarBindings {
             self.undo_log.push(AddVar(vid));
         }
         debug!("created new region variable %? with span %?",
-               vid, codemap::span_to_str(span, self.tcx.sess.codemap));
+               vid, self.tcx.sess.codemap.span_to_str(span));
         return vid;
     }
 
diff --git a/src/librustc/rustc.rs b/src/librustc/rustc.rs
index 8b832b9ab9f87..789c7ca7073a8 100644
--- a/src/librustc/rustc.rs
+++ b/src/librustc/rustc.rs
@@ -193,7 +193,7 @@ fn monitor(+f: fn~(diagnostic::emitter)) {
 
         // The 'diagnostics emitter'. Every error, warning, etc. should
         // go through this function.
-        let demitter = fn@(cmsp: Option<(codemap::CodeMap, codemap::span)>,
+        let demitter = fn@(cmsp: Option<(@codemap::CodeMap, codemap::span)>,
                            msg: &str, lvl: diagnostic::level) {
             if lvl == diagnostic::fatal {
                 comm::send(ch, fatal);
diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
index a9b67a7ff29c9..198b26c4ecc69 100644
--- a/src/librustc/util/ppaux.rs
+++ b/src/librustc/util/ppaux.rs
@@ -105,8 +105,9 @@ fn explain_region_and_span(cx: ctxt, region: ty::Region)
     fn explain_span(cx: ctxt, heading: ~str, span: span)
         -> (~str, Option<span>)
     {
-        let lo = codemap::lookup_char_pos_adj(cx.sess.codemap, span.lo);
-        (fmt!("the %s at %u:%u", heading, lo.line, lo.col), Some(span))
+        let lo = cx.sess.codemap.lookup_char_pos_adj(span.lo);
+        (fmt!("the %s at %u:%u", heading,
+              lo.line, lo.col.to_uint()), Some(span))
     }
 }
 
@@ -131,17 +132,17 @@ fn re_scope_id_to_str(cx: ctxt, node_id: ast::node_id) -> ~str {
     match cx.items.find(node_id) {
       Some(ast_map::node_block(blk)) => {
         fmt!("<block at %s>",
-             codemap::span_to_str(blk.span, cx.sess.codemap))
+             cx.sess.codemap.span_to_str(blk.span))
       }
       Some(ast_map::node_expr(expr)) => {
         match expr.node {
           ast::expr_call(*) => {
             fmt!("<call at %s>",
-                 codemap::span_to_str(expr.span, cx.sess.codemap))
+                 cx.sess.codemap.span_to_str(expr.span))
           }
           ast::expr_match(*) => {
             fmt!("<alt at %s>",
-                 codemap::span_to_str(expr.span, cx.sess.codemap))
+                 cx.sess.codemap.span_to_str(expr.span))
           }
           ast::expr_assign_op(*) |
           ast::expr_field(*) |
@@ -149,11 +150,11 @@ fn re_scope_id_to_str(cx: ctxt, node_id: ast::node_id) -> ~str {
           ast::expr_binary(*) |
           ast::expr_index(*) => {
             fmt!("<method at %s>",
-                 codemap::span_to_str(expr.span, cx.sess.codemap))
+                 cx.sess.codemap.span_to_str(expr.span))
           }
           _ => {
             fmt!("<expression at %s>",
-                 codemap::span_to_str(expr.span, cx.sess.codemap))
+                 cx.sess.codemap.span_to_str(expr.span))
           }
         }
       }
diff --git a/src/librustdoc/astsrv.rs b/src/librustdoc/astsrv.rs
index 7b2c6fe5f0cbc..cb97d38b20854 100644
--- a/src/librustdoc/astsrv.rs
+++ b/src/librustdoc/astsrv.rs
@@ -120,7 +120,7 @@ fn build_ctxt(sess: Session,
 
 fn build_session() -> Session {
     let sopts: @options = basic_options();
-    let codemap = codemap::new_codemap();
+    let codemap = @codemap::CodeMap::new();
     let error_handlers = build_error_handlers(codemap);
     let {emitter, span_handler} = error_handlers;
 
@@ -137,7 +137,7 @@ type ErrorHandlers = {
 // Build a custom error handler that will allow us to ignore non-fatal
 // errors
 fn build_error_handlers(
-    codemap: codemap::CodeMap
+    codemap: @codemap::CodeMap
 ) -> ErrorHandlers {
 
     type DiagnosticHandler = {
@@ -156,13 +156,13 @@ fn build_error_handlers(
         fn note(msg: &str) { self.inner.note(msg) }
         fn bug(msg: &str) -> ! { self.inner.bug(msg) }
         fn unimpl(msg: &str) -> ! { self.inner.unimpl(msg) }
-        fn emit(cmsp: Option<(codemap::CodeMap, codemap::span)>,
+        fn emit(cmsp: Option<(@codemap::CodeMap, codemap::span)>,
                 msg: &str, lvl: diagnostic::level) {
             self.inner.emit(cmsp, msg, lvl)
         }
     }
 
-    let emitter = fn@(cmsp: Option<(codemap::CodeMap, codemap::span)>,
+    let emitter = fn@(cmsp: Option<(@codemap::CodeMap, codemap::span)>,
                        msg: &str, lvl: diagnostic::level) {
         diagnostic::emit(cmsp, msg, lvl);
     };
diff --git a/src/librustdoc/attr_parser.rs b/src/librustdoc/attr_parser.rs
index 2b16112fe16c7..4e8b11d2ca6fa 100644
--- a/src/librustdoc/attr_parser.rs
+++ b/src/librustdoc/attr_parser.rs
@@ -30,7 +30,7 @@ mod test {
 
         let parse_sess = syntax::parse::new_parse_sess(None);
         let parser = parse::new_parser_from_source_str(
-            parse_sess, ~[], ~"-", codemap::fss_none, @source);
+            parse_sess, ~[], ~"-", codemap::FssNone, @source);
 
         parser.parse_outer_attributes()
     }
diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 7452e41fac337..4455db0882695 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -4,7 +4,7 @@ use std::serialization::{Serializable,
                          Deserializable,
                          Serializer,
                          Deserializer};
-use codemap::{span, filename};
+use codemap::{span, FileName};
 use parse::token;
 
 #[auto_serialize]
diff --git a/src/libsyntax/ast_util.rs b/src/libsyntax/ast_util.rs
index d3b879da7dd95..73a1c4b7530a0 100644
--- a/src/libsyntax/ast_util.rs
+++ b/src/libsyntax/ast_util.rs
@@ -1,7 +1,7 @@
-use codemap::span;
+use codemap::{span, BytePos};
 use ast::*;
 
-pure fn spanned<T>(lo: uint, hi: uint, +t: T) -> spanned<T> {
+pure fn spanned<T>(+lo: BytePos, +hi: BytePos, +t: T) -> spanned<T> {
     respan(mk_sp(lo, hi), move t)
 }
 
@@ -14,12 +14,12 @@ pure fn dummy_spanned<T>(+t: T) -> spanned<T> {
 }
 
 /* assuming that we're not in macro expansion */
-pure fn mk_sp(lo: uint, hi: uint) -> span {
-    {lo: lo, hi: hi, expn_info: None}
+pure fn mk_sp(+lo: BytePos, +hi: BytePos) -> span {
+    span {lo: lo, hi: hi, expn_info: None}
 }
 
 // make this a const, once the compiler supports it
-pure fn dummy_sp() -> span { return mk_sp(0u, 0u); }
+pure fn dummy_sp() -> span { return mk_sp(BytePos(0), BytePos(0)); }
 
 
 
diff --git a/src/libsyntax/attr.rs b/src/libsyntax/attr.rs
index 8c19814350ca7..da80e26b1afe9 100644
--- a/src/libsyntax/attr.rs
+++ b/src/libsyntax/attr.rs
@@ -6,6 +6,7 @@ use either::Either;
 use diagnostic::span_handler;
 use ast_util::{spanned, dummy_spanned};
 use parse::comments::{doc_comment_style, strip_doc_comment_decoration};
+use codemap::BytePos;
 
 // Constructors
 export mk_name_value_item_str;
@@ -74,7 +75,8 @@ fn mk_attr(item: @ast::meta_item) -> ast::attribute {
                        is_sugared_doc: false});
 }
 
-fn mk_sugared_doc_attr(text: ~str, lo: uint, hi: uint) -> ast::attribute {
+fn mk_sugared_doc_attr(text: ~str,
+                       +lo: BytePos, +hi: BytePos) -> ast::attribute {
     let lit = spanned(lo, hi, ast::lit_str(@text));
     let attr = {
         style: doc_comment_style(text),
diff --git a/src/libsyntax/codemap.rs b/src/libsyntax/codemap.rs
index 4278e1f199a62..d291d9545eb6a 100644
--- a/src/libsyntax/codemap.rs
+++ b/src/libsyntax/codemap.rs
@@ -1,179 +1,144 @@
+/*!
+
+The CodeMap tracks all the source code used within a single crate, mapping
+from integer byte positions to the original source code location. Each bit of
+source parsed during crate parsing (typically files, in-memory strings, or
+various bits of macro expansion) cover a continuous range of bytes in the
+CodeMap and are represented by FileMaps. Byte positions are stored in `spans`
+and used pervasively in the compiler. They are absolute positions within the
+CodeMap, which upon request can be converted to line and column information,
+source code snippets, etc.
+
+*/
+
 use dvec::DVec;
 use std::serialization::{Serializable,
                          Deserializable,
                          Serializer,
                          Deserializer};
 
-export filename;
-export filemap;
-export span;
-export file_substr;
-export fss_none;
-export fss_internal;
-export fss_external;
-export CodeMap;
-export expn_info;
-export expn_info_;
-export expanded_from;
-export new_filemap;
-export new_filemap_w_substr;
-export mk_substr_filename;
-export lookup_char_pos;
-export lookup_char_pos_adj;
-export adjust_span;
-export span_to_str;
-export span_to_filename;
-export span_to_lines;
-export file_lines;
-export get_line;
-export next_line;
-export span_to_snippet;
-export loc;
-export get_filemap;
-export new_codemap;
-
-type filename = ~str;
-
-type file_pos = {ch: uint, byte: uint};
-
-impl file_pos : cmp::Eq {
-    pure fn eq(other: &file_pos) -> bool {
-        self.ch == (*other).ch && self.byte == (*other).byte
-    }
-    pure fn ne(other: &file_pos) -> bool { !self.eq(other) }
+trait Pos {
+    static pure fn from_uint(n: uint) -> self;
+    pure fn to_uint(&self) -> uint;
 }
 
-/* A codemap is a thing that maps uints to file/line/column positions
- * in a crate. This to make it possible to represent the positions
- * with single-word things, rather than passing records all over the
- * compiler.
- */
-
-enum file_substr {
-    fss_none,
-    fss_internal(span),
-    fss_external({filename: ~str, line: uint, col: uint})
-}
+/// A byte offset
+pub enum BytePos = uint;
+/// A character offset. Because of multibyte utf8 characters, a byte offset
+/// is not equivalent to a character offset. The CodeMap will convert BytePos
+/// values to CharPos values as necessary.
+pub enum CharPos = uint;
 
-type filemap =
-    @{name: filename, substr: file_substr, src: @~str,
-      start_pos: file_pos, mut lines: ~[file_pos]};
+// XXX: Lots of boilerplate in these impls, but so far my attempts to fix
+// have been unsuccessful
 
-type CodeMap = @{files: DVec<filemap>};
-
-type loc = {file: filemap, line: uint, col: uint};
-
-fn new_codemap() -> CodeMap { @{files: DVec()} }
-
-fn new_filemap_w_substr(+filename: filename, +substr: file_substr,
-                        src: @~str,
-                        start_pos_ch: uint, start_pos_byte: uint)
-   -> filemap {
-    return @{name: filename, substr: substr, src: src,
-          start_pos: {ch: start_pos_ch, byte: start_pos_byte},
-          mut lines: ~[{ch: start_pos_ch, byte: start_pos_byte}]};
+impl BytePos: Pos {
+    static pure fn from_uint(n: uint) -> BytePos { BytePos(n) }
+    pure fn to_uint(&self) -> uint { **self }
 }
 
-fn new_filemap(+filename: filename, src: @~str,
-               start_pos_ch: uint, start_pos_byte: uint)
-    -> filemap {
-    return new_filemap_w_substr(filename, fss_none, src,
-                             start_pos_ch, start_pos_byte);
+impl BytePos: cmp::Eq {
+    pure fn eq(other: &BytePos) -> bool {
+        *self == **other
+    }
+    pure fn ne(other: &BytePos) -> bool { !self.eq(other) }
 }
 
-fn mk_substr_filename(cm: CodeMap, sp: span) -> ~str
-{
-    let pos = lookup_char_pos(cm, sp.lo);
-    return fmt!("<%s:%u:%u>", pos.file.name, pos.line, pos.col);
+impl BytePos: cmp::Ord {
+    pure fn lt(other: &BytePos) -> bool { *self < **other }
+    pure fn le(other: &BytePos) -> bool { *self <= **other }
+    pure fn ge(other: &BytePos) -> bool { *self >= **other }
+    pure fn gt(other: &BytePos) -> bool { *self > **other }
 }
 
-fn next_line(file: filemap, chpos: uint, byte_pos: uint) {
-    file.lines.push({ch: chpos, byte: byte_pos + file.start_pos.byte});
+impl BytePos: Num {
+    pure fn add(other: &BytePos) -> BytePos {
+        BytePos(*self + **other)
+    }
+    pure fn sub(other: &BytePos) -> BytePos {
+        BytePos(*self - **other)
+    }
+    pure fn mul(other: &BytePos) -> BytePos {
+        BytePos(*self * (**other))
+    }
+    pure fn div(other: &BytePos) -> BytePos {
+        BytePos(*self / **other)
+    }
+    pure fn modulo(other: &BytePos) -> BytePos {
+        BytePos(*self % **other)
+    }
+    pure fn neg() -> BytePos {
+        BytePos(-*self)
+    }
+    pure fn to_int() -> int { *self as int }
+    static pure fn from_int(+n: int) -> BytePos { BytePos(n as uint) }
 }
 
-type lookup_fn = pure fn(file_pos) -> uint;
-
-fn lookup_line(map: CodeMap, pos: uint, lookup: lookup_fn)
-    -> {fm: filemap, line: uint}
-{
-    let len = map.files.len();
-    let mut a = 0u;
-    let mut b = len;
-    while b - a > 1u {
-        let m = (a + b) / 2u;
-        if lookup(map.files[m].start_pos) > pos { b = m; } else { a = m; }
-    }
-    if (a >= len) {
-        fail fmt!("position %u does not resolve to a source location", pos)
-    }
-    let f = map.files[a];
-    a = 0u;
-    b = vec::len(f.lines);
-    while b - a > 1u {
-        let m = (a + b) / 2u;
-        if lookup(f.lines[m]) > pos { b = m; } else { a = m; }
-    }
-    return {fm: f, line: a};
+impl BytePos: to_bytes::IterBytes {
+    pure fn iter_bytes(+lsb0: bool, f: to_bytes::Cb) {
+        (*self).iter_bytes(lsb0, f)
+    }
 }
 
-fn lookup_pos(map: CodeMap, pos: uint, lookup: lookup_fn) -> loc {
-    let {fm: f, line: a} = lookup_line(map, pos, lookup);
-    return {file: f, line: a + 1u, col: pos - lookup(f.lines[a])};
+impl CharPos: Pos {
+    static pure fn from_uint(n: uint) -> CharPos { CharPos(n) }
+    pure fn to_uint(&self) -> uint { **self }
 }
 
-fn lookup_char_pos(map: CodeMap, pos: uint) -> loc {
-    pure fn lookup(pos: file_pos) -> uint { return pos.ch; }
-    return lookup_pos(map, pos, lookup);
+impl CharPos: cmp::Eq {
+    pure fn eq(other: &CharPos) -> bool {
+        *self == **other
+    }
+    pure fn ne(other: &CharPos) -> bool { !self.eq(other) }
 }
 
-fn lookup_byte_pos(map: CodeMap, pos: uint) -> loc {
-    pure fn lookup(pos: file_pos) -> uint { return pos.byte; }
-    return lookup_pos(map, pos, lookup);
+impl CharPos: cmp::Ord {
+    pure fn lt(other: &CharPos) -> bool { *self < **other }
+    pure fn le(other: &CharPos) -> bool { *self <= **other }
+    pure fn ge(other: &CharPos) -> bool { *self >= **other }
+    pure fn gt(other: &CharPos) -> bool { *self > **other }
 }
 
-fn lookup_char_pos_adj(map: CodeMap, pos: uint)
-    -> {filename: ~str, line: uint, col: uint, file: Option<filemap>}
-{
-    let loc = lookup_char_pos(map, pos);
-    match (loc.file.substr) {
-      fss_none => {
-        {filename: /* FIXME (#2543) */ copy loc.file.name,
-         line: loc.line,
-         col: loc.col,
-         file: Some(loc.file)}
-      }
-      fss_internal(sp) => {
-        lookup_char_pos_adj(map, sp.lo + (pos - loc.file.start_pos.ch))
-      }
-      fss_external(eloc) => {
-        {filename: /* FIXME (#2543) */ copy eloc.filename,
-         line: eloc.line + loc.line - 1u,
-         col: if loc.line == 1u {eloc.col + loc.col} else {loc.col},
-         file: None}
-      }
+impl CharPos: Num {
+    pure fn add(other: &CharPos) -> CharPos {
+        CharPos(*self + **other)
     }
+    pure fn sub(other: &CharPos) -> CharPos {
+        CharPos(*self - **other)
+    }
+    pure fn mul(other: &CharPos) -> CharPos {
+        CharPos(*self * (**other))
+    }
+    pure fn div(other: &CharPos) -> CharPos {
+        CharPos(*self / **other)
+    }
+    pure fn modulo(other: &CharPos) -> CharPos {
+        CharPos(*self % **other)
+    }
+    pure fn neg() -> CharPos {
+        CharPos(-*self)
+    }
+    pure fn to_int() -> int { *self as int }
+    static pure fn from_int(+n: int) -> CharPos { CharPos(n as uint) }
 }
 
-fn adjust_span(map: CodeMap, sp: span) -> span {
-    pure fn lookup(pos: file_pos) -> uint { return pos.ch; }
-    let line = lookup_line(map, sp.lo, lookup);
-    match (line.fm.substr) {
-      fss_none => sp,
-      fss_internal(s) => {
-        adjust_span(map, {lo: s.lo + (sp.lo - line.fm.start_pos.ch),
-                          hi: s.lo + (sp.hi - line.fm.start_pos.ch),
-                          expn_info: sp.expn_info})}
-      fss_external(_) => sp
+impl CharPos: to_bytes::IterBytes {
+    pure fn iter_bytes(+lsb0: bool, f: to_bytes::Cb) {
+        (*self).iter_bytes(lsb0, f)
     }
 }
 
-enum expn_info_ {
-    expanded_from({call_site: span,
-                   callie: {name: ~str, span: Option<span>}})
+/**
+Spans represent a region of code, used for error reporting. Positions in spans
+are *absolute* positions from the beginning of the codemap, not positions
+relative to FileMaps. Methods on the CodeMap can be used to relate spans back
+to the original source.
+*/
+pub struct span {
+    lo: BytePos,
+    hi: BytePos,
+    expn_info: Option<@ExpnInfo>
 }
-type expn_info = Option<@expn_info_>;
-
-type span = {lo: uint, hi: uint, expn_info: expn_info};
 
 impl span : cmp::Eq {
     pure fn eq(other: &span) -> bool {
@@ -193,74 +158,308 @@ impl<D: Deserializer> span: Deserializable<D> {
     }
 }
 
-fn span_to_str_no_adj(sp: span, cm: CodeMap) -> ~str {
-    let lo = lookup_char_pos(cm, sp.lo);
-    let hi = lookup_char_pos(cm, sp.hi);
-    return fmt!("%s:%u:%u: %u:%u", lo.file.name,
-             lo.line, lo.col, hi.line, hi.col)
+/// A source code location used for error reporting
+pub struct Loc {
+    /// Information about the original source
+    file: @FileMap,
+    /// The (1-based) line number
+    line: uint,
+    /// The (0-based) column offset
+    col: CharPos
 }
 
-fn span_to_str(sp: span, cm: CodeMap) -> ~str {
-    let lo = lookup_char_pos_adj(cm, sp.lo);
-    let hi = lookup_char_pos_adj(cm, sp.hi);
-    return fmt!("%s:%u:%u: %u:%u", lo.filename,
-             lo.line, lo.col, hi.line, hi.col)
+/// Extra information for tracking macro expansion of spans
+pub enum ExpnInfo {
+    ExpandedFrom({call_site: span,
+                  callie: {name: ~str, span: Option<span>}})
 }
 
-type file_lines = {file: filemap, lines: ~[uint]};
+pub type FileName = ~str;
 
-fn span_to_filename(sp: span, cm: codemap::CodeMap) -> filename {
-    let lo = lookup_char_pos(cm, sp.lo);
-    return /* FIXME (#2543) */ copy lo.file.name;
+pub struct FileLines {
+    file: @FileMap,
+    lines: ~[uint]
 }
 
-fn span_to_lines(sp: span, cm: codemap::CodeMap) -> @file_lines {
-    let lo = lookup_char_pos(cm, sp.lo);
-    let hi = lookup_char_pos(cm, sp.hi);
-    let mut lines = ~[];
-    for uint::range(lo.line - 1u, hi.line as uint) |i| {
-        lines.push(i);
-    };
-    return @{file: lo.file, lines: lines};
+pub enum FileSubstr {
+    pub FssNone,
+    pub FssInternal(span),
+    pub FssExternal({filename: ~str, line: uint, col: CharPos})
 }
 
-fn get_line(fm: filemap, line: int) -> ~str unsafe {
-    let begin: uint = fm.lines[line].byte - fm.start_pos.byte;
-    let end = match str::find_char_from(*fm.src, '\n', begin) {
-      Some(e) => e,
-      None => str::len(*fm.src)
-    };
-    str::slice(*fm.src, begin, end)
+/// Identifies an offset of a multi-byte character in a FileMap
+pub struct MultiByteChar {
+    /// The absolute offset of the character in the CodeMap
+    pos: BytePos,
+    /// The number of bytes, >=2
+    bytes: uint,
 }
 
-fn lookup_byte_offset(cm: codemap::CodeMap, chpos: uint)
-    -> {fm: filemap, pos: uint} {
-    pure fn lookup(pos: file_pos) -> uint { return pos.ch; }
-    let {fm, line} = lookup_line(cm, chpos, lookup);
-    let line_offset = fm.lines[line].byte - fm.start_pos.byte;
-    let col = chpos - fm.lines[line].ch;
-    let col_offset = str::count_bytes(*fm.src, line_offset, col);
-    {fm: fm, pos: line_offset + col_offset}
+/// A single source in the CodeMap
+pub struct FileMap {
+    /// The name of the file that the source came from, source that doesn't
+    /// originate from files has names between angle brackets by convention,
+    /// e.g. `<anon>`
+    name: FileName,
+    /// Extra information used by qquote
+    substr: FileSubstr,
+    /// The complete source code
+    src: @~str,
+    /// The start position of this source in the CodeMap
+    start_pos: BytePos,
+    /// Locations of lines beginnings in the source code
+    mut lines: ~[BytePos],
+    /// Locations of multi-byte characters in the source code
+    multibyte_chars: DVec<MultiByteChar>
 }
 
-fn span_to_snippet(sp: span, cm: codemap::CodeMap) -> ~str {
-    let begin = lookup_byte_offset(cm, sp.lo);
-    let end = lookup_byte_offset(cm, sp.hi);
-    assert begin.fm.start_pos == end.fm.start_pos;
-    return str::slice(*begin.fm.src, begin.pos, end.pos);
+pub impl FileMap {
+    fn next_line(&self, +pos: BytePos) {
+        self.lines.push(pos);
+    }
+
+    pub fn get_line(&self, line: int) -> ~str unsafe {
+        let begin: BytePos = self.lines[line] - self.start_pos;
+        let begin = begin.to_uint();
+        let end = match str::find_char_from(*self.src, '\n', begin) {
+            Some(e) => e,
+            None => str::len(*self.src)
+        };
+        str::slice(*self.src, begin, end)
+    }
+
+    pub fn record_multibyte_char(&self, pos: BytePos, bytes: uint) {
+        assert bytes >=2 && bytes <= 4;
+        let mbc = MultiByteChar {
+            pos: pos,
+            bytes: bytes,
+        };
+        self.multibyte_chars.push(mbc);
+    }
 }
 
-fn get_snippet(cm: codemap::CodeMap, fidx: uint, lo: uint, hi: uint) -> ~str
-{
-    let fm = cm.files[fidx];
-    return str::slice(*fm.src, lo, hi)
+pub struct CodeMap {
+    files: DVec<@FileMap>
 }
 
-fn get_filemap(cm: CodeMap, filename: ~str) -> filemap {
-    for cm.files.each |fm| { if fm.name == filename { return *fm; } }
-    //XXjdm the following triggers a mismatched type bug
-    //      (or expected function, found _|_)
-    fail; // ("asking for " + filename + " which we don't know about");
+pub impl CodeMap {
+    static pub fn new() -> CodeMap {
+        CodeMap {
+            files: DVec()
+        }
+    }
+
+    /// Add a new FileMap to the CodeMap and return it
+    fn new_filemap(+filename: FileName, src: @~str) -> @FileMap {
+        return self.new_filemap_w_substr(filename, FssNone, src);
+    }
+
+    fn new_filemap_w_substr(+filename: FileName, +substr: FileSubstr,
+                            src: @~str) -> @FileMap {
+        let start_pos = if self.files.len() == 0 {
+            0
+        } else {
+            let last_start = self.files.last().start_pos.to_uint();
+            let last_len = self.files.last().src.len();
+            last_start + last_len
+        };
+
+        let filemap = @FileMap {
+            name: filename, substr: substr, src: src,
+            start_pos: BytePos(start_pos),
+            mut lines: ~[],
+            multibyte_chars: DVec()
+        };
+
+        self.files.push(filemap);
+
+        return filemap;
+    }
+
+    pub fn mk_substr_filename(&self, sp: span) -> ~str {
+        let pos = self.lookup_char_pos(sp.lo);
+        return fmt!("<%s:%u:%u>", pos.file.name,
+                    pos.line, pos.col.to_uint());
+    }
+
+    /// Lookup source information about a BytePos
+    pub fn lookup_char_pos(&self, +pos: BytePos) -> Loc {
+        return self.lookup_pos(pos);
+    }
+
+    pub fn lookup_char_pos_adj(&self, +pos: BytePos)
+        -> {filename: ~str, line: uint, col: CharPos, file: Option<@FileMap>}
+    {
+        let loc = self.lookup_char_pos(pos);
+        match (loc.file.substr) {
+            FssNone => {
+                {filename: /* FIXME (#2543) */ copy loc.file.name,
+                 line: loc.line,
+                 col: loc.col,
+                 file: Some(loc.file)}
+            }
+            FssInternal(sp) => {
+                self.lookup_char_pos_adj(
+                    sp.lo + (pos - loc.file.start_pos))
+            }
+            FssExternal(eloc) => {
+                {filename: /* FIXME (#2543) */ copy eloc.filename,
+                 line: eloc.line + loc.line - 1u,
+                 col: if loc.line == 1u {eloc.col + loc.col} else {loc.col},
+                 file: None}
+            }
+        }
+    }
+
+    pub fn adjust_span(&self, sp: span) -> span {
+        let line = self.lookup_line(sp.lo);
+        match (line.fm.substr) {
+            FssNone => sp,
+            FssInternal(s) => {
+                self.adjust_span(span {
+                    lo: s.lo + (sp.lo - line.fm.start_pos),
+                    hi: s.lo + (sp.hi - line.fm.start_pos),
+                    expn_info: sp.expn_info
+                })
+            }
+            FssExternal(_) => sp
+        }
+    }
+
+    pub fn span_to_str(&self, sp: span) -> ~str {
+        let lo = self.lookup_char_pos_adj(sp.lo);
+        let hi = self.lookup_char_pos_adj(sp.hi);
+        return fmt!("%s:%u:%u: %u:%u", lo.filename,
+                    lo.line, lo.col.to_uint(), hi.line, hi.col.to_uint())
+    }
+
+    pub fn span_to_filename(&self, sp: span) -> FileName {
+        let lo = self.lookup_char_pos(sp.lo);
+        return /* FIXME (#2543) */ copy lo.file.name;
+    }
+
+    pub fn span_to_lines(&self, sp: span) -> @FileLines {
+        let lo = self.lookup_char_pos(sp.lo);
+        let hi = self.lookup_char_pos(sp.hi);
+        let mut lines = ~[];
+        for uint::range(lo.line - 1u, hi.line as uint) |i| {
+            lines.push(i);
+        };
+        return @FileLines {file: lo.file, lines: lines};
+    }
+
+    pub fn span_to_snippet(&self, sp: span) -> ~str {
+        let begin = self.lookup_byte_offset(sp.lo);
+        let end = self.lookup_byte_offset(sp.hi);
+        assert begin.fm.start_pos == end.fm.start_pos;
+        return str::slice(*begin.fm.src,
+                          begin.pos.to_uint(), end.pos.to_uint());
+    }
+
+    pub fn get_filemap(&self, filename: ~str) -> @FileMap {
+        for self.files.each |fm| { if fm.name == filename { return *fm; } }
+        //XXjdm the following triggers a mismatched type bug
+        //      (or expected function, found _|_)
+        fail; // ("asking for " + filename + " which we don't know about");
+    }
+
+}
+
+priv impl CodeMap {
+
+    fn lookup_filemap_idx(&self, +pos: BytePos) -> uint {
+        let len = self.files.len();
+        let mut a = 0u;
+        let mut b = len;
+        while b - a > 1u {
+            let m = (a + b) / 2u;
+            if self.files[m].start_pos > pos {
+                b = m;
+            } else {
+                a = m;
+            }
+        }
+        if (a >= len) {
+            fail fmt!("position %u does not resolve to a source location",
+                      pos.to_uint())
+        }
+
+        return a;
+    }
+
+    fn lookup_line(&self, +pos: BytePos)
+        -> {fm: @FileMap, line: uint}
+    {
+        let idx = self.lookup_filemap_idx(pos);
+        let f = self.files[idx];
+        let mut a = 0u;
+        let mut b = vec::len(f.lines);
+        while b - a > 1u {
+            let m = (a + b) / 2u;
+            if f.lines[m] > pos { b = m; } else { a = m; }
+        }
+        return {fm: f, line: a};
+    }
+
+    fn lookup_pos(&self, +pos: BytePos) -> Loc {
+        let {fm: f, line: a} = self.lookup_line(pos);
+        let line = a + 1u; // Line numbers start at 1
+        let chpos = self.bytepos_to_local_charpos(pos);
+        let linebpos = f.lines[a];
+        let linechpos = self.bytepos_to_local_charpos(linebpos);
+        debug!("codemap: byte pos %? is on the line at byte pos %?",
+               pos, linebpos);
+        debug!("codemap: char pos %? is on the line at char pos %?",
+               chpos, linechpos);
+        debug!("codemap: byte is on line: %?", line);
+        assert chpos >= linechpos;
+        return Loc {
+            file: f,
+            line: line,
+            col: chpos - linechpos
+        };
+    }
+
+    fn span_to_str_no_adj(&self, sp: span) -> ~str {
+        let lo = self.lookup_char_pos(sp.lo);
+        let hi = self.lookup_char_pos(sp.hi);
+        return fmt!("%s:%u:%u: %u:%u", lo.file.name,
+                    lo.line, lo.col.to_uint(), hi.line, hi.col.to_uint())
+    }
+
+    fn lookup_byte_offset(&self, +bpos: BytePos)
+        -> {fm: @FileMap, pos: BytePos} {
+        let idx = self.lookup_filemap_idx(bpos);
+        let fm = self.files[idx];
+        let offset = bpos - fm.start_pos;
+        return {fm: fm, pos: offset};
+    }
+
+    // Converts an absolute BytePos to a CharPos relative to the file it is
+    // located in
+    fn bytepos_to_local_charpos(&self, +bpos: BytePos) -> CharPos {
+        debug!("codemap: converting %? to char pos", bpos);
+        let idx = self.lookup_filemap_idx(bpos);
+        let map = self.files[idx];
+
+        // The number of extra bytes due to multibyte chars in the FileMap
+        let mut total_extra_bytes = 0;
+
+        for map.multibyte_chars.each |mbc| {
+            debug!("codemap: %?-byte char at %?", mbc.bytes, mbc.pos);
+            if mbc.pos < bpos {
+                total_extra_bytes += mbc.bytes;
+                // We should never see a byte position in the middle of a
+                // character
+                assert bpos == mbc.pos
+                    || bpos.to_uint() >= mbc.pos.to_uint() + mbc.bytes;
+            } else {
+                break;
+            }
+        }
+
+        CharPos(bpos.to_uint() - total_extra_bytes)
+    }
 }
 
 //
diff --git a/src/libsyntax/diagnostic.rs b/src/libsyntax/diagnostic.rs
index 855b0ca3ef568..007100856ebc4 100644
--- a/src/libsyntax/diagnostic.rs
+++ b/src/libsyntax/diagnostic.rs
@@ -9,7 +9,7 @@ export codemap_span_handler, codemap_handler;
 export ice_msg;
 export expect;
 
-type emitter = fn@(cmsp: Option<(codemap::CodeMap, span)>,
+type emitter = fn@(cmsp: Option<(@codemap::CodeMap, span)>,
                    msg: &str, lvl: level);
 
 
@@ -33,7 +33,7 @@ trait handler {
     fn note(msg: &str);
     fn bug(msg: &str) -> !;
     fn unimpl(msg: &str) -> !;
-    fn emit(cmsp: Option<(codemap::CodeMap, span)>, msg: &str, lvl: level);
+    fn emit(cmsp: Option<(@codemap::CodeMap, span)>, msg: &str, lvl: level);
 }
 
 type handler_t = @{
@@ -43,7 +43,7 @@ type handler_t = @{
 
 type codemap_t = @{
     handler: handler,
-    cm: codemap::CodeMap
+    cm: @codemap::CodeMap
 };
 
 impl codemap_t: span_handler {
@@ -107,7 +107,7 @@ impl handler_t: handler {
         self.fatal(ice_msg(msg));
     }
     fn unimpl(msg: &str) -> ! { self.bug(~"unimplemented " + msg); }
-    fn emit(cmsp: Option<(codemap::CodeMap, span)>, msg: &str, lvl: level) {
+    fn emit(cmsp: Option<(@codemap::CodeMap, span)>, msg: &str, lvl: level) {
         self.emit(cmsp, msg, lvl);
     }
 }
@@ -116,7 +116,7 @@ fn ice_msg(msg: &str) -> ~str {
     fmt!("internal compiler error: %s", msg)
 }
 
-fn mk_span_handler(handler: handler, cm: codemap::CodeMap) -> span_handler {
+fn mk_span_handler(handler: handler, cm: @codemap::CodeMap) -> span_handler {
     @{ handler: handler, cm: cm } as span_handler
 }
 
@@ -125,7 +125,7 @@ fn mk_handler(emitter: Option<emitter>) -> handler {
     let emit = match emitter {
       Some(e) => e,
       None => {
-        let f = fn@(cmsp: Option<(codemap::CodeMap, span)>,
+        let f = fn@(cmsp: Option<(@codemap::CodeMap, span)>,
             msg: &str, t: level) {
             emit(cmsp, msg, t);
         };
@@ -189,12 +189,12 @@ fn print_diagnostic(topic: ~str, lvl: level, msg: &str) {
     io::stderr().write_str(fmt!(" %s\n", msg));
 }
 
-fn emit(cmsp: Option<(codemap::CodeMap, span)>, msg: &str, lvl: level) {
+fn emit(cmsp: Option<(@codemap::CodeMap, span)>, msg: &str, lvl: level) {
     match cmsp {
       Some((cm, sp)) => {
-        let sp = codemap::adjust_span(cm,sp);
-        let ss = codemap::span_to_str(sp, cm);
-        let lines = codemap::span_to_lines(sp, cm);
+        let sp = cm.adjust_span(sp);
+        let ss = cm.span_to_str(sp);
+        let lines = cm.span_to_lines(sp);
         print_diagnostic(ss, lvl, msg);
         highlight_lines(cm, sp, lines);
         print_macro_backtrace(cm, sp);
@@ -205,8 +205,8 @@ fn emit(cmsp: Option<(codemap::CodeMap, span)>, msg: &str, lvl: level) {
     }
 }
 
-fn highlight_lines(cm: codemap::CodeMap, sp: span,
-                   lines: @codemap::file_lines) {
+fn highlight_lines(cm: @codemap::CodeMap, sp: span,
+                   lines: @codemap::FileLines) {
 
     let fm = lines.file;
 
@@ -221,7 +221,7 @@ fn highlight_lines(cm: codemap::CodeMap, sp: span,
     // Print the offending lines
     for display_lines.each |line| {
         io::stderr().write_str(fmt!("%s:%u ", fm.name, *line + 1u));
-        let s = codemap::get_line(fm, *line as int) + ~"\n";
+        let s = fm.get_line(*line as int) + ~"\n";
         io::stderr().write_str(s);
     }
     if elided {
@@ -237,7 +237,7 @@ fn highlight_lines(cm: codemap::CodeMap, sp: span,
 
     // If there's one line at fault we can easily point to the problem
     if vec::len(lines.lines) == 1u {
-        let lo = codemap::lookup_char_pos(cm, sp.lo);
+        let lo = cm.lookup_char_pos(sp.lo);
         let mut digits = 0u;
         let mut num = (lines.lines[0] + 1u) / 10u;
 
@@ -245,28 +245,28 @@ fn highlight_lines(cm: codemap::CodeMap, sp: span,
         while num > 0u { num /= 10u; digits += 1u; }
 
         // indent past |name:## | and the 0-offset column location
-        let mut left = str::len(fm.name) + digits + lo.col + 3u;
+        let mut left = str::len(fm.name) + digits + lo.col.to_uint() + 3u;
         let mut s = ~"";
         while left > 0u { str::push_char(&mut s, ' '); left -= 1u; }
 
         s += ~"^";
-        let hi = codemap::lookup_char_pos(cm, sp.hi);
+        let hi = cm.lookup_char_pos(sp.hi);
         if hi.col != lo.col {
             // the ^ already takes up one space
-            let mut width = hi.col - lo.col - 1u;
+            let mut width = hi.col.to_uint() - lo.col.to_uint() - 1u;
             while width > 0u { str::push_char(&mut s, '~'); width -= 1u; }
         }
         io::stderr().write_str(s + ~"\n");
     }
 }
 
-fn print_macro_backtrace(cm: codemap::CodeMap, sp: span) {
+fn print_macro_backtrace(cm: @codemap::CodeMap, sp: span) {
     do option::iter(&sp.expn_info) |ei| {
         let ss = option::map_default(&ei.callie.span, @~"",
-                                     |span| @codemap::span_to_str(*span, cm));
+                                     |span| @cm.span_to_str(*span));
         print_diagnostic(*ss, note,
                          fmt!("in expansion of %s!", ei.callie.name));
-        let ss = codemap::span_to_str(ei.call_site, cm);
+        let ss = cm.span_to_str(ei.call_site);
         print_diagnostic(ss, note, ~"expansion site");
         print_macro_backtrace(cm, ei.call_site);
     }
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index ddf58ce0fef1c..66ef3bec2a747 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -1,7 +1,8 @@
 use std::map::HashMap;
 use parse::parser;
 use diagnostic::span_handler;
-use codemap::{CodeMap, span, expn_info, expanded_from};
+use codemap::{CodeMap, span, ExpnInfo, ExpandedFrom};
+use ast_util::dummy_sp;
 
 // obsolete old-style #macro code:
 //
@@ -124,15 +125,15 @@ fn syntax_expander_table() -> HashMap<~str, syntax_extension> {
 // when a macro expansion occurs, the resulting nodes have the backtrace()
 // -> expn_info of their expansion context stored into their span.
 trait ext_ctxt {
-    fn codemap() -> CodeMap;
+    fn codemap() -> @CodeMap;
     fn parse_sess() -> parse::parse_sess;
     fn cfg() -> ast::crate_cfg;
     fn print_backtrace();
-    fn backtrace() -> expn_info;
+    fn backtrace() -> Option<@ExpnInfo>;
     fn mod_push(mod_name: ast::ident);
     fn mod_pop();
     fn mod_path() -> ~[ast::ident];
-    fn bt_push(ei: codemap::expn_info_);
+    fn bt_push(ei: codemap::ExpnInfo);
     fn bt_pop();
     fn span_fatal(sp: span, msg: &str) -> !;
     fn span_err(sp: span, msg: &str);
@@ -152,32 +153,34 @@ fn mk_ctxt(parse_sess: parse::parse_sess,
            cfg: ast::crate_cfg) -> ext_ctxt {
     type ctxt_repr = {parse_sess: parse::parse_sess,
                       cfg: ast::crate_cfg,
-                      mut backtrace: expn_info,
+                      mut backtrace: Option<@ExpnInfo>,
                       mut mod_path: ~[ast::ident],
                       mut trace_mac: bool};
     impl ctxt_repr: ext_ctxt {
-        fn codemap() -> CodeMap { self.parse_sess.cm }
+        fn codemap() -> @CodeMap { self.parse_sess.cm }
         fn parse_sess() -> parse::parse_sess { self.parse_sess }
         fn cfg() -> ast::crate_cfg { self.cfg }
         fn print_backtrace() { }
-        fn backtrace() -> expn_info { self.backtrace }
+        fn backtrace() -> Option<@ExpnInfo> { self.backtrace }
         fn mod_push(i: ast::ident) { self.mod_path.push(i); }
         fn mod_pop() { self.mod_path.pop(); }
         fn mod_path() -> ~[ast::ident] { return self.mod_path; }
-        fn bt_push(ei: codemap::expn_info_) {
+        fn bt_push(ei: codemap::ExpnInfo) {
             match ei {
-              expanded_from({call_site: cs, callie: callie}) => {
+              ExpandedFrom({call_site: cs, callie: callie}) => {
                 self.backtrace =
-                    Some(@expanded_from({
-                        call_site: {lo: cs.lo, hi: cs.hi,
-                                    expn_info: self.backtrace},
+                    Some(@ExpandedFrom({
+                        call_site: span {lo: cs.lo, hi: cs.hi,
+                                         expn_info: self.backtrace},
                         callie: callie}));
               }
             }
         }
         fn bt_pop() {
             match self.backtrace {
-              Some(@expanded_from({call_site: {expn_info: prev, _}, _})) => {
+              Some(@ExpandedFrom({
+                  call_site: span {expn_info: prev, _}, _
+              })) => {
                 self.backtrace = prev
               }
               _ => self.bug(~"tried to pop without a push")
@@ -311,7 +314,7 @@ fn tt_args_to_original_flavor(cx: ext_ctxt, sp: span, arg: ~[ast::token_tree])
 
     // these spans won't matter, anyways
     fn ms(m: matcher_) -> matcher {
-        {node: m, span: {lo: 0u, hi: 0u, expn_info: None}}
+        {node: m, span: dummy_sp()}
     }
     let arg_nm = cx.parse_sess().interner.gensym(@~"arg");
 
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 22e2cfcde6b51..69d067f1ddb0a 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -8,7 +8,7 @@ use ext::qquote::{qq_helper};
 use parse::{parser, parse_expr_from_source_str, new_parser_from_tt};
 
 
-use codemap::{span, expanded_from};
+use codemap::{span, ExpandedFrom};
 
 fn expand_expr(exts: HashMap<~str, syntax_extension>, cx: ext_ctxt,
                e: expr_, s: span, fld: ast_fold,
@@ -41,7 +41,7 @@ fn expand_expr(exts: HashMap<~str, syntax_extension>, cx: ext_ctxt,
                   Some(normal({expander: exp, span: exp_sp})) => {
                     let expanded = exp(cx, mac.span, args, body);
 
-                    cx.bt_push(expanded_from({call_site: s,
+                    cx.bt_push(ExpandedFrom({call_site: s,
                                 callie: {name: *extname, span: exp_sp}}));
                     //keep going, outside-in
                     let fully_expanded = fld.fold_expr(expanded).node;
@@ -86,7 +86,7 @@ fn expand_expr(exts: HashMap<~str, syntax_extension>, cx: ext_ctxt,
                                          *extname))
                     };
 
-                    cx.bt_push(expanded_from({call_site: s,
+                    cx.bt_push(ExpandedFrom({call_site: s,
                                 callie: {name: *extname, span: exp_sp}}));
                     //keep going, outside-in
                     let fully_expanded = fld.fold_expr(expanded).node;
@@ -100,7 +100,7 @@ fn expand_expr(exts: HashMap<~str, syntax_extension>, cx: ext_ctxt,
                                                                tts);
                     let expanded = exp(cx, mac.span, arg, None);
 
-                    cx.bt_push(expanded_from({call_site: s,
+                    cx.bt_push(ExpandedFrom({call_site: s,
                                 callie: {name: *extname, span: exp_sp}}));
                     //keep going, outside-in
                     let fully_expanded = fld.fold_expr(expanded).node;
@@ -206,7 +206,7 @@ fn expand_item_mac(exts: HashMap<~str, syntax_extension>,
           }
           Some(item_tt(expand)) => {
             let expanded = expand.expander(cx, it.span, it.ident, tts);
-            cx.bt_push(expanded_from({call_site: it.span,
+            cx.bt_push(ExpandedFrom({call_site: it.span,
                                       callie: {name: *extname,
                                                span: expand.span}}));
             let maybe_it = match expanded {
@@ -232,7 +232,7 @@ fn expand_item_mac(exts: HashMap<~str, syntax_extension>,
 
 fn new_span(cx: ext_ctxt, sp: span) -> span {
     /* this discards information in the case of macro-defining macros */
-    return {lo: sp.lo, hi: sp.hi, expn_info: cx.backtrace()};
+    return span {lo: sp.lo, hi: sp.hi, expn_info: cx.backtrace()};
 }
 
 // FIXME (#2247): this is a terrible kludge to inject some macros into
diff --git a/src/libsyntax/ext/pipes/ast_builder.rs b/src/libsyntax/ext/pipes/ast_builder.rs
index f03adb90f0bcf..652ad5533c4c7 100644
--- a/src/libsyntax/ext/pipes/ast_builder.rs
+++ b/src/libsyntax/ext/pipes/ast_builder.rs
@@ -4,7 +4,7 @@
 // something smarter.
 
 use ast::{ident, node_id};
-use ast_util::{ident_to_path, respan};
+use ast_util::{ident_to_path, respan, dummy_sp};
 use codemap::span;
 use ext::base::mk_ctxt;
 
@@ -23,10 +23,6 @@ fn path(ids: ~[ident], span: span) -> @ast::path {
       types: ~[]}
 }
 
-fn empty_span() -> span {
-    {lo: 0, hi: 0, expn_info: None}
-}
-
 trait append_types {
     fn add_ty(ty: @ast::Ty) -> @ast::path;
     fn add_tys(+tys: ~[@ast::Ty]) -> @ast::path;
@@ -83,26 +79,21 @@ trait ext_ctxt_ast_builder {
     fn stmt_let(ident: ident, e: @ast::expr) -> @ast::stmt;
     fn stmt_expr(e: @ast::expr) -> @ast::stmt;
     fn block_expr(b: ast::blk) -> @ast::expr;
-    fn empty_span() -> span;
     fn ty_option(ty: @ast::Ty) -> @ast::Ty;
 }
 
 impl ext_ctxt: ext_ctxt_ast_builder {
     fn ty_option(ty: @ast::Ty) -> @ast::Ty {
         self.ty_path_ast_builder(path(~[self.ident_of(~"Option")],
-                                      self.empty_span())
+                                      dummy_sp())
                                  .add_ty(ty))
     }
 
-    fn empty_span() -> span {
-        {lo: 0, hi: 0, expn_info: self.backtrace()}
-    }
-
     fn block_expr(b: ast::blk) -> @ast::expr {
         @{id: self.next_id(),
           callee_id: self.next_id(),
           node: ast::expr_block(b),
-          span: self.empty_span()}
+          span: dummy_sp()}
     }
 
     fn move_expr(e: @ast::expr) -> @ast::expr {
@@ -114,7 +105,7 @@ impl ext_ctxt: ext_ctxt_ast_builder {
 
     fn stmt_expr(e: @ast::expr) -> @ast::stmt {
         @{node: ast::stmt_expr(e, self.next_id()),
-          span: self.empty_span()}
+          span: dummy_sp()}
     }
 
     fn stmt_let(ident: ident, e: @ast::expr) -> @ast::stmt {
@@ -130,43 +121,43 @@ impl ext_ctxt: ext_ctxt_ast_builder {
                      pat: @{id: self.next_id(),
                             node: ast::pat_ident(ast::bind_by_implicit_ref,
                                                  path(~[ident],
-                                                      self.empty_span()),
+                                                      dummy_sp()),
                                                  None),
-                            span: self.empty_span()},
+                            span: dummy_sp()},
                      init: Some(self.move_expr(e)),
                      id: self.next_id()},
-              span: self.empty_span()}]),
-                               span: self.empty_span()}, self.next_id()),
-         span: self.empty_span()}
+              span: dummy_sp()}]),
+                               span: dummy_sp()}, self.next_id()),
+         span: dummy_sp()}
     }
 
     fn field_imm(name: ident, e: @ast::expr) -> ast::field {
         {node: {mutbl: ast::m_imm, ident: name, expr: e},
-         span: self.empty_span()}
+         span: dummy_sp()}
     }
 
     fn rec(+fields: ~[ast::field]) -> @ast::expr {
         @{id: self.next_id(),
           callee_id: self.next_id(),
           node: ast::expr_rec(fields, None),
-          span: self.empty_span()}
+          span: dummy_sp()}
     }
 
     fn ty_field_imm(name: ident, ty: @ast::Ty) -> ast::ty_field {
         {node: {ident: name, mt: { ty: ty, mutbl: ast::m_imm } },
-          span: self.empty_span()}
+          span: dummy_sp()}
     }
 
     fn ty_rec(+fields: ~[ast::ty_field]) -> @ast::Ty {
         @{id: self.next_id(),
           node: ast::ty_rec(fields),
-          span: self.empty_span()}
+          span: dummy_sp()}
     }
 
     fn ty_infer() -> @ast::Ty {
         @{id: self.next_id(),
           node: ast::ty_infer,
-          span: self.empty_span()}
+          span: dummy_sp()}
     }
 
     fn ty_param(id: ast::ident, +bounds: ~[ast::ty_param_bound])
@@ -181,9 +172,9 @@ impl ext_ctxt: ext_ctxt_ast_builder {
          pat: @{id: self.next_id(),
                 node: ast::pat_ident(
                     ast::bind_by_value,
-                    ast_util::ident_to_path(self.empty_span(), name),
+                    ast_util::ident_to_path(dummy_sp(), name),
                     None),
-                span: self.empty_span()},
+                span: dummy_sp()},
          id: self.next_id()}
     }
 
@@ -195,7 +186,7 @@ impl ext_ctxt: ext_ctxt_ast_builder {
                    rules: ast::default_blk};
 
         {node: blk,
-         span: self.empty_span()}
+         span: dummy_sp()}
     }
 
     fn expr_block(e: @ast::expr) -> ast::blk {
@@ -215,11 +206,11 @@ impl ext_ctxt: ext_ctxt_ast_builder {
 
         // XXX: Would be nice if our generated code didn't violate
         // Rust coding conventions
-        let non_camel_case_attribute = respan(self.empty_span(), {
+        let non_camel_case_attribute = respan(dummy_sp(), {
             style: ast::attr_outer,
-            value: respan(self.empty_span(),
+            value: respan(dummy_sp(),
                           ast::meta_list(~"allow", ~[
-                              @respan(self.empty_span(),
+                              @respan(dummy_sp(),
                                       ast::meta_word(~"non_camel_case_types"))
                           ])),
             is_sugared_doc: false
@@ -239,7 +230,7 @@ impl ext_ctxt: ext_ctxt_ast_builder {
                     +ty_params: ~[ast::ty_param],
                     +body: ast::blk) -> @ast::item {
         self.item(name,
-                  self.empty_span(),
+                  dummy_sp(),
                   ast::item_fn(self.fn_decl(inputs, output),
                                ast::impure_fn,
                                ty_params,
@@ -298,7 +289,7 @@ impl ext_ctxt: ext_ctxt_ast_builder {
     fn ty_nil_ast_builder() -> @ast::Ty {
         @{id: self.next_id(),
           node: ast::ty_nil,
-          span: self.empty_span()}
+          span: dummy_sp()}
     }
 
     fn item_ty_poly(name: ident,
@@ -314,6 +305,6 @@ impl ext_ctxt: ext_ctxt_ast_builder {
 
     fn ty_vars(+ty_params: ~[ast::ty_param]) -> ~[@ast::Ty] {
         ty_params.map(|p| self.ty_path_ast_builder(
-            path(~[p.ident], self.empty_span())))
+            path(~[p.ident], dummy_sp())))
     }
 }
diff --git a/src/libsyntax/ext/pipes/check.rs b/src/libsyntax/ext/pipes/check.rs
index fcc0c84a4ff39..a90b679f6974c 100644
--- a/src/libsyntax/ext/pipes/check.rs
+++ b/src/libsyntax/ext/pipes/check.rs
@@ -22,7 +22,6 @@ that.
 use ext::base::ext_ctxt;
 
 use proto::{state, protocol, next_state};
-use ast_builder::empty_span;
 
 impl ext_ctxt: proto::visitor<(), (), ()>  {
     fn visit_proto(_proto: protocol,
diff --git a/src/libsyntax/ext/pipes/liveness.rs b/src/libsyntax/ext/pipes/liveness.rs
index a9bfd87ab0eb3..e86b3f0ea59e4 100644
--- a/src/libsyntax/ext/pipes/liveness.rs
+++ b/src/libsyntax/ext/pipes/liveness.rs
@@ -29,8 +29,6 @@ updating the states using rule (2) until there are no changes.
 
 use std::bitv::{Bitv};
 
-use ast_builder::empty_span;
-
 fn analyze(proto: protocol, _cx: ext_ctxt) {
     debug!("initializing colive analysis");
     let num_states = proto.num_states();
diff --git a/src/libsyntax/ext/pipes/pipec.rs b/src/libsyntax/ext/pipes/pipec.rs
index 7e1cbe9ad0dbf..d03a0fde66c97 100644
--- a/src/libsyntax/ext/pipes/pipec.rs
+++ b/src/libsyntax/ext/pipes/pipec.rs
@@ -5,6 +5,7 @@ use to_str::ToStr;
 use dvec::DVec;
 
 use ast::ident;
+use ast_util::dummy_sp;
 use util::interner;
 use print::pprust;
 use pprust::{item_to_str, ty_to_str};
@@ -12,7 +13,7 @@ use ext::base::{mk_ctxt, ext_ctxt};
 use parse::*;
 use proto::*;
 
-use ast_builder::{append_types, path, empty_span};
+use ast_builder::{append_types, path};
 
 // Transitional reexports so qquote can find the paths it is looking for
 mod syntax {
@@ -256,11 +257,11 @@ impl state: to_type_decls {
                     cx.ty_path_ast_builder(
                         path(~[cx.ident_of(~"pipes"),
                                cx.ident_of(dir.to_str() + ~"Packet")],
-                             empty_span())
+                             dummy_sp())
                         .add_ty(cx.ty_path_ast_builder(
                             path(~[cx.ident_of(self.proto.name),
                                    self.data_name()],
-                                 empty_span())
+                                 dummy_sp())
                             .add_tys(cx.ty_vars(self.ty_params))))),
                     self.ty_params));
         }
@@ -273,11 +274,11 @@ impl state: to_type_decls {
                         path(~[cx.ident_of(~"pipes"),
                                cx.ident_of(dir.to_str()
                                            + ~"PacketBuffered")],
-                             empty_span())
+                             dummy_sp())
                         .add_tys(~[cx.ty_path_ast_builder(
                             path(~[cx.ident_of(self.proto.name),
                                    self.data_name()],
-                                 empty_span())
+                                 dummy_sp())
                             .add_tys(cx.ty_vars(self.ty_params))),
                                    self.proto.buffer_ty_path(cx)])),
                     self.ty_params));
@@ -394,7 +395,7 @@ impl protocol: gen_init {
 
         cx.item_ty_poly(
             cx.ident_of(~"__Buffer"),
-            cx.empty_span(),
+            dummy_sp(),
             cx.ty_rec(fields),
             params)
     }
diff --git a/src/libsyntax/ext/qquote.rs b/src/libsyntax/ext/qquote.rs
index af7ffaa73f5bf..888932e58e713 100644
--- a/src/libsyntax/ext/qquote.rs
+++ b/src/libsyntax/ext/qquote.rs
@@ -4,6 +4,7 @@ use parse::parser;
 use parse::parser::{Parser, parse_from_source_str};
 use dvec::DVec;
 use parse::token::ident_interner;
+use codemap::{CharPos, BytePos};
 
 use fold::*;
 use visit::*;
@@ -15,13 +16,13 @@ use io::*;
 use codemap::span;
 
 struct gather_item {
-    lo: uint,
-    hi: uint,
+    lo: BytePos,
+    hi: BytePos,
     e: @ast::expr,
     constr: ~str
 }
 
-type aq_ctxt = @{lo: uint, gather: DVec<gather_item>};
+type aq_ctxt = @{lo: BytePos, gather: DVec<gather_item>};
 enum fragment {
     from_expr(@ast::expr),
     from_ty(@ast::Ty)
@@ -114,7 +115,7 @@ impl @ast::pat: qq_helper {
     fn get_fold_fn() -> ~str {~"fold_pat"}
 }
 
-fn gather_anti_quotes<N: qq_helper>(lo: uint, node: N) -> aq_ctxt
+fn gather_anti_quotes<N: qq_helper>(lo: BytePos, node: N) -> aq_ctxt
 {
     let v = @{visit_expr: |node, &&cx, v| visit_aq(node, ~"from_expr", cx, v),
               visit_ty: |node, &&cx, v| visit_aq(node, ~"from_ty", cx, v),
@@ -204,13 +205,13 @@ fn finish<T: qq_helper>
     -> @ast::expr
 {
     let cm = ecx.codemap();
-    let str = @codemap::span_to_snippet(body.span, cm);
+    let str = @cm.span_to_snippet(body.span);
     debug!("qquote--str==%?", str);
-    let fname = codemap::mk_substr_filename(cm, body.span);
+    let fname = cm.mk_substr_filename(body.span);
     let node = parse_from_source_str
-        (f, fname, codemap::fss_internal(body.span), str,
+        (f, fname, codemap::FssInternal(body.span), str,
          ecx.cfg(), ecx.parse_sess());
-    let loc = codemap::lookup_char_pos(cm, body.span.lo);
+    let loc = cm.lookup_char_pos(body.span.lo);
 
     let sp = node.span();
     let qcx = gather_anti_quotes(sp.lo, node);
@@ -226,7 +227,8 @@ fn finish<T: qq_helper>
     let mut str2 = ~"";
     enum state {active, skip(uint), blank};
     let mut state = active;
-    let mut i = 0u, j = 0u;
+    let mut i = BytePos(0u);
+    let mut j = 0u;
     let g_len = cx.gather.len();
     for str::chars_each(*str) |ch| {
         if (j < g_len && i == cx.gather[j].lo) {
@@ -242,7 +244,7 @@ fn finish<T: qq_helper>
           blank if is_space(ch) => str::push_char(&mut str2, ch),
           blank => str::push_char(&mut str2, ' ')
         }
-        i += 1u;
+        i += BytePos(1u);
         if (j < g_len && i == cx.gather[j].hi) {
             assert ch == ')';
             state = active;
@@ -270,7 +272,7 @@ fn finish<T: qq_helper>
                                  ~"qquote", ~"mk_file_substr"]),
                                 ~[mk_uniq_str(cx,sp, loc.file.name),
                                  mk_uint(cx,sp, loc.line),
-                                 mk_uint(cx,sp, loc.col)]),
+                                 mk_uint(cx,sp, loc.col.to_uint())]),
                         mk_unary(cx,sp, ast::box(ast::m_imm),
                                  mk_uniq_str(cx,sp, str2)),
                         cfg_call(),
@@ -345,8 +347,8 @@ fn replace_ty(repls: ~[fragment],
 }
 
 fn mk_file_substr(fname: ~str, line: uint, col: uint) ->
-    codemap::file_substr {
-    codemap::fss_external({filename: fname, line: line, col: col})
+    codemap::FileSubstr {
+    codemap::FssExternal({filename: fname, line: line, col: CharPos(col)})
 }
 
 // Local Variables:
diff --git a/src/libsyntax/ext/simplext.rs b/src/libsyntax/ext/simplext.rs
index bec29c9a83540..df7674264ca11 100644
--- a/src/libsyntax/ext/simplext.rs
+++ b/src/libsyntax/ext/simplext.rs
@@ -177,7 +177,7 @@ fn transcribe(cx: ext_ctxt, b: bindings, body: @expr) -> @expr {
     fn new_id(_old: node_id, cx: ext_ctxt) -> node_id { return cx.next_id(); }
     fn new_span(cx: ext_ctxt, sp: span) -> span {
         /* this discards information in the case of macro-defining macros */
-        return {lo: sp.lo, hi: sp.hi, expn_info: cx.backtrace()};
+        return span {lo: sp.lo, hi: sp.hi, expn_info: cx.backtrace()};
     }
     let afp = default_ast_fold();
     let f_pre =
diff --git a/src/libsyntax/ext/source_util.rs b/src/libsyntax/ext/source_util.rs
index 9b41d90e6d045..93cfaadcbd378 100644
--- a/src/libsyntax/ext/source_util.rs
+++ b/src/libsyntax/ext/source_util.rs
@@ -1,5 +1,5 @@
 use base::*;
-use codemap::span;
+use codemap::{span, Loc, FileMap};
 use print::pprust;
 use build::{mk_base_vec_e,mk_uint,mk_u8,mk_uniq_str};
 
@@ -16,7 +16,7 @@ export expand_include_bin;
 fn expand_line(cx: ext_ctxt, sp: span, arg: ast::mac_arg,
                _body: ast::mac_body) -> @ast::expr {
     get_mac_args(cx, sp, arg, 0u, option::Some(0u), ~"line");
-    let loc = codemap::lookup_char_pos(cx.codemap(), sp.lo);
+    let loc = cx.codemap().lookup_char_pos(sp.lo);
     return mk_uint(cx, sp, loc.line);
 }
 
@@ -24,8 +24,8 @@ fn expand_line(cx: ext_ctxt, sp: span, arg: ast::mac_arg,
 fn expand_col(cx: ext_ctxt, sp: span, arg: ast::mac_arg,
               _body: ast::mac_body) -> @ast::expr {
     get_mac_args(cx, sp, arg, 0u, option::Some(0u), ~"col");
-    let loc = codemap::lookup_char_pos(cx.codemap(), sp.lo);
-    return mk_uint(cx, sp, loc.col);
+    let loc = cx.codemap().lookup_char_pos(sp.lo);
+    return mk_uint(cx, sp, loc.col.to_uint());
 }
 
 /* file!(): expands to the current filename */
@@ -34,8 +34,8 @@ fn expand_col(cx: ext_ctxt, sp: span, arg: ast::mac_arg,
 fn expand_file(cx: ext_ctxt, sp: span, arg: ast::mac_arg,
                _body: ast::mac_body) -> @ast::expr {
     get_mac_args(cx, sp, arg, 0u, option::Some(0u), ~"file");
-    let { file: @{ name: filename, _ }, _ } =
-        codemap::lookup_char_pos(cx.codemap(), sp.lo);
+    let Loc { file: @FileMap { name: filename, _ }, _ } =
+        cx.codemap().lookup_char_pos(sp.lo);
     return mk_uniq_str(cx, sp, filename);
 }
 
@@ -58,10 +58,12 @@ fn expand_include(cx: ext_ctxt, sp: span, arg: ast::mac_arg,
                   _body: ast::mac_body) -> @ast::expr {
     let args = get_mac_args(cx, sp, arg, 1u, option::Some(1u), ~"include");
     let file = expr_to_str(cx, args[0], ~"#include_str requires a string");
-    let p = parse::new_parser_from_file(cx.parse_sess(), cx.cfg(),
-                                        &res_rel_file(cx, sp, &Path(file)),
-                                        parse::parser::SOURCE_FILE);
-    return p.parse_expr();
+    let p = parse::new_parser_from_file(
+        cx.parse_sess(), cx.cfg(),
+        &res_rel_file(cx, sp, &Path(file)),
+        parse::parser::SOURCE_FILE);
+    let e = p.parse_expr();
+    return e;
 }
 
 fn expand_include_str(cx: ext_ctxt, sp: codemap::span, arg: ast::mac_arg,
@@ -103,7 +105,7 @@ fn expand_include_bin(cx: ext_ctxt, sp: codemap::span, arg: ast::mac_arg,
 fn res_rel_file(cx: ext_ctxt, sp: codemap::span, arg: &Path) -> Path {
     // NB: relative paths are resolved relative to the compilation unit
     if !arg.is_absolute {
-        let cu = Path(codemap::span_to_filename(sp, cx.codemap()));
+        let cu = Path(cx.codemap().span_to_filename(sp));
         cu.dir_path().push_many(arg.components)
     } else {
         copy *arg
diff --git a/src/libsyntax/ext/tt/macro_parser.rs b/src/libsyntax/ext/tt/macro_parser.rs
index 76814a688f5b7..6779ed263d5a8 100644
--- a/src/libsyntax/ext/tt/macro_parser.rs
+++ b/src/libsyntax/ext/tt/macro_parser.rs
@@ -11,6 +11,7 @@ use dvec::DVec;
 use ast::{matcher, match_tok, match_seq, match_nonterminal, ident};
 use ast_util::mk_sp;
 use std::map::HashMap;
+use codemap::BytePos;
 
 /* This is an Earley-like parser, without support for in-grammar nonterminals,
 only by calling out to the main rust parser for named nonterminals (which it
@@ -102,7 +103,7 @@ type matcher_pos = ~{
     mut up: matcher_pos_up, // mutable for swapping only
     matches: ~[DVec<@named_match>],
     match_lo: uint, match_hi: uint,
-    sp_lo: uint,
+    sp_lo: BytePos,
 };
 
 fn copy_up(&& mpu: matcher_pos_up) -> matcher_pos {
@@ -122,7 +123,7 @@ fn count_names(ms: &[matcher]) -> uint {
 }
 
 #[allow(non_implicitly_copyable_typarams)]
-fn initial_matcher_pos(ms: ~[matcher], sep: Option<Token>, lo: uint)
+fn initial_matcher_pos(ms: ~[matcher], sep: Option<Token>, lo: BytePos)
     -> matcher_pos {
     let mut match_idx_hi = 0u;
     for ms.each() |elt| {
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index 31bc375a76d56..8bfd1c0a18d39 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -9,12 +9,13 @@ use macro_parser::{parse, parse_or_else, success, failure, named_match,
                       matched_seq, matched_nonterminal, error};
 use std::map::HashMap;
 use parse::token::special_idents;
+use ast_util::dummy_sp;
 
 fn add_new_extension(cx: ext_ctxt, sp: span, name: ident,
                      arg: ~[ast::token_tree]) -> base::mac_result {
     // these spans won't matter, anyways
     fn ms(m: matcher_) -> matcher {
-        {node: m, span: {lo: 0u, hi: 0u, expn_info: None}}
+        {node: m, span: dummy_sp()}
     }
 
     let lhs_nm =  cx.parse_sess().interner.gensym(@~"lhs");
@@ -65,7 +66,7 @@ fn add_new_extension(cx: ext_ctxt, sp: span, name: ident,
         }
 
         // Which arm's failure should we report? (the one furthest along)
-        let mut best_fail_spot = {lo: 0u, hi: 0u, expn_info: None};
+        let mut best_fail_spot = dummy_sp();
         let mut best_fail_msg = ~"internal error: ran no matchers";
 
         let s_d = cx.parse_sess().span_diagnostic;
diff --git a/src/libsyntax/ext/tt/transcribe.rs b/src/libsyntax/ext/tt/transcribe.rs
index 238f9db6ac537..78f0e4fc8f8bf 100644
--- a/src/libsyntax/ext/tt/transcribe.rs
+++ b/src/libsyntax/ext/tt/transcribe.rs
@@ -53,7 +53,7 @@ fn new_tt_reader(sp_diag: span_handler, itr: @ident_interner,
               mut repeat_len: ~[],
               /* dummy values, never read: */
               mut cur_tok: EOF,
-              mut cur_span: ast_util::mk_sp(0u,0u)
+              mut cur_span: ast_util::dummy_sp()
              };
     tt_next_token(r); /* get cur_tok and cur_span set up */
     return r;
diff --git a/src/libsyntax/parse.rs b/src/libsyntax/parse.rs
index e38ee7ff03763..593ff6d034ee0 100644
--- a/src/libsyntax/parse.rs
+++ b/src/libsyntax/parse.rs
@@ -20,33 +20,31 @@ use util::interner;
 use diagnostic::{span_handler, mk_span_handler, mk_handler, emitter};
 use lexer::{reader, string_reader};
 use parse::token::{ident_interner, mk_ident_interner};
+use codemap::{CodeMap, FileMap, CharPos, BytePos};
 
 type parse_sess = @{
-    cm: codemap::CodeMap,
+    cm: @codemap::CodeMap,
     mut next_id: node_id,
     span_diagnostic: span_handler,
     interner: @ident_interner,
-    // these two must be kept up to date
-    mut chpos: uint,
-    mut byte_pos: uint
 };
 
 fn new_parse_sess(demitter: Option<emitter>) -> parse_sess {
-    let cm = codemap::new_codemap();
+    let cm = @CodeMap::new();
     return @{cm: cm,
              mut next_id: 1,
              span_diagnostic: mk_span_handler(mk_handler(demitter), cm),
              interner: mk_ident_interner(),
-             mut chpos: 0u, mut byte_pos: 0u};
+            };
 }
 
-fn new_parse_sess_special_handler(sh: span_handler, cm: codemap::CodeMap)
+fn new_parse_sess_special_handler(sh: span_handler, cm: @codemap::CodeMap)
     -> parse_sess {
     return @{cm: cm,
              mut next_id: 1,
              span_diagnostic: sh,
              interner: mk_ident_interner(),
-             mut chpos: 0u, mut byte_pos: 0u};
+             };
 }
 
 fn parse_crate_from_file(input: &Path, cfg: ast::crate_cfg,
@@ -63,15 +61,13 @@ fn parse_crate_from_file(input: &Path, cfg: ast::crate_cfg,
 
 fn parse_crate_from_crate_file(input: &Path, cfg: ast::crate_cfg,
                                sess: parse_sess) -> @ast::crate {
-    let (p, rdr) = new_parser_etc_from_file(sess, cfg, input,
-                                            parser::CRATE_FILE);
+    let p = new_parser_from_file(sess, cfg, input,
+                                 parser::CRATE_FILE);
     let lo = p.span.lo;
     let prefix = input.dir_path();
     let leading_attrs = p.parse_inner_attrs_and_next();
     let { inner: crate_attrs, next: first_cdir_attr } = leading_attrs;
     let cdirs = p.parse_crate_directives(token::EOF, first_cdir_attr);
-    sess.chpos = rdr.chpos;
-    sess.byte_pos = sess.byte_pos + rdr.pos;
     let cx = @{sess: sess, cfg: /* FIXME (#2543) */ copy p.cfg};
     let companionmod = input.filestem().map(|s| Path(*s));
     let (m, attrs) = eval::eval_crate_directives_to_mod(
@@ -88,75 +84,63 @@ fn parse_crate_from_crate_file(input: &Path, cfg: ast::crate_cfg,
 
 fn parse_crate_from_source_file(input: &Path, cfg: ast::crate_cfg,
                                 sess: parse_sess) -> @ast::crate {
-    let (p, rdr) = new_parser_etc_from_file(sess, cfg, input,
-                                            parser::SOURCE_FILE);
+    let p = new_parser_from_file(sess, cfg, input,
+                                 parser::SOURCE_FILE);
     let r = p.parse_crate_mod(cfg);
-    sess.chpos = rdr.chpos;
-    sess.byte_pos = sess.byte_pos + rdr.pos;
     return r;
 }
 
 fn parse_crate_from_source_str(name: ~str, source: @~str, cfg: ast::crate_cfg,
                                sess: parse_sess) -> @ast::crate {
-    let (p, rdr) = new_parser_etc_from_source_str(sess, cfg, name,
-                                                  codemap::fss_none, source);
+    let p = new_parser_from_source_str(sess, cfg, name,
+                                       codemap::FssNone, source);
     let r = p.parse_crate_mod(cfg);
     p.abort_if_errors();
-    sess.chpos = rdr.chpos;
-    sess.byte_pos = sess.byte_pos + rdr.pos;
     return r;
 }
 
 fn parse_expr_from_source_str(name: ~str, source: @~str, cfg: ast::crate_cfg,
                               sess: parse_sess) -> @ast::expr {
-    let (p, rdr) = new_parser_etc_from_source_str(sess, cfg, name,
-                                                  codemap::fss_none, source);
+    let p = new_parser_from_source_str(sess, cfg, name,
+                                       codemap::FssNone, source);
     let r = p.parse_expr();
     p.abort_if_errors();
-    sess.chpos = rdr.chpos;
-    sess.byte_pos = sess.byte_pos + rdr.pos;
     return r;
 }
 
 fn parse_item_from_source_str(name: ~str, source: @~str, cfg: ast::crate_cfg,
                               +attrs: ~[ast::attribute],
                               sess: parse_sess) -> Option<@ast::item> {
-    let (p, rdr) = new_parser_etc_from_source_str(sess, cfg, name,
-                                                  codemap::fss_none, source);
+    let p = new_parser_from_source_str(sess, cfg, name,
+                                       codemap::FssNone, source);
     let r = p.parse_item(attrs);
     p.abort_if_errors();
-    sess.chpos = rdr.chpos;
-    sess.byte_pos = sess.byte_pos + rdr.pos;
     return r;
 }
 
 fn parse_stmt_from_source_str(name: ~str, source: @~str, cfg: ast::crate_cfg,
                               +attrs: ~[ast::attribute],
                               sess: parse_sess) -> @ast::stmt {
-    let (p, rdr) = new_parser_etc_from_source_str(sess, cfg, name,
-                                                  codemap::fss_none, source);
+    let p = new_parser_from_source_str(sess, cfg, name,
+                                       codemap::FssNone, source);
     let r = p.parse_stmt(attrs);
     p.abort_if_errors();
-    sess.chpos = rdr.chpos;
-    sess.byte_pos = sess.byte_pos + rdr.pos;
     return r;
 }
 
 fn parse_from_source_str<T>(f: fn (p: Parser) -> T,
-                            name: ~str, ss: codemap::file_substr,
+                            name: ~str, ss: codemap::FileSubstr,
                             source: @~str, cfg: ast::crate_cfg,
                             sess: parse_sess)
     -> T
 {
-    let (p, rdr) = new_parser_etc_from_source_str(sess, cfg, name, ss,
-                                                  source);
+    let p = new_parser_from_source_str(sess, cfg, name, ss,
+                                       source);
     let r = f(p);
     if !p.reader.is_eof() {
         p.reader.fatal(~"expected end-of-string");
     }
     p.abort_if_errors();
-    sess.chpos = rdr.chpos;
-    sess.byte_pos = sess.byte_pos + rdr.pos;
     move r
 }
 
@@ -168,47 +152,28 @@ fn next_node_id(sess: parse_sess) -> node_id {
     return rv;
 }
 
-fn new_parser_etc_from_source_str(sess: parse_sess, cfg: ast::crate_cfg,
-                                  +name: ~str, +ss: codemap::file_substr,
-                                  source: @~str) -> (Parser, string_reader) {
+fn new_parser_from_source_str(sess: parse_sess, cfg: ast::crate_cfg,
+                              +name: ~str, +ss: codemap::FileSubstr,
+                              source: @~str) -> Parser {
     let ftype = parser::SOURCE_FILE;
-    let filemap = codemap::new_filemap_w_substr
-        (name, ss, source, sess.chpos, sess.byte_pos);
-    sess.cm.files.push(filemap);
+    let filemap = sess.cm.new_filemap_w_substr(name, ss, source);
     let srdr = lexer::new_string_reader(sess.span_diagnostic, filemap,
                                         sess.interner);
-    return (Parser(sess, cfg, srdr as reader, ftype), srdr);
+    return Parser(sess, cfg, srdr as reader, ftype);
 }
 
-fn new_parser_from_source_str(sess: parse_sess, cfg: ast::crate_cfg,
-                              +name: ~str, +ss: codemap::file_substr,
-                              source: @~str) -> Parser {
-    let (p, _) = new_parser_etc_from_source_str(sess, cfg, name, ss, source);
-    move p
-}
-
-
-fn new_parser_etc_from_file(sess: parse_sess, cfg: ast::crate_cfg,
-                            path: &Path, ftype: parser::file_type) ->
-   (Parser, string_reader) {
+fn new_parser_from_file(sess: parse_sess, cfg: ast::crate_cfg,
+                        path: &Path, ftype: parser::file_type) -> Parser {
     let res = io::read_whole_file_str(path);
     match res {
       result::Ok(_) => { /* Continue. */ }
       result::Err(e) => sess.span_diagnostic.handler().fatal(e)
     }
     let src = @result::unwrap(res);
-    let filemap = codemap::new_filemap(path.to_str(), src,
-                                       sess.chpos, sess.byte_pos);
-    sess.cm.files.push(filemap);
+    let filemap = sess.cm.new_filemap(path.to_str(), src);
     let srdr = lexer::new_string_reader(sess.span_diagnostic, filemap,
                                         sess.interner);
-    return (Parser(sess, cfg, srdr as reader, ftype), srdr);
-}
-
-fn new_parser_from_file(sess: parse_sess, cfg: ast::crate_cfg, path: &Path,
-                        ftype: parser::file_type) -> Parser {
-    let (p, _) = new_parser_etc_from_file(sess, cfg, path, ftype);
-    move p
+    return Parser(sess, cfg, srdr as reader, ftype);
 }
 
 fn new_parser_from_tt(sess: parse_sess, cfg: ast::crate_cfg,
diff --git a/src/libsyntax/parse/attr.rs b/src/libsyntax/parse/attr.rs
index 42101a431d6c6..f0cb1d4ba3e1c 100644
--- a/src/libsyntax/parse/attr.rs
+++ b/src/libsyntax/parse/attr.rs
@@ -14,7 +14,7 @@ trait parser_attr {
         -> attr_or_ext;
     fn parse_outer_attributes() -> ~[ast::attribute];
     fn parse_attribute(style: ast::attr_style) -> ast::attribute;
-    fn parse_attribute_naked(style: ast::attr_style, lo: uint) ->
+    fn parse_attribute_naked(style: ast::attr_style, lo: BytePos) ->
         ast::attribute;
     fn parse_inner_attrs_and_next() ->
         {inner: ~[ast::attribute], next: ~[ast::attribute]};
@@ -85,7 +85,7 @@ impl Parser: parser_attr {
         return self.parse_attribute_naked(style, lo);
     }
 
-    fn parse_attribute_naked(style: ast::attr_style, lo: uint) ->
+    fn parse_attribute_naked(style: ast::attr_style, lo: BytePos) ->
         ast::attribute {
         self.expect(token::LBRACKET);
         let meta_item = self.parse_meta_item();
diff --git a/src/libsyntax/parse/comments.rs b/src/libsyntax/parse/comments.rs
index 4f265e1919c2e..2a8bbe3b6d862 100644
--- a/src/libsyntax/parse/comments.rs
+++ b/src/libsyntax/parse/comments.rs
@@ -3,6 +3,7 @@ use io::ReaderUtil;
 use util::interner;
 use lexer::{string_reader, bump, is_eof, nextch,
                is_whitespace, get_str_from, reader};
+use codemap::{FileMap, CharPos};
 
 export cmnt;
 export lit;
@@ -27,7 +28,7 @@ impl cmnt_style : cmp::Eq {
     }
 }
 
-type cmnt = {style: cmnt_style, lines: ~[~str], pos: uint};
+type cmnt = {style: cmnt_style, lines: ~[~str], pos: BytePos};
 
 fn is_doc_comment(s: ~str) -> bool {
     s.starts_with(~"///") ||
@@ -130,13 +131,13 @@ fn consume_non_eol_whitespace(rdr: string_reader) {
 fn push_blank_line_comment(rdr: string_reader, comments: &mut ~[cmnt]) {
     debug!(">>> blank-line comment");
     let v: ~[~str] = ~[];
-    comments.push({style: blank_line, lines: v, pos: rdr.chpos});
+    comments.push({style: blank_line, lines: v, pos: rdr.last_pos});
 }
 
 fn consume_whitespace_counting_blank_lines(rdr: string_reader,
                                            comments: &mut ~[cmnt]) {
     while is_whitespace(rdr.curr) && !is_eof(rdr) {
-        if rdr.col == 0u && rdr.curr == '\n' {
+        if rdr.col == CharPos(0u) && rdr.curr == '\n' {
             push_blank_line_comment(rdr, comments);
         }
         bump(rdr);
@@ -147,7 +148,7 @@ fn consume_whitespace_counting_blank_lines(rdr: string_reader,
 fn read_shebang_comment(rdr: string_reader, code_to_the_left: bool,
                                             comments: &mut ~[cmnt]) {
     debug!(">>> shebang comment");
-    let p = rdr.chpos;
+    let p = rdr.last_pos;
     debug!("<<< shebang comment");
     comments.push({
         style: if code_to_the_left { trailing } else { isolated },
@@ -159,7 +160,7 @@ fn read_shebang_comment(rdr: string_reader, code_to_the_left: bool,
 fn read_line_comments(rdr: string_reader, code_to_the_left: bool,
                                           comments: &mut ~[cmnt]) {
     debug!(">>> line comments");
-    let p = rdr.chpos;
+    let p = rdr.last_pos;
     let mut lines: ~[~str] = ~[];
     while rdr.curr == '/' && nextch(rdr) == '/' {
         let line = read_one_line_comment(rdr);
@@ -180,6 +181,8 @@ fn read_line_comments(rdr: string_reader, code_to_the_left: bool,
     }
 }
 
+// FIXME #3961: This is not the right way to convert string byte
+// offsets to characters.
 fn all_whitespace(s: ~str, begin: uint, end: uint) -> bool {
     let mut i: uint = begin;
     while i != end {
@@ -189,9 +192,11 @@ fn all_whitespace(s: ~str, begin: uint, end: uint) -> bool {
 }
 
 fn trim_whitespace_prefix_and_push_line(lines: &mut ~[~str],
-                                        s: ~str, col: uint) {
+                                        s: ~str, col: CharPos) {
     let mut s1;
     let len = str::len(s);
+    // FIXME #3961: Doing bytewise comparison and slicing with CharPos
+    let col = col.to_uint();
     if all_whitespace(s, 0u, uint::min(len, col)) {
         if col < len {
             s1 = str::slice(s, col, len);
@@ -204,9 +209,9 @@ fn trim_whitespace_prefix_and_push_line(lines: &mut ~[~str],
 fn read_block_comment(rdr: string_reader, code_to_the_left: bool,
                                           comments: &mut ~[cmnt]) {
     debug!(">>> block comment");
-    let p = rdr.chpos;
+    let p = rdr.last_pos;
     let mut lines: ~[~str] = ~[];
-    let mut col: uint = rdr.col;
+    let mut col: CharPos = rdr.col;
     bump(rdr);
     bump(rdr);
 
@@ -279,7 +284,7 @@ fn consume_comment(rdr: string_reader, code_to_the_left: bool,
     debug!("<<< consume comment");
 }
 
-type lit = {lit: ~str, pos: uint};
+type lit = {lit: ~str, pos: BytePos};
 
 fn gather_comments_and_literals(span_diagnostic: diagnostic::span_handler,
                                 path: ~str,
@@ -287,8 +292,10 @@ fn gather_comments_and_literals(span_diagnostic: diagnostic::span_handler,
    {cmnts: ~[cmnt], lits: ~[lit]} {
     let src = @str::from_bytes(srdr.read_whole_stream());
     let itr = parse::token::mk_fake_ident_interner();
-    let rdr = lexer::new_low_level_string_reader
-        (span_diagnostic, codemap::new_filemap(path, src, 0u, 0u), itr);
+    let cm = CodeMap::new();
+    let filemap = cm.new_filemap(path, src);
+    let rdr = lexer::new_low_level_string_reader(
+        span_diagnostic, filemap, itr);
 
     let mut comments: ~[cmnt] = ~[];
     let mut literals: ~[lit] = ~[];
diff --git a/src/libsyntax/parse/common.rs b/src/libsyntax/parse/common.rs
index 50c22c08f4f88..1811951fc0e9a 100644
--- a/src/libsyntax/parse/common.rs
+++ b/src/libsyntax/parse/common.rs
@@ -205,7 +205,7 @@ impl Parser: parser_common {
         if self.token == token::GT {
             self.bump();
         } else if self.token == token::BINOP(token::SHR) {
-            self.swap(token::GT, self.span.lo + 1u, self.span.hi);
+            self.swap(token::GT, self.span.lo + BytePos(1u), self.span.hi);
         } else {
             let mut s: ~str = ~"expected `";
             s += token_to_str(self.reader, token::GT);
diff --git a/src/libsyntax/parse/eval.rs b/src/libsyntax/parse/eval.rs
index 56c9d4de9f3cd..f08f195446442 100644
--- a/src/libsyntax/parse/eval.rs
+++ b/src/libsyntax/parse/eval.rs
@@ -62,12 +62,10 @@ fn parse_companion_mod(cx: ctx, prefix: &Path, suffix: &Option<Path>)
     let modpath = &companion_file(prefix, suffix);
     if file_exists(modpath) {
         debug!("found companion mod");
-        let (p0, r0) = new_parser_etc_from_file(cx.sess, cx.cfg,
-                                                modpath, SOURCE_FILE);
+        let p0 = new_parser_from_file(cx.sess, cx.cfg,
+                                      modpath, SOURCE_FILE);
         let inner_attrs = p0.parse_inner_attrs_and_next();
         let m0 = p0.parse_mod_items(token::EOF, inner_attrs.next);
-        cx.sess.chpos = r0.chpos;
-        cx.sess.byte_pos = cx.sess.byte_pos + r0.pos;
         return (m0.view_items, m0.items, inner_attrs.inner);
     } else {
         return (~[], ~[], ~[]);
@@ -93,9 +91,9 @@ fn eval_crate_directive(cx: ctx, cdir: @ast::crate_directive, prefix: &Path,
         } else {
             prefix.push_many(file_path.components)
         };
-        let (p0, r0) =
-            new_parser_etc_from_file(cx.sess, cx.cfg,
-                                     &full_path, SOURCE_FILE);
+        let p0 =
+            new_parser_from_file(cx.sess, cx.cfg,
+                                 &full_path, SOURCE_FILE);
         let inner_attrs = p0.parse_inner_attrs_and_next();
         let mod_attrs = vec::append(attrs, inner_attrs.inner);
         let first_item_outer_attrs = inner_attrs.next;
@@ -104,9 +102,6 @@ fn eval_crate_directive(cx: ctx, cdir: @ast::crate_directive, prefix: &Path,
         let i = p0.mk_item(cdir.span.lo, cdir.span.hi,
                            /* FIXME (#2543) */ copy id,
                            ast::item_mod(m0), vis, mod_attrs);
-        // Thread defids, chpos and byte_pos through the parsers
-        cx.sess.chpos = r0.chpos;
-        cx.sess.byte_pos = cx.sess.byte_pos + r0.pos;
         items.push(i);
       }
       ast::cdir_dir_mod(vis, id, cdirs, attrs) => {
diff --git a/src/libsyntax/parse/lexer.rs b/src/libsyntax/parse/lexer.rs
index 8f57d733eb51f..6f1f644ab27b1 100644
--- a/src/libsyntax/parse/lexer.rs
+++ b/src/libsyntax/parse/lexer.rs
@@ -1,5 +1,5 @@
 use diagnostic::span_handler;
-use codemap::span;
+use codemap::{span, CodeMap, CharPos, BytePos};
 use ext::tt::transcribe::{tt_reader,  new_tt_reader, dup_tt_reader,
                              tt_next_token};
 
@@ -21,11 +21,15 @@ trait reader {
 type string_reader = @{
     span_diagnostic: span_handler,
     src: @~str,
-    mut col: uint,
-    mut pos: uint,
+    // The absolute offset within the codemap of the next character to read
+    mut pos: BytePos,
+    // The absolute offset within the codemap of the last character read(curr)
+    mut last_pos: BytePos,
+    // The column of the next character to read
+    mut col: CharPos,
+    // The last character to be read
     mut curr: char,
-    mut chpos: uint,
-    filemap: codemap::filemap,
+    filemap: @codemap::FileMap,
     interner: @token::ident_interner,
     /* cached: */
     mut peek_tok: token::Token,
@@ -33,7 +37,7 @@ type string_reader = @{
 };
 
 fn new_string_reader(span_diagnostic: span_handler,
-                     filemap: codemap::filemap,
+                     filemap: @codemap::FileMap,
                      itr: @token::ident_interner) -> string_reader {
     let r = new_low_level_string_reader(span_diagnostic, filemap, itr);
     string_advance_token(r); /* fill in peek_* */
@@ -42,27 +46,29 @@ fn new_string_reader(span_diagnostic: span_handler,
 
 /* For comments.rs, which hackily pokes into 'pos' and 'curr' */
 fn new_low_level_string_reader(span_diagnostic: span_handler,
-                               filemap: codemap::filemap,
+                               filemap: @codemap::FileMap,
                                itr: @token::ident_interner)
     -> string_reader {
+    // Force the initial reader bump to start on a fresh line
+    let initial_char = '\n';
     let r = @{span_diagnostic: span_diagnostic, src: filemap.src,
-              mut col: 0u, mut pos: 0u, mut curr: -1 as char,
-              mut chpos: filemap.start_pos.ch,
+              mut pos: filemap.start_pos,
+              mut last_pos: filemap.start_pos,
+              mut col: CharPos(0),
+              mut curr: initial_char,
               filemap: filemap, interner: itr,
               /* dummy values; not read */
               mut peek_tok: token::EOF,
-              mut peek_span: ast_util::mk_sp(0u,0u)};
-    if r.pos < (*filemap.src).len() {
-        let next = str::char_range_at(*r.src, r.pos);
-        r.pos = next.next;
-        r.curr = next.ch;
-    }
+              mut peek_span: ast_util::dummy_sp()};
+    bump(r);
     return r;
 }
 
 fn dup_string_reader(&&r: string_reader) -> string_reader {
     @{span_diagnostic: r.span_diagnostic, src: r.src,
-      mut col: r.col, mut pos: r.pos, mut curr: r.curr, mut chpos: r.chpos,
+      mut pos: r.pos,
+      mut last_pos: r.last_pos,
+      mut col: r.col, mut curr: r.curr,
       filemap: r.filemap, interner: r.interner,
       mut peek_tok: r.peek_tok, mut peek_span: r.peek_span}
 }
@@ -117,34 +123,48 @@ fn string_advance_token(&&r: string_reader) {
     if is_eof(r) {
         r.peek_tok = token::EOF;
     } else {
-        let start_chpos = r.chpos;
+        let start_bytepos = r.last_pos;
         r.peek_tok = next_token_inner(r);
-        r.peek_span = ast_util::mk_sp(start_chpos, r.chpos);
+        r.peek_span = ast_util::mk_sp(start_bytepos, r.last_pos);
     };
 
 }
 
-fn get_str_from(rdr: string_reader, start: uint) -> ~str unsafe {
+fn byte_offset(rdr: string_reader) -> BytePos {
+    (rdr.pos - rdr.filemap.start_pos)
+}
+
+fn get_str_from(rdr: string_reader, start: BytePos) -> ~str unsafe {
     // I'm pretty skeptical about this subtraction. What if there's a
     // multi-byte character before the mark?
-    return str::slice(*rdr.src, start - 1u, rdr.pos - 1u);
+    return str::slice(*rdr.src, start.to_uint() - 1u,
+                      byte_offset(rdr).to_uint() - 1u);
 }
 
 fn bump(rdr: string_reader) {
-    if rdr.pos < (*rdr.src).len() {
-        rdr.col += 1u;
-        rdr.chpos += 1u;
-        if rdr.curr == '\n' {
-            codemap::next_line(rdr.filemap, rdr.chpos, rdr.pos);
-            rdr.col = 0u;
-        }
-        let next = str::char_range_at(*rdr.src, rdr.pos);
-        rdr.pos = next.next;
+    rdr.last_pos = rdr.pos;
+    let current_byte_offset = byte_offset(rdr).to_uint();;
+    if current_byte_offset < (*rdr.src).len() {
+        let last_char = rdr.curr;
+        let next = str::char_range_at(*rdr.src, current_byte_offset);
+        let byte_offset_diff = next.next - current_byte_offset;
+        rdr.pos = rdr.pos + BytePos(byte_offset_diff);
         rdr.curr = next.ch;
+        rdr.col += CharPos(1u);
+        if last_char == '\n' {
+            rdr.filemap.next_line(rdr.last_pos);
+            rdr.col = CharPos(0u);
+        }
+
+        if byte_offset_diff > 1 {
+            rdr.filemap.record_multibyte_char(
+                BytePos(current_byte_offset), byte_offset_diff);
+        }
     } else {
+        // XXX: What does this accomplish?
         if (rdr.curr != -1 as char) {
-            rdr.col += 1u;
-            rdr.chpos += 1u;
+            rdr.pos = rdr.pos + BytePos(1u);
+            rdr.col += CharPos(1u);
             rdr.curr = -1 as char;
         }
     }
@@ -153,8 +173,9 @@ fn is_eof(rdr: string_reader) -> bool {
     rdr.curr == -1 as char
 }
 fn nextch(rdr: string_reader) -> char {
-    if rdr.pos < (*rdr.src).len() {
-        return str::char_at(*rdr.src, rdr.pos);
+    let offset = byte_offset(rdr).to_uint();
+    if offset < (*rdr.src).len() {
+        return str::char_at(*rdr.src, offset);
     } else { return -1 as char; }
 }
 
@@ -211,7 +232,7 @@ fn consume_any_line_comment(rdr: string_reader)
             bump(rdr);
             // line comments starting with "///" or "//!" are doc-comments
             if rdr.curr == '/' || rdr.curr == '!' {
-                let start_chpos = rdr.chpos - 2u;
+                let start_bpos = rdr.pos - BytePos(2u);
                 let mut acc = ~"//";
                 while rdr.curr != '\n' && !is_eof(rdr) {
                     str::push_char(&mut acc, rdr.curr);
@@ -219,7 +240,7 @@ fn consume_any_line_comment(rdr: string_reader)
                 }
                 return Some({
                     tok: token::DOC_COMMENT(rdr.interner.intern(@acc)),
-                    sp: ast_util::mk_sp(start_chpos, rdr.chpos)
+                    sp: ast_util::mk_sp(start_bpos, rdr.pos)
                 });
             } else {
                 while rdr.curr != '\n' && !is_eof(rdr) { bump(rdr); }
@@ -232,10 +253,10 @@ fn consume_any_line_comment(rdr: string_reader)
         }
     } else if rdr.curr == '#' {
         if nextch(rdr) == '!' {
-            let cmap = codemap::new_codemap();
+            let cmap = @CodeMap::new();
             (*cmap).files.push(rdr.filemap);
-            let loc = codemap::lookup_char_pos_adj(cmap, rdr.chpos);
-            if loc.line == 1u && loc.col == 0u {
+            let loc = cmap.lookup_char_pos_adj(rdr.last_pos);
+            if loc.line == 1u && loc.col == CharPos(0u) {
                 while rdr.curr != '\n' && !is_eof(rdr) { bump(rdr); }
                 return consume_whitespace_and_comments(rdr);
             }
@@ -250,7 +271,7 @@ fn consume_block_comment(rdr: string_reader)
 
     // block comments starting with "/**" or "/*!" are doc-comments
     if rdr.curr == '*' || rdr.curr == '!' {
-        let start_chpos = rdr.chpos - 2u;
+        let start_bpos = rdr.pos - BytePos(2u);
         let mut acc = ~"/*";
         while !(rdr.curr == '*' && nextch(rdr) == '/') && !is_eof(rdr) {
             str::push_char(&mut acc, rdr.curr);
@@ -264,7 +285,7 @@ fn consume_block_comment(rdr: string_reader)
             bump(rdr);
             return Some({
                 tok: token::DOC_COMMENT(rdr.interner.intern(@acc)),
-                sp: ast_util::mk_sp(start_chpos, rdr.chpos)
+                sp: ast_util::mk_sp(start_bpos, rdr.pos)
             });
         }
     } else {
@@ -584,7 +605,7 @@ fn next_token_inner(rdr: string_reader) -> token::Token {
         return token::LIT_INT(c2 as i64, ast::ty_char);
       }
       '"' => {
-        let n = rdr.chpos;
+        let n = byte_offset(rdr);
         bump(rdr);
         while rdr.curr != '"' {
             if is_eof(rdr) {
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 2b42dcc0ed06a..74d06789ad899 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -5,7 +5,7 @@ use either::{Either, Left, Right};
 use std::map::HashMap;
 use token::{can_begin_expr, is_ident, is_ident_or_path, is_plain_ident,
             INTERPOLATED, special_idents};
-use codemap::{span,fss_none};
+use codemap::{span,FssNone, BytePos};
 use util::interner::Interner;
 use ast_util::{spanned, respan, mk_sp, ident_to_path, operator_prec};
 use lexer::reader;
@@ -244,7 +244,7 @@ impl Parser {
         self.token = next.tok;
         self.span = next.sp;
     }
-    fn swap(next: token::Token, lo: uint, hi: uint) {
+    fn swap(next: token::Token, +lo: BytePos, +hi: BytePos) {
         self.token = next;
         self.span = mk_sp(lo, hi);
     }
@@ -904,12 +904,12 @@ impl Parser {
         return spanned(lo, e.span.hi, {mutbl: m, ident: i, expr: e});
     }
 
-    fn mk_expr(lo: uint, hi: uint, +node: expr_) -> @expr {
+    fn mk_expr(+lo: BytePos, +hi: BytePos, +node: expr_) -> @expr {
         return @{id: self.get_id(), callee_id: self.get_id(),
               node: node, span: mk_sp(lo, hi)};
     }
 
-    fn mk_mac_expr(lo: uint, hi: uint, m: mac_) -> @expr {
+    fn mk_mac_expr(+lo: BytePos, +hi: BytePos, m: mac_) -> @expr {
         return @{id: self.get_id(),
               callee_id: self.get_id(),
               node: expr_mac({node: m, span: mk_sp(lo, hi)}),
@@ -1134,7 +1134,7 @@ impl Parser {
         return self.mk_expr(lo, hi, ex);
     }
 
-    fn parse_block_expr(lo: uint, blk_mode: blk_check_mode) -> @expr {
+    fn parse_block_expr(lo: BytePos, blk_mode: blk_check_mode) -> @expr {
         self.expect(token::LBRACE);
         let blk = self.parse_block_tail(lo, blk_mode);
         return self.mk_expr(blk.span.lo, blk.span.hi, expr_block(blk));
@@ -1146,7 +1146,7 @@ impl Parser {
         return self.parse_syntax_ext_naked(lo);
     }
 
-    fn parse_syntax_ext_naked(lo: uint) -> @expr {
+    fn parse_syntax_ext_naked(lo: BytePos) -> @expr {
         match self.token {
           token::IDENT(_, _) => (),
           _ => self.fatal(~"expected a syntax expander name")
@@ -2279,11 +2279,11 @@ impl Parser {
     // I guess that also means "already parsed the 'impure'" if
     // necessary, and this should take a qualifier.
     // some blocks start with "#{"...
-    fn parse_block_tail(lo: uint, s: blk_check_mode) -> blk {
+    fn parse_block_tail(lo: BytePos, s: blk_check_mode) -> blk {
         self.parse_block_tail_(lo, s, ~[])
     }
 
-    fn parse_block_tail_(lo: uint, s: blk_check_mode,
+    fn parse_block_tail_(lo: BytePos, s: blk_check_mode,
                          +first_item_attrs: ~[attribute]) -> blk {
         let mut stmts = ~[];
         let mut expr = None;
@@ -2581,7 +2581,7 @@ impl Parser {
         return {ident: id, tps: ty_params};
     }
 
-    fn mk_item(lo: uint, hi: uint, +ident: ident,
+    fn mk_item(+lo: BytePos, +hi: BytePos, +ident: ident,
                +node: item_, vis: visibility,
                +attrs: ~[attribute]) -> @item {
         return @{ident: ident,
@@ -3037,7 +3037,7 @@ impl Parser {
             items: items};
     }
 
-    fn parse_item_foreign_mod(lo: uint,
+    fn parse_item_foreign_mod(lo: BytePos,
                               visibility: visibility,
                               attrs: ~[attribute],
                               items_allowed: bool)
@@ -3092,7 +3092,7 @@ impl Parser {
         });
     }
 
-    fn parse_type_decl() -> {lo: uint, ident: ident} {
+    fn parse_type_decl() -> {lo: BytePos, ident: ident} {
         let lo = self.last_span.lo;
         let id = self.parse_ident();
         return {lo: lo, ident: id};
@@ -3415,9 +3415,8 @@ impl Parser {
                 |p| p.parse_token_tree());
             let m = ast::mac_invoc_tt(pth, tts);
             let m: ast::mac = {node: m,
-                               span: {lo: self.span.lo,
-                                      hi: self.span.hi,
-                                      expn_info: None}};
+                               span: mk_sp(self.span.lo,
+                                           self.span.hi)};
             let item_ = item_mac(m);
             return iovi_item(self.mk_item(lo, self.last_span.hi, id, item_,
                                           visibility, attrs));
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 0418f6776de6b..949d2defa9a2a 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -1,5 +1,5 @@
 use parse::{comments, lexer, token};
-use codemap::CodeMap;
+use codemap::{CodeMap, BytePos};
 use pp::{break_offset, word, printer, space, zerobreak, hardbreak, breaks};
 use pp::{consistent, inconsistent, eof};
 use ast::{required, provided};
@@ -25,7 +25,7 @@ fn no_ann() -> pp_ann {
 
 type ps =
     @{s: pp::printer,
-      cm: Option<CodeMap>,
+      cm: Option<@CodeMap>,
       intr: @token::ident_interner,
       comments: Option<~[comments::cmnt]>,
       literals: Option<~[comments::lit]>,
@@ -46,7 +46,7 @@ fn end(s: ps) {
 
 fn rust_printer(writer: io::Writer, intr: @ident_interner) -> ps {
     return @{s: pp::mk_printer(writer, default_columns),
-             cm: None::<CodeMap>,
+             cm: None::<@CodeMap>,
              intr: intr,
              comments: None::<~[comments::cmnt]>,
              literals: None::<~[comments::lit]>,
@@ -64,7 +64,7 @@ const default_columns: uint = 78u;
 // Requires you to pass an input filename and reader so that
 // it can scan the input text for comments and literals to
 // copy forward.
-fn print_crate(cm: CodeMap, intr: @ident_interner,
+fn print_crate(cm: @CodeMap, intr: @ident_interner,
                span_diagnostic: diagnostic::span_handler,
                crate: @ast::crate, filename: ~str, in: io::Reader,
                out: io::Writer, ann: pp_ann, is_expanded: bool) {
@@ -631,7 +631,7 @@ fn print_variants(s: ps, variants: ~[ast::variant], span: ast::span) {
         print_variant(s, *v);
         word(s.s, ~",");
         end(s);
-        maybe_print_trailing_comment(s, v.span, None::<uint>);
+        maybe_print_trailing_comment(s, v.span, None);
     }
     bclose(s, span);
 }
@@ -886,7 +886,7 @@ fn print_stmt(s: ps, st: ast::stmt) {
       }
     }
     if parse::classify::stmt_ends_with_semi(st) { word(s.s, ~";"); }
-    maybe_print_trailing_comment(s, st.span, None::<uint>);
+    maybe_print_trailing_comment(s, st.span, None);
 }
 
 fn print_block(s: ps, blk: ast::blk) {
@@ -1898,15 +1898,15 @@ fn print_ty_fn(s: ps,
 }
 
 fn maybe_print_trailing_comment(s: ps, span: codemap::span,
-                                next_pos: Option<uint>) {
+                                next_pos: Option<BytePos>) {
     let mut cm;
     match s.cm { Some(ccm) => cm = ccm, _ => return }
     match next_comment(s) {
       Some(cmnt) => {
         if cmnt.style != comments::trailing { return; }
-        let span_line = codemap::lookup_char_pos(cm, span.hi);
-        let comment_line = codemap::lookup_char_pos(cm, cmnt.pos);
-        let mut next = cmnt.pos + 1u;
+        let span_line = cm.lookup_char_pos(span.hi);
+        let comment_line = cm.lookup_char_pos(cmnt.pos);
+        let mut next = cmnt.pos + BytePos(1u);
         match next_pos { None => (), Some(p) => next = p }
         if span.hi < cmnt.pos && cmnt.pos < next &&
                span_line.line == comment_line.line {
@@ -1981,7 +1981,7 @@ fn lit_to_str(l: @ast::lit) -> ~str {
     return to_str(l, print_literal, parse::token::mk_fake_ident_interner());
 }
 
-fn next_lit(s: ps, pos: uint) -> Option<comments::lit> {
+fn next_lit(s: ps, pos: BytePos) -> Option<comments::lit> {
     match s.literals {
       Some(lits) => {
         while s.cur_lit < vec::len(lits) {
@@ -1996,7 +1996,7 @@ fn next_lit(s: ps, pos: uint) -> Option<comments::lit> {
     }
 }
 
-fn maybe_print_comment(s: ps, pos: uint) {
+fn maybe_print_comment(s: ps, pos: BytePos) {
     loop {
         match next_comment(s) {
           Some(cmnt) => {
diff --git a/src/libsyntax/syntax.rc b/src/libsyntax/syntax.rc
index 7c73deed1a91f..9195f1fd8f7d9 100644
--- a/src/libsyntax/syntax.rc
+++ b/src/libsyntax/syntax.rc
@@ -25,7 +25,6 @@ use core::*;
 mod attr;
 #[legacy_exports]
 mod diagnostic;
-#[legacy_exports]
 mod codemap;
 #[legacy_exports]
 mod ast;