refactoring mod.rs

3 files changed, 435 insertions, 161 deletions

diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index 4d8fdcfe617..0063c7ea876 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -13,7 +13,7 @@
 
 use ast::node_id;
 use ast;
-use codemap::{span, CodeMap};
+use codemap::{span, CodeMap, FileMap, FileSubstr};
 use codemap;
 use diagnostic::{span_handler, mk_span_handler, mk_handler, Emitter};
 use parse::attr::parser_attr;
@@ -22,7 +22,7 @@ use parse::parser::Parser;
 use parse::token::{ident_interner, mk_ident_interner};
 
 use core::io;
-use core::option::{None, Option};
+use core::option::{None, Option, Some};
 use core::path::Path;
 use core::result::{Err, Ok, Result};
 
@@ -82,31 +82,15 @@ pub fn new_parse_sess_special_handler(sh: @span_handler,
 // uses a HOF to parse anything, and <source> includes file and
 // source_str.
 
-// this appears to be the main entry point for rust parsing by
-// rustc and crate:
 pub fn parse_crate_from_file(
     input: &Path,
     cfg: ast::crate_cfg,
     sess: @mut ParseSess
 ) -> @ast::crate {
-    let p = new_parser_from_file(sess, /*bad*/ copy cfg, input);
-    p.parse_crate_mod(/*bad*/ copy cfg)
+    new_parser_from_file(sess, /*bad*/ copy cfg, input).parse_crate_mod()
     // why is there no p.abort_if_errors here?
 }
 
-pub fn parse_crate_from_file_using_tts(
-    input: &Path,
-    cfg: ast::crate_cfg,
-    sess: @mut ParseSess
-) -> @ast::crate {
-    let p = new_parser_from_file(sess, /*bad*/ copy cfg, input);
-    let tts = p.parse_all_token_trees();
-    new_parser_from_tts(sess,cfg,tts).parse_crate_mod(/*bad*/ copy cfg)
-    // why is there no p.abort_if_errors here?
-}
-
-
-
 pub fn parse_crate_from_source_str(
     name: ~str,
     source: @~str,
@@ -117,10 +101,9 @@ pub fn parse_crate_from_source_str(
         sess,
         /*bad*/ copy cfg,
         /*bad*/ copy name,
-        codemap::FssNone,
         source
     );
-    maybe_aborted(p.parse_crate_mod(/*bad*/ copy cfg),p)
+    maybe_aborted(p.parse_crate_mod(),p)
 }
 
 pub fn parse_expr_from_source_str(
@@ -133,7 +116,6 @@ pub fn parse_expr_from_source_str(
         sess,
         cfg,
         /*bad*/ copy name,
-        codemap::FssNone,
         source
     );
     maybe_aborted(p.parse_expr(), p)
@@ -150,7 +132,6 @@ pub fn parse_item_from_source_str(
         sess,
         cfg,
         /*bad*/ copy name,
-        codemap::FssNone,
         source
     );
     maybe_aborted(p.parse_item(attrs),p)
@@ -166,7 +147,6 @@ pub fn parse_meta_from_source_str(
         sess,
         cfg,
         /*bad*/ copy name,
-        codemap::FssNone,
         source
     );
     maybe_aborted(p.parse_meta_item(),p)
@@ -183,7 +163,6 @@ pub fn parse_stmt_from_source_str(
         sess,
         cfg,
         /*bad*/ copy name,
-        codemap::FssNone,
         source
     );
     maybe_aborted(p.parse_stmt(attrs),p)
@@ -199,13 +178,18 @@ pub fn parse_tts_from_source_str(
         sess,
         cfg,
         /*bad*/ copy name,
-        codemap::FssNone,
         source
     );
     *p.quote_depth += 1u;
+    // right now this is re-creating the token trees from ... token trees.
     maybe_aborted(p.parse_all_token_trees(),p)
 }
 
+// given a function and parsing information (source str,
+// filename, crate cfg, and sess), create a parser,
+// apply the function, and check that the parser
+// consumed all of the input before returning the function's
+// result.
 pub fn parse_from_source_str<T>(
     f: &fn(&Parser) -> T,
     name: ~str, ss: codemap::FileSubstr,
@@ -213,7 +197,7 @@ pub fn parse_from_source_str<T>(
     cfg: ast::crate_cfg,
     sess: @mut ParseSess
 ) -> T {
-    let p = new_parser_from_source_str(
+    let p = new_parser_from_source_substr(
         sess,
         cfg,
         name,
@@ -227,6 +211,7 @@ pub fn parse_from_source_str<T>(
     maybe_aborted(r,p)
 }
 
+// return the next unused node id.
 pub fn next_node_id(sess: @mut ParseSess) -> node_id {
     let rv = sess.next_id;
     sess.next_id += 1;
@@ -235,39 +220,24 @@ pub fn next_node_id(sess: @mut ParseSess) -> node_id {
     return rv;
 }
 
+// Create a new parser from a source string
 pub fn new_parser_from_source_str(sess: @mut ParseSess,
                                   cfg: ast::crate_cfg,
                                   name: ~str,
-                                  ss: codemap::FileSubstr,
                                   source: @~str)
                                -> Parser {
-    let filemap = sess.cm.new_filemap_w_substr(name, ss, source);
-    let srdr = lexer::new_string_reader(
-        copy sess.span_diagnostic,
-        filemap,
-        sess.interner
-    );
-    Parser(sess, cfg, srdr as @reader)
+    filemap_to_parser(sess,string_to_filemap(sess,source,name),cfg)
 }
 
-/// Read the entire source file, return a parser
-/// that draws from that string
-pub fn new_parser_result_from_file(
-    sess: @mut ParseSess,
-    cfg: ast::crate_cfg,
-    path: &Path
-) -> Result<Parser, ~str> {
-    match io::read_whole_file_str(path) {
-        Ok(src) => {
-            let filemap = sess.cm.new_filemap(path.to_str(), @src);
-            let srdr = lexer::new_string_reader(copy sess.span_diagnostic,
-                                                filemap,
-                                                sess.interner);
-            Ok(Parser(sess, cfg, srdr as @reader))
-
-        }
-        Err(e) => Err(e)
-    }
+// Create a new parser from a source string where the origin
+// is specified as a substring of another file.
+pub fn new_parser_from_source_substr(sess: @mut ParseSess,
+                                  cfg: ast::crate_cfg,
+                                  name: ~str,
+                                  ss: codemap::FileSubstr,
+                                  source: @~str)
+                               -> Parser {
+    filemap_to_parser(sess,substring_to_filemap(sess,source,name,ss),cfg)
 }
 
 /// Create a new parser, handling errors as appropriate
@@ -277,35 +247,85 @@ pub fn new_parser_from_file(
     cfg: ast::crate_cfg,
     path: &Path
 ) -> Parser {
-    match new_parser_result_from_file(sess, cfg, path) {
-        Ok(parser) => parser,
-        Err(e) => {
-            sess.span_diagnostic.handler().fatal(e)
-        }
-    }
+    filemap_to_parser(sess,file_to_filemap(sess,path,None),cfg)
 }
 
-/// Create a new parser based on a span from an existing parser. Handles
-/// error messages correctly when the file does not exist.
+/// Given a session, a crate config, a path, and a span, add
+/// the file at the given path to the codemap, and return a parser.
+/// On an error, use the given span as the source of the problem.
 pub fn new_sub_parser_from_file(
     sess: @mut ParseSess,
     cfg: ast::crate_cfg,
     path: &Path,
     sp: span
 ) -> Parser {
-    match new_parser_result_from_file(sess, cfg, path) {
-        Ok(parser) => parser,
+    filemap_to_parser(sess,file_to_filemap(sess,path,Some(sp)),cfg)
+}
+
+/// Given a filemap and config, return a parser
+pub fn filemap_to_parser(sess: @mut ParseSess,
+                         filemap: @FileMap,
+                         cfg: ast::crate_cfg) -> Parser {
+    tts_to_parser(sess,filemap_to_tts(sess,filemap),cfg)
+}
+
+// must preserve old name for now, because quote! from the *existing*
+// compiler expands into it
+pub fn new_parser_from_tts(sess: @mut ParseSess,
+                     cfg: ast::crate_cfg,
+                     tts: ~[ast::token_tree]) -> Parser {
+    tts_to_parser(sess,tts,cfg)
+}
+
+
+// base abstractions
+
+/// Given a session and a path and an optional span (for error reporting),
+/// add the path to the session's codemap and return the new filemap.
+pub fn file_to_filemap(sess: @mut ParseSess, path: &Path, spanopt: Option<span>)
+    -> @FileMap {
+    match io::read_whole_file_str(path) {
+        Ok(src) => string_to_filemap(sess, @src, path.to_str()),
         Err(e) => {
-            sess.span_diagnostic.span_fatal(sp, e)
+            match spanopt {
+                Some(span) => sess.span_diagnostic.span_fatal(span, e),
+                None => sess.span_diagnostic.handler().fatal(e)
+            }
         }
     }
 }
 
-pub fn new_parser_from_tts(
-    sess: @mut ParseSess,
-    cfg: ast::crate_cfg,
-    tts: ~[ast::token_tree]
-) -> Parser {
+// given a session and a string, add the string to
+// the session's codemap and return the new filemap
+pub fn string_to_filemap(sess: @mut ParseSess, source: @~str, path: ~str)
+    -> @FileMap {
+    sess.cm.new_filemap(path, source)
+}
+
+// given a session and a string and a path and a FileSubStr, add
+// the string to the CodeMap and return the new FileMap
+pub fn substring_to_filemap(sess: @mut ParseSess, source: @~str, path: ~str,
+                           filesubstr: FileSubstr) -> @FileMap {
+    sess.cm.new_filemap_w_substr(path,filesubstr,source)
+}
+
+// given a filemap, produce a sequence of token-trees
+pub fn filemap_to_tts(sess: @mut ParseSess, filemap: @FileMap)
+    -> ~[ast::token_tree] {
+    // it appears to me that the cfg doesn't matter here... indeed,
+    // parsing tt's probably shouldn't require a parser at all.
+    let cfg = ~[];
+    let srdr = lexer::new_string_reader(copy sess.span_diagnostic,
+                                        filemap,
+                                        sess.interner);
+    let p1 = Parser(sess, cfg, srdr as @reader);
+    p1.parse_all_token_trees()
+}
+
+// given tts and cfg, produce a parser
+pub fn tts_to_parser(sess: @mut ParseSess,
+                     tts: ~[ast::token_tree],
+                     cfg: ast::crate_cfg) -> Parser {
     let trdr = lexer::new_tt_reader(
         copy sess.span_diagnostic,
         sess.interner,
@@ -329,8 +349,76 @@ mod test {
     use std::serialize::Encodable;
     use std;
     use core::io;
+    use core::option::Option;
+    use core::option::Some;
     use core::option::None;
+    use core::int;
+    use core::num::NumCast;
+    use codemap::{dummy_sp, CodeMap, span, BytePos, spanned};
+    use opt_vec;
     use ast;
+    use abi;
+    use ast_util::mk_ident;
+    use parse::parser::Parser;
+    use parse::token::{ident_interner, mk_ident_interner, mk_fresh_ident_interner};
+    use diagnostic::{span_handler, mk_span_handler, mk_handler, Emitter};
+
+    // add known names to interner for testing
+    fn mk_testing_interner() -> @ident_interner {
+        let i = mk_fresh_ident_interner();
+        // baby hack; in order to put the identifiers
+        // 'a' and 'b' at known locations, we're going
+        // to fill up the interner to length 100. If
+        // the # of preloaded items on the interner
+        // ever gets larger than 100, we'll have to
+        // adjust this number (say, to 200) and
+        // change the numbers in the identifier
+        // test cases below.
+
+        assert!(i.len() < 100);
+        for int::range(0,100-((i.len()).to_int())) |_dc| {
+            i.gensym(@~"dontcare");
+        }
+        i.intern(@~"a");
+        i.intern(@~"b");
+        i.intern(@~"c");
+        i.intern(@~"d");
+        i.intern(@~"return");
+        assert!(i.get(ast::ident{repr:101,ctxt:0}) == @~"b");
+        i
+    }
+
+    // make a parse_sess that's closed over a
+    // testing interner (where a -> 100, b -> 101)
+    fn mk_testing_parse_sess() -> @mut ParseSess {
+        let interner = mk_testing_interner();
+        let cm = @CodeMap::new();
+        @mut ParseSess {
+            cm: cm,
+            next_id: 1,
+            span_diagnostic: mk_span_handler(mk_handler(None), cm),
+            interner: interner,
+        }
+    }
+
+    // map a string to tts, using a made-up filename: return both the token_trees
+    // and the ParseSess
+    fn string_to_tts_t (source_str : @~str) -> (~[ast::token_tree],@mut ParseSess) {
+        let ps = mk_testing_parse_sess();
+        (filemap_to_tts(ps,string_to_filemap(ps,source_str,~"bogofile")),ps)
+    }
+
+    // map a string to tts, return the tt without its parsesess
+    fn string_to_tts_only(source_str : @~str) -> ~[ast::token_tree] {
+        let (tts,ps) = string_to_tts_t(source_str);
+        tts
+    }
+
+    // map string to parser (via tts)
+    fn string_to_parser(source_str: @~str) -> Parser {
+        let ps = mk_testing_parse_sess();
+        new_parser_from_source_str(ps,~[],~"bogofile",source_str)
+    }
 
     #[test] fn to_json_str<E : Encodable<std::json::Encoder>>(val: @E) -> ~str {
         do io::with_str_writer |writer| {
@@ -339,49 +427,71 @@ mod test {
     }
 
     fn string_to_crate (source_str : @~str) -> @ast::crate {
-        parse_crate_from_source_str(
-            ~"bogofile",
-            source_str,
-            ~[],
-            new_parse_sess(None))
+        string_to_parser(source_str).parse_crate_mod()
     }
 
-    fn string_to_tt_to_crate (source_str : @~str) -> @ast::crate {
-        let tts = parse_tts_from_source_str(
-            ~"bogofile",
-           source_str,
-           ~[],
-           new_parse_sess(None));
-        new_parser_from_tts(new_parse_sess(None),~[],tts)
-            .parse_crate_mod(~[])
+    fn string_to_expr (source_str : @~str) -> @ast::expr {
+        string_to_parser(source_str).parse_expr()
     }
 
-    // make sure that parsing from TTs produces the same result
-    // as parsing from strings
-    #[test] fn tts_produce_the_same_result () {
-        let source_str = @~"fn foo (x : int) { x; }";
-        assert_eq!(string_to_tt_to_crate(source_str),
-                     string_to_crate(source_str));
+    fn string_to_item (source_str : @~str) -> Option<@ast::item> {
+        string_to_parser(source_str).parse_item(~[])
     }
 
-    // check the contents of the tt manually:
-    #[test] fn alltts () {
-        let source_str = @~"fn foo (x : int) { x; }";
-        let tts = parse_tts_from_source_str(
-            ~"bogofile",
-            source_str,
-            ~[],
-            new_parse_sess(None));
-        assert_eq!(
-            to_json_str(@tts),
-            ~"[\
+    fn string_to_stmt (source_str : @~str) -> @ast::stmt {
+        string_to_parser(source_str).parse_stmt(~[])
+    }
+
+    // produce a codemap::span
+    fn sp (a: uint, b: uint) -> span {
+        span{lo:BytePos(a),hi:BytePos(b),expn_info:None}
+    }
+
+    // convert a vector of uints to a vector of ast::idents
+    fn ints_to_idents(ids: ~[uint]) -> ~[ast::ident] {
+        ids.map(|u| mk_ident(*u))
+    }
+
+    #[test] fn path_exprs_1 () {
+        assert_eq!(string_to_expr(@~"a"),
+                   @ast::expr{id:1,
+                              callee_id:2,
+                              node:ast::expr_path(@ast::Path {span:sp(0,1),
+                                                              global:false,
+                                                              idents:~[mk_ident(100)],
+                                                              rp:None,
+                                                              types:~[]}),
+                              span:sp(0,1)})
+    }
+
+    #[test] fn path_exprs_2 () {
+        assert_eq!(string_to_expr(@~"::a::b"),
+                   @ast::expr{id:1,
+                               callee_id:2,
+                               node:ast::expr_path(@ast::Path {span:sp(0,6),
+                                                               global:true,
+                                                               idents:ints_to_idents(~[100,101]),
+                                                               rp:None,
+                                                               types:~[]}),
+                              span:sp(0,6)})
+    }
+
+    #[should_fail]
+    #[test] fn bad_path_expr_1() {
+        string_to_expr(@~"::abc::def::return");
+    }
+
+    #[test] fn string_to_tts_1 () {
+        let (tts,ps) = string_to_tts_t(@~"fn a (b : int) { b; }");
+        assert_eq!(to_json_str(@tts),
+                   ~"[\
                 [\"tt_tok\",null,[\"IDENT\",\"fn\",false]],\
-                [\"tt_tok\",null,[\"IDENT\",\"foo\",false]],\
+                [\"tt_tok\",null,[\"IDENT\",\"a\",false]],\
                 [\
                     \"tt_delim\",\
                     [\
                         [\"tt_tok\",null,\"LPAREN\"],\
-                        [\"tt_tok\",null,[\"IDENT\",\"x\",false]],\
+                        [\"tt_tok\",null,[\"IDENT\",\"b\",false]],\
                         [\"tt_tok\",null,\"COLON\"],\
                         [\"tt_tok\",null,[\"IDENT\",\"int\",false]],\
                         [\"tt_tok\",null,\"RPAREN\"]\
@@ -391,21 +501,177 @@ mod test {
                     \"tt_delim\",\
                     [\
                         [\"tt_tok\",null,\"LBRACE\"],\
-                        [\"tt_tok\",null,[\"IDENT\",\"x\",false]],\
+                        [\"tt_tok\",null,[\"IDENT\",\"b\",false]],\
                         [\"tt_tok\",null,\"SEMI\"],\
                         [\"tt_tok\",null,\"RBRACE\"]\
                     ]\
                 ]\
             ]"
-        );
-        let ast1 = new_parser_from_tts(new_parse_sess(None),~[],tts)
-            .parse_item(~[]);
-        let ast2 = parse_item_from_source_str(
-            ~"bogofile",
-            @~"fn foo (x : int) { x; }",
-            ~[],~[],
-            new_parse_sess(None));
-        assert_eq!(ast1,ast2);
+                  );
+    }
+
+    #[test] fn ret_expr() {
+        assert_eq!(string_to_expr(@~"return d"),
+                   @ast::expr{id:3,
+                              callee_id:4,
+                              node:ast::expr_ret(
+                                  Some(@ast::expr{id:1,callee_id:2,
+                                                  node:ast::expr_path(
+                                                      @ast::Path{span:sp(7,8),
+                                                                 global:false,
+                                                                 idents:~[mk_ident(103)],
+                                                                 rp:None,
+                                                                 types:~[]
+                                                                }),
+                                                  span:sp(7,8)})),
+                              span:sp(0,8)})
+    }
+
+    #[test] fn parse_stmt_1 () {
+        assert_eq!(string_to_stmt(@~"b;"),
+                   @spanned{
+                       node: ast::stmt_expr(@ast::expr{
+                           id: 1,
+                           callee_id: 2,
+                           node: ast::expr_path(
+                               @ast::Path{
+                                   span:sp(0,1),
+                                   global:false,
+                                   idents:~[mk_ident(101)],
+                                   rp:None,
+                                   types: ~[]}),
+                           span: sp(0,1)},
+                                            3), // fixme
+                       span: sp(0,1)})
+
+    }
+
+    #[test] fn parse_ident_pat () {
+        let parser = string_to_parser(@~"b");
+        assert_eq!(parser.parse_pat(false),
+                   @ast::pat{id:1, // fixme
+                             node: ast::pat_ident(ast::bind_by_copy,
+                                                  @ast::Path{
+                                                      span:sp(0,1),
+                                                      global:false,
+                                                      idents:~[mk_ident(101)],
+                                                      rp: None,
+                                                      types: ~[]},
+                                                  None // no idea
+                                                 ),
+                             span: sp(0,1)});
+        assert_eq!(*parser.token,token::EOF);
+    }
+
+    #[test] fn parse_arg () {
+        let parser = string_to_parser(@~"b : int");
+        assert_eq!(parser.parse_arg_general(true),
+                   ast::arg{
+                       mode: ast::infer(1),
+                       is_mutbl: false,
+                       ty: @ast::Ty{id:4, // fixme
+                                    node: ast::ty_path(@ast::Path{
+                                        span:sp(4,4), // this is bizarre...
+                                        // check this in the original parser?
+                                        global:false,
+                                        idents:~[mk_ident(105)],
+                                        rp: None,
+                                        types: ~[]},
+                                                       3),
+                                    span:sp(4,7)},
+                       pat: @ast::pat{id:2,
+                                      node: ast::pat_ident(ast::bind_by_copy,
+                                                           @ast::Path{
+                                                               span:sp(0,1),
+                                                               global:false,
+                                                               idents:~[mk_ident(101)],
+                                                               rp: None,
+                                                               types: ~[]},
+                                                           None // no idea
+                                                          ),
+                                      span: sp(0,3)}, // really?
+                       id: 5 // fixme
+                   })
+    }
+
+    // check the contents of the tt manually:
+    #[test] fn parse_fundecl () {
+        // this test depends on the intern order of "fn" and "int", and on the
+        // assignment order of the node_ids.
+        assert_eq!(string_to_item(@~"fn a (b : int) { b; }"),
+                  Some(
+                      @ast::item{ident:mk_ident(100),
+                            attrs:~[],
+                            id: 11, // fixme
+                            node: ast::item_fn(ast::fn_decl{
+                                inputs: ~[ast::arg{
+                                    mode: ast::infer(1),
+                                    is_mutbl: false,
+                                    ty: @ast::Ty{id:4, // fixme
+                                                node: ast::ty_path(@ast::Path{
+                                        span:sp(10,13),
+                                        global:false,
+                                        idents:~[mk_ident(106)],
+                                        rp: None,
+                                        types: ~[]},
+                                                       3),
+                                                span:sp(10,13)},
+                                    pat: @ast::pat{id:2, // fixme
+                                                   node: ast::pat_ident(
+                                                       ast::bind_by_copy,
+                                                       @ast::Path{
+                                                           span:sp(6,7),
+                                                           global:false,
+                                                           idents:~[mk_ident(101)],
+                                                           rp: None,
+                                                           types: ~[]},
+                                                       None // no idea
+                                                   ),
+                                                  span: sp(6,9)}, // bleah.
+                                    id: 5 // fixme
+                                }],
+                                output: @ast::Ty{id:6, // fixme
+                                                 node: ast::ty_nil,
+                                                 span:sp(15,15)}, // not sure
+                                cf: ast::return_val
+                            },
+                                    ast::impure_fn,
+                                    abi::AbiSet::Rust(),
+                                    ast::Generics{ // no idea on either of these:
+                                        lifetimes: opt_vec::Empty,
+                                        ty_params: opt_vec::Empty,
+                                    },
+                                    spanned{
+                                        span: sp(15,21),
+                                        node: ast::blk_{
+                                            view_items: ~[],
+                                            stmts: ~[@spanned{
+                                                node: ast::stmt_semi(@ast::expr{
+                                                    id: 7,
+                                                    callee_id: 8,
+                                                    node: ast::expr_path(
+                                                        @ast::Path{
+                                                            span:sp(17,18),
+                                                            global:false,
+                                                            idents:~[mk_ident(101)],
+                                                            rp:None,
+                                                            types: ~[]}),
+                                                    span: sp(17,18)},
+                                                                     9), // fixme
+                                                span: sp(17,18)}],
+                                            expr: None,
+                                            id: 10, // fixme
+                                            rules: ast::default_blk // no idea
+                                        }}),
+                            vis: ast::inherited,
+                            span: sp(0,21)}));
+    }
+
+
+    #[test] fn parse_exprs () {
+        // just make sure that they parse....
+        string_to_expr(@~"3 + 4");
+        string_to_expr(@~"a::z.froob(b,@(987+3))");
     }
 }
 
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index c35b0e2e8c2..cc20e996dba 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -4463,7 +4463,7 @@ pub impl Parser {
     }
 
     // Parses a source module as a crate
-    fn parse_crate_mod(&self, _cfg: crate_cfg) -> @crate {
+    fn parse_crate_mod(&self) -> @crate {
         let lo = self.span.lo;
         // parse the crate's inner attrs, maybe (oops) one
         // of the attrs of an item:
diff --git a/src/libsyntax/parse/token.rs b/src/libsyntax/parse/token.rs
index 413f1688df1..2f8acbcece7 100644
--- a/src/libsyntax/parse/token.rs
+++ b/src/libsyntax/parse/token.rs
@@ -390,60 +390,68 @@ pub impl ident_interner {
     }
 }
 
+// return a fresh interner, preloaded with special identifiers.
+// EFFECT: stores this interner in TLS
+pub fn mk_fresh_ident_interner() -> @ident_interner {
+    // the indices here must correspond to the numbers in
+    // special_idents.
+    let init_vec = ~[
+        @~"_",                  // 0
+        @~"anon",               // 1
+        @~"drop",               // 2
+        @~"",                   // 3
+        @~"unary",              // 4
+        @~"!",                  // 5
+        @~"[]",                 // 6
+        @~"unary-",             // 7
+        @~"__extensions__",     // 8
+        @~"self",               // 9
+        @~"item",               // 10
+        @~"block",              // 11
+        @~"stmt",               // 12
+        @~"pat",                // 13
+        @~"expr",               // 14
+        @~"ty",                 // 15
+        @~"ident",              // 16
+        @~"path",               // 17
+        @~"tt",                 // 18
+        @~"matchers",           // 19
+        @~"str",                // 20
+        @~"TyVisitor",          // 21
+        @~"arg",                // 22
+        @~"descrim",            // 23
+        @~"__rust_abi",         // 24
+        @~"__rust_stack_shim",  // 25
+        @~"TyDesc",             // 26
+        @~"dtor",               // 27
+        @~"main",               // 28
+        @~"<opaque>",           // 29
+        @~"blk",                // 30
+        @~"static",             // 31
+        @~"intrinsic",          // 32
+        @~"__foreign_mod__",    // 33
+        @~"__field__",          // 34
+        @~"C",                  // 35
+        @~"Self",               // 36
+    ];
+
+    let rv = @ident_interner {
+        interner: interner::Interner::prefill(init_vec)
+    };
+    unsafe {
+        task::local_data::local_data_set(interner_key!(), @rv);
+    }
+    rv
+}
+
+// if an interner exists in TLS, return it. Otherwise, prepare a
+// fresh one.
 pub fn mk_ident_interner() -> @ident_interner {
     unsafe {
         match task::local_data::local_data_get(interner_key!()) {
             Some(interner) => *interner,
             None => {
-                // the indices here must correspond to the numbers in
-                // special_idents.
-                let init_vec = ~[
-                    @~"_",                  // 0
-                    @~"anon",               // 1
-                    @~"drop",               // 2
-                    @~"",                   // 3
-                    @~"unary",              // 4
-                    @~"!",                  // 5
-                    @~"[]",                 // 6
-                    @~"unary-",             // 7
-                    @~"__extensions__",     // 8
-                    @~"self",               // 9
-                    @~"item",               // 10
-                    @~"block",              // 11
-                    @~"stmt",               // 12
-                    @~"pat",                // 13
-                    @~"expr",               // 14
-                    @~"ty",                 // 15
-                    @~"ident",              // 16
-                    @~"path",               // 17
-                    @~"tt",                 // 18
-                    @~"matchers",           // 19
-                    @~"str",                // 20
-                    @~"TyVisitor",          // 21
-                    @~"arg",                // 22
-                    @~"descrim",            // 23
-                    @~"__rust_abi",         // 24
-                    @~"__rust_stack_shim",  // 25
-                    @~"TyDesc",             // 26
-                    @~"dtor",               // 27
-                    @~"main",               // 28
-                    @~"<opaque>",           // 29
-                    @~"blk",                // 30
-                    @~"static",             // 31
-                    @~"intrinsic",          // 32
-                    @~"__foreign_mod__",    // 33
-                    @~"__field__",          // 34
-                    @~"C",                  // 35
-                    @~"Self",               // 36
-                ];
-
-                let rv = @ident_interner {
-                    interner: interner::Interner::prefill(init_vec)
-                };
-
-                task::local_data::local_data_set(interner_key!(), @rv);
-
-                rv
+                mk_fresh_ident_interner()
             }
         }
     }