change to parsing using tts

also, updates test cases a bit

src/librustc/driver/driver.rs

@@ -150,7 +150,7 @@ pub fn parse_input(sess: Session, +cfg: ast::crate_cfg, input: input)
     -> @ast::crate {
     match input {
       file_input(ref file) => {
-        parse::parse_crate_from_file(&(*file), cfg, sess.parse_sess)
+        parse::parse_crate_from_file_using_tts(&(*file), cfg, sess.parse_sess)
       }
       str_input(ref src) => {
         // FIXME (#2319): Don't really want to box the source string

src/libsyntax/parse/mod.rs

@@ -94,6 +94,19 @@ pub fn parse_crate_from_file(
     // 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,
@@ -317,17 +330,46 @@ mod test {
     use std;
     use core::io;
     use core::option::None;
+    use ast;
 
     #[test] fn to_json_str<E : Encodable<std::json::Encoder>>(val: @E) -> ~str {
         do io::with_str_writer |writer| {
             val.encode(~std::json::Encoder(writer));
         }
     }
 
+    fn string_to_crate (source_str : @~str) -> @ast::crate {
+        parse_crate_from_source_str(
+            ~"bogofile",
+            source_str,
+            ~[],
+            new_parse_sess(None))
+    }
+
+    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(~[])
+    }
+
+    // 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));
+    }
+
+    // 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",
-            @~"fn foo (x : int) { x; }",
+            source_str,
             ~[],
             new_parse_sess(None));
         assert_eq!(