syntax: Refactor diagnostics to focus on Writers

This commit alters the diagnostic emission machinery to be focused around a
Writer for emitting errors. This allows it to not hard-code emission of errors
to stderr (useful for other applications).

Author: alexcrichton

src/librustc/driver/driver.rs

@@ -931,7 +931,7 @@ pub fn build_session(sopts: @session::Options,
                      -> Session {
     let codemap = @codemap::CodeMap::new();
     let diagnostic_handler =
-        diagnostic::mk_handler();
+        diagnostic::default_handler();
     let span_diagnostic_handler =
         diagnostic::mk_span_handler(diagnostic_handler, codemap);
 
@@ -1149,7 +1149,8 @@ pub fn build_output_filenames(input: &Input,
 }
 
 pub fn early_error(msg: &str) -> ! {
-    diagnostic::DefaultEmitter.emit(None, msg, diagnostic::Fatal);
+    let mut emitter = diagnostic::EmitterWriter::stderr();
+    emitter.emit(None, msg, diagnostic::Fatal);
     fail!(diagnostic::FatalError);
 }
 

src/librustc/lib.rs

@@ -394,7 +394,8 @@ pub fn monitor(f: proc()) {
         Err(value) => {
             // Task failed without emitting a fatal diagnostic
             if !value.is::<diagnostic::FatalError>() {
-                diagnostic::DefaultEmitter.emit(
+                let mut emitter = diagnostic::EmitterWriter::stderr();
+                emitter.emit(
                     None,
                     diagnostic::ice_msg("unexpected failure"),
                     diagnostic::Error);
@@ -404,9 +405,7 @@ pub fn monitor(f: proc()) {
                      this is a bug",
                 ];
                 for note in xs.iter() {
-                    diagnostic::DefaultEmitter.emit(None,
-                                                    *note,
-                                                    diagnostic::Note)
+                    emitter.emit(None, *note, diagnostic::Note)
                 }
 
                 println!("{}", r.read_to_str());

src/librustdoc/test.rs

@@ -25,6 +25,7 @@ use rustc::metadata::creader::Loader;
 use getopts;
 use syntax::diagnostic;
 use syntax::parse;
+use syntax::codemap::CodeMap;
 
 use core;
 use clean;
@@ -35,7 +36,6 @@ use passes;
 use visit_ast::RustdocVisitor;
 
 pub fn run(input: &str, matches: &getopts::Matches) -> int {
-    let parsesess = parse::new_parse_sess();
     let input_path = Path::new(input);
     let input = driver::FileInput(input_path.clone());
     let libs = matches.opt_strs("L").map(|s| Path::new(s.as_slice()));
@@ -49,9 +49,12 @@ pub fn run(input: &str, matches: &getopts::Matches) -> int {
     };
 
 
+    let cm = @CodeMap::new();
     let diagnostic_handler = diagnostic::mk_handler();
     let span_diagnostic_handler =
-        diagnostic::mk_span_handler(diagnostic_handler, parsesess.cm);
+        diagnostic::mk_span_handler(diagnostic_handler, cm);
+    let parsesess = parse::new_parse_sess_special_handler(span_diagnostic_handler,
+                                                          cm);
 
     let sess = driver::build_session_(sessopts,
                                       Some(input_path),