Auto merge of #34789 - jonathandturner:simplify_liberror, r=alexcrichton

Simplify librustc_errors

This is part 2 of the error crate refactor, starting with #34403.

In this refactor, I focused on slimming down the error crate to fewer moving parts.  As such, I've removed quite a few parts and replaced the with simpler, straight-line code.  Specifically, this PR:

* Removes BasicEmitter
* Remove emit from emitter, leaving emit_struct
* Renames emit_struct to emit
* Removes CoreEmitter and focuses on a single Emitter
* Implements the latest changes to error format RFC (#1644)
* Removes (now-unused) code in emitter.rs and snippet.rs
* Moves more tests to the UI tester, removing some duplicate tests in the process

There is probably more that could be done with some additional refactoring, but this felt like it was getting to a good state.

r? @alexcrichton   cc: @Manishearth (as there may be breaking changes in stuff I removed/changed)

src/librustc/infer/error_reporting.rs

@@ -94,7 +94,7 @@ use syntax::ast;
 use syntax::parse::token;
 use syntax::ptr::P;
 use syntax_pos::{self, Pos, Span};
-use errors::{DiagnosticBuilder, check_old_skool};
+use errors::{DiagnosticBuilder, check_old_school};
 
 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     pub fn note_and_explain_region(self,
@@ -485,7 +485,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                                        "{}",
                                        trace.origin);
 
-        if !is_simple_error || check_old_skool() {
+        if !is_simple_error || check_old_school() {
             err.note_expected_found(&"type", &expected, &found);
         }
 

src/librustc/session/mod.rs

@@ -22,7 +22,8 @@ use mir::transform as mir_pass;
 
 use syntax::ast::{NodeId, Name};
 use errors::{self, DiagnosticBuilder};
-use errors::emitter::{Emitter, BasicEmitter, EmitterWriter};
+use errors::emitter::{Emitter, EmitterWriter};
+use errors::snippet::FormatMode;
 use syntax::json::JsonEmitter;
 use syntax::feature_gate;
 use syntax::parse;
@@ -439,7 +440,7 @@ pub fn build_session_with_codemap(sopts: config::Options,
         config::ErrorOutputType::HumanReadable(color_config) => {
             Box::new(EmitterWriter::stderr(color_config,
                                            Some(registry),
-                                           codemap.clone(),
+                                           Some(codemap.clone()),
                                            errors::snippet::FormatMode::EnvironmentSelected))
         }
         config::ErrorOutputType::Json => {
@@ -575,24 +576,32 @@ unsafe fn configure_llvm(sess: &Session) {
 }
 
 pub fn early_error(output: config::ErrorOutputType, msg: &str) -> ! {
-    let mut emitter: Box<Emitter> = match output {
+    let emitter: Box<Emitter> = match output {
         config::ErrorOutputType::HumanReadable(color_config) => {
-            Box::new(BasicEmitter::stderr(color_config))
+            Box::new(EmitterWriter::stderr(color_config,
+                                           None,
+                                           None,
+                                           FormatMode::EnvironmentSelected))
         }
         config::ErrorOutputType::Json => Box::new(JsonEmitter::basic()),
     };
-    emitter.emit(&MultiSpan::new(), msg, None, errors::Level::Fatal);
+    let handler = errors::Handler::with_emitter(true, false, emitter);
+    handler.emit(&MultiSpan::new(), msg, errors::Level::Fatal);
     panic!(errors::FatalError);
 }
 
 pub fn early_warn(output: config::ErrorOutputType, msg: &str) {
-    let mut emitter: Box<Emitter> = match output {
+    let emitter: Box<Emitter> = match output {
         config::ErrorOutputType::HumanReadable(color_config) => {
-            Box::new(BasicEmitter::stderr(color_config))
+            Box::new(EmitterWriter::stderr(color_config,
+                                           None,
+                                           None,
+                                           FormatMode::EnvironmentSelected))
         }
         config::ErrorOutputType::Json => Box::new(JsonEmitter::basic()),
     };
-    emitter.emit(&MultiSpan::new(), msg, None, errors::Level::Warning);
+    let handler = errors::Handler::with_emitter(true, false, emitter);
+    handler.emit(&MultiSpan::new(), msg, errors::Level::Warning);
 }
 
 // Err(0) means compilation was stopped, but no errors were found.

src/librustc_driver/lib.rs

@@ -100,6 +100,7 @@ use syntax::feature_gate::{GatedCfg, UnstableFeatures};
 use syntax::parse::{self, PResult};
 use syntax_pos::MultiSpan;
 use errors::emitter::Emitter;
+use errors::snippet::FormatMode;
 
 #[cfg(test)]
 pub mod test;
@@ -138,10 +139,15 @@ pub fn run(args: Vec<String>) -> isize {
                 match session {
                     Some(sess) => sess.fatal(&abort_msg(err_count)),
                     None => {
-                        let mut emitter =
-                            errors::emitter::BasicEmitter::stderr(errors::ColorConfig::Auto);
-                        emitter.emit(&MultiSpan::new(), &abort_msg(err_count), None,
-                            errors::Level::Fatal);
+                        let emitter =
+                            errors::emitter::EmitterWriter::stderr(errors::ColorConfig::Auto,
+                                                                   None,
+                                                                   None,
+                                                                   FormatMode::EnvironmentSelected);
+                        let handler = errors::Handler::with_emitter(true, false, Box::new(emitter));
+                        handler.emit(&MultiSpan::new(),
+                                     &abort_msg(err_count),
+                                     errors::Level::Fatal);
                         exit_on_err();
                     }
                 }
@@ -373,23 +379,26 @@ fn handle_explain(code: &str,
 
 fn check_cfg(sopts: &config::Options,
              output: ErrorOutputType) {
-    let mut emitter: Box<Emitter> = match output {
+    let emitter: Box<Emitter> = match output {
         config::ErrorOutputType::HumanReadable(color_config) => {
-            Box::new(errors::emitter::BasicEmitter::stderr(color_config))
+            Box::new(errors::emitter::EmitterWriter::stderr(color_config,
+                                                            None,
+                                                            None,
+                                                            FormatMode::EnvironmentSelected))
         }
         config::ErrorOutputType::Json => Box::new(json::JsonEmitter::basic()),
     };
+    let handler = errors::Handler::with_emitter(true, false, emitter);
 
     let mut saw_invalid_predicate = false;
     for item in sopts.cfg.iter() {
         match item.node {
             ast::MetaItemKind::List(ref pred, _) => {
                 saw_invalid_predicate = true;
-                emitter.emit(&MultiSpan::new(),
+                handler.emit(&MultiSpan::new(),
                              &format!("invalid predicate in --cfg command line argument: `{}`",
                                       pred),
-                             None,
-                             errors::Level::Fatal);
+                                errors::Level::Fatal);
             }
             _ => {},
         }
@@ -1046,26 +1055,34 @@ pub fn monitor<F: FnOnce() + Send + 'static>(f: F) {
      if let Err(value) = thread.unwrap().join() {
         // Thread panicked without emitting a fatal diagnostic
         if !value.is::<errors::FatalError>() {
-            let mut emitter = errors::emitter::BasicEmitter::stderr(errors::ColorConfig::Auto);
+            let emitter =
+                Box::new(errors::emitter::EmitterWriter::stderr(errors::ColorConfig::Auto,
+                                                       None,
+                                                       None,
+                                                       FormatMode::EnvironmentSelected));
+            let handler = errors::Handler::with_emitter(true, false, emitter);
 
             // a .span_bug or .bug call has already printed what
             // it wants to print.
             if !value.is::<errors::ExplicitBug>() {
-                emitter.emit(&MultiSpan::new(), "unexpected panic", None, errors::Level::Bug);
+                handler.emit(&MultiSpan::new(),
+                             "unexpected panic",
+                             errors::Level::Bug);
             }
 
             let xs = ["the compiler unexpectedly panicked. this is a bug.".to_string(),
                       format!("we would appreciate a bug report: {}", BUG_REPORT_URL)];
             for note in &xs {
-                emitter.emit(&MultiSpan::new(), &note[..], None, errors::Level::Note)
+                handler.emit(&MultiSpan::new(),
+                             &note[..],
+                             errors::Level::Note);
             }
             if match env::var_os("RUST_BACKTRACE") {
                 Some(val) => &val != "0",
                 None => false,
             } {
-                emitter.emit(&MultiSpan::new(),
+                handler.emit(&MultiSpan::new(),
                              "run with `RUST_BACKTRACE=1` for a backtrace",
-                             None,
                              errors::Level::Note);
             }
 

src/librustc_driver/test.rs

@@ -33,8 +33,8 @@ use syntax::ast;
 use syntax::abi::Abi;
 use syntax::codemap::CodeMap;
 use errors;
-use errors::emitter::{CoreEmitter, Emitter};
-use errors::{Level, RenderSpan};
+use errors::emitter::Emitter;
+use errors::{Level, DiagnosticBuilder};
 use syntax::parse::token;
 use syntax::feature_gate::UnstableFeatures;
 use syntax_pos::DUMMY_SP;
@@ -76,15 +76,12 @@ fn remove_message(e: &mut ExpectErrorEmitter, msg: &str, lvl: Level) {
     }
 }
 
-impl CoreEmitter for ExpectErrorEmitter {
-    fn emit_message(&mut self,
-                    _sp: &RenderSpan,
-                    msg: &str,
-                    _: Option<&str>,
-                    lvl: Level,
-                    _is_header: bool,
-                    _show_snippet: bool) {
-        remove_message(self, msg, lvl);
+impl Emitter for ExpectErrorEmitter {
+    fn emit(&mut self, db: &DiagnosticBuilder) {
+        remove_message(self, &db.message, db.level);
+        for child in &db.children {
+            remove_message(self, &child.message, child.level);
+        }
     }
 }