diff --git a/src/librustc_driver/test.rs b/src/librustc_driver/test.rs
index 911becd3f569b..ace469680df27 100644
--- a/src/librustc_driver/test.rs
+++ b/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, RenderSpan, 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, lvl);
+        for child in &db.children {
+            remove_message(self, &child.message, child.level);
+        }
     }
 }
 
diff --git a/src/librustc_errors/emitter.rs b/src/librustc_errors/emitter.rs
index 697f9687b0a15..a0d7120dd4f46 100644
--- a/src/librustc_errors/emitter.rs
+++ b/src/librustc_errors/emitter.rs
@@ -25,47 +25,29 @@ use std::io;
 use std::rc::Rc;
 use term;
 
-/// Emitter trait for emitting errors. Do not implement this directly:
-/// implement `CoreEmitter` instead.
+/// Emitter trait for emitting errors.
 pub trait Emitter {
     /// Emit a structured diagnostic.
     fn emit(&mut self, db: &DiagnosticBuilder);
 }
 
-pub trait CoreEmitter {
-    fn emit_message(&mut self,
-                    rsp: &RenderSpan,
-                    msg: &str,
-                    code: Option<&str>,
-                    lvl: Level,
-                    is_header: bool,
-                    show_snippet: bool);
-}
-
-impl<T: CoreEmitter> Emitter for T {
+impl Emitter for EmitterWriter {
     fn emit(&mut self, db: &DiagnosticBuilder) {
-        let old_school = check_old_skool();
-        let db_span = FullSpan(db.span.clone());
         self.emit_message(&FullSpan(db.span.clone()),
                           &db.message,
                           db.code.as_ref().map(|s| &**s),
                           db.level,
                           true,
                           true);
-        for child in &db.children {
-            let render_span = child.render_span
-                                   .clone()
-                                   .unwrap_or_else(
-                                       || FullSpan(child.span.clone()));
 
-            if !old_school {
-                self.emit_message(&render_span,
-                                    &child.message,
-                                    None,
-                                    child.level,
-                                    false,
-                                    true);
-            } else {
+        if check_old_skool() {
+            let db_span = FullSpan(db.span.clone());
+
+            for child in &db.children {
+                let render_span = child.render_span
+                                    .clone()
+                                    .unwrap_or_else(
+                                        || FullSpan(child.span.clone()));
                 let (render_span, show_snippet) = match render_span.span().primary_span() {
                     None => (db_span.clone(), false),
                     _ => (render_span, true)
@@ -77,6 +59,19 @@ impl<T: CoreEmitter> Emitter for T {
                                     false,
                                     show_snippet);
             }
+        } else {
+            for child in &db.children {
+                let render_span = child.render_span
+                                    .clone()
+                                    .unwrap_or_else(
+                                        || FullSpan(child.span.clone()));
+                self.emit_message(&render_span,
+                                    &child.message,
+                                    None,
+                                    child.level,
+                                    false,
+                                    true);
+            }
         }
     }
 }
@@ -114,21 +109,6 @@ pub struct EmitterWriter {
     format_mode: FormatMode
 }
 
-impl CoreEmitter for EmitterWriter {
-    fn emit_message(&mut self,
-                    rsp: &RenderSpan,
-                    msg: &str,
-                    code: Option<&str>,
-                    lvl: Level,
-                    is_header: bool,
-                    show_snippet: bool) {
-        match self.emit_message_(rsp, msg, code, lvl, is_header, show_snippet) {
-            Ok(()) => { }
-            Err(e) => panic!("failed to emit error: {}", e)
-        }
-    }
-}
-
 /// Do not use this for messages that end in `\n` – use `println_maybe_styled` instead. See
 /// `EmitterWriter::print_maybe_styled` for details.
 macro_rules! print_maybe_styled {
@@ -177,6 +157,19 @@ impl EmitterWriter {
                         format_mode: format_mode.clone() }
     }
 
+    fn emit_message(&mut self,
+                    rsp: &RenderSpan,
+                    msg: &str,
+                    code: Option<&str>,
+                    lvl: Level,
+                    is_header: bool,
+                    show_snippet: bool) {
+        match self.emit_message_(rsp, msg, code, lvl, is_header, show_snippet) {
+            Ok(()) => { }
+            Err(e) => panic!("failed to emit error: {}", e)
+        }
+    }
+
     fn emit_message_(&mut self,
                      rsp: &RenderSpan,
                      msg: &str,
diff --git a/src/librustc_trans/back/write.rs b/src/librustc_trans/back/write.rs
index 071960f1944cf..33cffa8a48013 100644
--- a/src/librustc_trans/back/write.rs
+++ b/src/librustc_trans/back/write.rs
@@ -19,8 +19,8 @@ use llvm::SMDiagnosticRef;
 use {CrateTranslation, ModuleTranslation};
 use util::common::time;
 use util::common::path2cstr;
-use errors::{self, Handler, Level, RenderSpan};
-use errors::emitter::CoreEmitter;
+use errors::{self, Handler, Level, DiagnosticBuilder};
+use errors::emitter::Emitter;
 use syntax_pos::MultiSpan;
 
 use std::collections::HashMap;
@@ -100,23 +100,23 @@ impl SharedEmitter {
     }
 }
 
-impl CoreEmitter for SharedEmitter {
-    fn emit_message(&mut self,
-                    _rsp: &RenderSpan,
-                    msg: &str,
-                    code: Option<&str>,
-                    lvl: Level,
-                    _is_header: bool,
-                    _show_snippet: bool) {
+impl Emitter for SharedEmitter {
+    fn emit(&mut self, db: &DiagnosticBuilder) {
         self.buffer.lock().unwrap().push(Diagnostic {
-            msg: msg.to_string(),
-            code: code.map(|s| s.to_string()),
-            lvl: lvl,
+            msg: db.message.to_string(),
+            code: db.code.clone(),
+            lvl: db.level,
         });
+        for child in &db.children {
+            self.buffer.lock().unwrap().push(Diagnostic {
+                msg: child.message.to_string(),
+                code: None,
+                lvl: child.level,
+            });
+        }
     }
 }
 
-
 // On android, we by default compile for armv7 processors. This enables
 // things like double word CAS instructions (rather than emulating them)
 // which are *far* more efficient. This is obviously undesirable in some