Add locations to diagnostics.

dart/lib/compiler/implementation/compiler.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class WorkItem {
   final Element element;
   TreeElements resolutionTree;
   bool allowSpeculativeOptimization = true;
   List<HTypeGuard> guards = const <HTypeGuard>[];
 
@@ skipping 131 matching lines @@
                HInstruction instruction, Element element]) {
     SourceSpan span = const SourceSpan(null, null, null);
     if (node !== null) {
       span = spanFromNode(node);
     } else if (token !== null) {
       span = spanFromTokens(token, token);
     } else if (instruction !== null) {
       span = spanFromElement(currentElement);
     } else if (element !== null) {
       span = spanFromElement(element);
+    } else {
+      throw 'No error location for error: $reason';
     }
     reportDiagnostic(span, red(reason), true);
     throw new CompilerCancelledException(reason);
   }
 
+  void reportFatalError(String reason, Element element,
+                        [Node node, Token token, HInstruction instruction]) {
+    withCurrentElement(element, () {
+      cancel(reason, node, token, instruction, element);
+    });
+  }
+
   void log(message) {
     reportDiagnostic(null, message, false);
   }
 
   bool run(Uri uri) {
     try {
       runCompiler(uri);
     } catch (CompilerCancelledException exception) {
       log(exception.toString());
       log('compilation failed');
@@ skipping 99 matching lines @@
         const SourceString('JS_CALL_IN_ISOLATE'), library), this);
     library.define(new ForeignElement(
         const SourceString('DART_CLOSURE_TO_JS'), library), this);
   }
 
   void runCompiler(Uri uri) {
     scanBuiltinLibraries();
     mainApp = scanner.loadLibrary(uri, null);
     final Element main = mainApp.find(MAIN);
     if (main === null) {
-      withCurrentElement(mainApp, () => cancel('Could not find $MAIN'));
+      reportFatalError('Could not find $MAIN', mainApp);
     } else {
-      withCurrentElement(main, () {
-        if (!main.isFunction()) {
-          cancel('main is not a function', element: main);
-        }
-        FunctionElement mainMethod = main;
-        FunctionSignature parameters = mainMethod.computeSignature(this);
-        if (parameters.parameterCount > 0) {
-          cancel('main cannot have parameters', element: mainMethod);
-        }
+      if (!main.isFunction()) reportFatalError('main is not a function', main);
+      FunctionElement mainMethod = main;
+      FunctionSignature parameters = mainMethod.computeSignature(this);
+      parameters.forEachParameter((Element parameter) {
+        reportFatalError('main cannot have parameters', parameter);
       });
     }
     Collection<LibraryElement> libraries = universe.libraries.getValues();
     native.processNativeClasses(this, libraries);
     world.populate(this, libraries);
     addToWorkList(main);
     codegenProgress.reset();
     while (!codegenQueue.isEmpty()) {
       WorkItem work = codegenQueue.removeLast();
       withCurrentElement(work.element, () => work.run(this));
@@ skipping 171 matching lines @@
       // error" or "not implemented yet", so the vicinity is good
       // enough for now.
       element = element.enclosingElement;
       // TODO(ahe): I plan to overhaul this infrastructure anyways.
     }
     if (element === null) {
       element = currentElement;
     }
     Token position = element.position();
     if (position === null) {
-      // TODO(ahe): Find the enclosing library.
-      return const SourceSpan(null, null, null);
+      Uri uri = element.getCompilationUnit().script.uri;
+      return new SourceSpan(uri, 0, 0);
     }
     return spanFromTokens(position, position);
   }
 
   Script readScript(Uri uri, [ScriptTag node]) {
     unimplemented('Compiler.readScript');
   }
 
   String get legDirectory() {
     unimplemented('Compiler.legDirectory');
@@ skipping 55 matching lines @@
   }
 }
 
 class SourceSpan {
   final Uri uri;
   final int begin;
   final int end;
 
   const SourceSpan(this.uri, this.begin, this.end);
 }