better errors and error locations

frog/member.dart

 // Copyright (c) 2011, 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.
 
 /** A formal parameter to a [Method]. */
 class Parameter {
   FormalNode definition;
 
   String name;
   Type type;
@@ skipping 60 matching lines @@
   bool get isOptional() => definition != null && definition.value != null;
 }
 
 
 interface Named {
   String get name();
   Library get library();
   bool get isNative();
   String get jsname();
   set jsname(String name);
+
+  SourceSpan get span();
 }
 
 class Member implements Named {
   final String name;
   final Type declaringType;
 
   String _jsname;
 
   bool isGenerated;
   MethodGenerator generator;
@@ skipping 153 matching lines @@
 
   void resolve(Type inType) {}
 
   Value _get(MethodGenerator context, Node node, Value target,
       [bool isDynamic=false]) {
     return new Value.type(type, node.span);
   }
 
   Value _set(MethodGenerator context, Node node, Value target, Value value,
       [bool isDynamic=false]) {
-    world.error('can not set type', node.span);
+    world.error('cannot set type', node.span);
   }
 
   Value invoke(MethodGenerator context, Node node, Value target, Arguments args,
       [bool isDynamic=false]) {
-    world.error('can not invoke type', node.span);
+    world.error('cannot invoke type', node.span);
   }
 }
 
 /** Represents a Dart field from source code. */
 class FieldMember extends Member {
   final VariableDefinition definition;
   final Expression value;
 
   Type type;
   Value _computedValue;
@@ skipping 478 matching lines @@
     }
     return -1;
   }
 
   bool get prefersPropertySyntax() => true;
   bool get requiresFieldSyntax() => false;
 
   void provideFieldSyntax() { _provideFieldSyntax = true; }
   void providePropertySyntax() { _providePropertySyntax = true; }
 
-  Value _set(MethodGenerator context, Node, Value target, Value value,
+  Value _set(MethodGenerator context, Node node, Value target, Value value,
       [bool isDynamic=false]) {
-    world.error('can not set method', definition.span);
+    world.error('cannot set method', node.span);
   }
 
   Value _get(MethodGenerator context, Node node, Value target,
       [bool isDynamic=false]) {
     // TODO(jimhug): Would prefer to invoke!
     declaringType.genMethod(this);
     _provideOptionalParamInfo = true;
     if (isStatic) {
       // ensure the type is generated.
       // TODO(sigmund): can we avoid generating the entire type, but only what
@@ skipping 923 matching lines @@
   }
 
   void forEach(void f(Member member)) {
     factories.forEach((_, Map constructors) {
       constructors.forEach((_, Member member) {
         f(member);
       });
     });
   }
 }