Fix some crashes.

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

 // Copyright (c) 2016, 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.
 
 library fasta.body_builder;
 
 import '../fasta_codes.dart'
     show FastaMessage, codeExpectedButGot, codeExpectedFunctionBody;
 
 import '../parser/parser.dart' show FormalParameterType, optional;
@@ skipping 713 matching lines @@
     } else if (context.inDeclaration) {
       if (context == IdentifierContext.topLevelVariableDeclaration ||
           context == IdentifierContext.fieldDeclaration) {
         constantExpressionRequired = member.isConst;
       }
     } else if (constantExpressionRequired &&
         !context.allowedInConstantExpression) {
       addCompileTimeError(
           token.charOffset, "Not a constant expression: $context");
     }
-    push(new Identifier(name)..fileOffset = token.charOffset);
+    push(new Identifier(name, token.charOffset));
   }
 
   /// Look up [name] in [scope] using [charOffset] to report any
   /// problems. [isQualified] should be true if [name] is a qualified access
   /// (which implies that it shouldn't be turned into a [ThisPropertyAccessor]
   /// if the name doesn't resolve in the scope).
   @override
   scopeLookup(Scope scope, String name, int charOffset,
       {bool isQualified: false}) {
     Builder builder = scope.lookup(name, charOffset, uri);
@@ skipping 712 matching lines @@
     push(formals.toFunctionType(returnType));
     push(name);
     functionNestingLevel--;
   }
 
   @override
   void handleValuedFormalParameter(Token equals, Token token) {
     debugEvent("ValuedFormalParameter");
     Expression initializer = popForValue();
     Identifier name = pop();
-    push(new InitializedIdentifier(name.name, initializer));
+    push(new InitializedIdentifier(name.name, initializer, name.fileOffset));
   }
 
   @override
   void handleFormalParameterWithoutValue(Token token) {
     debugEvent("FormalParameterWithoutValue");
   }
 
   @override
   void endFormalParameters(int count, Token beginToken, Token endToken) {
     debugEvent("FormalParameters");
@@ skipping 177 matching lines @@
     if (type is List) {
       var prefix = type[0];
       identifier = type[1];
       if (prefix is PrefixBuilder) {
         type = scopeLookup(prefix.exports, identifier.name, start.charOffset,
             isQualified: true);
         identifier = null;
       } else if (prefix is ClassBuilder) {
         type = prefix;
       } else {
-        type = new Identifier(start.lexeme)..fileOffset = start.charOffset;
+        type = new Identifier(start.lexeme, start.charOffset);
       }
     }
     String name;
     if (identifier != null && suffix != null) {
       name = "${identifier.name}.${suffix.name}";
     } else if (identifier != null) {
       name = identifier.name;
     } else if (suffix != null) {
       name = suffix.name;
     } else {
@@ skipping 711 matching lines @@
   }
 
   @override
   void handleOperator(Token token) {
     debugEvent("Operator");
     push(new Operator(token.stringValue)..fileOffset = token.charOffset);
   }
 
   @override
   void handleSymbolVoid(Token token) {
-    logEvent("SymbolVoid");
+    debugEvent("SymbolVoid");
+    push(new Identifier(token.stringValue, token.charOffset));
   }
 
   dynamic addCompileTimeError(int charOffset, String message,
       {bool silent: false}) {
     // TODO(ahe): If constantExpressionRequired is set, set it to false to
     // avoid a long list of errors.
     return library.addCompileTimeError(charOffset, message, fileUri: uri);
   }
 
   @override
@@ skipping 33 matching lines @@
   @override
   void debugEvent(String name) {
     // printEvent(name);
   }
 }
 
 // TODO(ahe): Shouldn't need to be an expression.
 class Identifier extends InvalidExpression {
   final String name;
 
-  Identifier(this.name);
+  Identifier(this.name, int charOffset) {
+    fileOffset = charOffset;
+  }
 
   Expression get initializer => null;
 
   String toString() => "identifier($name)";
 }
 
 // TODO(ahe): Shouldn't need to be an expression.
 class Operator extends InvalidExpression {
   final String name;
 
   Operator(this.name);
 
   String toString() => "operator($name)";
 }
 
 class InitializedIdentifier extends Identifier {
   final Expression initializer;
 
-  InitializedIdentifier(String name, this.initializer) : super(name);
+  InitializedIdentifier(String name, this.initializer, int charOffset)
+      : super(name, charOffset);
 
   String toString() => "initialized-identifier($name, $initializer)";
 }
 
 // TODO(ahe): Shouldn't need to be an expression.
 class Label extends InvalidExpression {
   String name;
 
   Label(this.name);
 
@@ skipping 419 matching lines @@
   } else if (node is PrefixBuilder) {
     return node.name;
   } else if (node is ThisAccessor) {
     return node.isSuper ? "super" : "this";
   } else if (node is FastaAccessor) {
     return node.plainNameForRead;
   } else {
     return internalError("Unhandled: ${node.runtimeType}");
   }
 }