Fix for instance fields inference when a setter has no parameter.

pkg/analyzer/lib/src/task/strong_mode.dart

 // Copyright (c) 2015, 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 analyzer.src.task.strong_mode;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
@@ skipping 255 matching lines @@
 
     _FieldOverrideInferenceResult typeResult =
         _computeFieldOverrideType(element);
     if (typeResult.isError == null || typeResult.type == null) {
       return;
     }
 
     if (element.kind == ElementKind.GETTER) {
       (element as ExecutableElementImpl).returnType = typeResult.type;
     } else if (element.kind == ElementKind.SETTER) {
-      var parameter = element.parameters[0] as ParameterElementImpl;
-      if (parameter.hasImplicitType) {
-        parameter.type = typeResult.type;
+      List<ParameterElement> parameters = element.parameters;
+      if (parameters.isNotEmpty) {
+        var parameter = parameters[0] as ParameterElementImpl;
+        if (parameter.hasImplicitType) {
+          parameter.type = typeResult.type;
+        }
+        parameter.inheritsCovariant = typeResult.isCovariant;
       }
-      parameter.inheritsCovariant = typeResult.isCovariant;
     }
     setFieldType(element.variable, typeResult.type);
   }
 
   /**
    * Infer type information for all of the instance members in the given
    * [classElement].
    */
   void _inferClass(ClassElement classElement) {
     if (classElement is ClassElementImpl) {
@@ skipping 380 matching lines @@
       AstNode parent = node.parent;
       if (parent is PropertyAccess && parent.propertyName == node ||
           parent is PrefixedIdentifier && parent.identifier == node) {
         isValid = false;
       }
     } else if (element is PropertyAccessorElement && !element.isStatic) {
       isValid = false;
     }
   }
 }