fixes #202, check IndexExpression

lib/src/checker/checker.dart

Index: lib/src/checker/checker.dart
diff --git a/lib/src/checker/checker.dart b/lib/src/checker/checker.dart
index 3bd7c88f414eea7d01c504007e755a4f0b4ddfa8..72f920a99f83e86c18cfdc95ecb5ee6611394ce4 100644
--- a/lib/src/checker/checker.dart
+++ b/lib/src/checker/checker.dart
@@ -744,6 +744,22 @@ class CodeChecker extends RecursiveAstVisitor {
     node.visitChildren(this);
   }
 
+  @override
+  void visitIndexExpression(IndexExpression node) {
+    if (_rules.isDynamicTarget(node.target)) {
+      _recordDynamicInvoke(node);
+    } else {
+      var element = node.staticElement;
+      if (element is MethodElement) {
+        var type = element.type as FunctionType;
+        node.index = checkArgument(node.index, type.normalParameterTypes[0]);

[Leaf, 2015/06/02 23:59:11]

Analyzer should catch bad arity, but probably still worth being defensive
against having no parameter types.

[Jennifer Messerly, 2015/06/03 00:06:54]

hmmm, good catch. Guess I should fix visitBinaryExpr too

+      } else {
+        // TODO(vsm): Assert that the analyzer found an error here?
+      }
+    }
+    node.visitChildren(this);
+  }
+
   DartType getType(TypeName name) {
     return (name == null) ? _rules.provider.dynamicType : name.type;
   }