Implement type inference of constructor invocations in Fasta.

pkg/front_end/testcases/inference/infer_assign_to_index.dart

 // Copyright (c) 2017, 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.
 
 /*@testedFeatures=inference*/
 library test;
 
 List<double> a = <double>[];
 var /*@topType=dynamic*/ b = (/*error:TOP_LEVEL_UNSUPPORTED*/ a[0] = 1.0);
+
+main() {}