Implement type inference of method invocations in Fasta.

pkg/front_end/testcases/inference/inferred_type_custom_index_op.dart.strong.expect

Index: pkg/front_end/testcases/inference/inferred_type_custom_index_op.dart.strong.expect
diff --git a/pkg/front_end/testcases/inference/inferred_type_custom_index_op.dart.strong.expect b/pkg/front_end/testcases/inference/inferred_type_custom_index_op.dart.strong.expect
new file mode 100644
index 0000000000000000000000000000000000000000..6a9dfc24d0bcee9505e9214cdef5817381b6cf2d
--- /dev/null
+++ b/pkg/front_end/testcases/inference/inferred_type_custom_index_op.dart.strong.expect
@@ -0,0 +1,15 @@
+library test;
+import self as self;
+import "dart:core" as core;
+
+class C extends core::Object {
+  constructor •() → void
+    : super core::Object::•()
+    ;
+  operator [](core::int index) → core::bool
+    return true;
+}
+static method main() → dynamic {
+  self::C c = new self::C::•();
+  core::bool x = c.[](0);
+}