This is required by the spec. It also prevents crashes resulting from the attempt to read type feedback for the RHS of an invalid assignment which full codegen never actually allocated info for.

To do: check properly in preparser already.

R=marja@chromium.org, mstarzinger@chromium.org
BUG=351658
LOG=Y

Review URL: https://codereview.chromium.org/200473003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19976 ce2b1a6d-e550-0410-aec6-3dcde31c8c00