(function() { let x = let({} = 7) x })() asserts js debug shell on m-c changeset 3b7921328fc1 with --no-threads at Assertion failure: !IsUninitializedLexical((activation.regs()).sp[-1]), at vm/Interpreter.cpp. Debug configure flags: CC="clang -Qunused-arguments" CXX="clang++ -Qunused-arguments" AR=ar sh /Users/skywalker/trees/mozilla-central/js/src/configure --target=x86_64-apple-darwin12.5.0 --enable-debug --enable-optimize --enable-nspr-build --enable-more-deterministic --with-ccache --enable-gczeal --enable-debug-symbols --disable-tests autoBisect shows this is probably related to the following changeset: The first bad revision is: changeset: https://hg.mozilla.org/mozilla-central/rev/7027efe7fae3 user: Shu-yu Guo date: Mon Sep 15 16:30:45 2014 -0700 summary: Bug 1001090 - Part 1: Implement let temporal dead zone in the frontend and interpreter. (r=Waldo) Shu-yu, is bug 1001090 a possible regressor?

This is a dup of bug 1067805. I messed up and pushed the wrong version of a patch.