Do not permit binding over catch parameters in for-of

Do not permit binding over catch parameters in for-of

This is banned by the ES6 spec (see sections 13.15.1
and B.3.5). When done inside an eval, throw a runtime
SyntaxError. We should get an early SyntaxError otherwise.

R=littledan@chromium.org
LOG=N
BUG=v8:4231

[rossberg, 2015-09-03 00:10:28]

rossberg@chromium.org changed reviewers:
+ rossberg@chromium.org

[rossberg, 2015-09-03 00:10:29]

Hm, I don't quite understand this CL. It seems to special-case for-loops, but
there are many other constructs that could introduce conflicting bindings.
Shouldn't these conflicts be detected in a more central place? Specifically, I
think you want to invoke something similar to the existing
CheckConflictingDeclarations in the function that parses the `catch` phrase.

[Eric Caruso, 2015-09-03 00:31:20]

On 2015/09/03 00:10:29, rossberg wrote:
> Hm, I don't quite understand this CL. It seems to special-case for-loops, but
> there are many other constructs that could introduce conflicting bindings.
> Shouldn't these conflicts be detected in a more central place? Specifically, I
> think you want to invoke something similar to the existing
> CheckConflictingDeclarations in the function that parses the `catch` phrase.

We will also have to deal with let-/const-bindings, but the for-of case is
particularly awkward because B.3.5 specifies that var-/for-/for-in-bindings
are fine.

I wasn't sure if there was a better way to make sure for-of acts correctly given
those constraints.