Statically check for assignments to const in harmony mode.

Statically check for assignments to const in harmony mode.

The ES.next draft rev 4 in section 11.13 reads:
It is a Syntax Error if the AssignmentExpression is contained in extended code
and the LeftHandSideExpression is an Identifier that does not statically resolve
to a declarative environment record binding or if the resolved binding is an
immutable binding.

This CL adds corresponding static checks for the immutable binding case.

TEST=mjsunit/harmony/block-const-assign

Committed: http://code.google.com/p/v8/source/detail?r=10156

[Steven, 2011-11-24 16:26:11]

PTAL.

[fschneider, 2011-11-30 16:11:46]

http://codereview.chromium.org/8688007/diff/1/src/ast.h
File src/ast.h (right):

http://codereview.chromium.org/8688007/diff/1/src/ast.h#newcode1157
src/ast.h:1157: bool IsUsedAsLValue() {
Maybe rename to just IsLValue?

http://codereview.chromium.org/8688007/diff/1/src/ast.h#newcode1167
src/ast.h:1167: void MarkAsUsedAsLValue() { is_used_as_lvalue_ = true; }
Rename to MarkAsLValue?

http://codereview.chromium.org/8688007/diff/1/src/scopes.cc
File src/scopes.cc (right):

http://codereview.chromium.org/8688007/diff/1/src/scopes.cc#newcode288
src/scopes.cc:288: if (!info->is_native() && FLAG_harmony_scoping) {
Can you explain why you need to test for is_native here?

[Steven, 2011-12-05 11:56:57]

http://codereview.chromium.org/8688007/diff/1/src/ast.h
File src/ast.h (right):

http://codereview.chromium.org/8688007/diff/1/src/ast.h#newcode1157
src/ast.h:1157: bool IsUsedAsLValue() {
On 2011/11/30 16:11:46, fschneider wrote:
> Maybe rename to just IsLValue?

Done.

http://codereview.chromium.org/8688007/diff/1/src/ast.h#newcode1167
src/ast.h:1167: void MarkAsUsedAsLValue() { is_used_as_lvalue_ = true; }
On 2011/11/30 16:11:46, fschneider wrote:
> Rename to MarkAsLValue?

Done.

http://codereview.chromium.org/8688007/diff/1/src/scopes.cc
File src/scopes.cc (right):

http://codereview.chromium.org/8688007/diff/1/src/scopes.cc#newcode288
src/scopes.cc:288: if (!info->is_native() && FLAG_harmony_scoping) {
The test is not needed anymore, I'll remove it. It's an artifact from the time
before the extended mode was introduced. There harmony scoping features where
only enabled for non-native functions.
On 2011/11/30 16:11:46, fschneider wrote:
> Can you explain why you need to test for is_native here?

[fschneider, 2011-12-05 13:30:04]

LGTM with comments below.

http://codereview.chromium.org/8688007/diff/6013/src/ast.h
File src/ast.h (right):

http://codereview.chromium.org/8688007/diff/6013/src/ast.h#newcode1179
src/ast.h:1179: bool is_lvalue_;
Please make sure the instance size (sizeof) for VariableProxy is unchanged on
all platforms. I think it should be fine since each bool should not occupy more
than 1 bytes. But otherwise we should pack the booleans into one a one-word
bitfield.

http://codereview.chromium.org/8688007/diff/6013/src/parser.cc
File src/parser.cc (right):

http://codereview.chromium.org/8688007/diff/6013/src/parser.cc#newcode4322
src/parser.cc:4322: VariableProxy* lhs = expression != NULL
Maybe rename to

VariableProxy* proxy = ...

http://codereview.chromium.org/8688007/diff/6013/src/scopes.cc
File src/scopes.cc (right):

http://codereview.chromium.org/8688007/diff/6013/src/scopes.cc#newcode591
src/scopes.cc:591: return proxy;
This would fit on the line above for a single-line if-statement.

[Steven, 2011-12-05 14:41:09]

http://codereview.chromium.org/8688007/diff/6013/src/ast.h
File src/ast.h (right):

http://codereview.chromium.org/8688007/diff/6013/src/ast.h#newcode1179
src/ast.h:1179: bool is_lvalue_;
Still 28 bytes on arm, ia32 and 40 bytes on x64.

On 2011/12/05 13:30:05, fschneider wrote:
> Please make sure the instance size (sizeof) for VariableProxy is unchanged on
> all platforms. I think it should be fine since each bool should not occupy
more
> than 1 bytes. But otherwise we should pack the booleans into one a one-word
> bitfield.

http://codereview.chromium.org/8688007/diff/6013/src/parser.cc
File src/parser.cc (right):

http://codereview.chromium.org/8688007/diff/6013/src/parser.cc#newcode4322
src/parser.cc:4322: VariableProxy* lhs = expression != NULL
On 2011/12/05 13:30:05, fschneider wrote:
> Maybe rename to
> 
> VariableProxy* proxy = ...

Done.

http://codereview.chromium.org/8688007/diff/6013/src/scopes.cc
File src/scopes.cc (right):

http://codereview.chromium.org/8688007/diff/6013/src/scopes.cc#newcode591
src/scopes.cc:591: return proxy;
On 2011/12/05 13:30:05, fschneider wrote:
> This would fit on the line above for a single-line if-statement.

Done.