Implement for..in

[tofpie]

This Pull Request closes #670.

It changes the following:

• The tokenizer to prevent interpreting in as a binary operator in a for statement
• The parser to add for..in management
• The ForOfLoop node (renamed ForInOfLoop) to execute the for..in logic

[codecov]

Codecov Report

Merging #976 (11a3e72) into master (4cede75) will increase coverage by 0.12%.
The diff coverage is 65.90%.

@@            Coverage Diff             @@
##           master     #976      +/-   ##
==========================================
+ Coverage   60.07%   60.20%   +0.12%     
==========================================
  Files         167      169       +2     
  Lines       11132    11359     +227     
==========================================
+ Hits         6688     6839     +151     
- Misses       4444     4520      +76     

Impacted Files	Coverage Δ
boa/src/builtins/mod.rs	23.52% <ø> (ø)
boa/src/builtins/object/mod.rs	67.27% <ø> (ø)
...oa/src/syntax/ast/node/iteration/while_loop/mod.rs	59.37% <0.00%> (-3.96%)	⬇️
boa/src/syntax/parser/error.rs	38.23% <ø> (ø)
boa/src/object/mod.rs	51.23% <22.22%> (-0.74%)	⬇️
...oa/src/syntax/parser/statement/labelled_stm/mod.rs	68.42% <33.33%> (-18.25%)	⬇️
...a/src/syntax/ast/node/iteration/for_of_loop/mod.rs	57.14% <37.50%> (-1.84%)	⬇️
...src/syntax/ast/node/iteration/do_while_loop/mod.rs	48.57% <40.00%> (+0.84%)	⬆️
boa/src/syntax/ast/node/mod.rs	46.96% <50.00%> (+0.04%)	⬆️
...a/src/syntax/ast/node/iteration/for_in_loop/mod.rs	63.49% <63.49%> (ø)
... and 10 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 4cede75...11a3e72. Read the comment docs.

[tofpie]

This is really a WIP and I plan to add unit tests as soon as #974 and #972 are merged, but I submit it anyway to have some guidance. I am not quite sure of what I have done, especially around the lexer and parser.

@jcdickinson If you have some time, I would be happy to have your feedback

[jcdickinson]

This looks good to me, but I haven't touched the codebase in a while so I'm out of touch with the new parser.

[Razican]

I didn't check the code yet, but this is looking very good:

Test262 conformance changes:

Test result	master count	PR count	difference
Total	78,493	78,493	0
Passed	20,904	22,328	+1,424
Ignored	15,585	15,585	0
Failed	42,004	40,580	-1,424
Panics	388	388	0
Conformance	26.63	28.45	+1.81%

[tofpie]

I have implemented break and continue in for..in, and I have added some unit tests. It is now ready for review.

[Razican]

It's looking good. I did a small review, but I need to spend a bit more time with it. I'm not sure about unifying for...in and for...of, mostly because that will probably not be space efficient.

[Razican]

This is impressive. The conformance improvement is vastly good, and I have checked the implementation, and I see improvements in many other loops. Thanks for implementing the changes I proposed!