Fix internal methods

[tofpie]

This Pull Request fixes #591 and #602.

It changes the following:

• All internal methods of GcObject take a &Context and return a Result
• Implementation of specific internal methods for String
• Context becomes externally immutable, with only interior mutability
• LexicalEnvironment becomes externally immutable, with only interior mutability

[codecov]

Codecov Report

Merging #1076 (8446bb0) into master (d15f55e) will increase coverage by 0.06%.
The diff coverage is 67.70%.

@@            Coverage Diff             @@
##           master    #1076      +/-   ##
==========================================
+ Coverage   58.68%   58.75%   +0.06%     
==========================================
  Files         176      175       -1     
  Lines       12407    12459      +52     
==========================================
+ Hits         7281     7320      +39     
- Misses       5126     5139      +13     

Impacted Files	Coverage Δ
boa/examples/classes.rs	0.00% <0.00%> (ø)
boa/src/class.rs	0.00% <0.00%> (ø)
boa/src/exec/mod.rs	57.14% <ø> (ø)
boa/src/syntax/ast/node/await_expr/mod.rs	0.00% <0.00%> (ø)
...ax/ast/node/declaration/async_function_decl/mod.rs	22.22% <0.00%> (ø)
...ax/ast/node/declaration/async_function_expr/mod.rs	24.00% <0.00%> (ø)
boa/src/vm/mod.rs	0.00% <0.00%> (ø)
boa_cli/src/main.rs	33.33% <ø> (ø)
boa_tester/src/exec.rs	0.00% <0.00%> (ø)
boa_wasm/src/lib.rs	0.00% <0.00%> (ø)
... and 87 more

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[Razican]

Test262 conformance changes:

Test result	master count	PR count	difference
Total	78,497	78,497	0
Passed	24,805	24,857	+52
Ignored	15,587	15,587	0
Failed	38,105	38,053	-52
Panics	26	26	0
Conformance	31.60	31.67	+0.07%

[RageKnify]

Minor mistakest to fix. Can you explain the reason for:

• Context becomes externally immutable, with only interior mutability

Sounds, reasonable just trying to understand the reasoning.

[tofpie]

All internal methods (as defined by the spec, that is [[Get]], [[Set]] or [[DefineOwnProperty]] for instance) of a GcObject should have a parameter &mut Context as in some exotic objects implementation (such as Proxy) they can make calls to functions. If you add &mut Context to internal methods, then you must also add it to nearly all methods of EnvironmentTrait as the environment is sometimes itself an object (in ObjectEnvironmentRecord or GlobalEnvironmentRecord), but then each time the environment is modified (when declaring a variable or calling a function), then you have to borrow Context mutably twice, once to get the environment and another time when you call a method of EnvironmentTrait. And this is of course not allowed by the Rust compiler. And this is the same for LexicalEnvironment.

[HalidOdat]

I would like to try to fix the context/LexicalEnvironment mutable borrow problem, without introducing so much interior mutability.

Hopefully I'll be done with this by tomorrow and create a PR, now that I have a little more time to spend on the project :)

[Razican]

I would like to try to fix the context/LexicalEnvironment mutable borrow problem, without introducing so much interior mutability.

Hopefully I'll be done with this by tomorrow and create a PR, now that I have a little more time to spend on the project :)

How is this going?

BTW, this needs a rebase with all the changes in master now.

[HalidOdat]

I would like to try to fix the context/LexicalEnvironment mutable borrow problem, without introducing so much interior mutability.
Hopefully I'll be done with this by tomorrow and create a PR, now that I have a little more time to spend on the project :)

How is this going?

#1131 is going to fix this problem, without any additional interior mutability :)

[Razican]

Now that #1131 has been merged, I think that this only needs a rebase to use the latest changes, @tofpie.

[HalidOdat]

This has too many merge conflicts to try rebase this, it would be better to start over, besides most of the internal methods have already been implemented. So closing this PR.