SourceText collection & toString() for fns and methods

[Nikita-str]

This Pull Request closes #3780

In current approach all SourceText collected (because mostly a script consist of function codes and classes) and LinearSpan used to retrieve it when needed (to be fair toString() not often called); Gc::<SourceText> used for storage and therefore it can be deallocated only when we have access to no function from a source anymore.

It actually solve some tests from test262, but there is implementation for checking toString() correctness that take any [native code] as correct, without regard to whether it should accept in concrete case or not (assertToStringOrNativeFunction).

Also I don't sure about derive(arbitrary::Arbitrary) for core\ast\src\source.rs::Script & LinearSpan, just derive is ok here?

[codecov]

Codecov Report

Attention: Patch coverage is 81.19469% with 85 lines in your changes missing coverage. Please review.

Project coverage is 53.68%. Comparing base (6ddc2b4) to head (f000cfa).
Report is 287 commits behind head on main.

Files with missing lines	Patch %	Lines
core/parser/src/parser/statement/if_stm/mod.rs	0.00%	15 Missing ⚠️
core/engine/src/bytecompiler/mod.rs	56.66%	13 Missing ⚠️
core/ast/src/source_text.rs	73.91%	6 Missing ⚠️
core/parser/src/lexer/identifier.rs	16.66%	5 Missing ⚠️
.../statement/declaration/hoistable/class_decl/mod.rs	64.28%	5 Missing ⚠️
core/engine/src/spanned_source_text.rs	66.66%	4 Missing ⚠️
core/parser/src/lexer/mod.rs	91.11%	4 Missing ⚠️
core/ast/src/position.rs	93.47%	3 Missing ⚠️
core/parser/src/lexer/private_identifier.rs	50.00%	3 Missing ⚠️
...rser/expression/assignment/async_arrow_function.rs	75.00%	2 Missing ⚠️
... and 21 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4038      +/-   ##
==========================================
+ Coverage   47.24%   53.68%   +6.43%     
==========================================
  Files         476      485       +9     
  Lines       46892    47270     +378     
==========================================
+ Hits        22154    25376    +3222     
+ Misses      24738    21894    -2844     

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[raskad]

I have not done an in depth review yet, just an initial question. As far as I see, the positions you used for the function start and end (LinearSpan and LinearPosition) only contain the start and end line of the function, correct?

I think that would not work in cases where other stuff is in the same line, e.g.:

let a = 1; function f() {return a + 1}; let b = 3;

In this case f.toString() should only be function f() {return a + 1} but it would return the complete line, right?

[Nikita-str]

@raskad
No, it contains linear position, in source code, not line. It is position(and span) in representation of source code as ~vector of code points.
so f.toString() will return function f() {return a + 1}.

in details:

let a = 1; function f() {return a + 1}; let b = 3;
//         ↑                         ↑ 
//     span.start                span.end

here is tests
and in particular it tests that:

        ia1 = (b) => b * 2    ;
        // \\ // \\ // \\ // \\ // \\ // \\ // \\
        A    =    ia1 . toString(    );

A will be exactly (b) => b * 2

[Nikita-str]

also you can read the issue where it was accepted to collect the source code(it should slow down parse stage performance)