lazy builtins

[jasonwilliams]

Lazy Builtins

So, this creates 2 new data structs which are used inside of JS Objects. LazyBuiltIn and LazyPrototype.
Instead of calling initialize on array for example, we will setup array with a constructor that has a LazyBuiltin object and a prototype which lazy a LazyPrototype. If any properties or the constructor itself is called then we will call init at that point.

For now I've started with:

• Array

I also updated the VSCode task to always choose the debug/script.js path, as it makes debugging much faster

[codecov]

Codecov Report

Attention: Patch coverage is 46.18182% with 148 lines in your changes missing coverage. Please review.

Project coverage is 52.89%. Comparing base (6ddc2b4) to head (7f07739).
Report is 286 commits behind head on main.

Files with missing lines	Patch %	Lines
core/engine/src/object/builtins/lazy_prototype.rs	0.00%	62 Missing ⚠️
core/engine/src/object/builtins/lazy_builtin.rs	39.02%	50 Missing ⚠️
...engine/src/object/builtins/lazy_array_prototype.rs	67.74%	20 Missing ⚠️
core/engine/src/realm.rs	55.00%	9 Missing ⚠️
core/engine/src/object/jsobject.rs	63.63%	4 Missing ⚠️
core/engine/src/builtins/function/mod.rs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3973      +/-   ##
==========================================
+ Coverage   47.24%   52.89%   +5.65%     
==========================================
  Files         476      486      +10     
  Lines       46892    47127     +235     
==========================================
+ Hits        22154    24928    +2774     
+ Misses      24738    22199    -2539     

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[jedel1043]

Test262 conformance changes

Test result	main count	PR count	difference
Total	48,494	48,494	0
Passed	43,609	43,581	-28
Ignored	1,500	1,500	0
Failed	3,385	3,413	+28
Panics	0	2	+2
Conformance	89.93%	89.87%	-0.06%

Broken tests (26):

test/language/statements/for-of/arguments-unmapped-mutation.js (previously Passed)
test/language/statements/for-of/arguments-unmapped-aliasing.js (previously Passed)
test/language/statements/for-of/arguments-mapped-aliasing.js (previously Passed)
test/language/statements/for-of/arguments-mapped-mutation.js (previously Passed)
test/language/statements/for-of/arguments-unmapped.js (previously Passed)
test/language/statements/for-of/arguments-mapped.js (previously Passed)
test/built-ins/ArrayIteratorPrototype/next/args-unmapped-truncation-before-exhaustion.js (previously Passed)
test/built-ins/ArrayIteratorPrototype/next/args-mapped-iteration.js (previously Passed)
test/built-ins/ArrayIteratorPrototype/next/args-unmapped-iteration.js (previously Passed)
test/built-ins/ArrayIteratorPrototype/next/args-unmapped-expansion-before-exhaustion.js (previously Passed)
test/built-ins/ArrayIteratorPrototype/next/args-mapped-expansion-after-exhaustion.js (previously Passed)
test/built-ins/ArrayIteratorPrototype/next/args-unmapped-expansion-after-exhaustion.js (previously Passed)
test/built-ins/ArrayIteratorPrototype/next/args-mapped-expansion-before-exhaustion.js (previously Passed)
test/built-ins/ArrayIteratorPrototype/next/args-mapped-truncation-before-exhaustion.js (previously Passed)
test/built-ins/String/prototype/S15.5.4_A2.js (previously Passed)
test/built-ins/String/prototype/S15.5.4_A3.js (previously Passed)
test/built-ins/String/prototype/S15.5.4_A1.js (previously Passed)
test/built-ins/Array/isArray/15.4.3.2-0-5.js (previously Passed)
test/built-ins/Array/prototype/exotic-array.js (previously Passed)
test/built-ins/Array/prototype/filter/create-proto-from-ctor-realm-array.js (previously Passed)
test/built-ins/Array/prototype/concat/create-proto-from-ctor-realm-array.js (previously Passed)
test/built-ins/Array/prototype/slice/create-proto-from-ctor-realm-array.js (previously Passed)
test/built-ins/Array/prototype/map/create-proto-from-ctor-realm-array.js (previously Passed)
test/built-ins/Array/prototype/splice/create-proto-from-ctor-realm-array.js (previously Passed)
test/built-ins/TypedArray/prototype/toString/BigInt/detached-buffer.js (previously Passed)
test/built-ins/TypedArrayConstructors/ctors/no-species.js (previously Passed)

New panics (2):

test/built-ins/Array/prototype/forEach/S15.4.4.18_A1.js (previously Passed)
test/built-ins/Array/prototype/forEach/S15.4.4.18_A2.js (previously Passed)

[jedel1043]

Some tests regressed thanks to the changes. Is it potentially a typo/copypaste error, or do we need to go back to the drawing board?

[hansl]

I'll hold my review until it's up to date with main and green.

[jasonwilliams]

So there's been some (minor) performance regressions with this PR and I think its related to this, I'm going to assume because its not [inline]'d this is now calling 2 functions instead of 1, and because its on a hotpath its actually slowed it down. Ill try adding the inline attribute and see if thats what it is, but leaving this here as a reminder.