A record literal with a run-time field can be assigned to a class type (#487)

[ASDAlexander77]

const p: P = { x: 1, items: [i, 2] } was "invalid cast from {x:s32, items:s32[]} to P". A record with a field known only at run time is a tuple, not a constant tuple, and castTupleLikeVariants reported the tuple-to-class cast as invalid. It now builds the instance from the record's fields with castTupleToClass, as it already did for a constant record. This covers a record passed to a class parameter, returned as a class, or assigned from a record variable (which then shares its arrays with the instance).

A literal assigned to a class is now built with the class's field types (getTypeByFieldNameFromReceiverType), as a literal assigned to a tuple or an interface already was:

• rc leak: [i, 2] with let i = 7 was an s32[] that the cast copied into the field's number[] and then left with no count, so it was never freed. AOT, 1M iterations: 96.5 MB, now 4.4 MB. Constant records leaked this way on main too.
• { items: [] }: was an any[] the field could not take ("invalid cast from any[] to number[]").

Under own (agreed): this shape is a borrow error, "'this value' borrows a field and cannot be stored, returned or captured", because the instance reads its fields out of the record's temporary slot. That now includes a constant record assigned to a class, which compiled before because the cast copied its arrays. Filed as #492.

New test 00record_to_class.ts covers:

• a run-time record, with push;
• a constant record;
• an empty array;
• a record variable, sharing its array;
• a record passed to a class parameter;
• a record returned as a class;
• a fresh instance on each loop pass.

Gate	Result
Windows full suite (Release)	3800/3800
Linux (WSL) full suite	3785/3785
DefaultLib suite, release + debug, compile + JIT	gc 159/159; rc, none 158/159 (weakref_basic is gc-only, as on main)
own corpus	no flips: 459/616 and 457/616 with --opt; the one new failure is the new test (#492)
rc memory, 1M iterations (AOT)	constant, run-time, record variable, parameter: flat at 4.3-4.4 MB (constant and run-time were 96.5 MB)

Closes #487

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