single-field generic class with numeric type arg is scalar-replaced to its raw-f64 field — method call on the instance throws (number).method #6040

A single-field generic class monomorphized with a numeric type argument is scalar-replaced down to its raw-f64 field, so the instance itself becomes the field value — and any method call on it throws.

Repro

class SimpleContainer<T> {
    private _value: T;
    constructor(initial: T) { this._value = initial; }
    get(): T { return this._value; }
    set(value: T): void { this._value = value; }
}
const c = new SimpleContainer<number>(0);
c.set(42);
console.log(c.get());          // node: 42

Perry: TypeError: (number).get is not a function.

Mechanism

• The class monomorphizes to SimpleContainer$num with a raw_f64 typed shape (@perry_typed_shape_raw_f64_mask_*) because its single field _value: T = number.
• Scalar replacement then collapses the instance to that single raw-f64 field, so the local c holds the number (0/42), not an object pointer. c.get() dispatches on a number → (number).get is not a function.

Scope / not-affected

Fixed independently (generic-class method dispatch was also resolving to the number fast path when the base name wasn't in ctx.classes after monomorphization — receiver_class_name now tries the specialized base$mangled name):

• SimpleContainer<string> — works (hello).
• Multi<number> with a second field — works (7 99): scalar replacement only collapses the SINGLE-field shape.

So this issue is specifically scalar replacement eligibility: an object whose methods are called (get/set/...) must not be scalar-replaced away — the object has to exist for method dispatch. The raw-f64 single-field collapse needs to be gated on "no method calls / no escaping use of the instance as an object."

Bisected origin: the #5466 representation-lowering / typed-shape line (ce0117a60); surfaced by test-files/test_edge_interfaces.ts (the SimpleContainer<number> block) and the #5917 generic_class triage ((string).getValue was the dispatch half, now fixed).