Minimal runtime GC collects pinned objects.

[forcepusher]

UPDATE: See the short version of the repro.
However this one might still be useful because it has to pass the test.

Repro: MinimalGCBugRepro.zip
Steps to reproduce:

1. npm run asbuild:incremental then npm test.
2. Observe the expected repeating trace 123456.
3. npm run asbuild:minimal then npm test.
4. Observe the unexpected traces with random numbers.

Reproduction overview:

export class SomeClass {
  public someArray: StaticArray<SomeNestedClass>;

  public constructor() {
    this.someArray = new StaticArray<SomeNestedClass>(1);
    this.someArray[0] = new SomeNestedClass();
  }

  public growArray(): void {
    const resizedArray = new StaticArray<SomeNestedClass>(this.someArray.length * 2);
    memory.copy(changetype<usize>(resizedArray), changetype<usize>(this.someArray),
      offsetof<SomeNestedClass>() * this.someArray.length);
    this.someArray = resizedArray;
  }

  public outputFirstArrayElement(): void {
    trace(this.someArray[0].someField.toString());
  }
}

class SomeNestedClass {
  public someField: i32 = 123456;
}

const myModule = require("..");

const someClass = new myModule.SomeClass();
myModule.__pin(someClass);
someClass.growArray();
someClass.outputFirstArrayElement();
myModule.__collect();
someClass.growArray();
someClass.outputFirstArrayElement();

[forcepusher]

Seems like none of the memory copying magic, neither the StaticArray needed to break it. A regular Array drops the references to classes anyway.

Repro v3: MinimalGCBugReproV3.zip
Steps to reproduce:

1. npm run asbuild:incremental then npm test.
2. Observe the expected repeating trace 123456.
3. npm run asbuild:minimal then npm test.
4. Observe the error after a second trace.

Bonus: Web Editor reproduction link. Switching to incremental mitigates it.

Reproduction overview:

export class SomeClass {
  public someArray: Array<SomeNestedClass>;

  public constructor() {
    this.someArray = new Array<SomeNestedClass>(1);
    this.someArray[0] = new SomeNestedClass();
  }

  public outputFirstArrayElement(): void {
    trace(this.someArray[0].someField.toString());
  }
}

class SomeNestedClass {
  public someField: i32 = 123456;
}

const myModule = require("..");

const someClass = new myModule.SomeClass();
myModule.__pin(someClass);
someClass.outputFirstArrayElement();
myModule.__collect();
someClass.outputFirstArrayElement();
myModule.__collect();
someClass.outputFirstArrayElement();

[dcodeIO]

Thanks for digging through this, the repro was super helpful :) Should be fixed with the next release at 0 UTC.