Local function/class name shadows imported host item of same name

[jcbhmr]

Specific example:

package jcbhmr:hello-world-rust-wasm-component-lib;

interface cbh {
  resource p-string {
    call: func(a: string);
  }
  resource r-string {
    call: func() -> string;
  }
}
interface cb {
  use cbh.{p-string as h-p-string, r-string as h-r-string};
  resource p-string {
    constructor(cb: h-p-string);
    call: func(a: string);
  }
  resource r-string {
    constructor(cb: h-r-string);
    call: func() -> string;
  }
}

interface hello-world {
  use cb.{p-string, r-string};
  set-cb: func(cb: p-string);
  run-cb-with-result-of: func(cb: borrow<r-string>);
}

world hello-world-rust-wasm-component-lib {
  import cbh;
  export cb;

  export hello-world;
}

import { PString, RString } from '../../../tests/cbh.js';

// ...

const PString$1 = class PString{
  constructor(arg0) {
    console.error(`[module="jcbhmr:hello-world-rust-wasm-component-lib/cb", function="[constructor]p-string"] call cb=${arguments[0]}`);
    if (!(arg0 instanceof PString)) {
      throw new Error('Resource error: Not a valid "HPString" resource.');
    }
    var handle0 = handleCnt0++;
    handleTable0.set(handle0, { rep: arg0, own: true });
    const ret = exports1['jcbhmr:hello-world-rust-wasm-component-lib/cb#[constructor]p-string'](handle0);
    console.error(`[module="jcbhmr:hello-world-rust-wasm-component-lib/cb", function="[constructor]p-string"] return result=${toResultString(ret)}`);
    var handle2 = ret;
    var rsc1 = new.target === PString$1 ? this : Object.create(PString$1.prototype);
    var rep3 = handleTable2.get(handle2).rep;
    Object.defineProperty(rsc1, resourceHandleSymbol, { writable: true, value: rep3});
    finalizationRegistry2.register(rsc1, handle2, rsc1);
    Object.defineProperty(rsc1, symbolDispose, { writable: true, value: function () {} });

    handleTable2.delete(handle2);
    return rsc1;
  }
}

When inside the class PString { } for the exported guest PString resource type it checks that the arg0 is instanceof PString. That's SUPPOSED to check that arg0 is an instance of the host's PString class. Instead due to shadowing, it's referring to itself (the class PString {} declaration that it's inside of). This is incorrect behaviour.

Instead, the code should look like something like this:

import { PString, RString } from '../../../tests/cbh.js';

// ...

const PString$1 = class {
  static {
    Object.defineProperty(this, 'name', { value: 'PString', configurable: true })
  }
  constructor(arg0) {
    console.error(`[module="jcbhmr:hello-world-rust-wasm-component-lib/cb", function="[constructor]p-string"] call cb=${arguments[0]}`);
    if (!(arg0 instanceof PString)) {
      throw new Error('Resource error: Not a valid "HPString" resource.');
    }
    var handle0 = handleCnt0++;
    handleTable0.set(handle0, { rep: arg0, own: true });
    const ret = exports1['jcbhmr:hello-world-rust-wasm-component-lib/cb#[constructor]p-string'](handle0);
    console.error(`[module="jcbhmr:hello-world-rust-wasm-component-lib/cb", function="[constructor]p-string"] return result=${toResultString(ret)}`);
    var handle2 = ret;
    var rsc1 = new.target === PString$1 ? this : Object.create(PString$1.prototype);
    var rep3 = handleTable2.get(handle2).rep;
    Object.defineProperty(rsc1, resourceHandleSymbol, { writable: true, value: rep3});
    finalizationRegistry2.register(rsc1, handle2, rsc1);
    Object.defineProperty(rsc1, symbolDispose, { writable: true, value: function () {} });

    handleTable2.delete(handle2);
    return rsc1;
  }
}

OR like this

import { PString as $host_PString, RString as $host_RString } from '../../../tests/cbh.js';

// ...

const PString$1 = class PString{
  constructor(arg0) {
    console.error(`[module="jcbhmr:hello-world-rust-wasm-component-lib/cb", function="[constructor]p-string"] call cb=${arguments[0]}`);
    if (!(arg0 instanceof $host_PString)) {
      throw new Error('Resource error: Not a valid "HPString" resource.');
    }
    var handle0 = handleCnt0++;
    handleTable0.set(handle0, { rep: arg0, own: true });
    const ret = exports1['jcbhmr:hello-world-rust-wasm-component-lib/cb#[constructor]p-string'](handle0);
    console.error(`[module="jcbhmr:hello-world-rust-wasm-component-lib/cb", function="[constructor]p-string"] return result=${toResultString(ret)}`);
    var handle2 = ret;
    var rsc1 = new.target === PString$1 ? this : Object.create(PString$1.prototype);
    var rep3 = handleTable2.get(handle2).rep;
    Object.defineProperty(rsc1, resourceHandleSymbol, { writable: true, value: rep3});
    finalizationRegistry2.register(rsc1, handle2, rsc1);
    Object.defineProperty(rsc1, symbolDispose, { writable: true, value: function () {} });

    handleTable2.delete(handle2);
    return rsc1;
  }
}

Notice how now the instanceoof PString refers to the OUTER host-defined PString class.

Suggestion:
Rename the class using Object.defineProperty() either in static {} block or after defining it.
OR mangle the names of imports like { PString as $host_PString } to avoid having them be shadowed by local export declarations.

[guybedford]

Thanks for the detailed report on this. I've gone with the class PString$1 { ... } approach here instead of const PString$1 = class PString{, with the fix in #340.