[Bug] String interpolation can rewrite local variables when making function calls inside string

[willemneal]

Here is a minimal example.

And code copied:

class Obj  {
    _obj: Map<string, Obj>;

    constructor() {
      this._obj = new Map();
    }

    toString(): string {
      const keys = this._obj.keys();
      const objs: string[] = new Array<string>(keys.length);
      // log(this.keys)
      for (let i: i32 = 0; i < keys.length; i++) {
        const key = keys[i];
        const keyStr = `"${key}"`;
        const value = this._obj.get(key);
        const valStr = value.toString();
        const str = `"${key}":${value.toString()}`;
        objs[i] = str;
      }

      return `{${objs.join(",")}}`;
    }
}

const obj = new Obj();
const child = new Obj();
child._obj.set("isChild", new Obj())
obj._obj.set("child", child)


export function interpolate(): string {
  return obj.toString()
}

Running the example returns:

{"isChild":{"isChild":{}}}

But should be

{"child":{"isChild":{}}}

Changing value.toString() to valStr fixes the issue.

[dcodeIO]

Possible that this is not local confusion, but recursion using the same string literal, where an inner operation on the same static buffer overwrites the outer's state before the final string is produced.