message: Fix bug where a couple of assign operations aren't implemented
diff: @@ -954,6 +954,9 @@ impl Vm {
  }));
  }
  + // Calling index set should not produce a value on the stack, but all
  + // handler functions to produce a value. So pop it here.
  + self.stack.pop()?;
  Ok(())
  }
  @@ -2537,7 +2540,8 @@ impl Vm {
  }));
  }
  - self.stack.pop()?;
  + let value = self.stack.pop()?;
  + <()>::from_value(value)?;
  Ok(())
  }
  @@ -2633,7 +2637,8 @@ impl Vm {
  }));
  }
  - self.stack.pop()?;
  + let value = self.stack.pop()?;
  + <()>::from_value(value)?;
  Ok(())
  }
  @@ -2696,6 +2701,8 @@ impl Vm {
  }));
  }
  + let value = self.stack.pop()?;
  + <()>::from_value(value)?;
  Ok(())
  }
  