Goblin Welder interaction with Mox Diamond

[Zalren]

If I try to weld in Mox Diamond with Goblin Welder do I have to discard a land card to keep Mox Diamond in play?

If not, can I play Mox Diamond without a land in hand so as to put Mox Diamond into the graveyard to abuse Goblin Welder?

[Julian23]

If Mox Diamond would enter the battlefield, you may discard a land card instead. If you do, put Mox Diamond onto the battlefield. If you don't, put it into its owner's graveyard.

1. Yes. Mox Diamond's current errata requires discarding a land if it would enter the battlefield, not when being played from hand.

2. You can play Mox Diamond from your hand and decline to discard a land thus putting it into the graveyard. If you try to put it into play with Welder though, you will have to discard a land.

[(nameless one)]

If you try to weld Mox Diamond into play via Goblin Welder, you have to discard a land. Otherwise, Mox Diamond never enters the field. You can still target Mox Diamond if its in the graveyard via Goblin Welder.