Just to be clear, I've scoured forums and the sage advice website and found no info on this.
Considering the way Thirsting blade is written, would it trigger on the Attack action granted by the Haste spell? Considering that Haste says "Attack (one weapon attack only)... action" and the invocation says "you can attack with your pact weapon twice, instead of once, whenever you take the attack action", would the specificity of requiring a pact weapon trump the general effect of the Haste spell?
My brain is giving up on me and I can't seem to find a reason for this combination not to work, please guys, point me to where I've made a mistake.
EDIT: I know Haste is not a Warlock spell, but they can get it without much fuss by going sorlock or a similar multiclass.