must have · might have · should have · deducción y arrepentimiento
Cuatro estructuras clave
Los modales en pasado se forman con modal + have + participio pasado. Cada uno tiene un uso específico:
would have + pp
Resultado imaginado — algo que no ocurrió I would have loved to go.
should have + pp
Arrepentimiento o crítica sobre el pasado You should have told me.
needn't have + pp
Lo hiciste — pero no era necesario I needn't have hurried.
didn't need to + inf
No lo hiciste — correctamente, porque no era necesario I didn't need to pay.
Should have vs Would have
should have + pp → arrepentimiento o crítica
would have + pp → resultado imaginado en un pasado diferente
¡Debiste decírmelo!
→
You should have told me!
Debería haber estudiado más.
→
I should have studied harder.
Ella habría llamado si lo hubiera sabido.
→
She would have called if she'd known.
Atención:should have expresa que algo no se hizo pero debería haberse hecho. would have describe una consecuencia imaginaria de una condición no cumplida.
Needn't have vs Didn't need to
Ambos = innecesario — pero uno ocurrió, el otro no
needn't have + pp → LO HICISTE, pero era innecesario
didn't need to + infinitivo → NO LO HICISTE porque era innecesario
needn't have = esfuerzo desperdiciado
I needn't have bought a ticket — it was free.
Compraste una entrada. ¡Desperdicio!
didn't need to = evitado correctamente
I didn't need to buy a ticket — my brother had one.
No compraste una entrada. ¡Correcto!
Recuerda: 'Needn't have gone' = fuiste, pero no debías haber ido. 'Didn't need to go' = te quedaste en casa, y fue lo correcto.
Errores comunes — Trampas del FCE
You should went earlier
→
You should have gone earlier
should + have + participio pasado
I would have go if I'd known
→
I would have gone if I'd known
would have + participio pasado
She needn't have to buy it
→
She needn't have bought it
needn't have + pp (sin 'to')
He didn't need to have gone
→
He didn't need to go
didn't need to + infinitivo simple
They must have not told us
→
They can't have told us
Negación: can't have = imposibilidad
¡Importante! En negativo, must have casi nunca se usa. Para imposibilidad en el pasado, usa can't have + pp.