rw [decl] fails with optParams

[digama0]

rw does not know how to apply equation lemmas for a declaration when optParams are not set to their default values:

def foo (x := 0) : Nat := x
example : foo x = x := by simp only [foo] -- ok
example : foo x = x := by rw [foo]
-- failed to rewrite using equation theorems for 'foo'

rw [@foo] does not work either (it behaves the same, presumably because the @ needs to be applied not to foo but to the equation lemma).

[kmill]

#2243 might be related

[leodemoura]

Fixed.