raise assertion in Validator.new

reason: it's a programmer error when the identity
doesn't match the committee, not a runtime error

mysticeti/validator.nim

@@ -18,10 +18,10 @@ func new*[Dependencies](
   _: type Validator[Dependencies],
   identity: Dependencies.Identity,
   committee: Committee[Dependencies.Identifier]
-): ?!Validator[Dependencies] =
+): Validator[Dependencies] =
   without membership =? committee.membership(identity.identifier):
-    return failure "identity is not a member of the committee"
-  success Validator[Dependencies](
+    raiseAssert "identity is not a member of the committee"
+  Validator[Dependencies](
     identity: identity,
     committee: committee,
     membership: membership,

tests/mysticeti/simulator.nim

@@ -16,7 +16,7 @@ proc init*(_: type NetworkSimulator, numberOfValidators = 4): NetworkSimulator =
   let identities = newSeqWith(numberOfValidators, Identity.init())
   let stakes = identities.mapIt( (it.identifier, 1/numberOfValidators) )
   let committee = Committee.new(stakes)
-  let validators = identities.mapIt(!Validator.new(it, committee))
+  let validators = identities.mapIt(Validator.new(it, committee))
   NetworkSimulator(identities: identities, validators: validators)
 
 func identities*(simulator: NetworkSimulator): seq[Identity] =

tests/mysticeti/validator/testValidator.nim

@@ -13,7 +13,7 @@ suite "Validator":
   setup:
     let identity = Identity.init()
     let committee = Committee.new({identity.identifier: 1/1})
-    validator = !Validator.new(identity, committee)
+    validator = Validator.new(identity, committee)
 
   test "starts at round 0":
     check validator.round == 0

tests/mysticeti/validator/testValidatorNetwork.nim

@@ -69,7 +69,7 @@ suite "Validator Network":
   test "refuses proposals that are not signed by a committee member":
     let otherIdentity = Identity.example
     let otherCommittee = Committee.new({otherIdentity.identifier: 1/1})
-    let otherValidator = !Validator.new(otherIdentity, otherCommittee)
+    let otherValidator = Validator.new(otherIdentity, otherCommittee)
     let proposal = !otherValidator.propose(seq[Transaction].example)
     let checked = simulator.validators[0].check(proposal)
     check checked.verdict == BlockVerdict.invalid