signatures: reduce fork code bloat (#7711)

`withState` causes unnecessary template compared to `forky` - also,
`items` is ok to use post 1.4.2

Author: arnetheduck

beacon_chain/spec/signatures_batch.nim

@@ -120,7 +120,7 @@ func aggregateAttesters(
       if inited:
         attestersAgg.aggregate(key)
       else:
-        attestersAgg = AggregatePublicKey.init(key)
+        attestersAgg.init(key)
         inited = true
 
   if not inited:
@@ -287,135 +287,132 @@ proc collectSignatureSets*(
   # ----------------------------------------------------
   mixin load
 
+  const consensusFork = ForkySignedBeaconBlock.kind
+  template forkyState(): untyped =
+    state.forky(consensusFork)
+
   let
-    fork = getStateField(state, fork)
-    genesis_validators_root = getStateField(state, genesis_validators_root)
+    fork = forkyState.data.fork
+    genesis_validators_root = forkyState.data.genesis_validators_root
     proposer_index = signed_block.message.proposer_index
     proposer_key = validatorKeys.load(proposer_index).valueOr:
       return err("collectSignatureSets: invalid proposer index")
-    epoch = signed_block.message.slot.epoch()
 
 
   # 1. Block proposer
   # ----------------------------------------------------
-  sigs.add block_signature_set(
-    fork, genesis_validators_root,
-    signed_block.message.slot, signed_block.root,
-    proposer_key, signed_block.signature.load.valueOr do:
-      return err("collectSignatureSets: cannot load signature"))
+  block:
+    let sig = signed_block.signature.load.valueOr:
+      return err("collectSignatureSets: cannot load signature")
+
+    sigs.add block_signature_set(
+      fork, genesis_validators_root, signed_block.message.slot, signed_block.root,
+      proposer_key, sig,
+    )
 
   # 2. Randao Reveal
   # ----------------------------------------------------
-  sigs.add epoch_signature_set(
-    fork, genesis_validators_root, epoch, proposer_key,
-    signed_block.message.body.randao_reveal.load().valueOr do:
-      return err("collectSignatureSets: cannot load randao"))
+  block:
+    let
+      epoch = signed_block.message.slot.epoch()
+      sig = signed_block.message.body.randao_reveal.load().valueOr:
+        return err("collectSignatureSets: cannot load randao")
+    sigs.add epoch_signature_set(
+      fork, genesis_validators_root, epoch, proposer_key, sig
+    )
 
   # 3. Proposer slashings
   # ----------------------------------------------------
   # Denial-of-service:
   #   SSZ deserialization guarantees that blocks received from random sources
   #   including peer or RPC
   #   have at most MAX_PROPOSER_SLASHINGS proposer slashings.
-  for i in 0 ..< signed_block.message.body.proposer_slashings.len:
-    # don't use "items" for iterating over large type
-    # due to https://github.com/nim-lang/Nim/issues/14421
-    # fixed in 1.4.2
-
-    # Alias
-    template slashing: untyped = signed_block.message.body.proposer_slashings[i]
-
+  for slashing in signed_block.message.body.proposer_slashings:
     # Proposed block 1
     block:
       let
         header = slashing.signed_header_1
         key = validatorKeys.load(header.message.proposer_index).valueOr:
           return err("collectSignatureSets: invalid slashing proposer index 1")
+        sig = header.signature.load().valueOr:
+          return err("collectSignatureSets: cannot load proposer slashing 1 signature")
 
       sigs.add block_signature_set(
-        fork, genesis_validators_root, header.message.slot, header.message,
-        key, header.signature.load().valueOr do:
-          return err(
-            "collectSignatureSets: cannot load proposer slashing 1 signature"))
+        fork, genesis_validators_root, header.message.slot, header.message, key, sig
+      )
 
     # Conflicting block 2
     block:
       let
         header = slashing.signed_header_2
         key = validatorKeys.load(header.message.proposer_index).valueOr:
           return err("collectSignatureSets: invalid slashing proposer index 2")
+        sig = header.signature.load().valueOr:
+          return err("collectSignatureSets: cannot load proposer slashing 2 signature")
 
       sigs.add block_signature_set(
-        fork, genesis_validators_root, header.message.slot, header.message,
-        key, header.signature.load().valueOr do:
-          return err(
-            "collectSignatureSets: cannot load proposer slashing 2 signature"))
+        fork, genesis_validators_root, header.message.slot, header.message, key, sig
+      )
 
   # 4. Attester slashings
   # ----------------------------------------------------
   # Denial-of-service:
   #   SSZ deserialization guarantees that blocks received from random sources
   #   including peer or RPC
   #   have at most MAX_ATTESTER_SLASHINGS attester slashings.
-  for i in 0 ..< signed_block.message.body.attester_slashings.len:
-    # don't use "items" for iterating over large type
-    # due to https://github.com/nim-lang/Nim/issues/14421
-    # fixed in 1.4.2
-
-    # Alias
-    template slashing: untyped = signed_block.message.body.attester_slashings[i]
-
+  for slashing in signed_block.message.body.attester_slashings:
     # Attestation 1
     block:
       let
-        key = ? aggregateAttesters(
-          slashing.attestation_1.attesting_indices.asSeq(), validatorKeys)
+        key =
+          ?aggregateAttesters(
+            slashing.attestation_1.attesting_indices.asSeq(), validatorKeys
+          )
         sig = slashing.attestation_1.signature.load().valueOr:
           return err("Invalid attestation slashing signature 1")
       sigs.add attestation_signature_set(
-        fork, genesis_validators_root, slashing.attestation_1.data, key, sig)
+        fork, genesis_validators_root, slashing.attestation_1.data, key, sig
+      )
 
     # Conflicting attestation 2
     block:
       let
-        key = ? aggregateAttesters(
-          slashing.attestation_2.attesting_indices.asSeq(), validatorKeys)
+        key =
+          ?aggregateAttesters(
+            slashing.attestation_2.attesting_indices.asSeq(), validatorKeys
+          )
         sig = slashing.attestation_2.signature.load().valueOr:
           return err("Invalid attestation slashing signature 2")
       sigs.add attestation_signature_set(
-        fork, genesis_validators_root, slashing.attestation_2.data, key, sig)
+        fork, genesis_validators_root, slashing.attestation_2.data, key, sig
+      )
 
   # 5. Attestations
   # ----------------------------------------------------
   # Denial-of-service:
   #   SSZ deserialization guarantees that blocks received from random sources
   #   including peer or RPC
   #   have at most MAX_ATTESTATIONS attestations.
-  for i in 0 ..< signed_block.message.body.attestations.len:
-    # don't use "items" for iterating over large type
-    # due to https://github.com/nim-lang/Nim/issues/14421
-    # fixed in 1.4.2
-    template attestation: untyped = signed_block.message.body.attestations[i]
-
-    when typeof(signed_block).kind < ConsensusFork.Electra:
-      let
-        key = ? aggregateAttesters(
+  for attestation in signed_block.message.body.attestations:
+    let
+      attesting_indices =
+        when consensusFork < ConsensusFork.Electra:
           get_attesting_indices(
-            state, attestation.data, attestation.aggregation_bits, cache),
-          validatorKeys)
-    else:
-      let
-        key = ? aggregateAttesters(
+            forkyState.data, attestation.data, attestation.aggregation_bits, cache
+          )
+        else:
           get_attesting_indices(
-            state, attestation.data, attestation.aggregation_bits,
-              attestation.committee_bits, cache),
-          validatorKeys)
-    let
+            forkyState.data, attestation.data, attestation.aggregation_bits,
+            attestation.committee_bits, cache,
+          )
+
+      key = ?aggregateAttesters(attesting_indices, validatorKeys)
       sig = attestation.signature.load().valueOr:
         return err("Invalid attestation signature")
 
     sigs.add attestation_signature_set(
-      fork, genesis_validators_root, attestation.data, key, sig)
+      fork, genesis_validators_root, attestation.data, key, sig
+    )
 
   # 6. VoluntaryExits
   # ----------------------------------------------------
@@ -424,72 +421,67 @@ proc collectSignatureSets*(
   #   including peer or RPC
   #   have at most MAX_VOLUNTARY_EXITS voluntary exits.
   if signed_block.message.body.voluntary_exits.len > 0:
-    let voluntary_exit_fork = withConsensusFork(state.kind):
+    # https://eips.ethereum.org/EIPS/eip-7044
+    # https://github.com/ethereum/consensus-specs/blob/v1.4.0/specs/deneb/beacon-chain.md#modified-process_voluntary_exit
+    let voluntary_exit_fork =
       consensusFork.voluntary_exit_signature_fork(fork, capella_fork_version)
-    for i in 0 ..< signed_block.message.body.voluntary_exits.len:
-      # don't use "items" for iterating over large type
-      # due to https://github.com/nim-lang/Nim/issues/14421
-      # fixed in 1.4.2
-      template volex: untyped = signed_block.message.body.voluntary_exits[i]
-      let key = validatorKeys.load(volex.message.validator_index).valueOr:
-        return err("collectSignatureSets: invalid voluntary exit")
+    for volex in signed_block.message.body.voluntary_exits:
+      let
+        key = validatorKeys.load(volex.message.validator_index).valueOr:
+          return err("collectSignatureSets: invalid voluntary exit")
+        sig = volex.signature.load.valueOr:
+          return err("collectSignatureSets: cannot load voluntary exit signature")
 
       sigs.add voluntary_exit_signature_set(
-        # https://eips.ethereum.org/EIPS/eip-7044
-        # https://github.com/ethereum/consensus-specs/blob/v1.4.0/specs/deneb/beacon-chain.md#modified-process_voluntary_exit
-        voluntary_exit_fork, genesis_validators_root, volex.message, key,
-        volex.signature.load.valueOr do:
-          return err(
-            "collectSignatureSets: cannot load voluntary exit signature"))
+        voluntary_exit_fork, genesis_validators_root, volex.message, key, sig
+      )
 
-  block:
-    when signed_block is phase0.SignedBeaconBlock:
-      discard
+  # 7. SyncAggregate
+  # ----------------------------------------------------
+  when consensusFork >= ConsensusFork.Altair:
+    if signed_block.message.body.sync_aggregate.sync_committee_bits.isZeros:
+      if signed_block.message.body.sync_aggregate.sync_committee_signature !=
+          ValidatorSig.infinity():
+        return err(
+          "collectSignatureSets: empty sync aggregates need signature of point at infinity"
+        )
     else:
-      # 7. SyncAggregate
-      # ----------------------------------------------------
-      withState(state):
-        when consensusFork >= ConsensusFork.Altair:
-          if signed_block.message.body.sync_aggregate.sync_committee_bits.isZeros:
-            if signed_block.message.body.sync_aggregate.sync_committee_signature != ValidatorSig.infinity():
-              return err("collectSignatureSets: empty sync aggregates need signature of point at infinity")
-          else:
-            let
-              current_sync_committee =
-                forkyState.data.get_sync_committee_cache(cache).current_sync_committee
-              previous_slot = max(forkyState.data.slot, Slot(1)) - 1
-              beacon_block_root = get_block_root_at_slot(forkyState.data, previous_slot)
-              pubkey = ? aggregateAttesters(
-                current_sync_committee,
-                signed_block.message.body.sync_aggregate.sync_committee_bits,
-                validatorKeys)
-
-            sigs.add sync_committee_message_signature_set(
-              fork, genesis_validators_root, previous_slot, beacon_block_root,
-              pubkey,
-              signed_block.message.body.sync_aggregate.sync_committee_signature.load().valueOr do:
-                return err("collectSignatureSets: cannot load signature"))
+      let
+        current_sync_committee =
+          forkyState.data.get_sync_committee_cache(cache).current_sync_committee
+        previous_slot = max(forkyState.data.slot, Slot(1)) - 1
+        beacon_block_root = get_block_root_at_slot(forkyState.data, previous_slot)
+        pubkey =
+          ?aggregateAttesters(
+            current_sync_committee,
+            signed_block.message.body.sync_aggregate.sync_committee_bits, validatorKeys,
+          )
+        sig = signed_block.message.body.sync_aggregate.sync_committee_signature.load().valueOr:
+          return err("collectSignatureSets: cannot load signature")
+
+      sigs.add sync_committee_message_signature_set(
+        fork, genesis_validators_root, previous_slot, beacon_block_root, pubkey, sig
+      )
+
+  # 8. BLS to execution changes
+  when consensusFork >= ConsensusFork.Capella:
+    for bls_change in signed_block.message.body.bls_to_execution_changes:
+      # Otherwise, expensive loadWithCache can be spammed with irrelevant pubkeys
+      ?check_bls_to_execution_change(
+        genesis_fork_version, forkyState.data, bls_change, {skipBlsValidation}
+      )
 
-  block:
-    # 8. BLS to execution changes
-    when typeof(signed_block).kind >= ConsensusFork.Capella:
-      withState(state):
-        when consensusFork >= ConsensusFork.Capella:
-          for bls_change in signed_block.message.body.bls_to_execution_changes:
-            let sig = bls_change.signature.load.valueOr:
-              return err("collectSignatureSets: cannot load BLS to execution change signature")
-
-            # Otherwise, expensive loadWithCache can be spammed with irrelevant pubkeys
-            ? check_bls_to_execution_change(
-              genesis_fork_version, forkyState.data, bls_change, {skipBlsValidation})
-
-            let validator_pubkey =
-              bls_change.message.from_bls_pubkey.loadWithCache.valueOr:
-                return err("collectSignatureSets: cannot load BLS to execution change pubkey")
-
-            sigs.add bls_to_execution_change_signature_set(
-              genesis_fork_version, genesis_validators_root, bls_change.message,
-              validator_pubkey, sig)
+      let
+        sig = bls_change.signature.load.valueOr:
+          return
+            err("collectSignatureSets: cannot load BLS to execution change signature")
+        validator_pubkey = bls_change.message.from_bls_pubkey.loadWithCache.valueOr:
+          return err("collectSignatureSets: cannot load BLS to execution change pubkey")
+
+      sigs.add bls_to_execution_change_signature_set(
+        genesis_fork_version, genesis_validators_root, bls_change.message,
+        validator_pubkey, sig,
+      )
 
   ok()