Remove IndexedAttestation faulty Decode impl

consensus/types/src/indexed_attestation.rs

@@ -2,7 +2,6 @@ use crate::{test_utils::TestRandom, AggregateSignature, AttestationData, EthSpec
 use core::slice::Iter;
 use derivative::Derivative;
 use serde::{Deserialize, Serialize};
-use ssz::Decode;
 use ssz::Encode;
 use ssz_derive::{Decode, Encode};
 use std::hash::{Hash, Hasher};
@@ -187,26 +186,6 @@ impl<'a, E: EthSpec> IndexedAttestationRef<'a, E> {
     }
 }
 
-impl<E: EthSpec> Decode for IndexedAttestation<E> {
-    fn is_ssz_fixed_len() -> bool {
-        false
-    }
-
-    fn from_ssz_bytes(bytes: &[u8]) -> Result<Self, ssz::DecodeError> {
-        if let Ok(result) = IndexedAttestationBase::from_ssz_bytes(bytes) {
-            return Ok(IndexedAttestation::Base(result));
-        }
-
-        if let Ok(result) = IndexedAttestationElectra::from_ssz_bytes(bytes) {
-            return Ok(IndexedAttestation::Electra(result));
-        }
-
-        Err(ssz::DecodeError::BytesInvalid(String::from(
-            "bytes not valid for any fork variant",
-        )))
-    }
-}
-
 /// Implementation of non-crypto-secure `Hash`, for use with `HashMap` and `HashSet`.
 ///
 /// Guarantees `att1 == att2 -> hash(att1) == hash(att2)`.

slasher/src/database.rs

@@ -18,7 +18,8 @@ use std::marker::PhantomData;
 use std::sync::Arc;
 use tree_hash::TreeHash;
 use types::{
-    Epoch, EthSpec, Hash256, IndexedAttestation, ProposerSlashing, SignedBeaconBlockHeader, Slot,
+    Epoch, EthSpec, Hash256, IndexedAttestation, IndexedAttestationBase, ProposerSlashing,
+    SignedBeaconBlockHeader, Slot,
 };
 
 /// Current database schema version, to check compatibility of on-disk DB with software.
@@ -481,7 +482,11 @@ impl<E: EthSpec> SlasherDB<E> {
             .ok_or(Error::MissingIndexedAttestation {
                 id: indexed_attestation_id.as_u64(),
             })?;
-        ssz_decode(bytes)
+        // TODO(electra): make slasher fork-aware and return correct variant of attestation. Both
+        // Base and Electra variant can the same SSZ encoding, however the smaller list maximum of
+        // Base can error with an Electra attestation with heavy participation.
+        let indexed_attestation: IndexedAttestationBase<E> = ssz_decode(bytes)?;
+        Ok(IndexedAttestation::Base(indexed_attestation))
     }
 
     fn get_attestation_data_root(