> ## Documentation Index > Fetch the complete documentation index at: https://docs.inco.org/llms.txt > Use this file to discover all available pages before exploring further. # Error Reference > Custom errors thrown by the Inco Lightning smart contracts This page lists every custom error that a dApp developer may encounter when building on Inco Lightning. *** ## Access Control ### `SenderNotAllowedForHandle` ```solidity theme={null} error SenderNotAllowedForHandle(bytes32 handle, address sender); ``` The caller does not have read or use permission on this handle. Grant access first with `e.allow(handle, address)` or `inco.allow(handle, address)`. ### `SharerNotAllowedForHandle` ```solidity theme={null} error SharerNotAllowedForHandle(bytes32 handle, address sharer); ``` The sharer does not hold permission on this handle and therefore cannot delegate access to others. ### `HandleAlreadyExists` ```solidity theme={null} error HandleAlreadyExists(bytes32 handle); ``` An attempt was made to register a handle that already exists in the access control list. ### `ProofVerificationFailed` ```solidity theme={null} error ProofVerificationFailed(address verifyingContract, bytes4 callFunction, bytes argData); ``` The session verifier contract did not return `ALLOWANCE_GRANTED_MAGIC_VALUE`. The allowance proof failed — check that the voucher is valid and has not expired or been revoked. ### `InvalidVoucherWarning` ```solidity theme={null} error InvalidVoucherWarning(); ``` Thrown when a voucher's warning field does not match the required warning text ### `InvalidVoucherSignature` ```solidity theme={null} error InvalidVoucherSignature(address signer, bytes32 digest, bytes signature); ``` The allowance voucher signature does not match the sharer's address. ### `InvalidVoucherSessionNonce` ```solidity theme={null} error InvalidVoucherSessionNonce(bytes32 providedSessionNonce, bytes32 activeSessionNonce); ``` The voucher was signed under a session nonce that no longer matches the sharer's active nonce. The voucher has been revoked via `updateActiveVouchersSessionNonce`. ### `InvalidVerifyingContract` ```solidity theme={null} error InvalidVerifyingContract(); ``` The voucher specifies a zero-address verifying contract, which is not allowed. *** ## Encrypted Input ### `InvalidInputVersion` ```solidity theme={null} error InvalidInputVersion(uint16 version); ``` The ciphertext input uses an unsupported version number. ### `InputLengthTooShort` ```solidity theme={null} error InputLengthTooShort(uint256 length); ``` The input bytes are too short to be a valid encrypted input. ### `ExternalHandleDoesNotMatchComputedHandle` ```solidity theme={null} error ExternalHandleDoesNotMatchComputedHandle( bytes32 externalHandle, bytes32 computedHandle, uint256 chainId, address aclAddress, address userAddress, address contractAddress, uint16 version ); ``` The handle supplied by the user does not match the handle derived from the ciphertext content. This indicates the input data was constructed incorrectly or tampered with. *** ## Decryption & Attestation ### `HandleMismatch` ```solidity theme={null} error HandleMismatch(); ``` A decryption or computation attestation was submitted for a different handle than the one the contract expects. Always verify `decryption.handle` explicitly before accepting an attestation — see [Best Practices](./best-practices). ### `InvalidTEEAttestation` ```solidity theme={null} error InvalidTEEAttestation(); ``` The attestation signatures are invalid or fail TEE verification. ### `UnexpectedDecryptedValue` ```solidity theme={null} error UnexpectedDecryptedValue(); ``` The decrypted value does not match the expected value in a computation attestation. ### `AttestationsSignaturesLengthMismatch` ```solidity theme={null} error AttestationsSignaturesLengthMismatch(uint256 attestationsLength, uint256 signaturesLength); ``` The `attestations` and `signatures` arrays passed to a batch verification call have different lengths. *** ## EList Operations ### `IndexOutOfRange` ```solidity theme={null} error IndexOutOfRange(uint16 i, uint16 len); ``` An index access on an elist is beyond the list bounds. ### `SliceOutOfRange` ```solidity theme={null} error SliceOutOfRange(uint16 start, uint16 end, uint16 len); ``` The requested slice boundaries exceed the list length. ### `InvalidRange` ```solidity theme={null} error InvalidRange(uint16 start, uint16 end); ``` The start index is greater than or equal to the end index. ### `ListRangeExceedsType` ```solidity theme={null} error ListRangeExceedsType(uint16 end, ETypes listType); ``` The end value of a range operation does not fit within the bit width of the specified list type. ### `ZeroLength` ```solidity theme={null} error ZeroLength(); ``` An operation that requires a non-empty list received an empty one. ### `ListTooLong` ```solidity theme={null} error ListTooLong(uint32 provided, uint16 max); ``` The list exceeds the maximum allowed length. ### `ListTypeMismatch` ```solidity theme={null} error ListTypeMismatch(ETypes lhs, ETypes rhs); ``` Two lists have incompatible element types (for example, concatenating a `Uint256` list with a `Bool` list). ### `UnsupportedListType` ```solidity theme={null} error UnsupportedListType(ETypes listType); ``` The specified element type is not supported for this elist operation. *** ## Type System ### `UnsupportedType` ```solidity theme={null} error UnsupportedType(ETypes actual); ``` The handle type is not supported for this operation. ### `UnexpectedType` ```solidity theme={null} error UnexpectedType(ETypes actual, bytes32 expectedTypes); ``` The handle type does not match any of the expected types. `expectedTypes` is a bitmask of the valid types. ### `SameTypeCast` ```solidity theme={null} error SameTypeCast(ETypes t); ``` A cast was attempted from a type to itself. Use a different target type. *** ## Fees ### `FeeNotPaid` ```solidity theme={null} error FeeNotPaid(); ``` The `msg.value` sent with the transaction was insufficient to cover the required fee. Query `inco.getFee()` to determine the correct amount before calling. ### `FeeWithdrawalFailed` ```solidity theme={null} error FeeWithdrawalFailed(); ``` The ETH transfer during fee withdrawal failed. ### `NoFeesToWithdraw` ```solidity theme={null} error NoFeesToWithdraw(); ``` A withdrawal was attempted when there are no accumulated fees available. *** ## ETH Transfer ### `EthInboundTransferUnsupported` ```solidity theme={null} error EthInboundTransferUnsupported(); ``` Plain ETH transfers directly to the `IncoLightning` contract are rejected. Always attach `msg.value` to a specific function call to pay fees. ### `RefundFailed` ```solidity theme={null} error RefundFailed(); ``` An ETH refund transfer back to the caller failed. ### `ReentrantCall` ```solidity theme={null} error ReentrantCall(); ``` A reentrant call was detected and blocked.