Types and Values

Neo DevPack for Solidity enforces Solidity typing at compile time, then lowers values to NeoVM stack items, storage payloads, and ABI types.

Value Types

Solidity Type	NeoVM Representation	Notes
bool	Boolean	Direct stack item mapping.
uint* / int*	BigInteger	Width is enforced by the compiler; NeoVM integers are arbitrary precision.
address	UInt160 / 20-byte script hash	Neo addresses represent accounts or contracts by script hash.
address payable	UInt160 plus compatibility members	.transfer() and .send() map to GAS transfer warnings.
bytes1 ... bytes32	Fixed-length ByteArray	bytes32 maps to Neo ABI Hash256 and is common for NEP-11 token IDs.
string / dynamic bytes	ByteArray payload	Used as raw bytes in storage-key derivation.
enum	BigInteger backed by uint8	Solidity enum conversion rules still apply.
User-defined value type	Underlying value type	Zero-cost Solidity abstraction.

Reference Types

Solidity Type	NeoVM Representation	Notes
Memory arrays	NeoVM Array	Runtime stack representation.
Storage arrays	Neo storage keys	Length and element keys are derived deterministically.
Structs in memory	NeoVM Array	Fields keep their declared order.
Structs in storage	Serialized binary blob	Read/write is atomic for the full struct value.
calldata	Treated like memory	Accepted for source compatibility.
mapping(K => V)	Deterministic storage-key derivation	No length, no enumeration, and no "set" marker.

Integer Behavior

NeoVM represents integers as arbitrary-precision BigInteger values. Solidity width and signedness are type-checked by the compiler, but NeoVM does not impose fixed-width overflow boundaries at runtime. Code that depends on wrapping should use explicit modulo arithmetic.

Mapping Keys

Mapping keys can be built-in value types, bytes, string, contracts, or enums. Complex key types such as structs, arrays, and mappings are not valid. Mapping values can be any supported value, including nested mappings, arrays, and structs.

More Detail

• Types
• Storage and Mappings
• Contract Metadata