Type Widening

When an arithmetic or comparison expression mixes numeric types, Cambrian widens both operands to a common type that can represent every value of either operand. No explicit cast is required for ordinary same-sign mixes.

Rules

Rule 1 — Same sign

Result width is max(width); signedness is unchanged:

m_total: u128 + amount: u64    // amount widened to u128
m_x: i32 + m_y: i64            // m_x widened to i64

Rule 2 — Mixed signedness

Result is signed with width = max(2 × unsigned_width, signed_width):

m_count: u32 + delta: i8       // both → i64
m_val: u64 + offset: i64       // both → i128

Doubling the unsigned width keeps the full unsigned range representable in the signed result.

Rule 3 — u128 / U256 mixed with signed

There is no wider signed primitive than i128. Mixing u128 or U256 with any signed type is a compile-time error:

m_a: u128 + d: i8    // ERROR
m_b: U256 + d: i32   // ERROR

Any unsigned type combined with U256 widens to U256. Integer literals adapt automatically: m_balance + 1 with m_balance: U256 treats 1 as U256.

Full widening table

Cell at row A, column B is the result of A op B. Symmetric cells are omitted; ERR means compile-time error.

Practical guidance

• Prefer same-sign arithmetic so widening stays obvious.
• Mixing u64 with signed values yields i128 — fine, but larger than most balance fields; cast deliberately if you need a narrower store.
• Do not mix u128 / U256 with signed types; cast one side first.
• Widening applies to checked and wrapping operators alike; overflow checking (or wrap) happens on the result type after widening.

See Checked vs Wrapping Arithmetic.