EC
TryFromIntError
RustERRORCommonType Conversion

Integer conversion out of range

Quick Answer

Use try_from() and handle the error; avoid as casts which silently truncate.

What this means

Returned by TryFrom/TryInto conversions when a numeric value does not fit in the target integer type.

Why it happens
  1. 1Casting a large i64 to i32 when the value exceeds i32::MAX
  2. 2Negative value into an unsigned type

Fix

Use try_into() instead of as

Use try_into() instead of as
use std::convert::TryInto;
let big: i64 = 300;
let small: i32 = big.try_into().map_err(|_| "value too large for i32")?;

Why this works

try_into() returns Err on overflow rather than silently wrapping.

Code examples
Badrust
let x: i32 = 300i64 as i32; // silently wraps
Goodrust
let x: i32 = 300i64.try_into()?;
Sources

Content generated with AI assistance and reviewed for accuracy. Found an error? hello@errcodes.dev

← All Rust errors