from

A constructor function, strongly implying “type conversion”.

// Copyright 2025 Google LLC
// SPDX-License-Identifier: Apache-2.0

impl Duration {
    fn from_days(days: u64) -> Duration;
}

impl i32 {
    fn from_ascii(src: &[u8]) -> Result<i32, ParseIntError>;
}

impl u32 {
    fn from_le_bytes(bytes: [u8; 4]) -> u32;
}

  • Prefix for constructor-style, From-trait-style functions.

  • These functions can take multiple arguments, but usually imply the user is doing more of the work than a usual constructor would.

  • new is still preferred for most constructor-style functions, the implication for from is transformation of one data type to another.