125 lines
3.8 KiB
Rust
125 lines
3.8 KiB
Rust
// Additional type conversion abstractions
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//
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// Copyright (C) 2014-2022 Ryan Specialty Group, LLC.
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//
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// This file is part of TAME.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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//! TAMER opinionated traits for conversion between types.
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//!
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//! _This should not be used for error reporting to users!_
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//! Panics in TAMER represent internal compiler errors.
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//!
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//! This module introduces two new traits:
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//!
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//! - [`ExpectFrom`] implemented for all [`TryFrom`]; and
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//! - [`ExpectInto`] implemented for all [`TryInto`].
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//!
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//! These traits provide two new methods:
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//!
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//! - `expect_{from,into}`, which is equivalent to calling
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//! [`Result::expect`] on the result; and
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//! - `unwrap_{from,into}`, which is equivalent to calling
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//! [`Result::unwrap`] on the result.
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//!
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//! These two traits are intended to eliminate boilerplate in situations
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//! where _it is expected that these will never fail_.
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//! There may be better options;
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//! these are most useful in writing tests.
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use std::convert::{TryFrom, TryInto};
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use std::fmt::Debug;
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/// Safe type conversion that may panic under some circumstances.
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///
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/// This is implemented for every type implementing [`TryFrom`] and is
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/// intended to be used in situations where we are certain that failure
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/// cannot occur,
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/// or where failure would otherwise be folowed by [`Result::expect`] or
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/// [`Result::unwrap`].
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///
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/// See the [module-level documentation](self) for more information.
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pub trait ExpectFrom<T>: TryFrom<T>
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where
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<Self as TryFrom<T>>::Error: Debug,
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{
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/// Attempt to convert `value` using `T::try_from`,
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/// causing a panic with the given `msg` on failure.
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///
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/// Panics
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/// ======
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/// Causes a panic on failure.
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fn expect_from(value: T, msg: &str) -> T {
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T::try_from(value).expect(msg)
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}
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/// Attempt to convert and unwrap `value` using `T::try_from`.
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///
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/// Panics
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/// ======
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/// Causes a panic on failure.
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fn unwrap_from(value: T) -> T {
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T::try_from(value).unwrap()
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}
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}
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impl<T, U> ExpectFrom<U> for T
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where
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T: TryFrom<U>,
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<T as TryFrom<U>>::Error: Debug,
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{
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}
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/// An attempted conversion that consumes `self`,
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/// which may or may not be expensive and will panic on failure.
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///
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/// This is implemented for every type implementing [`TryInto`] and is
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/// intended to be used in situations where we are certain that failure
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/// cannot occur,
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/// or where failure would otherwise be folowed by [`Result::expect`] or
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/// [`Result::unwrap`].
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///
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/// See the [module-level documentation](self) for more information.
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pub trait ExpectInto<T>: TryInto<T>
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where
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<Self as TryInto<T>>::Error: Debug,
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{
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/// Attempt to convert a value using `self.try_into()`,
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/// causing a panic with the given `msg` on failure.
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///
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/// Panics
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/// ======
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/// Causes a panic on failure.
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fn expect_into(self, msg: &str) -> T {
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self.try_into().expect(msg)
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}
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/// Attempt to convert and unwrap a value using `self.try_into()`.
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///
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/// Panics
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/// ======
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/// Causes a panic on failure.
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fn unwrap_into(self) -> T {
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self.try_into().unwrap()
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}
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}
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impl<T, U> ExpectInto<U> for T
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where
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T: TryInto<U>,
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<T as TryInto<U>>::Error: Debug,
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{
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}
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