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Allow self as an identifier in patterns #3684
Description
Proposal
Allow the use of self as an identifier in identifier patterns (foo @ Foo { bar, baz }).
Motivation
As seen in the following search results within the rust-lang/rust repository, there are numerous instances where developers want to destructure a struct in a let statement with self on the right-hand side.
Search results in the rust-lang/rust repository
For example, consider the following code in library/std/src/sys/pal/sgx/net.rs:
fn try_into_inner(self) -> Result<FileDesc, Socket> {
let Socket { inner, local_addr } = self;
Arc::try_unwrap(inner).map_err(|inner| Socket { inner, local_addr })
}If self were allowed as an identifier in identifier patterns, this could be written more concisely as:
fn try_into_inner(self @ Socket { inner, local_addr }) -> Result<FileDesc, Socket> {
Arc::try_unwrap(inner).map_err(|inner| Socket { inner, local_addr })
}This is not only more concise but also more natural from a language specification standpoint.
Reacted by naskya, Yoni Peleg, Lucky_Cat, bbb651 🇮🇱 and Teoh Han Hui
Activity
fiveseven-lambda commentedon Aug 26, 2024
But what about
&selfand&mut self? We can write&selfas a shorthand forself: &Self, but it might be confusing if&self @ Foo { bar, baz }was desugared intoself @ Foo { bar, baz }: &Self. There are two possible ways:selfin patterns, and disallow&selfand&mut self(so that we have to write asself @ Foo { bar, baz }: &Self)&self @ Foo { bar, baz }and&mut self @ Foo { bar, baz }be shorthands forself @ Foo { bar, baz }: &Selfandself @ Foo { bar, baz }: &mut Self, respectively.