Compiler should be able to compile EnumVariant(foo) == function_returning_enum() without PartialEq

[In-line]

Given this pseudocode

let result: bool = Ok(something) == some_function_returning_result();

It should be transformed to this pseudocode

let result: bool = match some_function_returning_result() {
    Ok(something) => true,
    _ => false,
};

Currently I get this error.

error[E0277]: can't compare `errors::Error` with `errors::Error`
   --> src/rustup/toolchain.rs:349:35
    |
349 |                     Ok(something) == some_function_returning_result()
    |                                   ^^ no implementation for `errors::Error == errors::Error`
    |
    = help: the trait `std::cmp::PartialEq` is not implemented for `errors::Error`
    = note: required because of the requirements on the impl of `std::cmp::PartialEq` for `std::result::Result<std::string::String, errors::Error>`

It would be nice syntax sugar to have not only for Result, but for any generic enum.

[petrochenkov]

cc rust-lang/rfcs#929 (comment)

[scottmcm]

I think this is an RFC issue -- for example it could be made to work with enum variants being types, and PartialEq being defined on those against their enum parent type, or with something like the is expressions that petrochenkov linked, or the matches! macro. I suspect it's not something that would ever be done as written, though, since there's nothing that says equality needs to work the way this transformation would be assuming: different variants are allowed to be considered equal.

[In-line]

Thanks. I will think more carefully about this issue and try to write RFC.