fixed: differentiation between uninitialized and possibly uninitialized

[mazam-97]

Fix: #157267

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[Unique-Usman]

Thanks for the pr, can we change it commit message to something like "avoid reporting unreachable initializations for uninitialized uses" ?

[Unique-Usman]

Also, we need to add more test i.e one for match expression, one or two if we have multiple block of if or match expressions.

[Unique-Usman]

cc: @estebank

[Unique-Usman]

Here, we might want to have something like

"`x` used here, but all known initializations occur on control-flow paths that do not reach this use"  

or a shorter version

`x` used here, but it is not initialized on any path leading to this point

because, x was actually initialized but, it was initilized on another branch or block which will never reach the error block.

There would probably be another else if statement in this block -> https://github.com/rust-lang/rust/blob/main/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs#L820C86-L845C40

View changes since the review

[mazam-97]

I think what you say makes sense. The error should be more explicit. I will add one more block.

[mazam-97]

Thanks for the pr, can we change it commit message to something like "avoid reporting unreachable initializations for uninitialized uses" ?

Thanks for reviewing the PR @Unique-Usman. I will modify the commit messge as suggested.

[mazam-97]

Also, we need to add more test i.e one for match expression, one or two if we have multiple block of if or match expressions.

Sure, I will add more tests having match expression and if else blocks.

[Unique-Usman]

This should be something like

fn main() {
    let x;

    match true {
        true => x = 42,
        false =>  println!("{x}"), //~ ERROR E0381
    }
}

View changes since the review

[mazam-97]

Addressed.

[Unique-Usman]

if you want to have multiple match, do not nested it like this. You can have something like this.

enum PrimaryColor {
  RED,
  BLUE,
  GREEN
}

fn main() {
    let x;
    let pc = PrimaryColor::RED,

    match pc {
        PrimaryColor::RED => x = 1,
        PrimaryColor::BLUE => x = 3,
        PrimaryColor::GREEN =>  println!("{x}"); //~ ERROR E0381
    }

}

Also, something similar for the if and else i.e for multiple branch.

View changes since the review

[mazam-97]

Addressed. Added a test having an enum with match