Positive coverage: prove_existential_var_eq / existential-existential

7 tests exercised this rule:

Source location: tests/borrowck.rs:2041

fn foo() -> i32 {
    exists<'r0, 'r1> {
        let result: i32;
        {
            let v1: i32 = 22 _ i32;
            let v2: &'r0 i32 = &'r1 v1;
            result = *v2;
        }
        return result;
    }
}

Source location: tests/borrowck.rs:2410

fn foo () -> u32 {
    exists<'l_p, 'l_q, 'loan_0, 'loan_1, 'loan_2, 'loan_3> {
        let a: u32 = 0 _ u32;
        let b: u32 = 0 _ u32;
        // In Rustc, the 1-tuple is needed for some reason
        // Niko does not 100% understand, else rustc is able to
        // see that this program is safe.
        let q: &mut 'l_q u32 = &mut 'loan_0 a;
        let p: &mut 'l_p u32 = &mut 'loan_1 a;
        if true {
            p = &mut 'loan_1 a;
            q = &mut 'loan_2 b;
        } else {
            p = &mut 'loan_3 b;
        }
        *q = 1 _ u32;
        return *p;
    }
}

Source location: tests/borrowck.rs:2600

fn foo() -> u32 {
    exists<'r0, 'r1> {
        'a: loop {
            let x: i32 = 0 _ i32;
            let r: &'r0 i32 = &'r1 x;
            let _y: i32 = *r;
            continue 'a;
        }
    }
}

Source location: tests/borrowck.rs:2922

fn bar() -> u32 {
    exists<'r0, 'r1> {
        let v: u32 = 1 _ u32;
        let p: &'r0 u32 = &'r1 v;
        foo(0 _ u32);
        return *p;
    }
}

Source location: tests/borrowck.rs:2976

fn foo() -> u32 {
    exists<'r0, 'r1, 'r2, 'r3> {
        let p: Point = Point { x: 0 _ u32, y: 0 _ u32 };
        let b1: &mut 'r0 u32 = &mut 'r1 p.x;
        let b2: &mut 'r2 u32 = &mut 'r3 p.y;
        *b1 = 1 _ u32;
        *b2 = 2 _ u32;
        return 0 _ u32;
    }
}

Source location: tests/mir_typeck.rs:710

fn foo () -> u32 {
    exists<'a> {
        let v0: u32 = 0 _ u32;
        let v1: &'a u32 = &'a v0;
        let v2: u32 = *v1;
        return v2;
    }
}

Source location: tests/projection.rs:115

#[test]
fn projection_equality() {
    test_where_clause(
        PROJECTION_EQUALITY,
        "exists<U> {} => { Trait1(S), <S as Trait1<>>::Type = U }",
    )
    .assert_ok(expect_test::expect!["{Constraints { env: Env { variables: [?ty_1], bias: Soundness, pending: [], allow_pending_outlives: false }, known_true: true, substitution: {?ty_1 => u32} }, Constraints { env: Env { variables: [?ty_1], bias: Soundness, pending: [], allow_pending_outlives: false }, known_true: true, substitution: {?ty_1 => <S as Trait1>::Type} }}"]);

    test_where_clause(PROJECTION_EQUALITY, "exists<U> {} => { Trait2(S, U) }")
        .assert_ok(expect_test::expect!["{Constraints { env: Env { variables: [?ty_1], bias: Soundness, pending: [], allow_pending_outlives: false }, known_true: true, substitution: {?ty_1 => u32} }, Constraints { env: Env { variables: [?ty_1], bias: Soundness, pending: [], allow_pending_outlives: false }, known_true: true, substitution: {?ty_1 => <S as Trait1>::Type} }}"]);
}