Enum PoloniusResult

pub enum PoloniusResult<BorrowingOutput, OwnedOutput, InputBorrow = Placeholder> {
    Borrowing(BorrowingOutput),
    Owned {
        value: OwnedOutput,
        input_borrow: InputBorrow,
    },
}

Output type of both the polonius() function and the closure it takes.

It represents the conceptual code-flow / branch disjunction between:

• having some dependent type still Borrowing from the input_borrow given/forfeited to polonius();

• or having no such type, i.e., having only “Owned” (as far as the input_borrow is concerned) output.

  • polonius() magic makes it so, in this branch/case, its .input_borrow shall be populated for the caller to get back access to it.

Variants

Borrowing(BorrowingOutput)

Variant to return in the “happy” case where our tentative (re)borrow actually yielded some dependent / still-Borrowing type which we wish to keep hold of, e.g., to return it from the function.

Owned

Variant to return in the branches where we are done with any dependent value, and we would like to instead get our input_borrow back.

Fields

value: OwnedOutput

The inner value of the Self::Owned(value) case.

input_borrow: InputBorrow

When constructing this variant, inside polonius()’ closure, a Placeholder is to be put in its stead, to let polonius() replace it with its input_borrow.

Implementations

impl<BorrowingOutput, OwnedOutput> PoloniusResult<BorrowingOutput, OwnedOutput>

pub const fn Owned(value: OwnedOutput) -> Self

Tuple-variant-looking sugar to construct the Self::Owned variant.

It’s just convenience sugar for Self::Owned { value, input_borrow: Placeholder }.

PoloniusResult::Owned(42)
// is the same as:
PoloniusResult::Owned {
    value: 42,
    input_borrow: Placeholder,
}

See Placeholder for more info.