Enum polonius_the_crab::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

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.

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.

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.