Function inline_lets_helper

src/transform/src/normalize_lets.rs:895–935

Substitute `Get{id}` expressions for any proposed expressions. The proposed expressions can be proposed either to be taken or cloned.

(
        expr: &mut MirRelationExpr,
        inline_offer: &mut BTreeMap<LocalId, InlineOffer>,
    )

    ///
    /// The proposed expressions can be proposed either to be taken or cloned.
    fn inline_lets_helper(
        expr: &mut MirRelationExpr,
        inline_offer: &mut BTreeMap<LocalId, InlineOffer>,
    ) -> Result<(), crate::TransformError> {
        let mut worklist = vec![expr];
        while let Some(expr) = worklist.pop() {
            if let MirRelationExpr::Get {
                id: Id::Local(id), ..
            } = expr
            {
                if let Some(offer) = inline_offer.get_mut(id) {
                    // It is important that we *not* continue to iterate
                    // on the contents of `offer`, which has already been
                    // maximally inlined. If we did, we could mis-inline
                    // bindings into bodies that precede them, which would
                    // change the semantics of the expression.
                    match offer {
                        InlineOffer::Take(value, _max_iter) => {
                            *expr = value.take().ok_or_else(|| {
                                crate::TransformError::Internal(format!(
                                    "Value already taken for {:?}",
                                    id
                                ))
                            })?;
                        }
                        InlineOffer::Clone(value, _max_iter) => {
                            *expr = value.clone();
                        }
                        InlineOffer::Unavailable(_, _) => {
                            // Do nothing.
                        }
                    }
                } else {
                    // Presumably a reference to an outer scope.
                }
            } else {
                worklist.extend(expr.children_mut().rev());
            }
        }
        Ok(())
    }
}

mod renumbering {