flow-control: Support lowering of Deconstruct node.

[liorgold2]

Stack:

• flow-control: Support lowering of Deconstruct node. #8116 ⬅
• flow-control: Add cache node optimization. #8115

⚠️ Part of a stack created by spr. Do not merge manually using the UI - doing so may have unexpected results.

[reviewable-StarkWare]

This change is 

[ilyalesokhin-starkware]

crates/cairo-lang-lowering/src/lower/flow_control/lower_graph/lower_node.rs line 209 at r1 (raw file):

                location: ctx.ctx.variables[var_id].location,
            },
        );

this is weird, why does register_var takes a VarUsage and not a VarId?

Code quote:

        ctx.register_var(
            *output,
            VarUsage {
                var_id,
                // The variable is used immediately after the destructure, so the usage
                // location is the same as the definition location.
                location: ctx.ctx.variables[var_id].location,
            },
        );

[ilyalesokhin-starkware]

Reviewed 2 of 4 files at r1.
Reviewable status: 2 of 4 files reviewed, 1 unresolved discussion (waiting on @liorgold2)

[ilyalesokhin-starkware]

crates/cairo-lang-lowering/src/lower/flow_control/lower_graph/lower_node.rs line 193 at r1 (raw file):

        .outputs
        .iter()
        .map(|output| VarRequest { ty: output.ty(ctx.graph), location: output.location(ctx.graph) })

Can you improve the documentation of this function?
and
FlowControlGraph.var_locations?

Code quote:

 output.location(ctx.graph)

[ilyalesokhin-starkware]

crates/cairo-lang-lowering/src/lower/flow_control/lower_graph/lower_node.rs line 193 at r1 (raw file):

Previously, ilyalesokhin-starkware wrote…

Can you improve the documentation of this function?
and
FlowControlGraph.var_locations?

It seems to be the location that triggered the creation of the variable.