Pattern match bindings not accessible inside case block

[mjm918]

Description

When pattern matching an enum variant with data, the bound variable is not accessible inside the case block.

Steps to Reproduce

struct Node {
    value: int,
    next: option<Node>
}

fn main() {
    var n2: Node = Node { value: 2, next: none };
    var n1: Node = Node { value: 1, next: some(n2) };
    
    switch (n1.next) {
        case Some(n): {
            println("{}", n.value);  // ERROR: undefined variable 'n'
        }
        default: {
            println("none");
        }
    }
}

Expected: Prints 2
Actual: undefined variable 'n' at ...

Notes

The binding n from case Some(n) is recognized during parsing but not properly defined as a variable in scope during type checking or codegen, preventing field access on it.

[mjm918]

Closing — this is not a bug. Option unwrapping uses the var x = expr else { ... } pattern, not pattern match bindings in switch/case. Example:

var node: Node = opt_node else {
    return 0;
}
println(node.value);