TypeScript tagged union with generic

foo.ts

export type Node<P> = {
    value: P;
    children: Array<Tree<P>>;
};

type Leaf<P> = {
    value: P;
};

enum TreeTag {
    Node = 'Node',
    Leaf = 'Leaf',
}

type TreeRecord<P> = {
    [TreeTag.Node]: Node<P>;
    [TreeTag.Leaf]: Leaf<P>;
};

type TreeTaggedRecord<P> = {
    [Tag in TreeTag]: { tag: Tag; value: TreeRecord<P>[Tag] }
};

type Tree<P> = TreeTaggedRecord<P>[TreeTag];

// Constructors
const node = <P>(value: Node<P>): Tree<P> => ({
    tag: TreeTag.Node,
    value,
});
const leaf = <P>(value: Leaf<P>): Tree<P> => ({
    tag: TreeTag.Leaf,
    value,
});

type TreeTaggedNode<P> = TreeTaggedRecord<P>['Node'];
type TreeTaggedLeaf<P> = TreeTaggedRecord<P>['Leaf'];

// Predicates
const checkIsNode = <P>(tree: Tree<P>): tree is TreeTaggedNode<P> => tree.tag === TreeTag.Node;
const checkIsLeaf = <P>(tree: Tree<P>): tree is TreeTaggedLeaf<P> => tree.tag === TreeTag.Leaf;

// Example
const tree = node({ value: 'foo', children: [leaf({ value: 'bar' })] });

const matchExample = <P>(tree: Tree<P>) => {
    switch (tree.tag) {
        case TreeTag.Node:
            return tree.value.value;
        case TreeTag.Leaf:
            return tree.value.value;
    }
};

console.log(matchExample(tree));