Function mergeIntoNode

immutable.go:1412–1428

mergeIntoNode merges a key/value pair into an existing node. Caller must verify that node's keyHash is not equal to keyHash.

(node mapLeafNode[K, V], shift uint, keyHash uint32, key K, value V)

// mergeIntoNode merges a key/value pair into an existing node.
// Caller must verify that node's keyHash is not equal to keyHash.
func mergeIntoNode[K, V any](node mapLeafNode[K, V], shift uint, keyHash uint32, key K, value V) mapNode[K, V] {
	idx1 := (node.keyHashValue() >> shift) & mapNodeMask
	idx2 := (keyHash >> shift) & mapNodeMask

	// Recursively build branch nodes to combine the node and its key.
	other := &mapBitmapIndexedNode[K, V]{bitmap: (1 << idx1) | (1 << idx2)}
	if idx1 == idx2 {
		other.nodes = []mapNode[K, V]{mergeIntoNode(node, shift+mapNodeBits, keyHash, key, value)}
	} else {
		if newNode := newMapValueNode(keyHash, key, value); idx1 < idx2 {
			other.nodes = []mapNode[K, V]{node, newNode}
		} else {
			other.nodes = []mapNode[K, V]{newNode, node}
		}
	}
	return other
}

// mapEntry represents a single key/value pair.
type mapEntry[K, V any] struct {