Function new_syntax_node 

pub fn new_syntax_node<'db>(
    db: &'db dyn Database,
    green: GreenId<'db>,
    offset_in_parent: TextOffset,
    id: SyntaxNodeId<'db>,
    kind: SyntaxKind,
) -> SyntaxNode<'db>

Creates a new syntax node. offset_in_parent must be relative to the parent (absolute for a root) — see SyntaxNodeData::offset_in_parent.