Function call_argument_count 

pub fn call_argument_count(node: &SyntaxNode) -> usize

Number of argument expressions in a NodeCallExpr. Used for type inference so the call is inferred as the function’s return type. The grammar uses lparen, optional(expr, zero_or_more(comma, expr)), rparen; the optional may be one node (with 0, 1, or more children) or optional + zero_or_more as siblings.