The claimed subject matter relates to a formalization of operator patterns that can facilitate type flow of element types between an operator in a first clause of an expression to an operator in a next clause of the expression. The type that flows to, and the operator extant in, the next clause can be combined to infer the element type of the next clause. As such, type-checking, autocompletion and other advantageous features can be accomplished incrementally without the need for a prior full translation of the expression.