Function ExprAsKeyword

traversal_for_expr.go:111–127

ExprAsKeyword attempts to interpret the given expression as a static keyword, returning the keyword string if possible, and the empty string if not. A static keyword, for the sake of this function, is a single identifier. For example, the following attribute has an expression that would produce the

(expr Expression)

// a fixed set of keywords is used in a structural way in a special attribute
// to affect the further processing of a block.
func ExprAsKeyword(expr Expression) string {
	type asTraversal interface {
		AsTraversal() Traversal
	}

	physExpr := UnwrapExpressionUntil(expr, func(expr Expression) bool {
		_, supported := expr.(asTraversal)
		return supported
	})

	if asT, supported := physExpr.(asTraversal); supported {
		if traversal := asT.AsTraversal(); len(traversal) == 1 {
			return traversal.RootName()
		}
	}
	return ""
}