if as, ok := s.(*AssignStmt); ok && as.Op == 0 {
			// Emphasize complex Lhs and Rhs of assignment with parentheses to highlight '='.
			str = "assignment " + emphasize(as.Lhs) + " = " + emphasize(as.Rhs)
		} else {
			str = String(s)
		}
		p.syntaxErrorAt(s.Pos(), fmt.Sprintf("cannot use %s as value", str))
	}

	p.xnest = outer
	return
}

// emphasize returns a string representation of x, with (top-level)