[CALCITE-1530] Create a Shuttle for visiting linq4j expressions without mutating them

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.11.0
• Assignee: Julian Hyde
• Reporter: Julian Hyde
• Created: 06/Dec/16 05:27
• Updated: 06/Jan/17 19:30
• Resolved: 08/Dec/16 06:09

Description

Create a shuttle for visiting linq4j expressions without mutating them. Rename the current Visitor class to Shuttle, create a new Visitor<R> interface, and a default implementation VisitorImpl<R>, and add a method <R> R Node.accept(Visitor<R> visitor).

Note that accept's return type is R: not necessarily a node, in fact often Void.