Concise syntax for prototype-less, immutable data structures with named properties.

RecordLiteral ::= "#" "{" ("..." AssignmentExpression)? "}"
               |  "#" "{" PropertyDataAssignment ("," PropertyDataAssignment)* ("," "..." AssignmentExpression)? "}"

PropertyDataAssignment ::= PropertyName ":" AssignmentExpression

• typeof produces “record”
• enumeration always proceeds in lexicographic order of property names
• ellipsis form provides functional update: splices in own-properties of the result if typeof result is “object”, or properties if result of typeof result is “record”
• record properties are immutable
• == and === test value equality
• < etc. test value order/equality