Sum type (union) syntax

[jdpage]

Do we want unions? Would we prefer discriminated unions (i.e. you can tell at-runtime which branch of the union it is)? I am a huge fan of discriminated unions but they might be a feature to put off until later.

• decide if we want regular unions
• decide if we want discriminated unions
• decide on access syntax

[woodrowbarlow]

if we have unions, i want them to be discriminated.