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Sort out union subtyping

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Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
30/100
Issue type
Refactor
Clarity
Needs clarification
Activity status
Stale
Tech stack
graphql, scala

Research direction

Start by tracing the union case definition for <: and the fragmentApplies entry point, then identify which current subtype semantics those uses rely on. The issue is complete when the intended union subtype relation and the separate fragment-applicability relation are agreed and consistently represented.

Written by the indexing model from the issue text.

Description

bug

Currently the definition of the case(s) for unions in <:< don't implement a particularly sane subtype relation. Nonetheless the current semantics are relied on, eg. in fragmentApplies. Probably unions should only relate as subtypes to other unions and we should introduce a separate relation for fragment applicability.

Dominant language
Scala
Stars
189
Forks
32
Avg merge
18h 27m
Merged PRs (30d)
21

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