Type-Classes (in Scala 3)

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" summary

Scala 3 treats type classes as an officially supported pattern with givens and extension methods, opaque types and mirrors and saner macros for automatic derivation. The compiler proves constraints so the CanEqual multiversal equality enforces type-safe comparisons unless an instance is supplied. Implicit scope still finds instances in companions (put instances in the right roots) and Scala 3.7 flips prioritization so supertypes win over subtypes, avoiding many conflicts. Example: a working JSON codec is generated in about one hour using derivation and it works.

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" chapters (14)

1. 0:00Introduction
2. 1:51Object-oriented programming in Scala
3. 4:41Subtyping limitations
4. 6:05Type classes in Scala 2
5. 8:35Type classes in Scala 3
6. 11:28Type classes vs OOP
7. 13:13Multiversal equality
8. 16:04Type classes and proving
9. 18:52Design challenges
10. 21:24Implicit scope rules
11. 22:30Given prioritization in 3.7
12. 25:40Avoiding inheritance
13. 27:51Macros and derivation
14. 29:39Compile-time vs reflection

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