Definition-Checked Generics - Part 2 - The Why and How

This talk explores definition-checked generics and how they compare with C++20 concepts and approaches in Swift and Rust. It examines challenges such as undecidability, non-termination, and coherence, along with proposed approaches in Carbon.

Syllabus

Introduction
Outline
Open Design
Type Equality
Types
Rewrite Rules
Swift
Rust
Carbon
modal constraints
implicit conversion
summary
always terminate
ignore
recursion limit
recursion limits
disallow recursion
use cases
refinement
strictly more complex
Proof
Possible Improvements
Conclusion
Coherence
Trait Coherence
Decoder Ring
retroactive conformance
glue code
subtle bugs
similar disconnect
Swift regret
No retroactive performance
Coherent
ORF
Overlap Rule
Example
Orphan Rules
Root Cause
Rebalancing Coherence
Adapter
Other Questions
Conversion
Specialization