Clever Workaround for Conflicting Blanket Implementations in Rust
2025-07-04
Rust's trait system is powerful but strict about avoiding ambiguity in blanket implementations. The author encountered this while building Joydb, needing to support two mutually exclusive implementations of the `Adapter` trait: `UnifiedAdapter` and `PartitionedAdapter`. A direct approach using blanket implementations failed. The solution, detailed in this post, uses marker structs (`Unified` and `Partitioned`), a helper trait (`BlanketAdapter`), and an associated type within the `Adapter` trait. This cleverly allows for both behaviors without violating Rust's coherence rules, maintaining good code ergonomics and maintainability.
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Blanket Implementations