Optimize Effect.map with dedicated OP_MAP opcode (inspired by ZIO's Mapped)

[civilizeddev]

Hi Effect team! 👋

I'd like to propose a performance optimization for Effect.map inspired by recent work in the ZIO.

🔍 Current Situation

Currently, Effect.map is implemented as:

flatMap(self, (a) => sync(() => f(a)))

This involves 3 dispatch cycles and intermediate allocations for each map operation.

💡 Proposed Idea

Add a dedicated OP_MAP opcode with continuation chaining, similar to ZIO's Mapped operation.

Background: My colleague originally proposed this optimization for zio-prelude (PR #1607), and ZIO maintainers recently adopted this idea for ZIO core (PR #10405).

The key optimization is to apply continuation chaining (similar to OP_SYNC) to directly call the next continuation instead of returning a new primitive, reducing dispatch cycles from 3 to 2.

📊 Preliminary Results

I've implemented a prototype and ran some benchmarks:

Scenario	Improvement
Short map chains (3 ops)	+11%
Deep map chains (100 ops)	+33%
Latency reduction	17-28%

All existing functionality tests pass (error handling, Effect.gen integration, etc.).

💭 Thoughts

To be honest, I don't have deep knowledge of Effect's internals - just coded up a prototype based on vibes and following the OP_SYNC pattern. If you're curious to take a look, I'm happy to open a draft PR!

Let me know if this is worth exploring further 🙂