{
  "$type": "site.standard.document",
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  "path": "/t/pre-rfc-flow-directed-monomorphization-collection-in-mir/24366#post_3",
  "publishedAt": "2026-06-02T16:38:59.000Z",
  "site": "https://internals.rust-lang.org",
  "textContent": "Thanks for your advice!\n\nI have updated the pre-rfc. Link to the paper is attached.\n\nAnd in summary, the motivation is:\n\n  * **Finite lowering of hidden type flow.** `impl Trait`, `async fn`, TAIT, and RPITIT introduce opaque but concrete types. A type-flow graph makes their dependence on generic parameters explicit.\n\n  * **Closed-world generic dispatch.** A generic `dyn` method such as `encode<T>` is not open-world object-safe, but it may have a finite set of reachable instantiations in a closed world. Flow analysis is the decision procedure for that lowering.\n\n  * **Higher-rank and existential-like specialization.** The paper shows that these forms are monomorphizable when type flow has a finite solution; they do not require fundamentally different mechanisms. This makes powerful features possible for rust.\n\n  * **Non-finite cases are rejected structurally.** A cycle such as `T ↦ Option<T>` is evidence that specialization does not close; the compiler need not discover this by recursive expansion.\n\n\n",
  "title": "[Pre-RFC] Flow-Directed Monomorphization Collection in MIR"
}