[ryansolid]

Requested by Ryan · project thread

Ruled 2026-10-28 in the thread. Design doc: https://claude.ai/artifact/8Lv3dy6NY3cwwgy7U2B2Fj

What changes

• AC-1b, inferred action. An arrow in imperative scope, including an event handler, is an action when its own statements contain optimistic, affects, or both a write to a source and a statement-level await. It lowers to Solid's action() the same way action { … } does, so nothing is added at run time. An effect's apply block is never inferred, because its return value is the cleanup (EF-5). A guess there stays OPTIMISTIC_OUTSIDE_HOLD, and the message now says to declare an action.
• AC-1c, HELD_WRITE. Only for inferred actions: a plain write that reaches an await is an error. The fix depends on the write's purpose: optimistic for ephemeral state, onFlush for a reset, or a declared action to hold the write on purpose. Declared actions are not checked, because holding a write is what a transition is for (S-solid-20).
• AC-1d, STALE_OWN_READ. In every imperative run, reading a source the same change has already written is an error, matched key by key. The read would get the committed value (W-4). I confirmed in Solid 2.0.0-rc.19 that action() behaves the same way after a yield.
• Both checks follow calls into local closures (let f = () => { … }; f()).
• Shared analysis: ref/src/infer.ts, ported to compiler/src/infer.rs. Wired into the checker, interpreter, ref lowering, oracle, and crate check and emit.
• Spec: 02 (SC-4, W-3, W-4), 05 H-11, 06 (AC-1, AC-1b, AC-1c, AC-1d, AC-3, AC-5, diagnostics), 07 §5 and decision 17, 11, and 99. The guide's §3 and §5 are updated too.
• New scenarios S-infer-1 to S-infer-5. S-check-1's row handler read hits right after writing it, which was stale, so it now uses a local. S-solid-32's rejected handler guess now compiles, since the handler is inferred as an action, so it is a frames variant instead.

Checks (Solid next @ d2323b0, rc.19)

• interpreter, oracle, compiled (ref and RX_CRATE=1): 104/104
• ssr: 97 pass, 7 skip
• types: 143/143
• crate: 303/303 agree; --lower 175/175
• cargo test: pass

Not done: the language server doesn't show "inferred action" on hover yet, because hover comes from TypeScript over the projection.

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