LeanReact 0.1: expressing composable, provably correct React components in Lean
hargup13 · x · 2026-09-18
The author released LeanReact 0.1, aiming to express composable and correct React components in the Lean proof assistant.
Key idea: with ordinary React, each useState varies independently — a multi-step checkout becomes a 3×2×2×2×2 = 48-state space where only 10 states are valid; real components have far more states and developers almost always miss one. Lean's types rule out impossible states at the type level, moving correctness guarantees from runtime to compile time. The post walks through the multi-step checkout example in detail.
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