module_ m rewrites each function body, folding the conventional dense-switch shape — a stack of void blocks with a br_table in the innermost and a case body after each block — into a high-level dispatch with every case an arm. The outermost case's body is the code following the outermost block, so a block is folded together with the statements after it. This recovers the jump-table idiom when decompiling WAT/WASM to Wax (and lets a Wax dispatch survive a round trip through the binary).

Folding is the exact inverse of Ast_utils.lower_dispatch, so re-lowering reproduces the original blocks byte-for-byte and the rewrite always preserves runtime semantics. Meant to run on From_wasm.module_ output, before Sink_let.module_ (which would otherwise sink locals into the case blocks and hide the shape).