Promises Are Made to be Broken
summary
Presents a concrete migration: a dynamic analyzer called LazR that generates strictness signatures for R functions (52K functions, 204K parameters inferred) and validates them by running 2,000 client packages with only 0.56% of client programs broken. Signatures are shipped per package and read by the VM; a modified JIT (Řs) that removes promises yields a 1.17× average speedup and large reductions in promise allocations, while some signatures require manual inspection to avoid rare unsoundness.
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