fix(checker): validate sortBy order argument type #912
+48
−16
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The sortBy and sort functions accept an optional order argument that must be "asc" or "desc". Previously, passing a non-string value would cause a panic due to an unsafe type assertion in the VM. This adds compile-time validation in the type checker and defensive runtime checks in both the VM and builtin implementations to return proper errors instead of panicking. Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>
antonmedv
approved these changes
Jan 23, 2026
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Motivation
OSS-Fuzz discovered a panic in #910 when the
sortByfunction receives a non-string value as its third (order) argument. The panic occurred because the VM performed a type assertionvm.pop().(string)without verifying the type first. The documentation shows the order argument accepts "asc" or "desc", but there was no validation preventing other types from being passed.Changes
The type checker now validates the
sortBy's third argument is a string type, producing a compile-time error. For dynamic cases where type information isn't available at compile time, the VM and builtinsortfunction now use type assertions that return errors instead of panicking. A regression test reproduces the exact fuzz scenario.Further comments
This PR also removes three expressions from the generated test cases. These passed non-string values (integers and arrays) as the order argument. These appeared to work because the optimiser folded the patterns like
x && falsetofalseat compile time. Meaning thesortBycalls were never executed.If I understood the test corpus & the generator correctly, these test cases won't end up re-generated as they are now omitted as invalid ones.