Fix unsound constant folding of x in [x] for NaN values#1374
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Matching an identifier needle against a list element by name assumes the value is equal to itself, which is not true of a NaN double, so the optimizer rewrote expressions that evaluate to false into true. Limit the identifier match to the scalar types that cannot hold a NaN.
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TristonianJones
approved these changes
Jul 23, 2026
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Constant folding rewrites
x in [x]totrueMatching the needle against a list element by identifier name assumes the value is equal to itself, which does not hold for a NaN double: with
xbound to NaN,x in [1, 2, x]evaluates tofalsebefore optimization andtrueafter. The identifier match is now limited to the scalar types that cannot carry a NaN, so dyn, double, and aggregate needles keep their runtime behavior.