topdown/parse_units: Use big.Rat for units parsing. #4857
Merged
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Previously, we used
big.Float
for units parsing, but this resulted in occasional rounding issues, due to values like0.001
not being perfectly representable in floating-point format.This issue was fixed by switching units parsing to use
big.Rat
, since Rationals can generally handle such quantities with perfect precision.A few new regression test cases have been added to the test suite, lifted almost verbatim from the original issue.
Fixes #4856.