Assert field magnitude at control-flow join #1673
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As I was re-reading the xonly method I noticed that the author had taken some care about the magnitude of
gin each branch. It's probably worth documenting magnitude assumptions when control flows join like this.Actually I would even prefer a new field method (perhaps
_fe_join) that calls SECP256K1_FE_VERIFY_MAGNITUDE, and then sets the magnitude to that value. That would be more in line with the static analysis view of magnitudes that I recall being discussed, though I have not been following closely lately.