fix: invalid folded mutable constant value #250
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katat
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mimoo
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Jan 20, 2025
| for ii in 0..3 { | ||
| loopvar = loopvar + 1; | ||
| } | ||
| let arr = gen(loopvar); |
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I'm not sure I understand why this code shouldn't compile
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Because we don't support for loop unrolling, so the loopvar won't end up with the correct constant value during MAST.
With the wrong constant value for the loopvar, the generic function will be instantiated with wrong generic parameter.
So loopvar should be marked as a non constant field.
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what would it take to make this code work though? I feel like we should support simple constant folding like this
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as long as the gen(loopvar) is not accepting the loopvar as its const generic parameter, it would work.
mimoo
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Jan 22, 2025
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When mutable constant variable is modified in a for loop, it should be marked as a non constant field.
Otherwise the MAST phase will try to constant fold that variable into wrong constant value, because we don't support unrolling in for loop.