Alternative fix for #10044 #15129
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Alternative fix for #10044 #15129
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odersky
commented
May 6, 2022
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I think I found and fixed the bug with signature generation. |
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@smarter ping for review |
This addresses the specific problem raised by scala#10044: A denotation of a NamedType goes from a UniqueRefDenotation to a SymDenotation after erasure and is then not reset to the original since the SymDenotation is valid at all phases. We remember in this case in the NamedType the first phase in which the SymDenotaton is valid and force a recompute in earlier phases. Fixes scala#10044
smarter
requested changes
May 17, 2022
| denot match | ||
| case denot: SymDenotation | ||
| if denot.validFor.firstPhaseId < ctx.phase.id | ||
| && lastDenot != null |
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I'm not completely sure that we won't run into issues where lastDenot didn't exist, but we need to get the denotation at an earlier phase in a subsequent run or via time-travelling. How expensive would it be to always create UniqueRefDenotation after erasure?
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I prefer caution here. I don't have the time to look into a change like this, which looks risky to me.
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This is a better alternative to fix #10044 than #15120. Unfortunately, it fails
dotty.tools.dotc.BootstrappedOnlyCompilationTests.runWithCompiler in the
tasty interpreter test. Here I see:
If I turn on printing in line 2583 in Types.scala, I see the last output as follows:
So it does overwrite, and the overwrite looks OK, but somehow changing a SymDenotation with a UniqueRefDenotation for the same symbol messes up generic signature generation.
Can someone help me digging deeper here?