Add maybe types - #26814
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- Enabled by experimental.magic - Independent of language.postfixOps - Highest precedence
ExtractDependencies fell into a "NoDenotation cannot be cast to ClassDenotation" assertioin violation. When recompiling after some changes. This fix avoids that.
Otherwise the maybe logic does not work correctly. It would be nice if we could link explicit-nulls with magic, but that does not work since explicit-nulls is a global flag that has to be set when the compiler starts up. We can't even change it from run to run.
Special cases needed for subtyping, erasure, and pattern matching.
The erasure of Maybe changes after bootstrapped. So anything that touches it can compile only with the bootstrapped compiler.
Also: Drop $ in front of Maybe, no harm in using it directly, since it is a sealed trait. Also: Fix exhaustivity checking for Ok patterns
- Drop OK unapply call, which is known to be the identity - Simplify leading null test for maybe types
Also, move back bootstrapped library and tests to regular. Since we now inline Ok.unapply, we are no longer affected by difference in erasure between bootstrapped and non-bootstrapped.
Plus a lot more tests
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Needed to avoid erasure difference between bootstrapped and non-bootstrapped compilers.
So for T not nullable, we now have T? =:= T | Null.
We don't need it directly, since source programs use `?` instead. Also: Fix printing of maybe type trees.
Also: drop overfitted condition by Claude in space engine.
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To reduce added linecount we drop a bunch of tests that are straightforward Option -> ? substitutions.
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Trial balloon for a new kind of maybe type
T?.