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odersky opened this issue Jun 23, 2022 · 0 comments · Fixed by #15508
Closed

Cyclic reference in type is not detected #15507

odersky opened this issue Jun 23, 2022 · 0 comments · Fixed by #15508
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@odersky
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area:typer itype:bug
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3.2.1

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@odersky
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odersky commented Jun 23, 2022

Compiler version

3.2.0-RC1

Minimized code

type _NestedSet2[_] = Set[_NestedSet2[?]]

Output

Compiles, but reduces the right hand side to Set[Any].

Expectation

Definition should be rejected since it contains a cycle.
@odersky odersky added itype:bug stat:needs triage Every issue needs to have an "area" and "itype" label and removed stat:needs triage Every issue needs to have an "area" and "itype" label labels Jun 23, 2022
@odersky odersky self-assigned this Jun 23, 2022
odersky added a commit to dotty-staging/dotty that referenced this issue Jun 23, 2022
@odersky
Fix cycle detection for type aliases with wildcard arguments
b6b2d12 
scala#15507 escaped the cycle detector since when the right hand side was typechecked,
the type constructor _NestedSet2's type was `[X] <: Any` and the constructor was marked Provisional.

Fixes scala#15507
@odersky odersky mentioned this issue Jun 23, 2022
Merged
@Kordyjan Kordyjan added this to the 3.2.1 milestone Aug 1, 2023
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Fix cycle detection for type aliases with wildcard arguments dotty-staging/dotty
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@odersky @Kordyjan