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makeLenses regression in lens-5 #972
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RyanGlScott
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Feb 24, 2021
Previously, `buildStab` would not consider kind variables when determining which type variables need to be fixed in a generated `Lens`'s type signature. This was not a problem in older versions of `lens`, which aggressively dropped kind variables, but now that `lens` attempts to include kind variables in generated type signatures, this problem has risen to the surface, resulting in the problems observed in #972. The solution is to take the set of fixed type variables in `buildStab` and close over kind variables. For more information, refer to the comments I have left near `closeOverKinds`. Fixes #972.
RyanGlScott
added a commit
that referenced
this issue
Feb 24, 2021
Previously, `buildStab` would not consider kind variables when determining which type variables need to be fixed in a generated `Lens`'s type signature. This was not a problem in older versions of `lens`, which aggressively dropped kind variables, but now that `lens` attempts to include kind variables in generated type signatures, this problem has risen to the surface, resulting in the problems observed in #972. The solution is to take the set of fixed type variables in `buildStab` and close over kind variables. For more information, refer to the comments I have left near `closeOverKinds`. Fixes #972.
See #973 for a fix. |
RyanGlScott
added a commit
that referenced
this issue
Feb 24, 2021
Previously, `buildStab` would not consider kind variables when determining which type variables need to be fixed in a generated `Lens`'s type signature. This was not a problem in older versions of `lens`, which aggressively dropped kind variables, but now that `lens` attempts to include kind variables in generated type signatures, this problem has risen to the surface, resulting in the problems observed in #972. The solution is to take the set of fixed type variables in `buildStab` and close over kind variables. For more information, refer to the comments I have left near `closeOverKinds`. Fixes #972.
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The following code, minimized from the
hgeometry-combinatorial-0.11.0.0
library, compiles successfully withlens-4.19.2
:However, it fails to compile with
lens-5
:The immediate culprit is the type that
lens
generates fordirection
, as shown in the-ddump-splices
output above:This has only one
s
type variable,s_a53w
, but it attempts to give it two different kinds,k_a546
andk_a54E
.The text was updated successfully, but these errors were encountered: