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Diffstat (limited to 'docs/users_guide/9.2.1-notes.rst')
| -rw-r--r-- | docs/users_guide/9.2.1-notes.rst | 44 |
1 files changed, 41 insertions, 3 deletions
diff --git a/docs/users_guide/9.2.1-notes.rst b/docs/users_guide/9.2.1-notes.rst index b691fc0537..aa495444db 100644 --- a/docs/users_guide/9.2.1-notes.rst +++ b/docs/users_guide/9.2.1-notes.rst @@ -43,14 +43,52 @@ Compiler - ``Void#`` is now a type synonym for the unboxed tuple ``(# #)``. Code using ``Void#`` now has to enable :extension:`UnboxedTuples`. +``ghc`` library +~~~~~~~~~~~~~ + +- The ``con_args`` field of ``ConDeclGADT`` has been renamed to ``con_g_args``. + This is because the type of ``con_g_args`` is now different from the type of + the ``con_args`` field in ``ConDeclH98``: :: + + data ConDecl pass + = ConDeclGADT + { ... + , con_g_args :: HsConDeclGADTDetails pass -- ^ Arguments; never infix + , ... + } + + | ConDeclH98 + { ... + , con_args :: HsConDeclH98Details pass -- ^ Arguments; can be infix + , ... + } + + Where: :: + + -- Introduced in GHC 9.2; was called `HsConDeclDetails` in previous versions of GHC + type HsConDeclH98Details pass + = HsConDetails (HsScaled pass (LBangType pass)) (XRec pass [LConDeclField pass]) + + -- Introduced in GHC 9.2 + data HsConDeclGADTDetails pass + = PrefixConGADT [HsScaled pass (LBangType pass)] + | RecConGADT (XRec pass [LConDeclField pass]) + + Unlike Haskell98-style constructors, GADT constructors cannot be declared + using infix syntax, which is why ``HsConDeclGADTDetails`` lacks an + ``InfixConGADT`` constructor. + + As a result of all this, the ``con_args`` field is now partial, so using + ``con_args`` as a top-level field selector is discouraged. + ``base`` library ~~~~~~~~~~~~~~~~ -- It's possible now to promote the ``Natural`` type: :: - +- It's possible now to promote the ``Natural`` type: :: + data Coordinate = Mk2D Natural Natural type MyCoordinate = Mk2D 1 10 - + The separate kind ``Nat`` is removed and now it is just a type synonym for ``Natural``. As a consequence, one must enable ``TypeSynonymInstances`` in order to define instances for ``Nat``. |