[Git][ghc/ghc][master] template-haskell: Improve documentation of strictness annotation types

[Marge Bot (@marge-bot)]

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC


Commits:
09ec7de2 by Teo Camarasu at 2022-10-21T13:23:07-04:00
template-haskell: Improve documentation of strictness annotation types

Before it was undocumentated that DecidedLazy can be returned by
reifyConStrictness for strict fields. This can happen when a field has
an unlifted type or its the single field of a newtype constructor.

Fixes #21380

- - - - -


1 changed file:

- libraries/template-haskell/Language/Haskell/TH/Syntax.hs


Changes:

=====================================
libraries/template-haskell/Language/Haskell/TH/Syntax.hs
=====================================
@@ -2617,24 +2617,36 @@ type Cxt = [Pred]                 -- ^ @(Eq a, Ord b)@
 -- be tuples of other constraints.
 type Pred = Type
 
+-- | 'SourceUnpackedness' corresponds to unpack annotations found in the source code.
+--
+-- This may not agree with the annotations returned by 'reifyConStrictness'.
+-- See 'reifyConStrictness' for more information.
 data SourceUnpackedness
   = NoSourceUnpackedness -- ^ @C a@
   | SourceNoUnpack       -- ^ @C { {\-\# NOUNPACK \#-\} } a@
   | SourceUnpack         -- ^ @C { {\-\# UNPACK \#-\} } a@
         deriving (Show, Eq, Ord, Data, Generic)
 
+-- | 'SourceStrictness' corresponds to strictness annotations found in the source code.
+--
+-- This may not agree with the annotations returned by 'reifyConStrictness'.
+-- See 'reifyConStrictness' for more information.
 data SourceStrictness = NoSourceStrictness    -- ^ @C a@
                       | SourceLazy            -- ^ @C {~}a@
                       | SourceStrict          -- ^ @C {!}a@
         deriving (Show, Eq, Ord, Data, Generic)
 
 -- | Unlike 'SourceStrictness' and 'SourceUnpackedness', 'DecidedStrictness'
--- refers to the strictness that the compiler chooses for a data constructor
--- field, which may be different from what is written in source code. See
--- 'reifyConStrictness' for more information.
-data DecidedStrictness = DecidedLazy
-                       | DecidedStrict
-                       | DecidedUnpack
+-- refers to the strictness annotations that the compiler chooses for a data constructor
+-- field, which may be different from what is written in source code.
+--
+-- Note that non-unpacked strict fields are assigned 'DecidedLazy' when a bang would be inappropriate,
+-- such as the field of a newtype constructor and fields that have an unlifted type.
+--
+-- See 'reifyConStrictness' for more information.
+data DecidedStrictness = DecidedLazy -- ^ Field inferred to not have a bang.
+                       | DecidedStrict -- ^ Field inferred to have a bang.
+                       | DecidedUnpack -- ^ Field inferred to be unpacked.
         deriving (Show, Eq, Ord, Data, Generic)
 
 -- | A single data constructor.



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/09ec7de23ea826cb7ac25cb96a214808693de377

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/09ec7de23ea826cb7ac25cb96a214808693de377
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