Simon Peyton Jones pushed to branch wip/T26548 at Glasgow Haskell Compiler / GHC

Commits:

• 57dcbdf7
  by Simon Peyton Jones at 2025-11-26T09:34:55+00:00

  Try making Reduction strict in its Coercion
  
  Just an experiment. The comment says
  
  -- N.B. the 'Coercion' field must be lazy: see for instance
  -- GHC.Tc.Solver.Rewrite.rewrite_tyvar2 which returns an error in the 'Coercion'
  -- field when dealing with a Derived constraint (which is OK as this Coercion
  -- gets ignored later).  We might want to revisit the strictness once Deriveds
  -- are removed.
  
  But Deriveds are in the rear view mirror.
  

1 changed file:

• compiler/GHC/Core/Reduction.hs

Changes:

 -- See Note [The Reduction type].

 data Reduction =

   Reduction

-    { reductionCoercion    :: Coercion

+    { reductionCoercion    :: !Coercion

     , reductionReducedType :: !Type

     }

 -- N.B. the 'Coercion' field must be lazy: see for instance GHC.Tc.Solver.Rewrite.rewrite_tyvar2