add MINIMAL pragma to ord

[aleeusgr]

addresses #6270

• fix PlutusTx.Ord
• check the existence of other minimal pragmas where such applies
  • get the list of all Type Classes in plinth
    git grep -e "^class .* where" -- **/*.hs
  • get the list of Type Classes where the pragma needs to be added.
• fix commit signing

Background

Ord is a type class that defines a total ordering for types.

A pragma is a special instruction or directive that provides additional information to the compiler, allowing for optimizations or modifications in how the code is processed. Pragmas are denoted by the syntax {-# ... #-}, and they do not generally affect the semantic meaning of the program, but they can influence performance and behavior during compilation.

the MINIMAL pragma is used to specify the minimal complete definition of a type class, indicating which methods must be implemented for an instance of that class. This is particularly useful for classes that have methods with circular defaults, ensuring that instances adhere to a defined interface.

https://downloads.haskell.org/~ghc/7.8.1/docs/html/users_guide/pragmas.html

base

Checklist

Pre-submit checklist:

• Branch
  • Tests are provided (if possible)
  • Commit sequence broadly makes sense
  • Key commits have useful messages
  • Changelog fragments have been written (if appropriate)
  • Relevant tickets are mentioned in commit messages
  • Formatting, PNG optimization, etc. are updated
• PR
  • (For external contributions) Corresponding issue exists and is linked in the description
  • Targeting master unless this is a cherry-pick backport
  • Self-reviewed the diff
  • Useful pull request description
  • Reviewer requested

[aleeusgr]

$ git grep -e "^class .* where" -- **/*.hs

output

src/PlutusTx/Applicative.hs:class Functor f => Applicative f where
src/PlutusTx/Blueprint/Class.hs:class HasBlueprintSchema (t :: Type) (referencedTypes :: [Type]) where
src/PlutusTx/Blueprint/Definition/Derive.hs:class DefinitionsFor' referencedTypes acc where
src/PlutusTx/Blueprint/Definition/Unroll.hs:class HasBlueprintDefinition (t :: Type) where
src/PlutusTx/Builtins/HasBuiltin.hs:class PLC.DefaultUni `PLC.Contains` a => HasToBuiltin a where
src/PlutusTx/Builtins/HasBuiltin.hs:class HasToBuiltin (FromBuiltin arep) => HasFromBuiltin arep where
src/PlutusTx/Builtins/HasOpaque.hs:class HasToOpaque a arep | a -> arep where
src/PlutusTx/Builtins/HasOpaque.hs:class HasFromOpaque arep a | arep -> a where
src/PlutusTx/Builtins/HasOpaque.hs:class MkNil arep where
src/PlutusTx/Enum.hs:class Enum a where
src/PlutusTx/Eq.hs:class Eq a where
src/PlutusTx/Foldable.hs:class Foldable t where
src/PlutusTx/Functor.hs:class Functor f where
src/PlutusTx/IsData/Class.hs:class ToData (a :: Type) where
src/PlutusTx/IsData/Class.hs:class FromData (a :: Type) where
src/PlutusTx/IsData/Class.hs:class UnsafeFromData (a :: Type) where
src/PlutusTx/Lattice.hs:class JoinSemiLattice a where
src/PlutusTx/Lattice.hs:class MeetSemiLattice a where
src/PlutusTx/Lattice.hs:class JoinSemiLattice a => BoundedJoinSemiLattice a where
src/PlutusTx/Lattice.hs:class MeetSemiLattice a => BoundedMeetSemiLattice a where
src/PlutusTx/Lift/Class.hs:class Typeable uni (a :: k) where
src/PlutusTx/Lift/Class.hs:class Lift uni a where
src/PlutusTx/Monoid.hs:class Semigroup a => Monoid a where
src/PlutusTx/Monoid.hs:class Monoid a => Group a where
src/PlutusTx/Numeric.hs:class AdditiveSemigroup a where
src/PlutusTx/Numeric.hs:class AdditiveSemigroup a => AdditiveMonoid a where
src/PlutusTx/Numeric.hs:class AdditiveMonoid a => AdditiveGroup a where
src/PlutusTx/Numeric.hs:class MultiplicativeSemigroup a where
src/PlutusTx/Numeric.hs:class MultiplicativeSemigroup a => MultiplicativeMonoid a where
src/PlutusTx/Numeric.hs:class (Ring s, AdditiveGroup v) => Module s v | v -> s where
src/PlutusTx/Ord.hs:class Eq a => Ord a where
src/PlutusTx/Semigroup.hs:class Semigroup a where
src/PlutusTx/Show/TH.hs:class Show a where
src/PlutusTx/Traversable.hs:class (Functor t, Foldable t) => Traversable t where

[effectfully]

Looks good, let's wait for Kenneth to respond and then we'll either ignore the warning in the nofib file or keep your change.

[effectfully]

@kwxm do you remember anything about the nofib implementation? Is it fine to make this change here? Should we just disable the warning not allowing us to make this change?

[effectfully]

OK, whatever, @aleeusgr could you please just add

{-# OPTIONS_GHC -Wno-missing-methods #-}

to the top of the file and that's it?

[effectfully]

... and keep the original

(a := b) < (a' := b') = (a<a') || (a==a' && b < b')

definition.

[effectfully]

Thanks for the list of the classes! I'll review it myself, that won't block the PR.

[effectfully]

Eek, I'm an idiot and forgot about this one. Sorry! Looking into it.

[effectfully]

The only other place where we might need a MINIMAL pragma is PlutusTx.Enum.Enum, but it doesn't have the default implementations for some reason, so let's ignore it. This PR looks good to me, but please address the comment above and you also need to sign your commits, otherwise merging is blocked and I can't do anything about it.