apply Emily's suggestions

* add `PMaxTimeRangeWidth`
* several `Default` instances for testing
* a bunch of docstrings
* fix the tests/samples

agora-sample/Sample/Effect/GovernorMutation.hs

@@ -11,14 +11,22 @@ module Sample.Effect.GovernorMutation (
   mkEffectDatum,
 ) where
 
+--------------------------------------------------------------------------------
+
 import Agora.Effect.GovernorMutation (
   MutateGovernorDatum (..),
   mutateGovernorValidator,
  )
 import Agora.Governor (GovernorDatum (..))
 import Agora.Proposal (ProposalId (..), ProposalThresholds (..))
+
+--------------------------------------------------------------------------------
+
 import Plutarch.Api.V1 (mkValidator, validatorHash)
 import Plutarch.SafeMoney (Tagged (Tagged))
+
+--------------------------------------------------------------------------------
+
 import Plutus.V1.Ledger.Address (scriptHashAddress)
 import Plutus.V1.Ledger.Api (
   Address,
@@ -35,11 +43,12 @@ import Plutus.V1.Ledger.Api (
 import Plutus.V1.Ledger.Api qualified as Interval
 import Plutus.V1.Ledger.Value (AssetClass, assetClass)
 import Plutus.V1.Ledger.Value qualified as Value
+
+--------------------------------------------------------------------------------
+
 import Sample.Shared (
   authorityTokenSymbol,
-  defaultCreateProposalTimeRangeMaxDuration,
   defaultProposalThresholds,
-  defaultProposalTimingConfig,
   govAssetClass,
   govValidatorAddress,
   governor,
@@ -48,6 +57,12 @@ import Sample.Shared (
  )
 import Test.Util (datumPair, toDatumHash)
 
+--------------------------------------------------------------------------------
+
+import Data.Default.Class (Default (def))
+
+--------------------------------------------------------------------------------
+
 -- | The effect validator instance.
 effectValidator :: Validator
 effectValidator = mkValidator $ mutateGovernorValidator governor
@@ -103,8 +118,8 @@ mkEffectTxInfo newGovDatum =
         GovernorDatum
           { proposalThresholds = defaultProposalThresholds
           , nextProposalId = ProposalId 0
-          , proposalTimings = defaultProposalTimingConfig
+          , proposalTimings = def
-          , createProposalTimeRangeMaxDuration = defaultCreateProposalTimeRangeMaxDuration
+          , createProposalTimeRangeMaxWidth = def
           }
       governorInputDatum :: Datum
       governorInputDatum = Datum $ toBuiltinData governorInputDatum'
@@ -165,8 +180,8 @@ validNewGovernorDatum =
   GovernorDatum
     { proposalThresholds = defaultProposalThresholds
     , nextProposalId = ProposalId 42
-    , proposalTimings = defaultProposalTimingConfig
+    , proposalTimings = def
-    , createProposalTimeRangeMaxDuration = defaultCreateProposalTimeRangeMaxDuration
+    , createProposalTimeRangeMaxWidth = def
     }
 
 invalidNewGovernorDatum :: GovernorDatum
@@ -177,6 +192,6 @@ invalidNewGovernorDatum =
           { countVoting = Tagged (-1)
           }
     , nextProposalId = ProposalId 42
-    , proposalTimings = defaultProposalTimingConfig
+    , proposalTimings = def
-    , createProposalTimeRangeMaxDuration = defaultCreateProposalTimeRangeMaxDuration
+    , createProposalTimeRangeMaxWidth = def
     }

agora-sample/Sample/Governor.hs

@@ -56,6 +56,10 @@ import Agora.Proposal (
   emptyVotesFor,
  )
 import Agora.Proposal qualified as P
+import Agora.Proposal.Time (
+  ProposalStartingTime (ProposalStartingTime),
+  ProposalTimingConfig (..),
+ )
 import Agora.Stake (
   ProposalLock (..),
   Stake (..),
@@ -64,15 +68,9 @@ import Agora.Stake (
 
 --------------------------------------------------------------------------------
 
-import Agora.Proposal.Time (
-  ProposalStartingTime (ProposalStartingTime),
-  ProposalTimingConfig (..),
- )
 import Sample.Shared (
   authorityTokenSymbol,
-  defaultCreateProposalTimeRangeMaxDuration,
   defaultProposalThresholds,
-  defaultProposalTimingConfig,
   govAssetClass,
   govSymbol,
   govValidatorAddress,
@@ -91,6 +89,10 @@ import Test.Util (closedBoundedInterval, datumPair, toDatumHash)
 
 --------------------------------------------------------------------------------
 
+import Data.Default.Class (Default (def))
+
+--------------------------------------------------------------------------------
+
 {- | A valid 'ScriptContext' for minting GST.
 
     - Only the minting policy will be ran in the transaction.
@@ -119,8 +121,8 @@ mintGST =
         GovernorDatum
           { proposalThresholds = defaultProposalThresholds
           , nextProposalId = ProposalId 0
-          , proposalTimings = defaultProposalTimingConfig
+          , proposalTimings = def
-          , createProposalTimeRangeMaxDuration = defaultCreateProposalTimeRangeMaxDuration
+          , createProposalTimeRangeMaxWidth = def
           }
       governorOutputDatum :: Datum
       governorOutputDatum = Datum $ toBuiltinData governorOutputDatum'
@@ -214,8 +216,8 @@ createProposal =
         GovernorDatum
           { proposalThresholds = defaultProposalThresholds
           , nextProposalId = thisProposalId
-          , proposalTimings = defaultProposalTimingConfig
+          , proposalTimings = def
-          , createProposalTimeRangeMaxDuration = defaultCreateProposalTimeRangeMaxDuration
+          , createProposalTimeRangeMaxWidth = def
           }
       governorInputDatum :: Datum
       governorInputDatum = Datum $ toBuiltinData governorInputDatum'
@@ -245,7 +247,7 @@ createProposal =
                 , cosigners = [signer]
                 , thresholds = defaultProposalThresholds
                 , votes = emptyVotesFor effects
-                , timingConfig = defaultProposalTimingConfig
+                , timingConfig = def
                 , startingTime = proposalStartingTimeFromTimeRange validTimeRange
                 }
           )
@@ -392,8 +394,8 @@ mintGATs =
         GovernorDatum
           { proposalThresholds = defaultProposalThresholds
           , nextProposalId = ProposalId 5
-          , proposalTimings = defaultProposalTimingConfig
+          , proposalTimings = def
-          , createProposalTimeRangeMaxDuration = defaultCreateProposalTimeRangeMaxDuration
+          , createProposalTimeRangeMaxWidth = def
           }
       governorInputDatum :: Datum
       governorInputDatum = Datum $ toBuiltinData governorInputDatum'
@@ -428,7 +430,7 @@ mintGATs =
           , cosigners = [signer, signer2]
           , thresholds = defaultProposalThresholds
           , votes = proposalVotes
-          , timingConfig = defaultProposalTimingConfig
+          , timingConfig = def
           , startingTime = ProposalStartingTime 10
           }
       proposalInputDatum :: Datum
@@ -485,8 +487,8 @@ mintGATs =
       --
       validTimeRange =
         closedBoundedInterval
-          (defaultProposalTimingConfig.lockingTime + 11)
+          ((def :: ProposalTimingConfig).lockingTime + 11)
-          (defaultProposalTimingConfig.executingTime - 11)
+          ((def :: ProposalTimingConfig).executingTime - 11)
    in ScriptContext
         { scriptContextTxInfo =
             TxInfo
@@ -587,8 +589,8 @@ mutateState =
         GovernorDatum
           { proposalThresholds = defaultProposalThresholds
           , nextProposalId = ProposalId 5
-          , proposalTimings = defaultProposalTimingConfig
+          , proposalTimings = def
-          , createProposalTimeRangeMaxDuration = defaultCreateProposalTimeRangeMaxDuration
+          , createProposalTimeRangeMaxWidth = def
           }
       governorInputDatum :: Datum
       governorInputDatum = Datum $ toBuiltinData governorInputDatum'

agora-sample/Sample/Proposal.hs

@@ -16,9 +16,14 @@ module Sample.Proposal (
 ) where
 
 --------------------------------------------------------------------------------
+
 import Plutarch.Api.V1 (
   validatorHash,
  )
+import Plutarch.SafeMoney (Tagged (Tagged), untag)
+
+--------------------------------------------------------------------------------
+
 import Plutus.V1.Ledger.Api (
   Address (Address),
   Credential (ScriptCredential),
@@ -34,6 +39,7 @@ import Plutus.V1.Ledger.Api (
   TxOutRef (TxOutRef),
  )
 import Plutus.V1.Ledger.Value qualified as Value
+import PlutusTx.AssocMap qualified as AssocMap
 
 --------------------------------------------------------------------------------
 
@@ -51,13 +57,18 @@ import Agora.Proposal (
  )
 import Agora.Proposal.Time (ProposalStartingTime (ProposalStartingTime), ProposalTimingConfig (..))
 import Agora.Stake (ProposalLock (ProposalLock), Stake (..), StakeDatum (..))
-import Plutarch.SafeMoney (Tagged (Tagged), untag)
+
-import PlutusTx.AssocMap qualified as AssocMap
+--------------------------------------------------------------------------------
+
 import Sample.Shared
 import Test.Util (closedBoundedInterval, datumPair, toDatumHash, updateMap)
 
 --------------------------------------------------------------------------------
 
+import Data.Default.Class (Default (def))
+
+--------------------------------------------------------------------------------
+
 -- | This script context should be a valid transaction.
 proposalCreation :: ScriptContext
 proposalCreation =
@@ -78,7 +89,7 @@ proposalCreation =
                 , cosigners = [signer]
                 , thresholds = defaultProposalThresholds
                 , votes = emptyVotesFor effects
-                , timingConfig = defaultProposalTimingConfig
+                , timingConfig = def
                 , startingTime = proposalStartingTimeFromTimeRange validTimeRange
                 }
           )
@@ -90,8 +101,8 @@ proposalCreation =
               GovernorDatum
                 { proposalThresholds = defaultProposalThresholds
                 , nextProposalId = ProposalId 0
-                , proposalTimings = defaultProposalTimingConfig
+                , proposalTimings = def
-                , createProposalTimeRangeMaxDuration = defaultCreateProposalTimeRangeMaxDuration
+                , createProposalTimeRangeMaxWidth = def
                 }
           )
       govAfter :: Datum
@@ -101,8 +112,8 @@ proposalCreation =
               GovernorDatum
                 { proposalThresholds = defaultProposalThresholds
                 , nextProposalId = ProposalId 1
-                , proposalTimings = defaultProposalTimingConfig
+                , proposalTimings = def
-                , createProposalTimeRangeMaxDuration = defaultCreateProposalTimeRangeMaxDuration
+                , createProposalTimeRangeMaxWidth = def
                 }
           )
 
@@ -179,7 +190,7 @@ cosignProposal newSigners =
           , cosigners = [signer]
           , thresholds = defaultProposalThresholds
           , votes = emptyVotesFor effects
-          , timingConfig = defaultProposalTimingConfig
+          , timingConfig = def
           , startingTime = ProposalStartingTime 0
           }
       stakeDatum :: StakeDatum
@@ -190,7 +201,7 @@ cosignProposal newSigners =
       validTimeRange =
         closedBoundedInterval
           10
-          (defaultProposalTimingConfig.draftTime - 10)
+          ((def :: ProposalTimingConfig).draftTime - 10)
    in TxInfo
         { txInfoInputs =
             [ TxInInfo
@@ -300,7 +311,7 @@ voteOnProposal params =
           , cosigners = [stakeOwner]
           , thresholds = defaultProposalThresholds
           , votes = ProposalVotes initialVotes
-          , timingConfig = defaultProposalTimingConfig
+          , timingConfig = def
           , startingTime = ProposalStartingTime 0
           }
       proposalInputDatum :: Datum
@@ -389,7 +400,9 @@ voteOnProposal params =
       ---
 
       validTimeRange =
-        closedBoundedInterval (defaultProposalTimingConfig.draftTime + 1) (defaultProposalTimingConfig.votingTime - 1)
+        closedBoundedInterval
+          ((def :: ProposalTimingConfig).draftTime + 1)
+          ((def :: ProposalTimingConfig).votingTime - 1)
    in TxInfo
         { txInfoInputs =
             [ TxInInfo proposalRef proposalInput

agora-sample/Sample/Shared.hs

@@ -1,3 +1,5 @@
+{-# OPTIONS_GHC -Wno-orphans #-}
+
 {- |
 Module     : Sample.Shared
 Maintainer : emi@haskell.fyi
@@ -36,8 +38,6 @@ module Sample.Shared (
   proposalPolicySymbol,
   proposalValidatorHash,
   proposalValidatorAddress,
-  defaultProposalTimingConfig,
-  defaultCreateProposalTimeRangeMaxDuration,
   proposalStartingTimeFromTimeRange,
 
   -- ** Authority
@@ -78,12 +78,14 @@ import Agora.Proposal (
   ProposalThresholds (..),
  )
 import Agora.Proposal.Time (
+  MaxTimeRangeWidth (..),
   ProposalStartingTime (ProposalStartingTime),
   ProposalTimingConfig (..),
  )
 import Agora.Stake (Stake (..))
 import Agora.Treasury (treasuryValidator)
 import Agora.Utils (validatorHashToTokenName)
+import Data.Default.Class (Default (..))
 import Plutarch.Api.V1 (
   mintingPolicySymbol,
   mkMintingPolicy,
@@ -100,7 +102,6 @@ import Plutus.V1.Ledger.Api (
   Interval (..),
   LowerBound (..),
   MintingPolicy (..),
-  POSIXTime,
   POSIXTimeRange,
   PubKeyHash,
   TxOutRef (TxOutRef),
@@ -197,18 +198,27 @@ authorityToken = authorityTokenFromGovernor governor
 authorityTokenSymbol :: CurrencySymbol
 authorityTokenSymbol = authorityTokenSymbolFromGovernor governor
 
-defaultProposalTimingConfig :: ProposalTimingConfig
+{- | Default value of 'Agora.Governor.GovernorDatum.proposalTimings'.
-defaultProposalTimingConfig =
+     For testing purpose only.
-  ProposalTimingConfig
+-}
-    { draftTime = 50
+instance Default ProposalTimingConfig where
-    , votingTime = 1000
+  def =
-    , lockingTime = 2000
+    ProposalTimingConfig
-    , executingTime = 3000
+      { draftTime = 50
-    }
+      , votingTime = 1000
+      , lockingTime = 2000
+      , executingTime = 3000
+      }
 
-defaultCreateProposalTimeRangeMaxDuration :: POSIXTime
+{- | Default value of 'Agora.Governor.GovernorDatum.createProposalTimeRangeMaxWidth'.
-defaultCreateProposalTimeRangeMaxDuration = 10
+     For testing purpose only.
+-}
+instance Default MaxTimeRangeWidth where
+  def = MaxTimeRangeWidth 10
 
+{- | Get the starting time of a proposal, given a closed finite time range.
+     Tightness of the time range is not checked. See 'Agora.Proposal.Time.createProposalStartingTime'.
+-}
 proposalStartingTimeFromTimeRange :: POSIXTimeRange -> ProposalStartingTime
 proposalStartingTimeFromTimeRange
   (Interval (LowerBound (Finite l) True) (UpperBound (Finite u) True)) =

agora-test/Spec/Effect/GovernorMutation.hs

@@ -4,6 +4,7 @@ import Agora.Effect.GovernorMutation (mutateGovernorValidator)
 import Agora.Governor (GovernorDatum (..), GovernorRedeemer (MutateGovernor))
 import Agora.Governor.Scripts (governorValidator)
 import Agora.Proposal (ProposalId (..))
+import Data.Default.Class (Default (def))
 import Plutus.V1.Ledger.Api (ScriptContext (ScriptContext), ScriptPurpose (Spending))
 import Sample.Effect.GovernorMutation (
   effectRef,
@@ -29,8 +30,8 @@ tests =
               ( GovernorDatum
                   Shared.defaultProposalThresholds
                   (ProposalId 0)
-                  Shared.defaultProposalTimingConfig
+                  def
-                  Shared.defaultCreateProposalTimeRangeMaxDuration
+                  def
               )
               MutateGovernor
               ( ScriptContext
@@ -51,8 +52,8 @@ tests =
               ( GovernorDatum
                   Shared.defaultProposalThresholds
                   (ProposalId 0)
-                  Shared.defaultProposalTimingConfig
+                  def
-                  Shared.defaultCreateProposalTimeRangeMaxDuration
+                  def
               )
               MutateGovernor
               ( ScriptContext

agora-test/Spec/Governor.hs

@@ -16,6 +16,7 @@ module Spec.Governor (tests) where
 import Agora.Governor (GovernorDatum (..), GovernorRedeemer (..))
 import Agora.Governor.Scripts (governorPolicy, governorValidator)
 import Agora.Proposal (ProposalId (..))
+import Data.Default.Class (Default (def))
 import Sample.Governor (createProposal, mintGATs, mintGST, mutateState)
 import Sample.Shared qualified as Shared
 import Test.Tasty (TestTree, testGroup)
@@ -41,8 +42,8 @@ tests =
           ( GovernorDatum
               Shared.defaultProposalThresholds
               (ProposalId 0)
-              Shared.defaultProposalTimingConfig
+              def
-              Shared.defaultCreateProposalTimeRangeMaxDuration
+              def
           )
           CreateProposal
           createProposal
@@ -52,8 +53,8 @@ tests =
           ( GovernorDatum
               Shared.defaultProposalThresholds
               (ProposalId 5)
-              Shared.defaultProposalTimingConfig
+              def
-              Shared.defaultCreateProposalTimeRangeMaxDuration
+              def
           )
           MintGATs
           mintGATs
@@ -63,8 +64,8 @@ tests =
           ( GovernorDatum
               Shared.defaultProposalThresholds
               (ProposalId 5)
-              Shared.defaultProposalTimingConfig
+              def
-              Shared.defaultCreateProposalTimeRangeMaxDuration
+              def
           )
           MutateGovernor
           mutateState

agora-test/Spec/Proposal.hs

@@ -38,6 +38,7 @@ import Agora.Stake (
   StakeRedeemer (PermitVote, WitnessStake),
  )
 import Agora.Stake.Scripts (stakeValidator)
+import Data.Default.Class (Default (def))
 import Plutarch.SafeMoney (Tagged (Tagged))
 import Plutus.V1.Ledger.Api (ScriptContext (..), ScriptPurpose (..))
 import PlutusTx.AssocMap qualified as AssocMap
@@ -83,7 +84,7 @@ tests =
                           [ (ResultTag 0, AssocMap.empty)
                           , (ResultTag 1, AssocMap.empty)
                           ]
-                  , timingConfig = Shared.defaultProposalTimingConfig
+                  , timingConfig = def
                   , startingTime = ProposalStartingTime 0
                   }
               )
@@ -118,7 +119,7 @@ tests =
                             , (ResultTag 1, 4242)
                             ]
                         )
-                  , timingConfig = Shared.defaultProposalTimingConfig
+                  , timingConfig = def
                   , startingTime = ProposalStartingTime 0
                   }
               )

agora.cabal

@@ -114,6 +114,7 @@ common test-deps
     , agora
     , apropos
     , apropos-tx
+    , data-default-class
     , mtl
     , QuickCheck
     , quickcheck-instances

agora/Agora/Governor.hs

@@ -37,13 +37,17 @@ import Agora.Proposal (
   ProposalId (ProposalId),
   ProposalThresholds,
  )
-import Agora.Proposal.Time (PProposalTimingConfig, ProposalTimingConfig)
+import Agora.Proposal.Time (
+  MaxTimeRangeWidth,
+  PMaxTimeRangeWidth,
+  PProposalTimingConfig,
+  ProposalTimingConfig,
+ )
 import Agora.SafeMoney (GTTag)
 import Agora.Utils (tclet)
 
 --------------------------------------------------------------------------------
 
-import Plutarch.Api.V1 (PPOSIXTime)
 import Plutarch.DataRepr (
   DerivePConstantViaData (..),
   PDataFields,
@@ -56,7 +60,7 @@ import Plutarch.Unsafe (punsafeCoerce)
 
 --------------------------------------------------------------------------------
 
-import Plutus.V1.Ledger.Api (POSIXTime, TxOutRef)
+import Plutus.V1.Ledger.Api (TxOutRef)
 import Plutus.V1.Ledger.Value (AssetClass (..))
 import PlutusTx qualified
 
@@ -71,7 +75,7 @@ data GovernorDatum = GovernorDatum
   , proposalTimings :: ProposalTimingConfig
   -- ^ The timing configuration for proposals.
   --   Will get copied over upon the creation of proposals.
-  , createProposalTimeRangeMaxDuration :: POSIXTime
+  , createProposalTimeRangeMaxWidth :: MaxTimeRangeWidth
   -- ^ The maximum valid duration of a transaction that creats a proposal.
   }
   deriving stock (Show, GHC.Generic)
@@ -126,7 +130,7 @@ newtype PGovernorDatum (s :: S) = PGovernorDatum
           '[ "proposalThresholds" ':= PProposalThresholds
            , "nextProposalId" ':= PProposalId
            , "proposalTimings" ':= PProposalTimingConfig
-           , "createProposalTimeRangeMaxDuration" ':= PPOSIXTime
+           , "createProposalTimeRangeMaxWidth" ':= PMaxTimeRangeWidth
            ]
       )
   }

agora/Agora/Governor/Scripts.hs

@@ -307,7 +307,7 @@ governorValidator gov =
           @'[ "proposalThresholds"
             , "nextProposalId"
             , "proposalTimings"
-            , "createProposalTimeRangeMaxDuration"
+            , "createProposalTimeRangeMaxWidth"
             ]
           oldGovernorDatum
 
@@ -347,8 +347,8 @@ governorValidator gov =
                   ( #proposalThresholds .= oldGovernorDatumF.proposalThresholds
                       .& #nextProposalId .= pdata expectedNextProposalId
                       .& #proposalTimings .= oldGovernorDatumF.proposalTimings
-                      .& #createProposalTimeRangeMaxDuration
+                      .& #createProposalTimeRangeMaxWidth
-                        .= oldGovernorDatumF.createProposalTimeRangeMaxDuration
+                        .= oldGovernorDatumF.createProposalTimeRangeMaxWidth
                   )
           tcassert "Unexpected governor state datum" $
             newGovernorDatum #== expectedNewDatum
@@ -436,7 +436,7 @@ governorValidator gov =
               expectedVotes = pemptyVotesFor # pfromData proposalOutputDatum.effects
               expectedStartingTime =
                 createProposalStartingTime
-                  # oldGovernorDatumF.createProposalTimeRangeMaxDuration
+                  # oldGovernorDatumF.createProposalTimeRangeMaxWidth
                   # txInfoF.validRange
               -- Id, thresholds and timings should be copied from the old governor state datum.
               expectedProposalOut =

agora/Agora/Proposal.hs

@@ -349,7 +349,7 @@ deriving via
   instance
     (PConstantDecl ProposalVotes)
 
--- Plutarch version of 'pemptyVotesFor'.
+-- Plutarch-level version of 'emptyVotesFor'.
 pemptyVotesFor :: forall s a. (PIsData a) => Term s (PMap PResultTag a :--> PProposalVotes)
 pemptyVotesFor =
   phoistAcyclic $

agora/Agora/Proposal/Time.hs

@@ -13,11 +13,13 @@ module Agora.Proposal.Time (
   ProposalTime (..),
   ProposalTimingConfig (..),
   ProposalStartingTime (..),
+  MaxTimeRangeWidth (..),
 
   -- * Plutarch-land
   PProposalTime (..),
   PProposalTimingConfig (..),
   PProposalStartingTime (..),
+  PMaxTimeRangeWidth (..),
 
   -- * Compute periods given config and starting time.
   createProposalStartingTime,
@@ -108,6 +110,11 @@ data ProposalTimingConfig = ProposalTimingConfig
 
 PlutusTx.makeIsDataIndexed ''ProposalTimingConfig [('ProposalTimingConfig, 0)]
 
+-- | Represents the maximum width of a 'POSIXTimeRange'.
+newtype MaxTimeRangeWidth = MaxTimeRangeWidth {getMaxWidth :: POSIXTime}
+  deriving stock (Eq, Show, Ord, GHC.Generic)
+  deriving newtype (PlutusTx.ToData, PlutusTx.FromData, PlutusTx.UnsafeFromData)
+
 --------------------------------------------------------------------------------
 
 -- | Plutarch-level version of 'ProposalTime'.
@@ -173,6 +180,17 @@ deriving via
   instance
     (PConstantDecl ProposalTimingConfig)
 
+-- | Plutarch-level version of 'MaxTimeRangeWidth'.
+newtype PMaxTimeRangeWidth (s :: S)
+  = PMaxTimeRangeWidth (Term s PPOSIXTime)
+  deriving (PlutusType, PIsData, PEq, POrd) via (DerivePNewtype PMaxTimeRangeWidth PPOSIXTime)
+
+instance PUnsafeLiftDecl PMaxTimeRangeWidth where type PLifted PMaxTimeRangeWidth = MaxTimeRangeWidth
+deriving via
+  (DerivePConstantViaNewtype MaxTimeRangeWidth PMaxTimeRangeWidth PPOSIXTime)
+  instance
+    (PConstantDecl MaxTimeRangeWidth)
+
 --------------------------------------------------------------------------------
 
 -- FIXME: Orphan instance, move this to plutarch-extra.
@@ -180,11 +198,12 @@ instance AdditiveSemigroup (Term s PPOSIXTime) where
   (punsafeCoerce @_ @_ @PInteger -> x) + (punsafeCoerce @_ @_ @PInteger -> y) = punsafeCoerce $ x + y
 
 {- | Get the starting time of a proposal, from the 'Plutus.V1.Ledger.Api.txInfoValidPeriod' field.
-     For every proposal, this is only meant to run once upon creation.
+     For every proposal, this is only meant to run once upon creation. Given time range should be
+     tight enough, meaning that the width of the time range should be less than the maximum value.
 -}
-createProposalStartingTime :: forall (s :: S). Term s (PPOSIXTime :--> PPOSIXTimeRange :--> PProposalStartingTime)
+createProposalStartingTime :: forall (s :: S). Term s (PMaxTimeRangeWidth :--> PPOSIXTimeRange :--> PProposalStartingTime)
 createProposalStartingTime = phoistAcyclic $
-  plam $ \maxDuration iv -> unTermCont $ do
+  plam $ \(pto -> maxDuration) iv -> unTermCont $ do
     currentTimeF <-
       tcont $
         pletFields @'["lowerBound", "upperBound"] $