diff --git a/cabal-install-solver/cabal-install-solver.cabal b/cabal-install-solver/cabal-install-solver.cabal
index fe440a78963..a3df740ea97 100644
--- a/cabal-install-solver/cabal-install-solver.cabal
+++ b/cabal-install-solver/cabal-install-solver.cabal
@@ -77,7 +77,6 @@ library
     Distribution.Solver.Modular.Version
     Distribution.Solver.Modular.WeightedPSQ
     Distribution.Solver.Types.ComponentDeps
-    Distribution.Solver.Types.ConstraintSource
     Distribution.Solver.Types.DependencyResolver
     Distribution.Solver.Types.Flag
     Distribution.Solver.Types.InstalledPreference
diff --git a/cabal-install-solver/src/Distribution/Solver/Modular.hs b/cabal-install-solver/src/Distribution/Solver/Modular.hs
index 2aac240318f..b3440219e0b 100644
--- a/cabal-install-solver/src/Distribution/Solver/Modular.hs
+++ b/cabal-install-solver/src/Distribution/Solver/Modular.hs
@@ -58,7 +58,7 @@ import Distribution.Verbosity
 
 -- | Ties the two worlds together: classic cabal-install vs. the modular
 -- solver. Performs the necessary translations before and after.
-modularResolver :: SolverConfig -> DependencyResolver loc
+modularResolver :: (Typeable cs, Show cs, Eq cs) => SolverConfig -> DependencyResolver loc cs
 modularResolver sc (Platform arch os) cinfo iidx sidx pkgConfigDB pprefs pcs pns =
   uncurry postprocess <$> -- convert install plan
   solve' sc cinfo idx pkgConfigDB pprefs gcs pns
@@ -113,12 +113,13 @@ modularResolver sc (Platform arch os) cinfo iidx sidx pkgConfigDB pprefs pcs pns
 -- Using the full log from a rerun of the solver ensures that the log is
 -- complete, i.e., it shows the whole chain of dependencies from the user
 -- targets to the conflicting packages.
-solve' :: SolverConfig
+solve' :: (Typeable cs, Eq cs, Show cs)
+       => SolverConfig
        -> CompilerInfo
        -> Index
        -> PkgConfigDb
        -> (PN -> PackagePreferences)
-       -> Map PN [LabeledPackageConstraint]
+       -> Map PN [LabeledPackageConstraint cs]
        -> Set PN
        -> Progress String String (Assignment, RevDepMap)
 solve' sc cinfo idx pkgConfigDB pprefs gcs pns =
diff --git a/cabal-install-solver/src/Distribution/Solver/Modular/IndexConversion.hs b/cabal-install-solver/src/Distribution/Solver/Modular/IndexConversion.hs
index 72d0b8193e3..cabb0fe8863 100644
--- a/cabal-install-solver/src/Distribution/Solver/Modular/IndexConversion.hs
+++ b/cabal-install-solver/src/Distribution/Solver/Modular/IndexConversion.hs
@@ -53,7 +53,7 @@ import Distribution.Solver.Modular.Version
 -- resolving these situations. However, the right thing to do is to
 -- fix the problem there, so for now, shadowing is only activated if
 -- explicitly requested.
-convPIs :: OS -> Arch -> CompilerInfo -> Map PN [LabeledPackageConstraint]
+convPIs :: OS -> Arch -> CompilerInfo -> Map PN [LabeledPackageConstraint cs]
         -> ShadowPkgs -> StrongFlags -> SolveExecutables
         -> SI.InstalledPackageIndex -> CI.PackageIndex (SourcePackage loc)
         -> Index
@@ -153,14 +153,14 @@ convIPId dr comp idx ipid =
 
 -- | Convert a cabal-install source package index to the simpler,
 -- more uniform index format of the solver.
-convSPI' :: OS -> Arch -> CompilerInfo -> Map PN [LabeledPackageConstraint]
+convSPI' :: OS -> Arch -> CompilerInfo -> Map PN [LabeledPackageConstraint cs]
          -> StrongFlags -> SolveExecutables
          -> CI.PackageIndex (SourcePackage loc) -> [(PN, I, PInfo)]
 convSPI' os arch cinfo constraints strfl solveExes =
     L.map (convSP os arch cinfo constraints strfl solveExes) . CI.allPackages
 
 -- | Convert a single source package into the solver-specific format.
-convSP :: OS -> Arch -> CompilerInfo -> Map PN [LabeledPackageConstraint]
+convSP :: OS -> Arch -> CompilerInfo -> Map PN [LabeledPackageConstraint cs]
        -> StrongFlags -> SolveExecutables -> SourcePackage loc -> (PN, I, PInfo)
 convSP os arch cinfo constraints strfl solveExes (SourcePackage (PackageIdentifier pn pv) gpd _ _pl) =
   let i = I pv InRepo
@@ -172,7 +172,7 @@ convSP os arch cinfo constraints strfl solveExes (SourcePackage (PackageIdentifi
 -- want to keep the condition tree, but simplify much of the test.
 
 -- | Convert a generic package description to a solver-specific 'PInfo'.
-convGPD :: OS -> Arch -> CompilerInfo -> [LabeledPackageConstraint]
+convGPD :: OS -> Arch -> CompilerInfo -> [LabeledPackageConstraint cs]
         -> StrongFlags -> SolveExecutables -> PN -> GenericPackageDescription
         -> PInfo
 convGPD os arch cinfo constraints strfl solveExes pn
@@ -249,7 +249,7 @@ convGPD os arch cinfo constraints strfl solveExes pn
 testConditionForComponent :: OS
                           -> Arch
                           -> CompilerInfo
-                          -> [LabeledPackageConstraint]
+                          -> [LabeledPackageConstraint cs]
                           -> (a -> Bool)
                           -> CondTree ConfVar [Dependency] a
                           -> Maybe Bool
diff --git a/cabal-install-solver/src/Distribution/Solver/Modular/Message.hs b/cabal-install-solver/src/Distribution/Solver/Modular/Message.hs
index 11fa7ca874d..c40910c9d29 100644
--- a/cabal-install-solver/src/Distribution/Solver/Modular/Message.hs
+++ b/cabal-install-solver/src/Distribution/Solver/Modular/Message.hs
@@ -28,7 +28,6 @@ import Distribution.Solver.Modular.Package
 import Distribution.Solver.Modular.Tree
          ( FailReason(..), POption(..), ConflictingDep(..) )
 import Distribution.Solver.Modular.Version
-import Distribution.Solver.Types.ConstraintSource
 import Distribution.Solver.Types.PackagePath
 import Distribution.Solver.Types.Progress
 import Distribution.Types.LibraryName
@@ -311,10 +310,10 @@ showFR _ NotExplicit                      = " (not a user-provided goal nor ment
 showFR _ Shadowed                         = " (shadowed by another installed package with same version)"
 showFR _ (Broken u)                       = " (package is broken, missing dependency " ++ prettyShow u ++ ")"
 showFR _ UnknownPackage                   = " (unknown package)"
-showFR _ (GlobalConstraintVersion vr src) = " (" ++ constraintSource src ++ " requires " ++ prettyShow vr ++ ")"
-showFR _ (GlobalConstraintInstalled src)  = " (" ++ constraintSource src ++ " requires installed instance)"
-showFR _ (GlobalConstraintSource src)     = " (" ++ constraintSource src ++ " requires source instance)"
-showFR _ (GlobalConstraintFlag src)       = " (" ++ constraintSource src ++ " requires opposite flag selection)"
+showFR _ (GlobalConstraintVersion vr src) = " (constraint from " ++ show src ++ " requires " ++ prettyShow vr ++ ")"
+showFR _ (GlobalConstraintInstalled src)  = " (constraint from " ++ show src ++ " requires installed instance)"
+showFR _ (GlobalConstraintSource src)     = " (constraint from " ++ show src ++ " requires source instance)"
+showFR _ (GlobalConstraintFlag src)       = " (constraint from " ++ show src ++ " requires opposite flag selection)"
 showFR _ ManualFlag                       = " (manual flag can only be changed explicitly)"
 showFR c Backjump                         = " (backjumping, conflict set: " ++ showConflictSet c ++ ")"
 showFR _ MultipleInstances                = " (multiple instances)"
@@ -333,9 +332,6 @@ showExposedComponent (ExposedLib LMainLibName)       = "library"
 showExposedComponent (ExposedLib (LSubLibName name)) = "library '" ++ unUnqualComponentName name ++ "'"
 showExposedComponent (ExposedExe name)               = "executable '" ++ unUnqualComponentName name ++ "'"
 
-constraintSource :: ConstraintSource -> String
-constraintSource src = "constraint from " ++ showConstraintSource src
-
 showConflictingDep :: ConflictingDep -> String
 showConflictingDep (ConflictingDep dr (PkgComponent qpn comp) ci) =
   let DependencyReason qpn' _ _ = dr
@@ -357,4 +353,4 @@ showConflictingDep (ConflictingDep dr (PkgComponent qpn comp) ci) =
 -- >>> let v0 = POption (I (mkVersion [0]) InRepo) Nothing
 -- >>> let v1 = POption (I (mkVersion [1]) InRepo) Nothing
 -- >>> let i0 = POption (I (mkVersion [0]) (Inst $ mkUnitId "foo-bar-0-inplace")) Nothing
--- >>> let i1 = POption (I (mkVersion [1]) (Inst $ mkUnitId "foo-bar-1-inplace")) Nothing
\ No newline at end of file
+-- >>> let i1 = POption (I (mkVersion [1]) (Inst $ mkUnitId "foo-bar-1-inplace")) Nothing
diff --git a/cabal-install-solver/src/Distribution/Solver/Modular/Preference.hs b/cabal-install-solver/src/Distribution/Solver/Modular/Preference.hs
index 9e0d5fb4d22..cd7c9342f87 100644
--- a/cabal-install-solver/src/Distribution/Solver/Modular/Preference.hs
+++ b/cabal-install-solver/src/Distribution/Solver/Modular/Preference.hs
@@ -172,10 +172,11 @@ preferPackageStanzaPreferences pcs = go
 -- given instance for a P-node. Translates the constraint into a
 -- tree-transformer that either leaves the subtree untouched, or replaces it
 -- with an appropriate failure node.
-processPackageConstraintP :: forall d c. QPN
+processPackageConstraintP :: forall d c cs. (Eq cs, Show cs, Typeable cs)
+                          => QPN
                           -> ConflictSet
                           -> I
-                          -> LabeledPackageConstraint
+                          -> LabeledPackageConstraint cs
                           -> Tree d c
                           -> Tree d c
 processPackageConstraintP qpn c i (LabeledPackageConstraint (PackageConstraint scope prop) src) r =
@@ -186,24 +187,25 @@ processPackageConstraintP qpn c i (LabeledPackageConstraint (PackageConstraint s
     go :: I -> PackageProperty -> Tree d c
     go (I v _) (PackagePropertyVersion vr)
         | checkVR vr v  = r
-        | otherwise     = Fail c (GlobalConstraintVersion vr src)
+        | otherwise     = Fail c (GlobalConstraintVersion vr (SomeSrc src))
     go _       PackagePropertyInstalled
         | instI i       = r
-        | otherwise     = Fail c (GlobalConstraintInstalled src)
+        | otherwise     = Fail c (GlobalConstraintInstalled (SomeSrc src))
     go _       PackagePropertySource
         | not (instI i) = r
-        | otherwise     = Fail c (GlobalConstraintSource src)
+        | otherwise     = Fail c (GlobalConstraintSource (SomeSrc src))
     go _       _        = r
 
 -- | Helper function that tries to enforce a single package constraint on a
 -- given flag setting for an F-node. Translates the constraint into a
 -- tree-transformer that either leaves the subtree untouched, or replaces it
 -- with an appropriate failure node.
-processPackageConstraintF :: forall d c. QPN
+processPackageConstraintF :: forall d c cs . (Eq cs, Show cs, Typeable cs)
+                          => QPN
                           -> Flag
                           -> ConflictSet
                           -> Bool
-                          -> LabeledPackageConstraint
+                          -> LabeledPackageConstraint cs
                           -> Tree d c
                           -> Tree d c
 processPackageConstraintF qpn f c b' (LabeledPackageConstraint (PackageConstraint scope prop) src) r =
@@ -216,18 +218,19 @@ processPackageConstraintF qpn f c b' (LabeledPackageConstraint (PackageConstrain
         case lookupFlagAssignment f fa of
           Nothing            -> r
           Just b | b == b'   -> r
-                 | otherwise -> Fail c (GlobalConstraintFlag src)
+                 | otherwise -> Fail c (GlobalConstraintFlag (SomeSrc src))
     go _                             = r
 
 -- | Helper function that tries to enforce a single package constraint on a
 -- given flag setting for an F-node. Translates the constraint into a
 -- tree-transformer that either leaves the subtree untouched, or replaces it
 -- with an appropriate failure node.
-processPackageConstraintS :: forall d c. QPN
+processPackageConstraintS :: forall d c cs. (Typeable cs, Eq cs, Show cs)
+                          => QPN
                           -> OptionalStanza
                           -> ConflictSet
                           -> Bool
-                          -> LabeledPackageConstraint
+                          -> LabeledPackageConstraint cs
                           -> Tree d c
                           -> Tree d c
 processPackageConstraintS qpn s c b' (LabeledPackageConstraint (PackageConstraint scope prop) src) r =
@@ -237,14 +240,15 @@ processPackageConstraintS qpn s c b' (LabeledPackageConstraint (PackageConstrain
   where
     go :: PackageProperty -> Tree d c
     go (PackagePropertyStanzas ss) =
-        if not b' && s `elem` ss then Fail c (GlobalConstraintFlag src)
+        if not b' && s `elem` ss then Fail c (GlobalConstraintFlag (SomeSrc src))
                                  else r
     go _                               = r
 
 -- | Traversal that tries to establish various kinds of user constraints. Works
 -- by selectively disabling choices that have been ruled out by global user
 -- constraints.
-enforcePackageConstraints :: M.Map PN [LabeledPackageConstraint]
+enforcePackageConstraints :: (Typeable cs, Eq cs, Show cs)
+                          => M.Map PN [LabeledPackageConstraint cs]
                           -> EndoTreeTrav d c
 enforcePackageConstraints pcs = go
   where
@@ -291,7 +295,7 @@ enforcePackageConstraints pcs = go
 --
 -- This function does not enforce any of the constraints, since that is done by
 -- 'enforcePackageConstraints'.
-enforceManualFlags :: M.Map PN [LabeledPackageConstraint] -> EndoTreeTrav d c
+enforceManualFlags :: M.Map PN [LabeledPackageConstraint cs] -> EndoTreeTrav d c
 enforceManualFlags pcs = go
   where
     go (FChoiceF qfn@(FN (Q _ pn) fn) rdm gr tr Manual d ts) =
diff --git a/cabal-install-solver/src/Distribution/Solver/Modular/Solver.hs b/cabal-install-solver/src/Distribution/Solver/Modular/Solver.hs
index 39bd7bf4690..e03ea680667 100644
--- a/cabal-install-solver/src/Distribution/Solver/Modular/Solver.hs
+++ b/cabal-install-solver/src/Distribution/Solver/Modular/Solver.hs
@@ -88,12 +88,13 @@ newtype PruneAfterFirstSuccess = PruneAfterFirstSuccess Bool
 -- has been added relatively recently. Cycles are only removed directly
 -- before exploration.
 --
-solve :: SolverConfig                         -- ^ solver parameters
+solve :: (Eq cs, Show cs, Typeable cs)
+      => SolverConfig                         -- ^ solver parameters
       -> CompilerInfo
       -> Index                                -- ^ all available packages as an index
       -> PkgConfigDb                          -- ^ available pkg-config pkgs
       -> (PN -> PackagePreferences)           -- ^ preferences
-      -> M.Map PN [LabeledPackageConstraint]  -- ^ global constraints
+      -> M.Map PN [LabeledPackageConstraint cs]  -- ^ global constraints
       -> S.Set PN                             -- ^ global goals
       -> RetryLog Message SolverFailure (Assignment, RevDepMap)
 solve sc cinfo idx pkgConfigDB userPrefs userConstraints userGoals =
diff --git a/cabal-install-solver/src/Distribution/Solver/Modular/Tree.hs b/cabal-install-solver/src/Distribution/Solver/Modular/Tree.hs
index 10d372525b1..5554e1bc5c2 100644
--- a/cabal-install-solver/src/Distribution/Solver/Modular/Tree.hs
+++ b/cabal-install-solver/src/Distribution/Solver/Modular/Tree.hs
@@ -1,10 +1,13 @@
 {-# LANGUAGE DeriveFunctor, DeriveFoldable, DeriveTraversable #-}
+{-# LANGUAGE GADTs #-}
+
 module Distribution.Solver.Modular.Tree
     ( POption(..)
     , Tree(..)
     , TreeF(..)
     , Weight
     , FailReason(..)
+    , SomeSrc(..)
     , ConflictingDep(..)
     , ana
     , cata
@@ -21,16 +24,16 @@ module Distribution.Solver.Modular.Tree
 import Control.Monad hiding (mapM, sequence)
 import Data.Foldable
 import Data.Traversable
+import Type.Reflection (Typeable, eqTypeRep, typeOf, (:~~:) (..))
 import Prelude hiding (foldr, mapM, sequence)
 
 import Distribution.Solver.Modular.Dependency
 import Distribution.Solver.Modular.Flag
-import Distribution.Solver.Modular.Package
 import Distribution.Solver.Modular.PSQ (PSQ)
+import Distribution.Solver.Modular.Package
 import Distribution.Solver.Modular.Version
 import Distribution.Solver.Modular.WeightedPSQ (WeightedPSQ)
 import qualified Distribution.Solver.Modular.WeightedPSQ as W
-import Distribution.Solver.Types.ConstraintSource
 import Distribution.Solver.Types.Flag
 import Distribution.Solver.Types.PackagePath
 import Distribution.Types.PkgconfigVersionRange
@@ -115,10 +118,7 @@ data FailReason = UnsupportedExtension Extension
                 | Shadowed
                 | Broken UnitId
                 | UnknownPackage
-                | GlobalConstraintVersion VR ConstraintSource
-                | GlobalConstraintInstalled ConstraintSource
-                | GlobalConstraintSource ConstraintSource
-                | GlobalConstraintFlag ConstraintSource
+                | GlobalConstraint GlobalConstraintReason
                 | ManualFlag
                 | MalformedFlagChoice QFN
                 | MalformedStanzaChoice QSN
@@ -128,8 +128,26 @@ data FailReason = UnsupportedExtension Extension
                 | DependenciesNotLinked String
                 | CyclicDependencies
                 | UnsupportedSpecVer Ver
+                deriving (Eq, Show)
+
+data GlobalConstraintReason
+  = GlobalConstraintVersion VR SomeSrc
+  | GlobalConstraintInstalled SomeSrc
+  | GlobalConstraintSource SomeSrc
+  | GlobalConstraintFlag SomeSrc
   deriving (Eq, Show)
 
+data SomeSrc = forall src. (Typeable src, Eq src, Show src) => SomeSrc src
+
+instance Eq SomeSrc where
+  SomeSrc lhs == SomeSrc rhs =
+    case eqTypeRep (typeOf lhs) (typeOf rhs) of
+      Nothing -> False
+      Just HRefl -> lhs == rhs
+
+instance Show SomeSrc where
+  showsPrec d (SomeSrc lhs) = showsPrec d lhs
+
 -- | Information about a dependency involved in a conflict, for error messages.
 data ConflictingDep = ConflictingDep (DependencyReason QPN) (PkgComponent QPN) CI
   deriving (Eq, Show)
diff --git a/cabal-install-solver/src/Distribution/Solver/Types/ConstraintSource.hs b/cabal-install-solver/src/Distribution/Solver/Types/ConstraintSource.hs
deleted file mode 100644
index dadf8bf08b1..00000000000
--- a/cabal-install-solver/src/Distribution/Solver/Types/ConstraintSource.hs
+++ /dev/null
@@ -1,78 +0,0 @@
-{-# LANGUAGE DeriveGeneric #-}
-module Distribution.Solver.Types.ConstraintSource
-    ( ConstraintSource(..)
-    , showConstraintSource
-    ) where
-
-import Distribution.Solver.Compat.Prelude
-import Prelude ()
-
--- | Source of a 'PackageConstraint'.
-data ConstraintSource =
-
-  -- | Main config file, which is ~/.cabal/config by default.
-  ConstraintSourceMainConfig FilePath
-
-  -- | Local cabal.project file
-  | ConstraintSourceProjectConfig FilePath
-
-  -- | User config file, which is ./cabal.config by default.
-  | ConstraintSourceUserConfig FilePath
-
-  -- | Flag specified on the command line.
-  | ConstraintSourceCommandlineFlag
-
-  -- | Target specified by the user, e.g., @cabal install package-0.1.0.0@
-  -- implies @package==0.1.0.0@.
-  | ConstraintSourceUserTarget
-
-  -- | Internal requirement to use installed versions of packages like ghc-prim.
-  | ConstraintSourceNonReinstallablePackage
-
-  -- | Internal constraint used by @cabal freeze@.
-  | ConstraintSourceFreeze
-
-  -- | Constraint specified by a config file, a command line flag, or a user
-  -- target, when a more specific source is not known.
-  | ConstraintSourceConfigFlagOrTarget
-
-  -- | Constraint introduced by --enable-multi-repl, which requires features
-  -- from Cabal >= 3.11
-  | ConstraintSourceMultiRepl
-
-  -- | The source of the constraint is not specified.
-  | ConstraintSourceUnknown
-
-  -- | An internal constraint due to compatibility issues with the Setup.hs
-  -- command line interface requires a minimum lower bound on Cabal
-  | ConstraintSetupCabalMinVersion
-
-  -- | An internal constraint due to compatibility issues with the Setup.hs
-  -- command line interface requires a maximum upper bound on Cabal
-  | ConstraintSetupCabalMaxVersion
-  deriving (Eq, Show, Generic)
-
-instance Binary ConstraintSource
-instance Structured ConstraintSource
-
--- | Description of a 'ConstraintSource'.
-showConstraintSource :: ConstraintSource -> String
-showConstraintSource (ConstraintSourceMainConfig path) =
-    "main config " ++ path
-showConstraintSource (ConstraintSourceProjectConfig path) =
-    "project config " ++ path
-showConstraintSource (ConstraintSourceUserConfig path)= "user config " ++ path
-showConstraintSource ConstraintSourceCommandlineFlag = "command line flag"
-showConstraintSource ConstraintSourceUserTarget = "user target"
-showConstraintSource ConstraintSourceNonReinstallablePackage =
-    "non-reinstallable package"
-showConstraintSource ConstraintSourceFreeze = "cabal freeze"
-showConstraintSource ConstraintSourceConfigFlagOrTarget =
-    "config file, command line flag, or user target"
-showConstraintSource ConstraintSourceMultiRepl =
-    "--enable-multi-repl"
-showConstraintSource ConstraintSourceUnknown = "unknown source"
-showConstraintSource ConstraintSetupCabalMinVersion =
-    "minimum version of Cabal used by Setup.hs"
-showConstraintSource ConstraintSetupCabalMaxVersion =
-    "maximum version of Cabal used by Setup.hs"
diff --git a/cabal-install-solver/src/Distribution/Solver/Types/DependencyResolver.hs b/cabal-install-solver/src/Distribution/Solver/Types/DependencyResolver.hs
index e773492ae74..d0a2b192239 100644
--- a/cabal-install-solver/src/Distribution/Solver/Types/DependencyResolver.hs
+++ b/cabal-install-solver/src/Distribution/Solver/Types/DependencyResolver.hs
@@ -1,6 +1,6 @@
 module Distribution.Solver.Types.DependencyResolver
-    ( DependencyResolver
-    ) where
+  ( DependencyResolver
+  ) where
 
 import Distribution.Solver.Compat.Prelude
 import Prelude ()
@@ -26,12 +26,12 @@ import Distribution.System ( Platform )
 -- solving the package dependency problem and we want to make it easy to swap
 -- in alternatives.
 --
-type DependencyResolver loc = Platform
+type DependencyResolver loc cs = Platform
                            -> CompilerInfo
                            -> InstalledPackageIndex
                            -> PackageIndex (SourcePackage loc)
                            -> PkgConfigDb
                            -> (PackageName -> PackagePreferences)
-                           -> [LabeledPackageConstraint]
+                           -> [LabeledPackageConstraint cs]
                            -> Set PackageName
                            -> Progress String String [ResolverPackage loc]
diff --git a/cabal-install-solver/src/Distribution/Solver/Types/LabeledPackageConstraint.hs b/cabal-install-solver/src/Distribution/Solver/Types/LabeledPackageConstraint.hs
index 8715e46fd22..3309c325cc0 100644
--- a/cabal-install-solver/src/Distribution/Solver/Types/LabeledPackageConstraint.hs
+++ b/cabal-install-solver/src/Distribution/Solver/Types/LabeledPackageConstraint.hs
@@ -3,12 +3,11 @@ module Distribution.Solver.Types.LabeledPackageConstraint
     , unlabelPackageConstraint
     ) where
 
-import Distribution.Solver.Types.ConstraintSource
 import Distribution.Solver.Types.PackageConstraint
 
 -- | 'PackageConstraint' labeled with its source.
-data LabeledPackageConstraint
-   = LabeledPackageConstraint PackageConstraint ConstraintSource
+data LabeledPackageConstraint cs
+   = LabeledPackageConstraint PackageConstraint cs
 
-unlabelPackageConstraint :: LabeledPackageConstraint -> PackageConstraint
+unlabelPackageConstraint :: LabeledPackageConstraint cs -> PackageConstraint
 unlabelPackageConstraint (LabeledPackageConstraint pc _) = pc
diff --git a/cabal-install/cabal-install.cabal b/cabal-install/cabal-install.cabal
index 373152e8f64..adc658a7360 100644
--- a/cabal-install/cabal-install.cabal
+++ b/cabal-install/cabal-install.cabal
@@ -160,6 +160,7 @@ library
         Distribution.Client.ProjectConfig
         Distribution.Client.ProjectConfig.Legacy
         Distribution.Client.ProjectConfig.Types
+        Distribution.Client.ProjectConfig.Types.ConstraintSource
         Distribution.Client.ProjectFlags
         Distribution.Client.ProjectOrchestration
         Distribution.Client.ProjectPlanOutput
diff --git a/cabal-install/src/Distribution/Client/CmdFreeze.hs b/cabal-install/src/Distribution/Client/CmdFreeze.hs
index 85c7eb137e2..91452b0655f 100644
--- a/cabal-install/src/Distribution/Client/CmdFreeze.hs
+++ b/cabal-install/src/Distribution/Client/CmdFreeze.hs
@@ -32,9 +32,6 @@ import Distribution.Client.Targets
   , UserConstraintScope (..)
   , UserQualifier (..)
   )
-import Distribution.Solver.Types.ConstraintSource
-  ( ConstraintSource (..)
-  )
 import Distribution.Solver.Types.PackageConstraint
   ( PackageProperty (..)
   )
@@ -71,6 +68,9 @@ import Distribution.Version
 import qualified Data.Map as Map
 
 import Distribution.Client.Errors
+import Distribution.Client.ProjectConfig.Types.ConstraintSource
+  ( ConstraintSource (..)
+  )
 import Distribution.Simple.Command
   ( CommandUI (..)
   , usageAlternatives
diff --git a/cabal-install/src/Distribution/Client/CmdRepl.hs b/cabal-install/src/Distribution/Client/CmdRepl.hs
index e243eb82974..44483200639 100644
--- a/cabal-install/src/Distribution/Client/CmdRepl.hs
+++ b/cabal-install/src/Distribution/Client/CmdRepl.hs
@@ -111,9 +111,6 @@ import Distribution.Simple.Utils
   , withTempDirectoryEx
   , wrapText
   )
-import Distribution.Solver.Types.ConstraintSource
-  ( ConstraintSource (ConstraintSourceMultiRepl)
-  )
 import Distribution.Solver.Types.PackageConstraint
   ( PackageProperty (PackagePropertyVersion)
   )
@@ -168,6 +165,9 @@ import Distribution.Client.ProjectConfig
   ( ProjectConfig (projectConfigShared)
   , ProjectConfigShared (projectConfigConstraints, projectConfigMultiRepl)
   )
+import Distribution.Client.ProjectConfig.Types.ConstraintSource 
+  ( ConstraintSource (..)
+  )
 import Distribution.Client.ReplFlags
   ( EnvFlags (envIncludeTransitive, envPackages)
   , ReplFlags (..)
diff --git a/cabal-install/src/Distribution/Client/Config.hs b/cabal-install/src/Distribution/Client/Config.hs
index 0fe93081bd7..841fd781156 100644
--- a/cabal-install/src/Distribution/Client/Config.hs
+++ b/cabal-install/src/Distribution/Client/Config.hs
@@ -118,6 +118,7 @@ import Distribution.Client.ParseUtils
   , ppFields
   , ppSection
   )
+import Distribution.Client.ProjectConfig.Types.ConstraintSource (ConstraintSource (..))
 import Distribution.Client.ProjectFlags (ProjectFlags (..))
 import Distribution.Client.ReplFlags
 import Distribution.Client.Version
@@ -202,7 +203,6 @@ import Distribution.Simple.Utils
   , toUTF8BS
   , warn
   )
-import Distribution.Solver.Types.ConstraintSource
 import Distribution.Verbosity
   ( normal
   )
diff --git a/cabal-install/src/Distribution/Client/Configure.hs b/cabal-install/src/Distribution/Client/Configure.hs
index b01681d9727..62d0ad812e1 100644
--- a/cabal-install/src/Distribution/Client/Configure.hs
+++ b/cabal-install/src/Distribution/Client/Configure.hs
@@ -59,7 +59,6 @@ import Distribution.Client.Targets
 import Distribution.Client.Types as Source
 
 import qualified Distribution.Solver.Types.ComponentDeps as CD
-import Distribution.Solver.Types.ConstraintSource
 import Distribution.Solver.Types.LabeledPackageConstraint
 import Distribution.Solver.Types.OptionalStanza
 import Distribution.Solver.Types.PackageIndex
@@ -129,6 +128,10 @@ import Distribution.Version
   )
 
 import Distribution.Client.Errors
+import Distribution.Client.ProjectConfig.Types.ConstraintSource
+  ( ConstraintSource (..)
+  , showConstraintSource
+  )
 import System.FilePath ((</>))
 
 -- | Choose the Cabal version such that the setup scripts compiled against this
diff --git a/cabal-install/src/Distribution/Client/Dependency.hs b/cabal-install/src/Distribution/Client/Dependency.hs
index 37e0cbdf1ee..50ac8aa663e 100644
--- a/cabal-install/src/Distribution/Client/Dependency.hs
+++ b/cabal-install/src/Distribution/Client/Dependency.hs
@@ -133,7 +133,6 @@ import Distribution.Version
 
 import Distribution.Solver.Types.ComponentDeps (ComponentDeps)
 import qualified Distribution.Solver.Types.ComponentDeps as CD
-import Distribution.Solver.Types.ConstraintSource
 import Distribution.Solver.Types.DependencyResolver
 import Distribution.Solver.Types.InstalledPreference as Preference
 import Distribution.Solver.Types.LabeledPackageConstraint
@@ -150,6 +149,7 @@ import Distribution.Solver.Types.SolverId
 import Distribution.Solver.Types.SolverPackage
 import Distribution.Solver.Types.SourcePackage
 import Distribution.Solver.Types.Variable
+import Distribution.Client.ProjectConfig.Types.ConstraintSource (ConstraintSource (..), showConstraintSource)
 
 import Control.Exception
   ( assert
@@ -171,7 +171,7 @@ import qualified Data.Set as Set
 -- implemented in terms of adjustments to the parameters.
 data DepResolverParams = DepResolverParams
   { depResolverTargets :: Set PackageName
-  , depResolverConstraints :: [LabeledPackageConstraint]
+  , depResolverConstraints :: [LabeledPackageConstraint ConstraintSource]
   , depResolverPreferences :: [PackagePreference]
   , depResolverPreferenceDefault :: PackagesPreferenceDefault
   , depResolverInstalledPkgIndex :: InstalledPackageIndex
@@ -241,7 +241,7 @@ showDepResolverParams p =
       show
       (depResolverMaxBackjumps p)
   where
-    showLabeledConstraint :: LabeledPackageConstraint -> String
+    showLabeledConstraint :: LabeledPackageConstraint ConstraintSource -> String
     showLabeledConstraint (LabeledPackageConstraint pc src) =
       showPackageConstraint pc ++ " (" ++ showConstraintSource src ++ ")"
 
@@ -308,7 +308,7 @@ addTargets extraTargets params =
     }
 
 addConstraints
-  :: [LabeledPackageConstraint]
+  :: [LabeledPackageConstraint ConstraintSource]
   -> DepResolverParams
   -> DepResolverParams
 addConstraints extraConstraints params =
@@ -752,7 +752,7 @@ standardInstallPolicy installedPkgIndex sourcePkgDb pkgSpecifiers =
 
 -- ------------------------------------------------------------
 
-runSolver :: SolverConfig -> DependencyResolver UnresolvedPkgLoc
+runSolver :: SolverConfig -> DependencyResolver UnresolvedPkgLoc ConstraintSource
 runSolver = modularResolver
 
 -- | Run the dependency solver.
diff --git a/cabal-install/src/Distribution/Client/Fetch.hs b/cabal-install/src/Distribution/Client/Fetch.hs
index 54db5ae607b..db6fedd9966 100644
--- a/cabal-install/src/Distribution/Client/Fetch.hs
+++ b/cabal-install/src/Distribution/Client/Fetch.hs
@@ -32,7 +32,6 @@ import qualified Distribution.Client.SolverInstallPlan as SolverInstallPlan
 import Distribution.Client.Targets
 import Distribution.Client.Types
 
-import Distribution.Solver.Types.ConstraintSource
 import Distribution.Solver.Types.LabeledPackageConstraint
 import Distribution.Solver.Types.OptionalStanza
 import Distribution.Solver.Types.PkgConfigDb (PkgConfigDb, readPkgConfigDb)
@@ -40,6 +39,7 @@ import Distribution.Solver.Types.SolverPackage
 import Distribution.Solver.Types.SourcePackage
 
 import Distribution.Client.Errors
+import Distribution.Client.ProjectConfig.Types.ConstraintSource (ConstraintSource (ConstraintSourceConfigFlagOrTarget))
 import Distribution.Package
   ( packageId
   )
diff --git a/cabal-install/src/Distribution/Client/Freeze.hs b/cabal-install/src/Distribution/Client/Freeze.hs
index 9bc4e3234b5..6924624899a 100644
--- a/cabal-install/src/Distribution/Client/Freeze.hs
+++ b/cabal-install/src/Distribution/Client/Freeze.hs
@@ -47,13 +47,13 @@ import qualified Distribution.Client.SolverInstallPlan as SolverInstallPlan
 import Distribution.Client.Targets
 import Distribution.Client.Types
 
-import Distribution.Solver.Types.ConstraintSource
 import Distribution.Solver.Types.LabeledPackageConstraint
 import Distribution.Solver.Types.OptionalStanza
 import Distribution.Solver.Types.PkgConfigDb
 import Distribution.Solver.Types.SolverId
 
 import Distribution.Client.Errors
+import Distribution.Client.ProjectConfig.Types.ConstraintSource
 import Distribution.Package
   ( Package
   , packageId
diff --git a/cabal-install/src/Distribution/Client/Install.hs b/cabal-install/src/Distribution/Client/Install.hs
index e1f855cdafe..f7a89b81b59 100644
--- a/cabal-install/src/Distribution/Client/Install.hs
+++ b/cabal-install/src/Distribution/Client/Install.hs
@@ -130,7 +130,6 @@ import qualified Distribution.InstalledPackageInfo as Installed
 import Distribution.Solver.Types.PackageFixedDeps
 
 import qualified Distribution.Solver.Types.ComponentDeps as CD
-import Distribution.Solver.Types.ConstraintSource
 import Distribution.Solver.Types.LabeledPackageConstraint
 import Distribution.Solver.Types.OptionalStanza
 import qualified Distribution.Solver.Types.PackageIndex as SourcePackageIndex
@@ -267,6 +266,7 @@ import Distribution.Version
 
 import qualified Data.ByteString as BS
 import Distribution.Client.Errors
+import Distribution.Client.ProjectConfig.Types.ConstraintSource (ConstraintSource (ConstraintSourceConfigFlagOrTarget))
 
 -- TODO:
 
diff --git a/cabal-install/src/Distribution/Client/NixStyleOptions.hs b/cabal-install/src/Distribution/Client/NixStyleOptions.hs
index 7a047774b2b..9e6bf5edf98 100644
--- a/cabal-install/src/Distribution/Client/NixStyleOptions.hs
+++ b/cabal-install/src/Distribution/Client/NixStyleOptions.hs
@@ -15,8 +15,8 @@ import Prelude ()
 
 import Distribution.Simple.Command (OptionField (..), ShowOrParseArgs)
 import Distribution.Simple.Setup (BenchmarkFlags, HaddockFlags, TestFlags)
-import Distribution.Solver.Types.ConstraintSource (ConstraintSource (..))
 
+import Distribution.Client.ProjectConfig.Types.ConstraintSource (ConstraintSource (..))
 import Distribution.Client.ProjectFlags
   ( ProjectFlags (..)
   , defaultProjectFlags
diff --git a/cabal-install/src/Distribution/Client/ProjectConfig/Legacy.hs b/cabal-install/src/Distribution/Client/ProjectConfig/Legacy.hs
index d949437f5d6..4500373460d 100644
--- a/cabal-install/src/Distribution/Client/ProjectConfig/Legacy.hs
+++ b/cabal-install/src/Distribution/Client/ProjectConfig/Legacy.hs
@@ -54,8 +54,6 @@ import Distribution.Client.CmdInstall.ClientInstallFlags
 
 import Distribution.Compat.Lens (toListOf, view)
 
-import Distribution.Solver.Types.ConstraintSource
-
 import Distribution.Client.NixStyleOptions (NixStyleFlags (..))
 import Distribution.Client.ProjectFlags (ProjectFlags (..), defaultProjectFlags, projectFlagsOptions)
 import Distribution.Client.Setup
@@ -182,6 +180,7 @@ import Network.URI (URI (..), parseURI)
 import Distribution.Fields.ConfVar (parseConditionConfVarFromClause)
 
 import Distribution.Client.HttpUtils
+import Distribution.Client.ProjectConfig.Types.ConstraintSource (ConstraintSource (..))
 import Distribution.Client.ReplFlags (multiReplOption)
 import System.Directory (createDirectoryIfMissing)
 import System.FilePath (isAbsolute, isPathSeparator, makeValid, takeDirectory, (</>))
diff --git a/cabal-install/src/Distribution/Client/ProjectConfig/Types.hs b/cabal-install/src/Distribution/Client/ProjectConfig/Types.hs
index 744a50ddc37..644dddc804a 100644
--- a/cabal-install/src/Distribution/Client/ProjectConfig/Types.hs
+++ b/cabal-install/src/Distribution/Client/ProjectConfig/Types.hs
@@ -51,7 +51,7 @@ import Distribution.Client.CmdInstall.ClientInstallFlags
   ( ClientInstallFlags (..)
   )
 
-import Distribution.Solver.Types.ConstraintSource
+import Distribution.Client.ProjectConfig.Types.ConstraintSource (ConstraintSource)
 import Distribution.Solver.Types.Settings
 
 import Distribution.Package
diff --git a/cabal-install/src/Distribution/Client/ProjectConfig/Types/ConstraintSource.hs b/cabal-install/src/Distribution/Client/ProjectConfig/Types/ConstraintSource.hs
new file mode 100644
index 00000000000..20f6dce400e
--- /dev/null
+++ b/cabal-install/src/Distribution/Client/ProjectConfig/Types/ConstraintSource.hs
@@ -0,0 +1,64 @@
+{-# LANGUAGE DeriveGeneric #-}
+
+module Distribution.Client.ProjectConfig.Types.ConstraintSource where
+
+import Distribution.Client.Compat.Prelude
+import Prelude ()
+
+-- | Source of a 'PackageConstraint'.
+data ConstraintSource
+  = -- | Main config file, which is ~/.cabal/config by default.
+    ConstraintSourceMainConfig FilePath
+  | -- | Local cabal.project file
+    ConstraintSourceProjectConfig FilePath
+  | -- | User config file, which is ./cabal.config by default.
+    ConstraintSourceUserConfig FilePath
+  | -- | Flag specified on the command line.
+    ConstraintSourceCommandlineFlag
+  | -- | Target specified by the user, e.g., @cabal install package-0.1.0.0@
+    -- implies @package==0.1.0.0@.
+    ConstraintSourceUserTarget
+  | -- | Internal requirement to use installed versions of packages like ghc-prim.
+    ConstraintSourceNonReinstallablePackage
+  | -- | Internal constraint used by @cabal freeze@.
+    ConstraintSourceFreeze
+  | -- | Constraint specified by a config file, a command line flag, or a user
+    -- target, when a more specific source is not known.
+    ConstraintSourceConfigFlagOrTarget
+  | -- | Constraint introduced by --enable-multi-repl, which requires features
+    -- from Cabal >= 3.11
+    ConstraintSourceMultiRepl
+  | -- | The source of the constraint is not specified.
+    ConstraintSourceUnknown
+  | -- | An internal constraint due to compatibility issues with the Setup.hs
+    -- command line interface requires a minimum lower bound on Cabal
+    ConstraintSetupCabalMinVersion
+  | -- | An internal constraint due to compatibility issues with the Setup.hs
+    -- command line interface requires a maximum upper bound on Cabal
+    ConstraintSetupCabalMaxVersion
+  deriving (Eq, Show, Generic)
+
+instance Binary ConstraintSource
+instance Structured ConstraintSource
+
+-- | Description of a 'ConstraintSource'.
+showConstraintSource :: ConstraintSource -> String
+showConstraintSource (ConstraintSourceMainConfig path) =
+  "main config " ++ path
+showConstraintSource (ConstraintSourceProjectConfig path) =
+  "project config " ++ path
+showConstraintSource (ConstraintSourceUserConfig path) = "user config " ++ path
+showConstraintSource ConstraintSourceCommandlineFlag = "command line flag"
+showConstraintSource ConstraintSourceUserTarget = "user target"
+showConstraintSource ConstraintSourceNonReinstallablePackage =
+  "non-reinstallable package"
+showConstraintSource ConstraintSourceFreeze = "cabal freeze"
+showConstraintSource ConstraintSourceConfigFlagOrTarget =
+  "config file, command line flag, or user target"
+showConstraintSource ConstraintSourceMultiRepl =
+  "--enable-multi-repl"
+showConstraintSource ConstraintSourceUnknown = "unknown source"
+showConstraintSource ConstraintSetupCabalMinVersion =
+  "minimum version of Cabal used by Setup.hs"
+showConstraintSource ConstraintSetupCabalMaxVersion =
+  "maximum version of Cabal used by Setup.hs"
diff --git a/cabal-install/src/Distribution/Client/ProjectPlanning.hs b/cabal-install/src/Distribution/Client/ProjectPlanning.hs
index 9fd24b45ccc..7b2bd411071 100644
--- a/cabal-install/src/Distribution/Client/ProjectPlanning.hs
+++ b/cabal-install/src/Distribution/Client/ProjectPlanning.hs
@@ -138,7 +138,6 @@ import Distribution.Utils.NubList
 
 import qualified Hackage.Security.Client as Sec
 
-import Distribution.Solver.Types.ConstraintSource
 import Distribution.Solver.Types.InstSolverPackage
 import Distribution.Solver.Types.LabeledPackageConstraint
 import Distribution.Solver.Types.OptionalStanza
@@ -208,6 +207,7 @@ import qualified Data.List.NonEmpty as NE
 import qualified Data.Map as Map
 import qualified Data.Set as Set
 import Distribution.Client.Errors
+import Distribution.Client.ProjectConfig.Types.ConstraintSource (ConstraintSource (..))
 import System.FilePath
 import Text.PrettyPrint (colon, comma, fsep, hang, punctuate, quotes, text, vcat, ($$))
 import qualified Text.PrettyPrint as Disp
diff --git a/cabal-install/src/Distribution/Client/Sandbox/PackageEnvironment.hs b/cabal-install/src/Distribution/Client/Sandbox/PackageEnvironment.hs
index 3033356493f..42fac7de7a3 100644
--- a/cabal-install/src/Distribution/Client/Sandbox/PackageEnvironment.hs
+++ b/cabal-install/src/Distribution/Client/Sandbox/PackageEnvironment.hs
@@ -58,7 +58,7 @@ import Distribution.Simple.Setup
   , HaddockFlags (..)
   )
 import Distribution.Simple.Utils (debug, warn)
-import Distribution.Solver.Types.ConstraintSource
+import Distribution.Client.ProjectConfig.Types.ConstraintSource (ConstraintSource (..))
 import System.Directory (doesFileExist)
 import System.FilePath ((</>))
 import System.IO.Error (isDoesNotExistError)
diff --git a/cabal-install/src/Distribution/Client/Setup.hs b/cabal-install/src/Distribution/Client/Setup.hs
index 85cc7665647..8cab586629e 100644
--- a/cabal-install/src/Distribution/Client/Setup.hs
+++ b/cabal-install/src/Distribution/Client/Setup.hs
@@ -129,7 +129,6 @@ import Distribution.Utils.NubList
   , toNubList
   )
 
-import Distribution.Solver.Types.ConstraintSource
 import Distribution.Solver.Types.Settings
 
 import Distribution.Client.GlobalFlags
@@ -139,6 +138,7 @@ import Distribution.Client.GlobalFlags
   , withRepoContext
   )
 import Distribution.Client.ManpageFlags (ManpageFlags, defaultManpageFlags, manpageOptions)
+import Distribution.Client.ProjectConfig.Types.ConstraintSource (ConstraintSource (..))
 import qualified Distribution.Compat.CharParsing as P
 import Distribution.FieldGrammar.Newtypes (SpecVersion (..))
 import Distribution.PackageDescription
diff --git a/cabal-install/src/Distribution/Client/Types/PackageSpecifier.hs b/cabal-install/src/Distribution/Client/Types/PackageSpecifier.hs
index 5f25be4aa77..67c6877827a 100644
--- a/cabal-install/src/Distribution/Client/Types/PackageSpecifier.hs
+++ b/cabal-install/src/Distribution/Client/Types/PackageSpecifier.hs
@@ -14,7 +14,7 @@ import Distribution.Package (Package (..), packageName, packageVersion)
 import Distribution.Types.PackageName (PackageName)
 import Distribution.Version (thisVersion)
 
-import Distribution.Solver.Types.ConstraintSource
+import Distribution.Client.ProjectConfig.Types.ConstraintSource
 import Distribution.Solver.Types.LabeledPackageConstraint
 import Distribution.Solver.Types.PackageConstraint
 
@@ -39,7 +39,7 @@ pkgSpecifierTarget (SpecificSourcePackage pkg) = packageName pkg
 pkgSpecifierConstraints
   :: Package pkg
   => PackageSpecifier pkg
-  -> [LabeledPackageConstraint]
+  -> [LabeledPackageConstraint ConstraintSource]
 pkgSpecifierConstraints (NamedPackage name props) = map toLpc props
   where
     toLpc prop =