diff --git a/Cabal-syntax/Cabal-syntax.cabal b/Cabal-syntax/Cabal-syntax.cabal
index 1bc8bcabeb2..3ece9dc516f 100644
--- a/Cabal-syntax/Cabal-syntax.cabal
+++ b/Cabal-syntax/Cabal-syntax.cabal
@@ -135,6 +135,7 @@ library
     Distribution.Types.ConfVar
     Distribution.Types.Dependency
     Distribution.Types.DependencyMap
+    Distribution.Types.DependencySatisfaction
     Distribution.Types.ExeDependency
     Distribution.Types.Executable
     Distribution.Types.Executable.Lens
@@ -158,6 +159,8 @@ library
     Distribution.Types.Library.Lens
     Distribution.Types.LibraryName
     Distribution.Types.LibraryVisibility
+    Distribution.Types.MissingDependency
+    Distribution.Types.MissingDependencyReason
     Distribution.Types.Mixin
     Distribution.Types.Module
     Distribution.Types.ModuleReexport
diff --git a/Cabal-syntax/src/Distribution/Compat/NonEmptySet.hs b/Cabal-syntax/src/Distribution/Compat/NonEmptySet.hs
index 17e3811e9a4..9e227459e84 100644
--- a/Cabal-syntax/src/Distribution/Compat/NonEmptySet.hs
+++ b/Cabal-syntax/src/Distribution/Compat/NonEmptySet.hs
@@ -12,6 +12,7 @@ module Distribution.Compat.NonEmptySet
 
     -- * Deletion
   , delete
+  , filter
 
     -- * Conversions
   , toNonEmpty
@@ -116,6 +117,9 @@ delete x (NES xs)
   where
     res = Set.delete x xs
 
+filter :: (a -> Bool) -> NonEmptySet a -> Set.Set a
+filter predicate (NES set) = Set.filter predicate set
+
 -------------------------------------------------------------------------------
 -- Conversions
 -------------------------------------------------------------------------------
diff --git a/Cabal-syntax/src/Distribution/PackageDescription/Configuration.hs b/Cabal-syntax/src/Distribution/PackageDescription/Configuration.hs
index e811c361221..eebf760094d 100644
--- a/Cabal-syntax/src/Distribution/PackageDescription/Configuration.hs
+++ b/Cabal-syntax/src/Distribution/PackageDescription/Configuration.hs
@@ -56,12 +56,13 @@ import Distribution.System
 import Distribution.Types.Component
 import Distribution.Types.ComponentRequestedSpec
 import Distribution.Types.DependencyMap
+import Distribution.Types.DependencySatisfaction (DependencySatisfaction (..))
+import Distribution.Types.MissingDependency (MissingDependency (..))
 import Distribution.Types.PackageVersionConstraint
 import Distribution.Utils.Generic
 import Distribution.Utils.Path (sameDirectory)
 import Distribution.Version
 
-import qualified Data.Map.Lazy as Map
 import Data.Tree (Tree (Node))
 
 ------------------------------------------------------------------------------
@@ -144,15 +145,17 @@ parseCondition = condOr
 
 ------------------------------------------------------------------------------
 
--- | Result of dependency test. Isomorphic to @Maybe d@ but renamed for
+-- | Result of dependency test. Isomorphic to @Maybe@ but renamed for
 --   clarity.
-data DepTestRslt d = DepOk | MissingDeps d
+data DepTestRslt
+  = DepOk
+  | MissingDeps [MissingDependency]
 
-instance Semigroup d => Monoid (DepTestRslt d) where
+instance Monoid DepTestRslt where
   mempty = DepOk
   mappend = (<>)
 
-instance Semigroup d => Semigroup (DepTestRslt d) where
+instance Semigroup DepTestRslt where
   DepOk <> x = x
   x <> DepOk = x
   (MissingDeps d) <> (MissingDeps d') = MissingDeps (d <> d')
@@ -190,13 +193,13 @@ resolveWithFlags
   -> [PackageVersionConstraint]
   -- ^ Additional constraints
   -> [CondTree ConfVar [Dependency] PDTagged]
-  -> ([Dependency] -> DepTestRslt [Dependency])
+  -> ([Dependency] -> DepTestRslt)
   -- ^ Dependency test function.
-  -> Either [Dependency] (TargetSet PDTagged, FlagAssignment)
+  -> Either [MissingDependency] (TargetSet PDTagged, FlagAssignment)
   -- ^ Either the missing dependencies (error case), or a pair of
   -- (set of build targets with dependencies, chosen flag assignments)
 resolveWithFlags dom enabled os arch impl constrs trees checkDeps =
-  either (Left . fromDepMapUnion) Right $ explore (build mempty dom)
+  explore (build mempty dom)
   where
     -- simplify trees by (partially) evaluating all conditions and converting
     -- dependencies to dependency maps.
@@ -216,7 +219,7 @@ resolveWithFlags dom enabled os arch impl constrs trees checkDeps =
     -- computation overhead in the successful case.
     explore
       :: Tree FlagAssignment
-      -> Either DepMapUnion (TargetSet PDTagged, FlagAssignment)
+      -> Either [MissingDependency] (TargetSet PDTagged, FlagAssignment)
     explore (Node flags ts) =
       let targetSet =
             TargetSet $
@@ -229,7 +232,7 @@ resolveWithFlags dom enabled os arch impl constrs trees checkDeps =
             DepOk
               | null ts -> Right (targetSet, flags)
               | otherwise -> tryAll $ map explore ts
-            MissingDeps mds -> Left (toDepMapUnion mds)
+            MissingDeps mds -> Left mds
 
     -- Builds a tree of all possible flag assignments.  Internal nodes
     -- have only partial assignments.
@@ -238,18 +241,18 @@ resolveWithFlags dom enabled os arch impl constrs trees checkDeps =
     build assigned ((fn, vals) : unassigned) =
       Node assigned $ map (\v -> build (insertFlagAssignment fn v assigned) unassigned) vals
 
-    tryAll :: [Either DepMapUnion a] -> Either DepMapUnion a
+    tryAll :: Monoid a => [Either a b] -> Either a b
     tryAll = foldr mp mz
 
     -- special version of `mplus' for our local purposes
-    mp :: Either DepMapUnion a -> Either DepMapUnion a -> Either DepMapUnion a
+    mp :: Monoid a => Either a b -> Either a b -> Either a b
     mp m@(Right _) _ = m
     mp _ m@(Right _) = m
     mp (Left xs) (Left ys) = Left (xs <> ys)
 
     -- `mzero'
-    mz :: Either DepMapUnion a
-    mz = Left (DepMapUnion Map.empty)
+    mz :: Monoid a => Either a b
+    mz = Left mempty
 
     env :: FlagAssignment -> FlagName -> Either FlagName Bool
     env flags flag = (maybe (Left flag) Right . lookupFlagAssignment flag) flags
@@ -323,27 +326,6 @@ extractConditions f gpkg =
     , extractCondition (f . benchmarkBuildInfo) . snd <$> condBenchmarks gpkg
     ]
 
--- | A map of package constraints that combines version ranges using 'unionVersionRanges'.
-newtype DepMapUnion = DepMapUnion {unDepMapUnion :: Map PackageName (VersionRange, NonEmptySet LibraryName)}
-
-instance Semigroup DepMapUnion where
-  DepMapUnion x <> DepMapUnion y =
-    DepMapUnion $
-      Map.unionWith unionVersionRanges' x y
-
-unionVersionRanges'
-  :: (VersionRange, NonEmptySet LibraryName)
-  -> (VersionRange, NonEmptySet LibraryName)
-  -> (VersionRange, NonEmptySet LibraryName)
-unionVersionRanges' (vr, cs) (vr', cs') = (unionVersionRanges vr vr', cs <> cs')
-
-toDepMapUnion :: [Dependency] -> DepMapUnion
-toDepMapUnion ds =
-  DepMapUnion $ Map.fromListWith unionVersionRanges' [(p, (vr, cs)) | Dependency p vr cs <- ds]
-
-fromDepMapUnion :: DepMapUnion -> [Dependency]
-fromDepMapUnion m = [Dependency p vr cs | (p, (vr, cs)) <- Map.toList (unDepMapUnion m)]
-
 freeVars :: CondTree ConfVar c a -> [FlagName]
 freeVars t = [f | PackageFlag f <- freeVars' t]
   where
@@ -453,7 +435,7 @@ finalizePD
   :: FlagAssignment
   -- ^ Explicitly specified flag assignments
   -> ComponentRequestedSpec
-  -> (Dependency -> Bool)
+  -> (Dependency -> DependencySatisfaction)
   -- ^ Is a given dependency satisfiable from the set of
   -- available packages?  If this is unknown then use
   -- True.
@@ -465,7 +447,7 @@ finalizePD
   -- ^ Additional constraints
   -> GenericPackageDescription
   -> Either
-      [Dependency]
+      [MissingDependency]
       (PackageDescription, FlagAssignment)
   -- ^ Either missing dependencies or the resolved package
   -- description along with the flag assignments chosen.
@@ -526,7 +508,11 @@ finalizePD
           | otherwise -> [b, not b]
       -- flagDefaults = map (\(n,x:_) -> (n,x)) flagChoices
       check ds =
-        let missingDeps = filter (not . satisfyDep) ds
+        let missingDeps =
+              [ MissingDependency dependency reason
+              | (dependency, Unsatisfied reason) <-
+                  map (\dependency -> (dependency, satisfyDep dependency)) ds
+              ]
          in if null missingDeps
               then DepOk
               else MissingDeps missingDeps
diff --git a/Cabal-syntax/src/Distribution/Pretty.hs b/Cabal-syntax/src/Distribution/Pretty.hs
index 3ddb806d81b..fcb0a7f0d0b 100644
--- a/Cabal-syntax/src/Distribution/Pretty.hs
+++ b/Cabal-syntax/src/Distribution/Pretty.hs
@@ -10,6 +10,8 @@ module Distribution.Pretty
   , showTokenStr
   , showFreeText
   , showFreeTextV3
+  , commaSpaceSep
+  , commaSep
 
     -- * Deprecated
   , Separator
@@ -118,3 +120,11 @@ lines_ s =
    in l : case s' of
         [] -> []
         (_ : s'') -> lines_ s''
+
+-- | Separate a list of documents by commas and spaces.
+commaSpaceSep :: Pretty a => [a] -> PP.Doc
+commaSpaceSep = PP.hsep . PP.punctuate PP.comma . map pretty
+
+-- | Separate a list of documents by commas.
+commaSep :: Pretty a => [a] -> PP.Doc
+commaSep = PP.hcat . PP.punctuate PP.comma . map pretty
diff --git a/Cabal-syntax/src/Distribution/Types/Dependency.hs b/Cabal-syntax/src/Distribution/Types/Dependency.hs
index 222a699a3f9..a152c9e3a68 100644
--- a/Cabal-syntax/src/Distribution/Types/Dependency.hs
+++ b/Cabal-syntax/src/Distribution/Types/Dependency.hs
@@ -78,31 +78,21 @@ instance NFData Dependency where rnf = genericRnf
 -- "pkg"
 --
 -- >>> prettyShow $ Dependency (mkPackageName "pkg") anyVersion $ NES.insert (LSubLibName $ mkUnqualComponentName "sublib") mainLibSet
--- "pkg:{pkg, sublib}"
+-- "pkg:{pkg,sublib}"
 --
 -- >>> prettyShow $ Dependency (mkPackageName "pkg") anyVersion $ NES.singleton (LSubLibName $ mkUnqualComponentName "sublib")
 -- "pkg:sublib"
 --
 -- >>> prettyShow $ Dependency (mkPackageName "pkg") anyVersion $ NES.insert (LSubLibName $ mkUnqualComponentName "sublib-b") $ NES.singleton (LSubLibName $ mkUnqualComponentName "sublib-a")
--- "pkg:{sublib-a, sublib-b}"
+-- "pkg:{sublib-a,sublib-b}"
 instance Pretty Dependency where
-  pretty (Dependency name ver sublibs) = withSubLibs (pretty name) <+> pver
+  pretty (Dependency name ver sublibs) = prettyLibraryNames name (NES.toNonEmpty sublibs) <+> pver
     where
       -- TODO: change to isAnyVersion after #6736
       pver
         | isAnyVersionLight ver = PP.empty
         | otherwise = pretty ver
 
-      withSubLibs doc = case NES.toList sublibs of
-        [LMainLibName] -> doc
-        [LSubLibName uq] -> doc <<>> PP.colon <<>> pretty uq
-        _ -> doc <<>> PP.colon <<>> PP.braces prettySublibs
-
-      prettySublibs = PP.hsep $ PP.punctuate PP.comma $ prettySublib <$> NES.toList sublibs
-
-      prettySublib LMainLibName = PP.text $ unPackageName name
-      prettySublib (LSubLibName un) = PP.text $ unUnqualComponentName un
-
 -- |
 --
 -- >>> simpleParsec "mylib:sub" :: Maybe Dependency
diff --git a/Cabal-syntax/src/Distribution/Types/DependencySatisfaction.hs b/Cabal-syntax/src/Distribution/Types/DependencySatisfaction.hs
new file mode 100644
index 00000000000..56ce74c1c45
--- /dev/null
+++ b/Cabal-syntax/src/Distribution/Types/DependencySatisfaction.hs
@@ -0,0 +1,14 @@
+module Distribution.Types.DependencySatisfaction
+  ( DependencySatisfaction (..)
+  ) where
+
+import Distribution.Types.MissingDependencyReason (MissingDependencyReason)
+
+-- | Whether or not a dependency constraint is satisfied.
+data DependencySatisfaction
+  = -- | The dependency constraint is satisfied.
+    Satisfied
+  | -- | The dependency constraint is not satisfied.
+    --
+    -- Includes a reason for explanation.
+    Unsatisfied MissingDependencyReason
diff --git a/Cabal-syntax/src/Distribution/Types/LibraryName.hs b/Cabal-syntax/src/Distribution/Types/LibraryName.hs
index 2b8f53f4f89..9073aae9a1f 100644
--- a/Cabal-syntax/src/Distribution/Types/LibraryName.hs
+++ b/Cabal-syntax/src/Distribution/Types/LibraryName.hs
@@ -10,6 +10,7 @@ module Distribution.Types.LibraryName
   , libraryNameString
 
     -- * Pretty & Parse
+  , prettyLibraryNames
   , prettyLibraryNameComponent
   , parsecLibraryNameComponent
   ) where
@@ -17,6 +18,7 @@ module Distribution.Types.LibraryName
 import Distribution.Compat.Prelude
 import Prelude ()
 
+import qualified Data.List.NonEmpty as NEL
 import Distribution.Parsec
 import Distribution.Pretty
 import Distribution.Types.UnqualComponentName
@@ -42,6 +44,22 @@ prettyLibraryNameComponent :: LibraryName -> Disp.Doc
 prettyLibraryNameComponent LMainLibName = Disp.text "lib"
 prettyLibraryNameComponent (LSubLibName str) = Disp.text "lib:" <<>> pretty str
 
+-- | Pretty print a 'LibraryName' after a package name.
+--
+-- Produces output like @foo@, @foo:bar@, or @foo:{bar,baz}@
+prettyLibraryNames :: Pretty a => a -> NonEmpty LibraryName -> Disp.Doc
+prettyLibraryNames package libraries =
+  let doc = pretty package
+
+      prettyComponent LMainLibName = pretty package
+      prettyComponent (LSubLibName component) = Disp.text $ unUnqualComponentName component
+
+      prettyComponents = commaSep $ prettyComponent <$> NEL.toList libraries
+   in case libraries of
+        LMainLibName :| [] -> doc
+        LSubLibName component :| [] -> doc <<>> Disp.colon <<>> pretty component
+        _ -> doc <<>> Disp.colon <<>> Disp.braces prettyComponents
+
 parsecLibraryNameComponent :: CabalParsing m => m LibraryName
 parsecLibraryNameComponent = do
   _ <- P.string "lib"
diff --git a/Cabal-syntax/src/Distribution/Types/MissingDependency.hs b/Cabal-syntax/src/Distribution/Types/MissingDependency.hs
new file mode 100644
index 00000000000..57d90276d8c
--- /dev/null
+++ b/Cabal-syntax/src/Distribution/Types/MissingDependency.hs
@@ -0,0 +1,34 @@
+module Distribution.Types.MissingDependency
+  ( MissingDependency (..)
+  ) where
+
+import Distribution.Compat.Prelude
+import Distribution.Pretty
+import Distribution.Types.Dependency
+  ( Dependency
+  , simplifyDependency
+  )
+import Distribution.Types.LibraryName
+  ( prettyLibraryNames
+  )
+import Distribution.Types.MissingDependencyReason
+  ( MissingDependencyReason (..)
+  )
+
+import qualified Text.PrettyPrint as PP
+
+-- | A missing dependency and information on why it's missing.
+data MissingDependency = MissingDependency Dependency MissingDependencyReason
+  deriving (Show)
+
+instance Pretty MissingDependency where
+  pretty (MissingDependency dependency reason) =
+    let prettyReason =
+          case reason of
+            MissingLibrary libraries ->
+              PP.text "missing" <+> prettyLibraryNames PP.empty libraries
+            MissingPackage -> PP.text "missing"
+            MissingComponent name -> PP.text "missing component" <+> pretty name
+            WrongVersion versions ->
+              PP.text "installed:" <+> commaSpaceSep versions
+     in pretty (simplifyDependency dependency) <+> PP.parens prettyReason
diff --git a/Cabal-syntax/src/Distribution/Types/MissingDependencyReason.hs b/Cabal-syntax/src/Distribution/Types/MissingDependencyReason.hs
new file mode 100644
index 00000000000..c1c37800f21
--- /dev/null
+++ b/Cabal-syntax/src/Distribution/Types/MissingDependencyReason.hs
@@ -0,0 +1,25 @@
+module Distribution.Types.MissingDependencyReason
+  ( MissingDependencyReason (..)
+  ) where
+
+import Data.List.NonEmpty (NonEmpty)
+import Distribution.Types.LibraryName (LibraryName)
+import Distribution.Types.PackageName (PackageName)
+import Distribution.Types.Version (Version)
+
+-- | A reason for a depency failing to solve.
+--
+-- This helps pinpoint dependencies that are installed with an incorrect
+-- version vs. dependencies that are not installed at all.
+data MissingDependencyReason
+  = -- | One or more libraries is missing.
+    MissingLibrary (NonEmpty LibraryName)
+  | -- | A package is not installed.
+    MissingPackage
+  | -- | A package is installed, but the versions don't match.
+    --
+    -- Contains the available versions.
+    WrongVersion [Version]
+  | -- | A component is not installed.
+    MissingComponent PackageName
+  deriving (Show)
diff --git a/Cabal-tests/tests/ParserTests/regressions/issue-5846.format b/Cabal-tests/tests/ParserTests/regressions/issue-5846.format
index 749a9c20524..93e53fc48bd 100644
--- a/Cabal-tests/tests/ParserTests/regressions/issue-5846.format
+++ b/Cabal-tests/tests/ParserTests/regressions/issue-5846.format
@@ -5,7 +5,7 @@ version:       5846
 library
     default-language: Haskell2010
     build-depends:
-        lib1:{a, b},
+        lib1:{a,b},
         lib2:c,
         lib3:d >=1,
-        lib4:{a, b} >=1
+        lib4:{a,b} >=1
diff --git a/Cabal/Cabal.cabal b/Cabal/Cabal.cabal
index 14e7050c5db..1e98be1a99c 100644
--- a/Cabal/Cabal.cabal
+++ b/Cabal/Cabal.cabal
@@ -248,6 +248,7 @@ library
     Distribution.Types.ConfVar,
     Distribution.Types.Dependency,
     Distribution.Types.DependencyMap,
+    Distribution.Types.DependencySatisfaction,
     Distribution.Types.ExeDependency,
     Distribution.Types.Executable,
     Distribution.Types.Executable.Lens,
@@ -271,6 +272,8 @@ library
     Distribution.Types.Library.Lens,
     Distribution.Types.LibraryName,
     Distribution.Types.LibraryVisibility,
+    Distribution.Types.MissingDependency,
+    Distribution.Types.MissingDependencyReason,
     Distribution.Types.Mixin,
     Distribution.Types.Module,
     Distribution.Types.ModuleReexport,
diff --git a/Cabal/src/Distribution/Simple/Configure.hs b/Cabal/src/Distribution/Simple/Configure.hs
index 04929bad030..b3d0b28d462 100644
--- a/Cabal/src/Distribution/Simple/Configure.hs
+++ b/Cabal/src/Distribution/Simple/Configure.hs
@@ -106,9 +106,11 @@ import qualified Distribution.Simple.SetupHooks.Internal as SetupHooks
 import Distribution.Simple.Utils
 import Distribution.System
 import Distribution.Types.ComponentRequestedSpec
+import Distribution.Types.DependencySatisfaction (DependencySatisfaction (..))
 import Distribution.Types.GivenComponent
 import qualified Distribution.Types.LocalBuildConfig as LBC
 import Distribution.Types.LocalBuildInfo
+import Distribution.Types.MissingDependencyReason (MissingDependencyReason (..))
 import Distribution.Types.PackageVersionConstraint
 import Distribution.Utils.LogProgress
 import Distribution.Utils.NubList
@@ -1480,7 +1482,7 @@ dependencySatisfiable
   -> Map (PackageName, ComponentName) ComponentId
   -> Map (PackageName, ComponentName) InstalledPackageInfo
   -- ^ required dependencies
-  -> (Dependency -> Bool)
+  -> (Dependency -> DependencySatisfaction)
 dependencySatisfiable
   use_external_internal_deps
   exact_config
@@ -1506,16 +1508,18 @@ dependencySatisfiable
             internalDepSatisfiable
           else -- Backward compatibility for the old sublibrary syntax
 
-            ( sublibs == mainLibSet
-                && Map.member
-                  ( pn
-                  , CLibName $
-                      LSubLibName $
-                        packageNameToUnqualComponentName depName
-                  )
-                  requiredDepsMap
-            )
-              || all visible sublibs
+            if sublibs == mainLibSet
+              then
+                let depComponentName =
+                      CLibName $ LSubLibName $ packageNameToUnqualComponentName depName
+                 in if Map.member (pn, depComponentName) requiredDepsMap
+                      then Satisfied
+                      else Unsatisfied $ MissingComponent depName
+              else
+                let invisibleLibraries = NES.filter (not . visible) sublibs
+                 in case nonEmpty $ Set.toList invisibleLibraries of
+                      Nothing -> Satisfied
+                      Just invisibleLibraries' -> Unsatisfied $ MissingLibrary invisibleLibraries'
     | isInternalDep =
         if use_external_internal_deps
           then -- When we are doing per-component configure, we now need to
@@ -1532,12 +1536,31 @@ dependencySatisfiable
       isInternalDep = pn == depName
 
       depSatisfiable =
-        not . null $ PackageIndex.lookupDependency installedPackageSet depName vr
+        let allVersions = PackageIndex.lookupPackageName installedPackageSet depName
+            eligibleVersions =
+              [ version
+              | (version, _infos) <- PackageIndex.eligibleDependencies allVersions
+              ]
+         in if null $ PackageIndex.matchingDependencies vr allVersions
+              then
+                if null eligibleVersions
+                  then Unsatisfied $ MissingPackage
+                  else Unsatisfied $ WrongVersion eligibleVersions
+              else Satisfied
 
       internalDepSatisfiable =
-        Set.isSubsetOf (NES.toSet sublibs) packageLibraries
+        let missingLibraries = (NES.toSet sublibs) `Set.difference` packageLibraries
+         in case nonEmpty $ Set.toList missingLibraries of
+              Nothing -> Satisfied
+              Just missingLibraries' -> Unsatisfied $ MissingLibrary missingLibraries'
+
       internalDepSatisfiableExternally =
-        all (\ln -> not $ null $ PackageIndex.lookupInternalDependency installedPackageSet pn vr ln) sublibs
+        -- TODO: Might need to propagate information on which versions _are_ available, if any...
+        let missingLibraries =
+              NES.filter (null . PackageIndex.lookupInternalDependency installedPackageSet pn vr) sublibs
+         in case nonEmpty $ Set.toList missingLibraries of
+              Nothing -> Satisfied
+              Just missingLibraries' -> Unsatisfied $ MissingLibrary missingLibraries'
 
       -- Check whether a library exists and is visible.
       -- We don't disambiguate between dependency on non-existent or private
@@ -1572,7 +1595,7 @@ configureFinalizedPackage
   -> ConfigFlags
   -> ComponentRequestedSpec
   -> [PackageVersionConstraint]
-  -> (Dependency -> Bool)
+  -> (Dependency -> DependencySatisfaction)
   -- ^ tests if a dependency is satisfiable.
   -- Might say it's satisfiable even when not.
   -> Compiler
diff --git a/Cabal/src/Distribution/Simple/Errors.hs b/Cabal/src/Distribution/Simple/Errors.hs
index c1cc75b5ad1..253b2f0dfbe 100644
--- a/Cabal/src/Distribution/Simple/Errors.hs
+++ b/Cabal/src/Distribution/Simple/Errors.hs
@@ -31,6 +31,7 @@ import Distribution.Simple.InstallDirs
 import Distribution.Simple.PreProcess.Types (Suffix)
 import Distribution.Simple.SetupHooks.Errors
 import Distribution.System (OS)
+import Distribution.Types.MissingDependency (MissingDependency)
 import Distribution.Types.VersionRange.Internal ()
 import Distribution.Version
 import Text.PrettyPrint
@@ -126,7 +127,7 @@ data CabalException
   | CantFindForeignLibraries [String]
   | ExpectedAbsoluteDirectory FilePath
   | FlagsNotSpecified [FlagName]
-  | EncounteredMissingDependency [Dependency]
+  | EncounteredMissingDependency [MissingDependency]
   | CompilerDoesn'tSupportThinning
   | CompilerDoesn'tSupportReexports
   | CompilerDoesn'tSupportBackpack
@@ -552,7 +553,7 @@ exceptionMessage e = case e of
             . nest 4
             . sep
             . punctuate comma
-            . map (pretty . simplifyDependency)
+            . map pretty
             $ missing
          )
   CompilerDoesn'tSupportThinning ->
diff --git a/Cabal/src/Distribution/Simple/PackageIndex.hs b/Cabal/src/Distribution/Simple/PackageIndex.hs
index 927e10ae878..e6944430755 100644
--- a/Cabal/src/Distribution/Simple/PackageIndex.hs
+++ b/Cabal/src/Distribution/Simple/PackageIndex.hs
@@ -68,6 +68,7 @@ module Distribution.Simple.PackageIndex
   , lookupSourcePackageId
   , lookupPackageId
   , lookupPackageName
+  , lookupInternalPackageName
   , lookupDependency
   , lookupInternalDependency
 
@@ -93,6 +94,10 @@ module Distribution.Simple.PackageIndex
   , dependencyCycles
   , dependencyGraph
   , moduleNameIndex
+
+    -- ** Filters on lookup results
+  , eligibleDependencies
+  , matchingDependencies
   ) where
 
 import qualified Data.Map.Strict as Map
@@ -474,7 +479,18 @@ lookupPackageName
   -> [(Version, [a])]
 lookupPackageName index name =
   -- Do not match internal libraries
-  case Map.lookup (name, LMainLibName) (packageIdIndex index) of
+  lookupInternalPackageName index name LMainLibName
+
+-- | Does a lookup by source package name and library name.
+--
+-- Also looks up internal packages.
+lookupInternalPackageName
+  :: PackageIndex a
+  -> PackageName
+  -> LibraryName
+  -> [(Version, [a])]
+lookupInternalPackageName index name library =
+  case Map.lookup (name, library) (packageIdIndex index) of
     Nothing -> []
     Just pvers -> Map.toList pvers
 
@@ -509,23 +525,46 @@ lookupInternalDependency
   -> LibraryName
   -> [(Version, [IPI.InstalledPackageInfo])]
 lookupInternalDependency index name versionRange libn =
-  case Map.lookup (name, libn) (packageIdIndex index) of
-    Nothing -> []
-    Just pvers ->
-      [ (ver, pkgs')
-      | (ver, pkgs) <- Map.toList pvers
-      , ver `withinRange` versionRange
-      , let pkgs' = filter eligible pkgs
-      , -- Enforce the invariant
-      not (null pkgs')
-      ]
+  matchingDependencies versionRange $
+    lookupInternalPackageName index name libn
+
+-- | Filter a set of installed packages to ones eligible as dependencies.
+--
+-- When we select for dependencies, we ONLY want to pick up indefinite
+-- packages, or packages with no instantiations.  We'll do mix-in linking to
+-- improve any such package into an instantiated one later.
+--
+-- INVARIANT: List of eligible 'IPI.InstalledPackageInfo' is non-empty.
+eligibleDependencies
+  :: [(Version, [IPI.InstalledPackageInfo])]
+  -> [(Version, [IPI.InstalledPackageInfo])]
+eligibleDependencies versions =
+  [ (ver, pkgs')
+  | (ver, pkgs) <- versions
+  , let pkgs' = filter eligible pkgs
+  , -- Enforce the invariant
+  not (null pkgs')
+  ]
   where
-    -- When we select for dependencies, we ONLY want to pick up indefinite
-    -- packages, or packages with no instantiations.  We'll do mix-in
-    -- linking to improve any such package into an instantiated one
-    -- later.
     eligible pkg = IPI.indefinite pkg || null (IPI.instantiatedWith pkg)
 
+-- | Get eligible dependencies from a list of versions.
+--
+-- This can be used to filter the output of 'lookupPackageName' or
+-- 'lookupInternalPackageName'.
+--
+-- INVARIANT: List of eligible 'IPI.InstalledPackageInfo' is non-empty.
+matchingDependencies
+  :: VersionRange
+  -> [(Version, [IPI.InstalledPackageInfo])]
+  -> [(Version, [IPI.InstalledPackageInfo])]
+matchingDependencies versionRange versions =
+  let eligibleVersions = eligibleDependencies versions
+   in [ (ver, pkgs)
+      | (ver, pkgs) <- eligibleVersions
+      , ver `withinRange` versionRange
+      ]
+
 --
 
 -- * Case insensitive name lookups
diff --git a/cabal-install/src/Distribution/Client/CmdOutdated.hs b/cabal-install/src/Distribution/Client/CmdOutdated.hs
index ed40a1a85e6..7674e67286f 100644
--- a/cabal-install/src/Distribution/Client/CmdOutdated.hs
+++ b/cabal-install/src/Distribution/Client/CmdOutdated.hs
@@ -129,6 +129,9 @@ import Distribution.Types.ComponentRequestedSpec
 import Distribution.Types.Dependency
   ( Dependency (..)
   )
+import Distribution.Types.DependencySatisfaction
+  ( DependencySatisfaction (..)
+  )
 import Distribution.Types.PackageVersionConstraint
   ( PackageVersionConstraint (..)
   , simplifyPackageVersionConstraint
@@ -443,7 +446,7 @@ depsFromPkgDesc verbosity comp platform = do
         finalizePD
           mempty
           (ComponentRequestedSpec True True)
-          (const True)
+          (const Satisfied)
           platform
           cinfo
           []
diff --git a/cabal-install/src/Distribution/Client/Configure.hs b/cabal-install/src/Distribution/Client/Configure.hs
index 0586a362dd2..34cd4dfea71 100644
--- a/cabal-install/src/Distribution/Client/Configure.hs
+++ b/cabal-install/src/Distribution/Client/Configure.hs
@@ -116,6 +116,9 @@ import Distribution.Simple.Utils as Utils
 import Distribution.System
   ( Platform
   )
+import Distribution.Types.DependencySatisfaction
+  ( DependencySatisfaction (..)
+  )
 import Distribution.Types.GivenComponent
   ( GivenComponent (..)
   )
@@ -555,7 +558,7 @@ configurePackage
       pkg = case finalizePD
         flags
         (enableStanzas stanzas)
-        (const True)
+        (const Satisfied)
         platform
         comp
         []
diff --git a/cabal-install/src/Distribution/Client/Dependency.hs b/cabal-install/src/Distribution/Client/Dependency.hs
index ae731cdc64b..d59bc611c44 100644
--- a/cabal-install/src/Distribution/Client/Dependency.hs
+++ b/cabal-install/src/Distribution/Client/Dependency.hs
@@ -127,6 +127,9 @@ import Distribution.System
   ( Platform
   )
 import Distribution.Types.Dependency
+import Distribution.Types.DependencySatisfaction
+  ( DependencySatisfaction (..)
+  )
 import Distribution.Verbosity
   ( normal
   )
@@ -1092,7 +1095,7 @@ configuredPackageProblems
         case finalizePD
           specifiedFlags
           compSpec
-          (const True)
+          (const Satisfied)
           platform
           cinfo
           []
diff --git a/cabal-install/src/Distribution/Client/GenBounds.hs b/cabal-install/src/Distribution/Client/GenBounds.hs
index ae78b50c004..0a49f185834 100644
--- a/cabal-install/src/Distribution/Client/GenBounds.hs
+++ b/cabal-install/src/Distribution/Client/GenBounds.hs
@@ -67,6 +67,9 @@ import Distribution.Types.ComponentRequestedSpec
   ( defaultComponentRequestedSpec
   )
 import Distribution.Types.Dependency
+import Distribution.Types.DependencySatisfaction
+  ( DependencySatisfaction (..)
+  )
 import Distribution.Utils.Path (relativeSymbolicPath)
 import Distribution.Version
   ( LowerBound (..)
@@ -138,7 +141,7 @@ genBounds verbosity packageDBs repoCtxt comp platform progdb globalFlags freezeF
         finalizePD
           mempty
           defaultComponentRequestedSpec
-          (const True)
+          (const Satisfied)
           platform
           cinfo
           []
diff --git a/cabal-install/src/Distribution/Client/Install.hs b/cabal-install/src/Distribution/Client/Install.hs
index 9cf80d3858c..aefc8ef3287 100644
--- a/cabal-install/src/Distribution/Client/Install.hs
+++ b/cabal-install/src/Distribution/Client/Install.hs
@@ -245,6 +245,9 @@ import Distribution.System
   , buildOS
   , buildPlatform
   )
+import Distribution.Types.DependencySatisfaction
+  ( DependencySatisfaction (..)
+  )
 import Distribution.Types.Flag
   ( FlagAssignment
   , PackageFlag (..)
@@ -1677,7 +1680,7 @@ installReadyPackage
       pkg = case finalizePD
         flags
         (enableStanzas stanzas)
-        (const True)
+        (const Satisfied)
         platform
         cinfo
         []
diff --git a/cabal-install/src/Distribution/Client/InstallSymlink.hs b/cabal-install/src/Distribution/Client/InstallSymlink.hs
index 7a470843779..46e1edaebef 100644
--- a/cabal-install/src/Distribution/Client/InstallSymlink.hs
+++ b/cabal-install/src/Distribution/Client/InstallSymlink.hs
@@ -74,6 +74,9 @@ import Distribution.Simple.Utils (info, withTempDirectory)
 import Distribution.System
   ( Platform
   )
+import Distribution.Types.DependencySatisfaction
+  ( DependencySatisfaction (..)
+  )
 import Distribution.Types.UnqualComponentName
 
 import System.Directory
@@ -205,7 +208,7 @@ symlinkBinaries
           case finalizePD
             flags
             (enableStanzas stanzas)
-            (const True)
+            (const Satisfied)
             platform
             cinfo
             []
diff --git a/cabal-install/src/Distribution/Client/ProjectPlanning.hs b/cabal-install/src/Distribution/Client/ProjectPlanning.hs
index 4efa5f313b1..4e5f1cb4918 100644
--- a/cabal-install/src/Distribution/Client/ProjectPlanning.hs
+++ b/cabal-install/src/Distribution/Client/ProjectPlanning.hs
@@ -176,6 +176,9 @@ import Distribution.System
 import Distribution.Types.AnnotatedId
 import Distribution.Types.ComponentInclude
 import Distribution.Types.ComponentName
+import Distribution.Types.DependencySatisfaction
+  ( DependencySatisfaction (..)
+  )
 import Distribution.Types.DumpBuildInfo
 import Distribution.Types.GivenComponent
 import Distribution.Types.LibraryName
@@ -2130,7 +2133,7 @@ elaborateInstallPlan
             elabPkgDescription = case PD.finalizePD
               flags
               elabEnabledSpec
-              (const True)
+              (const Satisfied)
               platform
               (compilerInfo compiler)
               []
diff --git a/cabal-testsuite/PackageTests/ConfigureComponent/SubLib/setup-explicit-fail.out b/cabal-testsuite/PackageTests/ConfigureComponent/SubLib/setup-explicit-fail.out
index fec347864e5..da9de233fab 100644
--- a/cabal-testsuite/PackageTests/ConfigureComponent/SubLib/setup-explicit-fail.out
+++ b/cabal-testsuite/PackageTests/ConfigureComponent/SubLib/setup-explicit-fail.out
@@ -11,4 +11,5 @@ Registering library 'sublib' for Lib-0.1.0.0...
 Configuring executable 'exe' for Lib-0.1.0.0...
 Error: [Cabal-8010]
 Encountered missing or private dependencies:
-    Lib:sublib
+    Lib:sublib (missing :sublib),
+    base ==4.20.0.0 (missing component base)