diff --git a/cabal-install/Distribution/Solver/Modular/IndexConversion.hs b/cabal-install/Distribution/Solver/Modular/IndexConversion.hs
index 45a671d69f982df83ffb68a2de9e24f714217f62..5f9d1d1c7d04839e95bf2a5b5345aca4f85fda7b 100644
--- a/cabal-install/Distribution/Solver/Modular/IndexConversion.hs
+++ b/cabal-install/Distribution/Solver/Modular/IndexConversion.hs
@@ -13,6 +13,7 @@ import Distribution.Compiler
import Distribution.InstalledPackageInfo as IPI
import Distribution.Package -- from Cabal
import Distribution.Simple.BuildToolDepends -- from Cabal
+import Distribution.Simple.Utils (cabalVersion) -- from Cabal
import Distribution.Types.ExeDependency -- from Cabal
import Distribution.Types.PkgconfigDependency -- from Cabal
import Distribution.Types.ComponentName -- from Cabal
@@ -186,8 +187,36 @@ convGPD os arch cinfo strfl sexes pi
(L.map (\(nm, ds) -> conv (ComponentBench nm) benchmarkBuildInfo ds) benchs)
++ maybe [] (convSetupBuildInfo pi) (setupBuildInfo pkg)
+ -- | We infer the maximally supported spec-version from @lib:Cabal@'s version
+ --
+ -- As we cannot predict the future, we can only properly support
+ -- spec-versions predating (and including) the @lib:Cabal@ version
+ -- used by @cabal-install@.
+ --
+ -- This relies on 'cabalVersion' having always at least 3 components to avoid
+ -- comparisons like @2.0.0 > 2.0@ which would result in confusing results.
+ --
+ -- NOTE: Before we can switch to a /normalised/ spec-version
+ -- comparison (e.g. by truncating to 3 components, and removing
+ -- trailing zeroes) we'd have to make sure all other places where
+ -- the spec-version is compared against a bound do it
+ -- consistently.
+ maxSpecVer = cabalVersion
+
+ -- | Required/declared spec-version of the package
+ --
+ -- We don't truncate patch-levels, as specifying a patch-level
+ -- spec-version is discouraged and not supported anymore starting
+ -- with spec-version 2.2.
+ reqSpecVer = specVersion pkg
+
+ -- | A too-new specVersion is turned into a global 'FailReason'
+ -- which prevents the solver from selecting this release (and if
+ -- forced to, emit a meaningful solver error message).
+ fr | reqSpecVer > maxSpecVer = Just (UnsupportedSpecVer reqSpecVer)
+ | otherwise = Nothing
in
- PInfo flagged_deps fds Nothing
+ PInfo flagged_deps fds fr
-- | Create a flagged dependency tree from a list @fds@ of flagged
-- dependencies, using @f@ to form the tree node (@f@ will be
diff --git a/cabal-install/Distribution/Solver/Modular/Message.hs b/cabal-install/Distribution/Solver/Modular/Message.hs
index d6542388c0bbf59b932e17ccacadd403484e75ea..fd50200f149ad15336aec391b7de93cd2ad595d2 100644
--- a/cabal-install/Distribution/Solver/Modular/Message.hs
+++ b/cabal-install/Distribution/Solver/Modular/Message.hs
@@ -144,6 +144,7 @@ showFR c Backjump = " (backjumping, conflict set: " ++ s
showFR _ MultipleInstances = " (multiple instances)"
showFR c (DependenciesNotLinked msg) = " (dependencies not linked: " ++ msg ++ "; conflict set: " ++ showConflictSet c ++ ")"
showFR c CyclicDependencies = " (cyclic dependencies; conflict set: " ++ showConflictSet c ++ ")"
+showFR _ (UnsupportedSpecVer ver) = " (unsupported spec-version " ++ display ver ++ ")"
-- The following are internal failures. They should not occur. In the
-- interest of not crashing unnecessarily, we still just print an error
-- message though.
diff --git a/cabal-install/Distribution/Solver/Modular/Tree.hs b/cabal-install/Distribution/Solver/Modular/Tree.hs
index 535127d84a1cfa49cb58cd52fe4f617bdc8754e6..8b6e42239b2ec2f32443b89b685ee3f933963eb2 100644
--- a/cabal-install/Distribution/Solver/Modular/Tree.hs
+++ b/cabal-install/Distribution/Solver/Modular/Tree.hs
@@ -111,6 +111,7 @@ data FailReason = InconsistentInitialConstraints
| MultipleInstances
| DependenciesNotLinked String
| CyclicDependencies
+ | UnsupportedSpecVer Ver
deriving (Eq, Show)
-- | Functor for the tree type. 'a' is the type of nodes' children. 'd' and 'c'
diff --git a/cabal-testsuite/PackageTests/CustomWithoutCabal/cabal.out b/cabal-testsuite/PackageTests/CustomWithoutCabal/cabal.out
index e6e102302ba60aaaab79ec03df66851619f60763..fd8234df0272660cf5452fcf67c1a8ef39356680 100644
--- a/cabal-testsuite/PackageTests/CustomWithoutCabal/cabal.out
+++ b/cabal-testsuite/PackageTests/CustomWithoutCabal/cabal.out
@@ -1,5 +1,4 @@
# cabal new-build
-Warning: <ROOT>/custom-setup-without-cabal.cabal: This package requires at least Cabal version 99999
Resolving dependencies...
In order, the following will be built:
- custom-setup-without-cabal-1.0 (lib:custom-setup-without-cabal) (first run)
diff --git a/cabal-testsuite/PackageTests/CustomWithoutCabal/custom-setup-without-cabal.cabal b/cabal-testsuite/PackageTests/CustomWithoutCabal/custom-setup-without-cabal.cabal
index 7abdee77c712184de2203d391c6288d7b3e536c1..64d2e55de4f91dc5e8a0a851b7bd7be508de3560 100644
--- a/cabal-testsuite/PackageTests/CustomWithoutCabal/custom-setup-without-cabal.cabal
+++ b/cabal-testsuite/PackageTests/CustomWithoutCabal/custom-setup-without-cabal.cabal
@@ -1,7 +1,7 @@
+cabal-version: 2.0
name: custom-setup-without-cabal
version: 1.0
build-type: Custom
-cabal-version: >= 99999
custom-setup
setup-depends: base
diff --git a/cabal-testsuite/PackageTests/Regression/T3436/cabal.out b/cabal-testsuite/PackageTests/Regression/T3436/cabal.out
index 392c2afb5e8e5c5b706b5b6add49298396e68adb..86d92c8be21c51fe7b0e7535c553d1e74b5e2724 100644
--- a/cabal-testsuite/PackageTests/Regression/T3436/cabal.out
+++ b/cabal-testsuite/PackageTests/Regression/T3436/cabal.out
@@ -1,5 +1,4 @@
# cabal new-build
-Warning: <ROOT>/custom-setup/custom-setup.cabal: This package requires at least Cabal version 99999
Resolving dependencies...
In order, the following will be built:
- Cabal-99999 (lib:Cabal) (first run)
diff --git a/cabal-testsuite/PackageTests/Regression/T3436/custom-setup/custom-setup.cabal b/cabal-testsuite/PackageTests/Regression/T3436/custom-setup/custom-setup.cabal
index 923de11e862a5f4290c41509f6b8efea4c4560aa..f06d6644610e880f5690b560e54ebd34a082c000 100644
--- a/cabal-testsuite/PackageTests/Regression/T3436/custom-setup/custom-setup.cabal
+++ b/cabal-testsuite/PackageTests/Regression/T3436/custom-setup/custom-setup.cabal
@@ -1,7 +1,7 @@
+cabal-version: 2.0
name: custom-setup
version: 1.0
build-type: Custom
-cabal-version: >= 99999
custom-setup
setup-depends: base, Cabal >= 99999
diff --git a/cabal-testsuite/PackageTests/Regression/T3436/sandbox.out b/cabal-testsuite/PackageTests/Regression/T3436/sandbox.out
index 536ab7d3415ea38005cad136b953f810ab9e2f00..761a5e3feeeaa06c52413aeda919039581fbe1f2 100644
--- a/cabal-testsuite/PackageTests/Regression/T3436/sandbox.out
+++ b/cabal-testsuite/PackageTests/Regression/T3436/sandbox.out
@@ -10,7 +10,6 @@ Installing library in <PATH>
Installed Cabal-99998
# cabal sandbox add-source
# cabal install
-Warning: custom-setup/custom-setup.cabal: This package requires at least Cabal version 99999
Resolving dependencies...
Configuring Cabal-99999...
Preprocessing library for Cabal-99999..