Add test for default-constraints

Cabal-tests/tests/UnitTests/Distribution/Utils/Structured.hs

@@ -27,9 +27,9 @@ tests = testGroup "Distribution.Utils.Structured"
     -- The difference is in encoding of newtypes
 #if MIN_VERSION_base(4,7,0)
     , testCase "GenericPackageDescription" $
-      md5Check (Proxy :: Proxy GenericPackageDescription) 0xb287a6f04e34ef990cdd15bc6cb01c76
+      md5Check (Proxy :: Proxy GenericPackageDescription) 938eba2cc4fe10bb1f954d05c253d575
     , testCase "LocalBuildInfo" $
-      md5Check (Proxy :: Proxy LocalBuildInfo) 0x26e91a71ebd19d4d6ce37f798ede249a
+      md5Check (Proxy :: Proxy LocalBuildInfo) 0x4adc7abeee033098c254f167d4521d64
 #endif
     ]
 

cabal-testsuite/PackageTests/DefaultConstraints/Main.hs

@@ -0,0 +1,4 @@
+module Main where
+
+main :: IO ()
+main = pure ()

cabal-testsuite/PackageTests/DefaultConstraints/cabal.out

@@ -0,0 +1,18 @@
+# cabal build
+Resolving dependencies...
+Build profile: -w ghc-<GHCVER> -O1
+In order, the following will be built:
+ - foo-0.1.0.0 (lib) (first run)
+Configuring library for foo-0.1.0.0...
+Preprocessing library for foo-0.1.0.0...
+Building library for foo-0.1.0.0...
+# cabal build
+Resolving dependencies...
+Error: [Cabal-7107]
+Could not resolve dependencies:
+[__0] trying: foo-0.1.0.0 (user goal)
+[__1] trying: foo:*test
+[__2] next goal: base (dependency of foo)
+[__2] rejecting: base-<VERSION>/installed-<HASH> (conflict: foo *test => base<0)
+[__2] fail (backjumping, conflict set: base, foo, foo:test)
+After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: foo (4), foo:test (3), base (2)

cabal-testsuite/PackageTests/DefaultConstraints/cabal.project

@@ -0,0 +1 @@
+packages: foo

cabal-testsuite/PackageTests/DefaultConstraints/cabal.test.hs

@@ -0,0 +1,5 @@
+import Test.Cabal.Prelude
+
+main = cabalTest $ withProjectFile "cabal.project" $ do
+  cabal "build" ["foo"]
+  fails $ cabal "build" ["foo", "--enable-tests"]

cabal-testsuite/PackageTests/DefaultConstraints/foo/foo.cabal

@@ -0,0 +1,18 @@
+cabal-version:      3.11
+name:               foo
+version:            0.1.0.0
+
+default-constraints:
+  , base ^>=4.18.1.0
+
+library
+    build-depends:    base
+    default-language: Haskell2010
+
+test-suite foo-test
+    default-language: Haskell2010
+    type:             exitcode-stdio-1.0
+    main-is:          Main.hs
+    build-depends:
+        base <0,
+        blah