Error out on `Main` without `main` in GHCi (#7765)

Summary:
GHC does 2 validation checks for module `Main`:
* does `main` exist
* is `main` exported (#414)

The second check is done in ghc as well as in ghci (and runghc and ghc -e).
The first check however is currently not done in ghci, to prevent "'main' is
not in scope" errors when loading simple scripts. See commit d28ba8c8009 for
more information.

This commit tightens the special case for ghci. When the file does not contain
a main function, but does contain an explicit module header (i.e. "module Main
where"), then /do/ raise an error in ghci (and runghc and ghc -e) as well

Test Plan:
module/T7765: a module Main with an explicit module header but without a
main function should be an error for all Ways.

Additionaly: delete test module/mod174. It was added in commit 5a54c38, but it
is a duplicate of module/T414.

Reviewers: austin

Reviewed By: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D649

GHC Trac Issues: #7765

13 files changed, 20 insertions, 29 deletions

diff --git a/testsuite/tests/deriving/should_fail/T5686.hs b/testsuite/tests/deriving/should_fail/T5686.hs
index 425a13c839..a61df0627b 100644
--- a/testsuite/tests/deriving/should_fail/T5686.hs
+++ b/testsuite/tests/deriving/should_fail/T5686.hs
@@ -1,7 +1,7 @@
-{-# LANGUAGE TypeFamilies, DeriveFunctor #-}

-module Main where

-

-data U a = U (G a) deriving Functor

-

-class A a where

-   type G a

+{-# LANGUAGE TypeFamilies, DeriveFunctor #-}
+module T5686 where
+
+data U a = U (G a) deriving Functor
+
+class A a where
+   type G a
diff --git a/testsuite/tests/ghci/prog012/Main.hs b/testsuite/tests/ghci/prog012/FooBar.hs
index d49d063551..eeb29bbdbb 100644
--- a/testsuite/tests/ghci/prog012/Main.hs
+++ b/testsuite/tests/ghci/prog012/FooBar.hs
@@ -1,4 +1,4 @@
-module Main where
+module FooBar where
 
 import Foo
 import Bar
diff --git a/testsuite/tests/ghci/prog012/prog012.script b/testsuite/tests/ghci/prog012/prog012.script
index 49af938b75..5e178389ac 100644
--- a/testsuite/tests/ghci/prog012/prog012.script
+++ b/testsuite/tests/ghci/prog012/prog012.script
@@ -10,7 +10,7 @@
 
 :shell cp Bar1.hs Bar.hs
 
-:load Main.hs
+:load FooBar.hs
 :shell sleep 1
 :shell cp Bar2.hs Bar.hs
 
diff --git a/testsuite/tests/ghci/scripts/ghci022.hs b/testsuite/tests/ghci/scripts/ghci022.hs
index d49fdba319..f87946a758 100644
--- a/testsuite/tests/ghci/scripts/ghci022.hs
+++ b/testsuite/tests/ghci/scripts/ghci022.hs
@@ -1,2 +1,2 @@
-module Main where
+module GHCi022 where
 'a' '
diff --git a/testsuite/tests/ghci/scripts/ghci027.script b/testsuite/tests/ghci/scripts/ghci027.script
index aaf0ac5544..7a24f527bb 100644
--- a/testsuite/tests/ghci/scripts/ghci027.script
+++ b/testsuite/tests/ghci/scripts/ghci027.script
@@ -1,8 +1,8 @@
 -- Test for #1617
 :!cp ghci027_1.hs ghci027.hs
 :load ghci027
-:browse *Main
+:browse *T1617
 :!sleep 1
 :!cp ghci027_2.hs ghci027.hs
 :reload
-:browse *Main
+:browse *T1617
diff --git a/testsuite/tests/ghci/scripts/ghci027_1.hs b/testsuite/tests/ghci/scripts/ghci027_1.hs
index a1a7bfac37..23d52f0fee 100644
--- a/testsuite/tests/ghci/scripts/ghci027_1.hs
+++ b/testsuite/tests/ghci/scripts/ghci027_1.hs
@@ -1,5 +1,5 @@
 -- Test for #1617
-module Main where
+module T1617 where
 import Prelude ()
 import Control.Monad (mplus)
 import qualified Control.Monad (mplus)
diff --git a/testsuite/tests/ghci/scripts/ghci027_2.hs b/testsuite/tests/ghci/scripts/ghci027_2.hs
index df99d7d1c0..c4db784dc2 100644
--- a/testsuite/tests/ghci/scripts/ghci027_2.hs
+++ b/testsuite/tests/ghci/scripts/ghci027_2.hs
@@ -1,5 +1,5 @@
 -- Test for #1617
-module Main where
+module T1617 where
 import Prelude ()
 --import Control.Monad (mplus)
 import qualified Control.Monad (mplus)
diff --git a/testsuite/tests/module/T7765.hs b/testsuite/tests/module/T7765.hs
new file mode 100644
index 0000000000..6ca9a1fce6
--- /dev/null
+++ b/testsuite/tests/module/T7765.hs
@@ -0,0 +1 @@
+module Main where
diff --git a/testsuite/tests/module/T7765.stderr b/testsuite/tests/module/T7765.stderr
new file mode 100644
index 0000000000..bc8377d20d
--- /dev/null
+++ b/testsuite/tests/module/T7765.stderr
@@ -0,0 +1,2 @@
+
+T7765.hs:1:1: The IO action ‘main’ is not defined in module ‘Main’
diff --git a/testsuite/tests/module/all.T b/testsuite/tests/module/all.T
index 58632bea73..c86a5f8806 100644
--- a/testsuite/tests/module/all.T
+++ b/testsuite/tests/module/all.T
@@ -319,8 +319,7 @@ test('mod172', extra_clean(['Mod172_B.hi', 'Mod172_B.o', 'Mod172_C.hi', 'Mod172_
 test('mod173', extra_clean(['Mod173_Aux.hi', 'Mod173_Aux.o']),
      multimod_compile, ['mod173', '-v0'])
 
-test('mod174', normal, compile_fail, [''])
-
+# mod174 has been deleted
 # mod175 is a sub-directory
 
 test('mod176', normal, compile, ['-fwarn-unused-imports'])
@@ -343,5 +342,6 @@ test('T414', normal, compile_fail, [''])
 test('T414a', normal, compile, [''])
 test('T414b', normal, compile, [''])
 test('T3776', normal, compile, [''])
+test('T7765', normal, compile_fail, [''])
 test('T9061', normal, compile, [''])
 test('T9997', normal, compile, [''])
diff --git a/testsuite/tests/module/mod174.hs b/testsuite/tests/module/mod174.hs
deleted file mode 100644
index 8e8149db7a..0000000000
--- a/testsuite/tests/module/mod174.hs
+++ /dev/null
@@ -1,9 +0,0 @@
-
--- Test for trac #414
--- If main is not exported from Main then we should emit an error
--- instead of running it anyway
-
-module Main () where
-
-main = putStrLn "Hello, World"
-
diff --git a/testsuite/tests/module/mod174.stderr b/testsuite/tests/module/mod174.stderr
deleted file mode 100644
index a035f92b90..0000000000
--- a/testsuite/tests/module/mod174.stderr
+++ /dev/null
@@ -1,3 +0,0 @@
-
-mod174.hs:1:1:
-    The IO action ‘main’ is not exported by module ‘Main’
diff --git a/testsuite/tests/parser/should_fail/readFail013.hs b/testsuite/tests/parser/should_fail/readFail013.hs
index 97e926d49c..4850f3a1a5 100644
--- a/testsuite/tests/parser/should_fail/readFail013.hs
+++ b/testsuite/tests/parser/should_fail/readFail013.hs
@@ -1,4 +1,4 @@
-module Main where
+module ReadFail013 where
 
 -- !!! unterminated ``
 a = ``s``