diff options
| -rw-r--r-- | compiler/typecheck/TcRnExports.hs | 6 | ||||
| -rw-r--r-- | docs/users_guide/bugs.rst | 38 | ||||
| -rw-r--r-- | testsuite/tests/module/T13704a.hs (renamed from testsuite/tests/module/T13704.hs) | 0 | ||||
| -rw-r--r-- | testsuite/tests/module/T13704b1.hs | 4 | ||||
| -rw-r--r-- | testsuite/tests/module/T13704b2.hs | 7 | ||||
| -rw-r--r-- | testsuite/tests/module/all.T | 3 |
6 files changed, 44 insertions, 14 deletions
diff --git a/compiler/typecheck/TcRnExports.hs b/compiler/typecheck/TcRnExports.hs index 1b57608a41..a2f892ba1e 100644 --- a/compiler/typecheck/TcRnExports.hs +++ b/compiler/typecheck/TcRnExports.hs @@ -127,9 +127,11 @@ tcRnExports explicit_mod exports -- In interactive mode, we behave as if he had -- written "module Main where ..." ; dflags <- getDynFlags + ; let is_main_mod = mainModIs dflags == this_mod ; let default_main = case mainFunIs dflags of - Just main_fun -> mkUnqual varName (fsLit main_fun) - Nothing -> main_RDR_Unqual + Just main_fun + | is_main_mod -> mkUnqual varName (fsLit main_fun) + _ -> main_RDR_Unqual ; let real_exports | explicit_mod = exports | ghcLink dflags == LinkInMemory = Nothing diff --git a/docs/users_guide/bugs.rst b/docs/users_guide/bugs.rst index 0290622b62..96cdd25f5a 100644 --- a/docs/users_guide/bugs.rst +++ b/docs/users_guide/bugs.rst @@ -171,35 +171,51 @@ same context. For example, this is fine: :: g :: Ord a => a -> Bool g y = (y <= y) || f True -.. _infelicities-Modules: +.. _infelicities-default-exports: Default Module headers with -main-is ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -The Haskell2010 report specifies in <https://www.haskell.org/onlinereport/haskell2010/haskellch5.html#x11-990005.1> that +The Haskell2010 Report specifies in <https://www.haskell.org/onlinereport/haskell2010/haskellch5.html#x11-990005.1> that "An abbreviated form of module, consisting only of the module body, is permitted. If this is used, the header is assumed to be `module Main(main) where`." +GHC's ``-main-is`` option can be used to change the name of the top-level entry +point from ``main`` to any other variable. When compiling the main module and +``-main-is`` has been used to rename the default entry point, GHC will also use +the alternate name in the default export list. + Consider the following program: :: -- file: Main.hs program :: IO () program = return () -Under the report, this would fail with ``ghc -main-is Main.program Main.hs`` -with the following errors: :: +GHC will successfully compile this module with +``ghc -main-is Main.program Main.hs``, because the default export list +will include ``program`` rather than ``main``, as the Haskell Report +typically requires. + +This change only applies to the main module. Other modules will still export +``main`` from a default export list, regardless of the ``-main-is`` flag. +This allows use of ``-main-is`` with existing modules that export ``main`` via +a default export list, even when ``-main-is`` points to a different entry +point, as in this example (compiled with ``-main-is MainWrapper.program``). :: - Main.hs:1:1: error: - Not in scope: 'main' - Perhaps you meant 'min' (imported from Prelude) + -- file MainWrapper.hs + module MainWrapper where + import Main - Main.hs:1:1: error: - The main IO action 'program' is not exported by module 'Main' + program :: IO () + program = putStrLn "Redirecting..." >> main + + -- file Main.hs + main :: IO () + main = putStrLn "I am main." -GHC's flag '-main-is' allows one to change the entry point name so that -the above example would succeed. +.. _infelicities-Modules: Module system and interface files ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/testsuite/tests/module/T13704.hs b/testsuite/tests/module/T13704a.hs index 38b1cb73fc..38b1cb73fc 100644 --- a/testsuite/tests/module/T13704.hs +++ b/testsuite/tests/module/T13704a.hs diff --git a/testsuite/tests/module/T13704b1.hs b/testsuite/tests/module/T13704b1.hs new file mode 100644 index 0000000000..28b8800706 --- /dev/null +++ b/testsuite/tests/module/T13704b1.hs @@ -0,0 +1,4 @@ +main :: IO () +main = return () + +-- wrapped by T13704b2.hs diff --git a/testsuite/tests/module/T13704b2.hs b/testsuite/tests/module/T13704b2.hs new file mode 100644 index 0000000000..d76206fe42 --- /dev/null +++ b/testsuite/tests/module/T13704b2.hs @@ -0,0 +1,7 @@ +module T13704b2 where +import Main (main) + +program :: IO () +program = main + +-- meant to be compiled with '-main-is T13704b2.program' diff --git a/testsuite/tests/module/all.T b/testsuite/tests/module/all.T index dbba44f0ba..33ce3aeefe 100644 --- a/testsuite/tests/module/all.T +++ b/testsuite/tests/module/all.T @@ -284,4 +284,5 @@ test('T11970B', normal, compile_fail, ['']) test('MultiExport', normal, compile, ['']) test('T13528', normal, compile, ['']) test('T13622', normal, compile, ['']) -test('T13704', normal, compile, ['-main-is Main.program']) +test('T13704a', normal, compile, ['-main-is Main.program']) +test('T13704b', [], multimod_compile, ['T13704b1.hs T13704b2.hs', '-main-is T13704b2.program -v0']) |