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Hannes Siebenhandl pushed to branch wip/romes/27461 at Glasgow Haskell Compiler / GHC

Commits:

b6011958

by fendor at 2026-08-03T16:02:02+02:00

Fixup: handle file targets gracefully that have a difference module name

We reject imports of modules that have a file name different to their module name.

Such files are only valid if they are not imported by the rest of the module graph.

10 changed files:

compiler/GHC/Driver/Downsweep.hs
+ testsuite/tests/driver/T27461/Main1.hs
+ testsuite/tests/driver/T27461/Main2.hs
+ testsuite/tests/driver/T27461/Makefile
+ testsuite/tests/driver/T27461/T27461a.stderr
+ testsuite/tests/driver/T27461/T27461b.script
+ testsuite/tests/driver/T27461/T27461b.stderr
+ testsuite/tests/driver/T27461/T27461b.stdout
+ testsuite/tests/driver/T27461/all.T
+ testsuite/tests/driver/T27461/src/Bar.hs

Changes:

compiler/GHC/Driver/Downsweep.hs

@@ -1555,7 +1555,23 @@ summariseModuleWithSource home_unit summ_cache_ref is_boot maybe_buf hsc_env loc
      -- hi file, object file, when is_boot says so
      let src_fn = expectJust (ml_hs_file location)
      summ_cache <- readIORef summ_cache_ref
 -    case ml_hs_file_ospath location >>= \p -> M.lookup (moduleUnitId mod, p) summ_cache of
 +    -- Reject the cache result if the module name doesn't match the inferred
 +    -- module name based on the file name.
 +    -- This happens if we `summariseFile` for a root file target (which has a different module name)
 +    -- and then we try to import it.
 +    --
 +    -- Fall through to `new_summary` if this happens to reject this module.
 +    let cached = do
 +          p   <- ml_hs_file_ospath location
 +          res <- M.lookup (moduleUnitId mod, p) summ_cache
 +          case res of
 +            Right (ms, _) | msKey ms /= moduleToMnk mod is_boot ->
 +              -- Module name doesn't match the file path name.
 +              -- We fall through to @new_summary@, where this will be
 +              -- discovered and the correct error message will be thrown.
 +              Nothing
 +            _ -> Just res
 +    case cached of
        Just (Right (chd_summary, SummFresh)) ->
          -- Fresh! just return it
          pure $ FoundHome (ModuleNodeCompile chd_summary)
@@ -1858,6 +1874,15 @@ twice).
     Note that (2) can't guarantee this alone: Two ModuleName imports in
     separate units can (and likely do) map to the same `Module`.
 +   Note:
 +   There is a special case where the module name doesn't have to match the file name.
 +   For example, the `Main` module is sometimes not defined in a file
 +   named `Main.hs`. We still want to compile such file targets, but reject the module
 +   if it is used as a module target.
 +   Thus, we accept this difference while `summariseFile`, but reject if we encounter expand
 +   this module node during `summariseModuleWithSource`.
 +   See tests T27461a and T27461b.
++
  See also Note [Downsweep: building and maintaining the module graph] and
  Note [The ModuleGraph].
  -}

testsuite/tests/driver/T27461/Main1.hs

 +module Main where
++
 +import Bar () -- resolves to src/Bar.hs, which declares module Foo
++
 +main :: IO ()
 +main = return ()

testsuite/tests/driver/T27461/Main2.hs

 +module Main where
++
 +main :: IO ()
 +main = return ()

testsuite/tests/driver/T27461/Makefile

 +TOP=../../..
 +include $(TOP)/mk/boilerplate.mk
 +include $(TOP)/mk/test.mk
++
 +# src/Bar.hs declares module Foo, which is fine for a file target, but Main's
 +# `import Bar` resolves to that same file and must be rejected.
 +T27461a :
 +	cp Main1.hs src/Main.hs
 +	! '$(TEST_HC)' $(TEST_HC_OPTS) --make -fno-code -v0 -isrc src/Main.hs src/Bar.hs

testsuite/tests/driver/T27461/T27461a.stderr

 +src/Bar.hs:1:8: error: [GHC-28623]
 +    File name does not match module name:
 +    Saw     : ‘Foo’
 +    Expected: ‘Bar’

testsuite/tests/driver/T27461/T27461b.script

 +"-- Successfully load modules if file target is not imported"
 +:! cp Main2.hs src/Main.hs
 +:load src/Main.hs src/Bar.hs
 +main
 +:! cp Main1.hs src/Main.hs
 +"-- Crash on reload as we import a file target that has the wrong module name"
 +:reload

testsuite/tests/driver/T27461/T27461b.stderr

 +src/Bar.hs:1:8: error: [GHC-28623]
 +    File name does not match module name:
 +    Saw     : ‘Foo’
 +    Expected: ‘Bar’
++

testsuite/tests/driver/T27461/T27461b.stdout

	1	+"-- Successfully load modules if file target is not imported"
	2	+"-- Crash on reload as we import a file target that has the wrong module name"

testsuite/tests/driver/T27461/all.T

 +test('T27461a', extra_files(['src/', 'Main1.hs']), makefile_test, [])
 +test('T27461b', [extra_files(['src/', 'Main1.hs', 'Main2.hs']), extra_hc_opts('-isrc')],
 +     ghci_script, ['T27461b.script'])

testsuite/tests/driver/T27461/src/Bar.hs

 +module Foo where
 +-- Named Bar.hs but declares module Foo: allowed for a file target.
++
 +foo :: Int
 +foo = 1