Handle hs-boot files in -Wmissing-home-modules (#16551)

compiler/main/GhcMake.hs

@@ -184,6 +184,10 @@ warnMissingHomeModules hsc_env mod_graph =
     is_my_target mod (TargetFile target_file _)
       | Just mod_file <- ml_hs_file (ms_location mod)
       = target_file == mod_file ||
+
+           --  Don't warn on B.hs-boot if B.hs is specified (#16551)
+           addBootSuffix target_file == mod_file ||
+
            --  We can get a file target even if a module name was
            --  originally specified in a command line because it can
            --  be converted in guessTarget (by appending .hs/.lhs).

testsuite/tests/warnings/should_compile/T16551.stderr

+[1 of 3] Compiling B[boot]          ( T16551/B.hs-boot, T16551/B.o-boot )
+[2 of 3] Compiling A                ( T16551/A.hs, T16551/A.o )
+[3 of 3] Compiling B                ( T16551/B.hs, T16551/B.o )

testsuite/tests/warnings/should_compile/T16551/A.hs

+module A where
+import {-# SOURCE #-} B

testsuite/tests/warnings/should_compile/T16551/B.hs

+module B where
+import A

testsuite/tests/warnings/should_compile/T16551/B.hs-boot

+module B where

testsuite/tests/warnings/should_compile/all.T

@@ -22,6 +22,7 @@ test('Werror01', normal, compile, [''])
 test('Werror02', normal, compile, [''])
 
 test('MissingMod', normal, multimod_compile, ['MissingMod', '-Wmissing-home-modules'])
+test('T16551', [extra_files(['T16551/'])], multimod_compile, ['T16551/A.hs T16551/B.hs', '-Wmissing-home-modules'])
 
 test('StarBinder', normal, compile, [''])