From c8380a4a738e5c2488337496b0d1b1faf6a7de9d Mon Sep 17 00:00:00 2001
From: Krzysztof Gogolewski <krzysztof.gogolewski@tweag.io>
Date: Tue, 9 Apr 2019 13:51:29 +0200
Subject: [PATCH] Handle hs-boot files in -Wmissing-home-modules (#16551)

---
 compiler/main/GhcMake.hs                                 | 4 ++++
 testsuite/tests/warnings/should_compile/T16551.stderr    | 3 +++
 testsuite/tests/warnings/should_compile/T16551/A.hs      | 2 ++
 testsuite/tests/warnings/should_compile/T16551/B.hs      | 2 ++
 testsuite/tests/warnings/should_compile/T16551/B.hs-boot | 1 +
 testsuite/tests/warnings/should_compile/all.T            | 1 +
 6 files changed, 13 insertions(+)
 create mode 100644 testsuite/tests/warnings/should_compile/T16551.stderr
 create mode 100644 testsuite/tests/warnings/should_compile/T16551/A.hs
 create mode 100644 testsuite/tests/warnings/should_compile/T16551/B.hs
 create mode 100644 testsuite/tests/warnings/should_compile/T16551/B.hs-boot

diff --git a/compiler/main/GhcMake.hs b/compiler/main/GhcMake.hs
index ac92f3b42b..c8442e2a71 100644
--- a/compiler/main/GhcMake.hs
+++ b/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).
diff --git a/testsuite/tests/warnings/should_compile/T16551.stderr b/testsuite/tests/warnings/should_compile/T16551.stderr
new file mode 100644
index 0000000000..352784c7d6
--- /dev/null
+++ b/testsuite/tests/warnings/should_compile/T16551.stderr
@@ -0,0 +1,3 @@
+[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 )
diff --git a/testsuite/tests/warnings/should_compile/T16551/A.hs b/testsuite/tests/warnings/should_compile/T16551/A.hs
new file mode 100644
index 0000000000..138a4faa1c
--- /dev/null
+++ b/testsuite/tests/warnings/should_compile/T16551/A.hs
@@ -0,0 +1,2 @@
+module A where
+import {-# SOURCE #-} B
diff --git a/testsuite/tests/warnings/should_compile/T16551/B.hs b/testsuite/tests/warnings/should_compile/T16551/B.hs
new file mode 100644
index 0000000000..af11916966
--- /dev/null
+++ b/testsuite/tests/warnings/should_compile/T16551/B.hs
@@ -0,0 +1,2 @@
+module B where
+import A
diff --git a/testsuite/tests/warnings/should_compile/T16551/B.hs-boot b/testsuite/tests/warnings/should_compile/T16551/B.hs-boot
new file mode 100644
index 0000000000..c759bc2d13
--- /dev/null
+++ b/testsuite/tests/warnings/should_compile/T16551/B.hs-boot
@@ -0,0 +1 @@
+module B where
diff --git a/testsuite/tests/warnings/should_compile/all.T b/testsuite/tests/warnings/should_compile/all.T
index 36e6b1beeb..fcf03443d3 100644
--- a/testsuite/tests/warnings/should_compile/all.T
+++ b/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, [''])
 
-- 
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