Fix #pragma warning not working with multifile modules (#7942)

* Initial plan

* Fix pragma warning not working with multifile modules

- Check if DiagnosticSink already has a WarningStateTracker before creating new one
- This preserves pragma warning state across __include'd files
- Add regression tests for multifile pragma warnings

Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>

* Add additional test cases for nested pragma warnings

- Test nested __include scenarios with pragma warning directives
- Verify pragma warnings work correctly with multiple levels of includes

Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>
Co-authored-by: Yong He <yonghe@outlook.com>

8 files changed, 100 insertions, 3 deletions

diff --git a/source/slang/slang-preprocessor.cpp b/source/slang/slang-preprocessor.cpp
index b29fa2716..a0e80473d 100644
--- a/source/slang/slang-preprocessor.cpp
+++ b/source/slang/slang-preprocessor.cpp
@@ -4878,9 +4878,14 @@ TokenList preprocessSource(
         desc.contentAssistInfo = &linkage->contentAssistInfo.preprocessorInfo;
     }
 
-    preprocessor::WarningStateTracker* wst =
-        new preprocessor::WarningStateTracker(desc.sourceManager);
-    desc.sink->setSourceWarningStateTracker(wst);
+    // Only create a new WarningStateTracker if the sink doesn't already have one.
+    // This ensures pragma warning states are preserved across included files.
+    if (!desc.sink->getSourceWarningStateTracker())
+    {
+        preprocessor::WarningStateTracker* wst =
+            new preprocessor::WarningStateTracker(desc.sourceManager);
+        desc.sink->setSourceWarningStateTracker(wst);
+    }
 
     return preprocessSource(file, desc, outDetectedLanguage, outLanguageVersion);
 }
diff --git a/tests/diagnostics/nested-pragma-impl1.slang b/tests/diagnostics/nested-pragma-impl1.slang
new file mode 100644
index 000000000..305162651
--- /dev/null
+++ b/tests/diagnostics/nested-pragma-impl1.slang
@@ -0,0 +1,12 @@
+implementing nested_pragma_test;
+
+__include "nested-pragma-impl2.slang";
+
+namespace impl1
+{
+    interface IConvertibleFrom<From> {}
+
+    // This should NOT produce warning 30856 due to outer pragma disable
+    extension<From : __BuiltinIntegerType, To : IConvertibleFrom<From>, let N : int>
+    vector<To, N> : IConvertibleFrom<vector<From, N>> {}
+}
\ No newline at end of file
diff --git a/tests/diagnostics/nested-pragma-impl2.slang b/tests/diagnostics/nested-pragma-impl2.slang
new file mode 100644
index 000000000..9a7e57562
--- /dev/null
+++ b/tests/diagnostics/nested-pragma-impl2.slang
@@ -0,0 +1,10 @@
+implementing nested_pragma_test;
+
+namespace impl2
+{
+    interface IConvertibleFrom<From> {}
+
+    // This should also NOT produce warning 30856 due to outer pragma disable
+    extension<From : __BuiltinFloatingPointType, To : IConvertibleFrom<From>, let N : int>
+    vector<To, N> : IConvertibleFrom<vector<From, N>> {}
+}
\ No newline at end of file
diff --git a/tests/diagnostics/nested-pragma-main.slang b/tests/diagnostics/nested-pragma-main.slang
new file mode 100644
index 000000000..1795f7d68
--- /dev/null
+++ b/tests/diagnostics/nested-pragma-main.slang
@@ -0,0 +1,9 @@
+//TEST:SIMPLE(filecheck=CHECK):
+
+module nested_pragma_test;
+
+#pragma warning(disable: 30856)
+
+__include "nested-pragma-impl1.slang";
+
+// CHECK-NOT: warning 30856
\ No newline at end of file
diff --git a/tests/diagnostics/pragma-warning-multifile-impl1.slang b/tests/diagnostics/pragma-warning-multifile-impl1.slang
new file mode 100644
index 000000000..464c0de39
--- /dev/null
+++ b/tests/diagnostics/pragma-warning-multifile-impl1.slang
@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+implementing test_pragma_warning;
+
+#pragma warning(push)
+#pragma warning(disable: 30856)
+
+namespace impl1
+{
+    interface IConvertibleFrom<From> {}
+
+    // This should NOT produce warning 30856 due to pragma disable
+    extension<From : __BuiltinIntegerType, To : IConvertibleFrom<From>, let N : int>
+    vector<To, N> : IConvertibleFrom<vector<From, N>> {}
+}
+
+#pragma warning(pop)
\ No newline at end of file
diff --git a/tests/diagnostics/pragma-warning-multifile-impl2.slang b/tests/diagnostics/pragma-warning-multifile-impl2.slang
new file mode 100644
index 000000000..16bffe6a8
--- /dev/null
+++ b/tests/diagnostics/pragma-warning-multifile-impl2.slang
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+implementing test_pragma_warning;
+
+namespace impl2
+{
+    interface IConvertibleFrom<From> {}
+
+    // This should still NOT produce warning 30856 (but currently does due to the bug)
+    extension<From : __BuiltinFloatingPointType, To : IConvertibleFrom<From>, let N : int>
+    vector<To, N> : IConvertibleFrom<vector<From, N>> {}
+}
\ No newline at end of file
diff --git a/tests/diagnostics/pragma-warning-multifile-main.slang b/tests/diagnostics/pragma-warning-multifile-main.slang
new file mode 100644
index 000000000..262b9abd1
--- /dev/null
+++ b/tests/diagnostics/pragma-warning-multifile-main.slang
@@ -0,0 +1,8 @@
+//TEST:SIMPLE(filecheck=CHECK):
+
+module test_pragma_warning;
+
+__include "pragma-warning-multifile-impl1.slang";
+__include "pragma-warning-multifile-impl2.slang";
+
+// CHECK-NOT: warning 30856
\ No newline at end of file
diff --git a/tests/diagnostics/pragma-warning-single-file.slang b/tests/diagnostics/pragma-warning-single-file.slang
new file mode 100644
index 000000000..df1e2b77e
--- /dev/null
+++ b/tests/diagnostics/pragma-warning-single-file.slang
@@ -0,0 +1,26 @@
+//TEST:SIMPLE(filecheck=CHECK):
+
+module test_pragma_warning_single;
+
+namespace test1
+{
+    interface IConvertibleFrom<From> {}
+
+    // This SHOULD produce warning 30856 because it's not disabled
+    extension<From : __BuiltinIntegerType, To : IConvertibleFrom<From>, let N : int>
+    vector<To, N> : IConvertibleFrom<vector<From, N>> {}
+}
+
+#pragma warning(disable: 30856)
+
+namespace test2
+{
+    interface IConvertibleFrom<From> {}
+
+    // This should NOT produce warning 30856 due to pragma disable
+    extension<From : __BuiltinFloatingPointType, To : IConvertibleFrom<From>, let N : int>
+    vector<To, N> : IConvertibleFrom<vector<From, N>> {}
+}
+
+// CHECK: warning 30856
+// CHECK-NOT: 30856
\ No newline at end of file