Support visibility control and default to `internal`. (#3380)

* Support visibility control and default to `internal`.

* Fix wip.

* Fixes.

* Fix.

* Fix test.

* Add legacy language detection and compatibility for existing code.

* Add doc.

---------

Co-authored-by: Yong He <yhe@nvidia.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/tests/diagnostics/internal-visibility/this-module.slang b/tests/diagnostics/internal-visibility/this-module.slang
new file mode 100644
index 000000000..98e0f3d08
--- /dev/null
+++ b/tests/diagnostics/internal-visibility/this-module.slang
@@ -0,0 +1,26 @@
+//DIAGNOSTIC_TEST:SIMPLE(filecheck=CHECK):
+
+module "this-module";
+
+import "that-module";
+
+void test()
+{
+    PublicStruct s;
+    // CHECK:{{.*}}(11): error 30600:
+    s.x = 1; // Error.
+    // CHECK-NOT:{{.*}}error
+    s.y = 2; // OK.
+    publicMethod(); // OK.
+    publicFunc2();  // OK.
+    Namespace.publicVar = 1; // OK.
+    Namespace.publicVar2 = 1; // OK.
+    // CHECK:{{.*}}(19): error 30600:
+    Namespace.internalVar = 1; // error.
+    // CHECK:{{.*}}(21): error 30600:
+    InternalEnum e; // Error.
+    // CHECK:{{.*}}(23): error 30600:
+    InternalStruct s1; // Error.
+    // CHECK:{{.*}}(25): error 30600:
+    internalMethod(); // Error.
+}