Diagnose for invalid decl nesting + namespace lookup fixes. (#3397)

* Diagnose for invalid decl nesting.

* Fix.

* Fix.

* Fix.

* Fix `namespace` lookup and `using` resolution.

* fix project files.

* revert project files.

* Enhance namespace syntax, docs.

* Fixes.

---------

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

4 files changed, 59 insertions, 0 deletions

diff --git a/tests/language-feature/namespaces/namespace-include/a.slang b/tests/language-feature/namespaces/namespace-include/a.slang
new file mode 100644
index 000000000..6660f590d
--- /dev/null
+++ b/tests/language-feature/namespaces/namespace-include/a.slang
@@ -0,0 +1,28 @@
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK): -shaderobj
+
+module a;
+
+__include b;
+
+namespace ns1
+{
+namespace ns2
+{
+    int l() { return k(); } // should be able to find k() in b.
+}
+}
+
+using ns1.ns2;
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<int> outputBuffer;
+
+[numthreads(4, 1, 1)]
+void computeMain(int3 dispatchThreadID: SV_DispatchThreadID)
+{
+    int tid = dispatchThreadID.x;
+    int inVal = tid;
+    int outVal = k() + l() + ns1.ns2.f();
+    outputBuffer[tid] = outVal;
+    // CHECK: 7
+}
diff --git a/tests/language-feature/namespaces/namespace-include/b.slang b/tests/language-feature/namespaces/namespace-include/b.slang
new file mode 100644
index 000000000..95f8b388a
--- /dev/null
+++ b/tests/language-feature/namespaces/namespace-include/b.slang
@@ -0,0 +1,11 @@
+implementing a;
+
+import m;
+
+namespace ns1
+{
+namespace ns2
+{
+    int k() { return f() + g(); } // should be able to find ns1::ns2::f in m.
+}
+}
diff --git a/tests/language-feature/namespaces/namespace-include/m.slang b/tests/language-feature/namespaces/namespace-include/m.slang
new file mode 100644
index 000000000..4eb3db527
--- /dev/null
+++ b/tests/language-feature/namespaces/namespace-include/m.slang
@@ -0,0 +1,11 @@
+module m;
+
+__include m2;
+
+namespace ns1
+{
+namespace ns2
+{
+    public int f() { return 1; }
+}
+}
diff --git a/tests/language-feature/namespaces/namespace-include/m2.slang b/tests/language-feature/namespaces/namespace-include/m2.slang
new file mode 100644
index 000000000..71a9be85a
--- /dev/null
+++ b/tests/language-feature/namespaces/namespace-include/m2.slang
@@ -0,0 +1,9 @@
+implementing m;
+
+namespace ns1
+{
+namespace ns2
+{
+    public int g() { return 2; }
+}
+}