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>

2 files changed, 34 insertions, 0 deletions

diff --git a/tests/language-feature/namespaces/namespace-import/m.slang b/tests/language-feature/namespaces/namespace-import/m.slang
new file mode 100644
index 000000000..16a35d9b4
--- /dev/null
+++ b/tests/language-feature/namespaces/namespace-import/m.slang
@@ -0,0 +1,5 @@
+module m;
+namespace ns1.ns2
+{
+    public int g() { return 1; }
+}
diff --git a/tests/language-feature/namespaces/namespace-import/test.slang b/tests/language-feature/namespaces/namespace-import/test.slang
new file mode 100644
index 000000000..285883c69
--- /dev/null
+++ b/tests/language-feature/namespaces/namespace-import/test.slang
@@ -0,0 +1,29 @@
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK): -shaderobj
+
+module test;
+
+import m;
+
+namespace ns1.ns2
+{
+    int f()
+    {
+        // Should be able to access g() from m.
+        return g();
+    }
+}
+
+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 = f() + g() + ns1.ns2.g();
+    outputBuffer[tid] = outVal;
+    // CHECK: 3
+}