Fix ambiguous reference for 'extern' and 'export'

source/slang/slang-check-overload.cpp

@@ -1328,6 +1328,20 @@ int SemanticsVisitor::CompareLookupResultItems(
     bool rightIsExtension = false;
     bool leftIsFreeFormExtension = false;
     bool rightIsFreeFormExtension = false;
+    bool leftIsExtern = left.declRef.getDecl()->hasModifier<ExternModifier>();
+    bool rigthIsExtern = right.declRef.getDecl()->hasModifier<ExternModifier>();
+
+    // If both left and right are extern, then they are equal.
+    // If only one of them is extern, then the other one is preferred.
+    // If neither is extern, then we continue with the rest of the checks.
+    if (leftIsExtern)
+    {
+        return (rigthIsExtern ? 0 : 1);
+    }
+    if (rigthIsExtern)
+    {
+        return (leftIsExtern ? -1 : 0);
+    }
 
     // Prefer declarations that are not in free-form generic extensions, i.e.
     // `extension<T:IFoo> T { /* declaration here should have lower precedence. */ }

tests/library/ambiguous-extern-export-entry.slang

@@ -0,0 +1,32 @@
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=BUFFER):-slang -compute -shaderobj
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=BUFFER):-slang -compute -dx12 -shaderobj
+//TEST(compute, vulkan):COMPARE_COMPUTE_EX(filecheck-buffer=BUFFER):-vk -compute -shaderobj
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=BUFFER):-cpu -compute -shaderobj
+
+import "ambiguous-extern-export-lib1.slang";
+import "ambiguous-extern-export-lib2.slang";
+
+export static const int call_data_len = 6;
+export static const int call_group_vector[call_data_len] = {1,2,3,4,5,6};
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<int> outputBuffer;
+
+[shader("compute")]
+[numthreads(1, 1, 1)]
+void computeMain()
+{
+    initCallId1();
+    initCallId2();
+
+    for (int i = 0; i < call_data_len; i++)
+    {
+        outputBuffer[i] = call_id_1[i] + call_id_2[i];
+    }
+    // BUFFER: 2
+    // BUFFER-NEXT: 4
+    // BUFFER-NEXT: 6
+    // BUFFER-NEXT: 8
+    // BUFFER-NEXT: A
+    // BUFFER-NEXT: C
+}

tests/library/ambiguous-extern-export-lib1.slang

@@ -0,0 +1,13 @@
+module "ambiguous-extern-export-lib1.slang";
+
+public extern static const int call_data_len;
+public extern static const int[call_data_len] call_group_vector;
+public static int[call_data_len] call_id_1 = {};
+
+public void initCallId1()
+{
+    for (int i = 0; i < call_data_len; i++)
+    {
+        call_id_1[i] = call_group_vector[i];
+    }
+}

tests/library/ambiguous-extern-export-lib2.slang

@@ -0,0 +1,15 @@
+
+module "ambiguous-extern-export-lib2.slang";
+
+public extern static const int call_data_len;
+public extern static const int[call_data_len] call_group_vector;
+
+public static int[call_data_len] call_id_2 = {};
+
+public void initCallId2()
+{
+    for (int i = 0; i < call_data_len; i++)
+    {
+        call_id_2[i] = call_group_vector[i];
+    }
+}