Fix exact-match witness synthesis for static functions (shader-slang#6204)

* fix non-static methods when trying to synthesize method requirement witness

* add tests

* update test

* improve test

---------

Co-authored-by: Yong He <[email protected]>

Author: fairywreath

source/slang/slang-check-decl.cpp

@@ -4621,6 +4621,25 @@ static bool matchParamDirection(ParameterDirection implDir, ParameterDirection r
     return false;
 }
 
+static void removeNonStaticLookupItems(LookupResult& lookupResult)
+{
+    List<LookupResultItem> newItems;
+    for (auto item : lookupResult)
+    {
+        if (item.declRef.getDecl()->hasModifier<HLSLStaticModifier>())
+        {
+            newItems.add(item);
+        }
+    }
+
+    lookupResult.items = newItems;
+    lookupResult.item = LookupResultItem();
+    if (lookupResult.items.getCount() > 0)
+    {
+        lookupResult.item = lookupResult.items[0];
+    }
+}
+
 bool SemanticsVisitor::trySynthesizeMethodRequirementWitness(
     ConformanceCheckingContext* context,
     LookupResult const& lookupResult,
@@ -4724,6 +4743,12 @@ bool SemanticsVisitor::trySynthesizeMethodRequirementWitness(
         baseOverloadedExpr->lookupResult2 = lookupResult;
     }
 
+    // Non-static methods cannot implement static methods, remove them.
+    if (requiredMemberDeclRef.getDecl()->hasModifier<HLSLStaticModifier>())
+    {
+        removeNonStaticLookupItems(baseOverloadedExpr->lookupResult2);
+    }
+
     // If `synThis` is non-null, then we will use it as the base of
     // the overloaded expression, so that we have an overloaded
     // member reference, and not just an overloaded reference to some

tests/language-feature/interfaces/non-static-method-implemented-by-static.slang

@@ -0,0 +1,45 @@
+//TEST(compute):COMPARE_COMPUTE_EX:-vk -compute  -output-using-type
+
+//TEST_INPUT: set outputBuffer = out ubuffer(data=[0 0 0 0 0], stride=4);
+RWStructuredBuffer<int> outputBuffer;
+
+interface Base
+{
+    int getValue();
+    int getValue(float a);
+}
+
+struct Impl1 : Base
+{
+    // This is static and allowed to implement interface's non-static method.
+    static int getValue() { return 5; }
+    int getValue(float a) { return int(a) + 5; }
+}
+
+struct Impl2 : Base
+{
+    // This is static with one default parameter and allowed to implement interface's non-static method.
+    static int getValue(int a = 3) { return a + 5; }
+    int getValue(float a) { return int(a) + 5; }
+}
+
+int callGet<T : Base>(T t)
+{
+    return t.getValue();
+}
+
+[numthreads(1, 1, 1)]
+void computeMain()
+{
+    Impl1 impl1;
+    Impl2 impl2;
+
+    uint index = 0;
+
+    outputBuffer[index++] = Impl1::getValue();
+    outputBuffer[index++] = callGet(impl1);
+
+    outputBuffer[index++] = Impl2::getValue();
+    outputBuffer[index++] = callGet(impl2);
+    outputBuffer[index++] = impl2.getValue(5);
+}

tests/language-feature/interfaces/non-static-method-implemented-by-static.slang.expected.txt

@@ -0,0 +1,6 @@
+type: int32_t
+5
+5
+8
+8
+10

tests/language-feature/interfaces/static-method-not-implemented.slang

@@ -0,0 +1,27 @@
+//DIAGNOSTIC_TEST:SIMPLE(filecheck=CHECK): -target spirv
+
+interface Base
+{
+    static int getValue();
+}
+
+struct Impl : Base
+{
+    // This is not static and not allowed to implement the interface's static method.
+    // CHECK: error 38105: member 'getValue' does not match interface requirement
+    int getValue() { return 5; }
+}
+
+int callGet<Foo : Base>()
+{
+    return Foo::getValue();
+}
+
+RWStructuredBuffer<int> result;
+
+[numthreads(1, 1, 1)]
+void computeMain()
+{
+    result[0] = callGet<Impl>();
+}
+