Add more diagnostics around use of custom derivatives. (#3291)

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

3 files changed, 92 insertions, 4 deletions

diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index f75f84e21..15831ba26 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -7203,10 +7203,17 @@ namespace Slang
     template<typename TDerivativeAttr>
     void checkDerivativeAttributeImpl(
         SemanticsVisitor* visitor,
+        Decl* funcDecl,
         TDerivativeAttr* attr,
         const List<Expr*>& imaginaryArguments,
         const List<ParameterDirection>& expectedParamDirections)
     {
+        if (isInterfaceRequirement(funcDecl))
+        {
+            visitor->getSink()->diagnose(attr, Diagnostics::cannotAssociateInterfaceRequirementWithDerivative);
+            return;
+        }
+
         SemanticsContext::ExprLocalScope scope;
         auto ctx = visitor->withExprLocalScope(&scope);
         auto subVisitor = SemanticsVisitor(ctx);
@@ -7264,6 +7271,20 @@ namespace Slang
                 // We'll detect both these incorrect cases here and issue an appropriate diagnostic.
                 // 
                 auto funcType = as<FuncType>(calleeDeclRef->type);
+                if (!funcType)
+                {
+                    // The best candidate does not have a function type.
+                    // If we reach here, it means the function is a generic and we can't deduce the
+                    // generic arguments from imaginary argument list.
+                    // In this case we issue a diagnostic to ask the user to explicitly provide the arguments.
+                    visitor->getSink()->diagnose(attr, Diagnostics::cannotResolveGenericArgumentForDerivativeFunction);
+                    return;
+                }
+                if (isInterfaceRequirement(calleeDeclRef->declRef.getDecl()))
+                {
+                    visitor->getSink()->diagnose(attr, Diagnostics::cannotUseInterfaceRequirementAsDerivative);
+                    return;
+                }
                 for (Index ii = 0; ii < imaginaryArguments.getCount(); ++ii)
                 {
                     // Check if the resolved invoke argument type is an error type.
@@ -7511,6 +7532,16 @@ namespace Slang
             visitor->getSink()->diagnose(derivativeOfAttr, Diagnostics::cannotResolveOriginalFunctionForDerivative);
             return;
         }
+        if (isInterfaceRequirement(calleeFunc))
+        {
+            visitor->getSink()->diagnose(derivativeOfAttr, Diagnostics::cannotAssociateInterfaceRequirementWithDerivative);
+            return;
+        }
+        if (isInterfaceRequirement(funcDecl))
+        {
+            visitor->getSink()->diagnose(derivativeOfAttr, Diagnostics::cannotUseInterfaceRequirementAsDerivative);
+            return;
+        }
 
         if (auto existingModifier = _findModifier<TDerivativeAttr>(calleeFunc))
         {
@@ -7546,7 +7577,7 @@ namespace Slang
             return;
 
         ArgsWithDirectionInfo imaginaryArguments = getImaginaryArgsToForwardDerivative(visitor, funcDecl, attr->loc);
-        checkDerivativeAttributeImpl(visitor, attr, imaginaryArguments.args, imaginaryArguments.directions);
+        checkDerivativeAttributeImpl(visitor, funcDecl, attr, imaginaryArguments.args, imaginaryArguments.directions);
     }
 
     static void checkDerivativeAttribute(SemanticsVisitor* visitor, FunctionDeclBase* funcDecl, BackwardDerivativeAttribute* attr)
@@ -7557,7 +7588,7 @@ namespace Slang
             return;
 
         ArgsWithDirectionInfo imaginaryArguments = getImaginaryArgsToBackwardDerivative(visitor, funcDecl, attr->loc);
-        checkDerivativeAttributeImpl(visitor, attr, imaginaryArguments.args, imaginaryArguments.directions);
+        checkDerivativeAttributeImpl(visitor, funcDecl, attr, imaginaryArguments.args, imaginaryArguments.directions);
     }
 
     static void checkDerivativeAttribute(SemanticsVisitor* visitor, FunctionDeclBase* funcDecl, PrimalSubstituteAttribute* attr)
@@ -7568,7 +7599,7 @@ namespace Slang
             return;
 
         ArgsWithDirectionInfo imaginaryArguments = getImaginaryArgsToFunc(visitor->getASTBuilder(), funcDecl, attr->loc);
-        checkDerivativeAttributeImpl(visitor, attr, imaginaryArguments.args, imaginaryArguments.directions);
+        checkDerivativeAttributeImpl(visitor, funcDecl, attr, imaginaryArguments.args, imaginaryArguments.directions);
     }
 
     template<typename TDerivativeAttr, typename TDerivativeOfAttr>
diff --git a/source/slang/slang-diagnostic-defs.h b/source/slang/slang-diagnostic-defs.h
index 656e28701..79889a39d 100644
--- a/source/slang/slang-diagnostic-defs.h
+++ b/source/slang/slang-diagnostic-defs.h
@@ -393,7 +393,13 @@ DIAGNOSTIC(31147, Error, cannotResolveOriginalFunctionForDerivative, "cannot res
 DIAGNOSTIC(31148, Error, cannotResolveDerivativeFunction, "cannot resolve the custom derivative function")
 DIAGNOSTIC(31149, Error, customDerivativeSignatureMismatchAtPosition, "invalid custom derivative. parameter type mismatch at position $0. expected '$1', got '$2'")
 DIAGNOSTIC(31150, Error, customDerivativeSignatureMismatch, "invalid custom derivative. could not resolve function with expected signature '$0'")
-
+DIAGNOSTIC(31151, Error, cannotResolveGenericArgumentForDerivativeFunction,
+    "The generic arguments to the derivative function cannot be deduced from the parameter list of the original function. "
+    "Consider using [ForwardDerivative], [BackwardDerivative] or [PrimalSubstitute] attributes on the primal function"
+    " with explicit generic arguments to associate it with a generic derivative function. Note that [ForwardDerivativeOf], "
+    "[BackwardDerivativeOf], and [PrimalSubstituteOf] attributes are not supported when the generic arguments to the derivatives cannot be automatically deduced.")
+DIAGNOSTIC(31152, Error, cannotAssociateInterfaceRequirementWithDerivative, "cannot associate an interface requirement with a derivative.")
+DIAGNOSTIC(31153, Error, cannotUseInterfaceRequirementAsDerivative, "cannot use an interface requirement as a derivative.")
 DIAGNOSTIC(31200, Warning, deprecatedUsage, "$0 has been deprecated: $1")
 
 // Enums
diff --git a/tests/diagnostics/custom-derivative-generic.slang b/tests/diagnostics/custom-derivative-generic.slang
new file mode 100644
index 000000000..5f2cd9951
--- /dev/null
+++ b/tests/diagnostics/custom-derivative-generic.slang
@@ -0,0 +1,51 @@
+//DIAGNOSTIC_TEST:SIMPLE(filecheck=CHECK):
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+typedef DifferentialPair<float> dpfloat;
+
+interface IFoo
+{
+    static float bar1(float x);
+
+    // CHECK-DAG: {{.*}}(13): error 31152
+    [PrimalSubstitute(bar1)]
+    static float bar(float x);
+
+    static DifferentialPair<float> dd(DifferentialPair<float> x);
+}
+
+__generic<let N:int>
+float f(float x)
+{
+    return N*x*x;
+}
+
+// CHECK-DAG: {{.*}}(26): error 31153
+[ForwardDerivative(IFoo.dd)]
+float bbb(float x);
+
+// CHECK-DAG: {{.*}}(30): error 31152
+[ForwardDerivativeOf(IFoo.bar)]
+DifferentialPair<float> dd1(DifferentialPair<float> x)
+{
+    return x;
+}
+
+// CHECK-DAG: {{.*}}(37): error 31151
+[BackwardDerivative(f)]
+DifferentialPair<float> df<let N:int>(inout DifferentialPair<float> x, float dOut)
+{
+    var primal = x.p * x.p;
+    var diff = 2 * x.p * x.d * N;
+    return DifferentialPair<float>(primal, diff);
+}
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID)
+{
+    {
+        dpfloat dpa = dpfloat(3.0, 1.0);
+        outputBuffer[1] = __fwd_diff(f<3>)(dpa).d; // Expect: 6.0
+    }
+}