[ImportVerilog] Enforce base class elaboration

lib/Conversion/ImportVerilog/Structure.cpp

@@ -1671,8 +1671,18 @@ ClassLowering *Context::declareClass(const slang::ast::ClassType &cls) {
     builder.setInsertionPoint(it->second);
 
   auto symName = fullyQualifiedClassName(*this, cls);
-  auto [base, impls] = buildBaseAndImplementsAttrs(*this, cls);
 
+  // Force build of base here.
+  if (const auto *maybeBaseClass = cls.getBaseClass())
+    if (const auto *baseClass = maybeBaseClass->as_if<slang::ast::ClassType>())
+      if (!classes.contains(baseClass) &&
+          failed(convertClassDeclaration(*baseClass))) {
+        mlir::emitError(loc) << "Failed to convert base class "
+                             << baseClass->name << " of class " << cls.name;
+        return {};
+      }
+
+  auto [base, impls] = buildBaseAndImplementsAttrs(*this, cls);
   auto classDeclOp =
       moore::ClassDeclOp::create(builder, loc, symName, base, impls);
 
@@ -1694,6 +1704,10 @@ Context::convertClassDeclaration(const slang::ast::ClassType &classdecl) {
   auto timeScaleGuard =
       llvm::make_scope_exit([&] { timeScale = prevTimeScale; });
 
+  // Check if there already is a declaration for this class.
+  if (classes.contains(&classdecl))
+    return success();
+
   auto *lowering = declareClass(classdecl);
   if (failed(ClassDeclVisitor(*this, *lowering).run(classdecl)))
     return failure();

test/Conversion/ImportVerilog/classes.sv

@@ -580,3 +580,15 @@ function void adder;
     a = a + 1;
 endfunction
 endclass
+
+/// Check that inheritance is enforced over specialized classes
+
+// CHECK-LABEL:  moore.class.classdecl @GenericBar {
+// CHECK:  }
+// CHECK:  moore.class.classdecl @SpecializedFoo extends @GenericBar {
+// CHECK:  }
+
+class GenericBar #(int X=0, int Y=1, int Z=2); endclass
+localparam x=3, y=4, z=5;
+
+class SpecializedFoo extends GenericBar #(x,y,z); endclass