v1800-2023: clarification: unpacked unions are allowed as net types

scripts/diagnostics.txt

@@ -381,7 +381,7 @@ error InheritFromAbstract "'{}' cannot inherit from virtual class '{}' without p
 error InheritFromAbstractConstraint "'{}' cannot inherit from virtual class '{}' without providing an implementation for pure constraint '{}'"
 error InvalidPortType "{} is not a valid type for a port"
 error InvalidPortSubType "{} is not a valid type for a port because it contains type {}"
-error InvalidNetType "{} is not a valid type for a net; only 4-state integral types and unpacked structs and arrays of such types are allowed"
+error InvalidNetType "{} is not a valid type for a net; only 4-state integral types and unpacked structs/unions and arrays of such types are allowed"
 error InvalidUserDefinedNetType "{} is not a valid type for a user-defined nettype; only integral types, floating types, and unpacked structs, unions, and arrays of such types are allowed"
 error ExtendIfaceFromClass "a normal (or virtual) class cannot extend interface class '{}'"
 error ExtendClassFromIface "an interface class cannot extend non-interface class '{}'"

source/ast/types/DeclaredType.cpp

@@ -163,6 +163,14 @@ static bool isValidForNet(const Type& type) {
         return true;
     }
 
+    if (ct.isUnpackedUnion()) {
+        for (auto field : ct.as<UnpackedUnionType>().fields) {
+            if (!isValidForNet(field->getType()))
+                return false;
+        }
+        return true;
+    }
+
     return false;
 }
 

tests/unittests/ast/MemberTests.cpp

@@ -62,6 +62,19 @@ endmodule
     CHECK(diags[5].code == diag::DelayNotNumeric);
 }
 
+TEST_CASE("Net types can be unpacked unions") {
+    auto tree = SyntaxTree::fromText(R"(
+module m;
+    typedef union { logic l; } u;
+    wire u w;
+endmodule
+)");
+
+    Compilation compilation;
+    compilation.addSyntaxTree(tree);
+    NO_COMPILATION_ERRORS;
+}
+
 TEST_CASE("Bad signed specifier") {
     auto tree = SyntaxTree::fromText(R"(
 module Top;