Fix duplicating parameter class types (#4115)

src/V3AstNodeDType.h

@@ -402,10 +402,7 @@ public:
     ASTGEN_MEMBERS_AstBasicDType;
     void dump(std::ostream& str) const override;
     // width/widthMin/numeric compared elsewhere
-    bool same(const AstNode* samep) const override {
-        const AstBasicDType* const sp = static_cast<const AstBasicDType*>(samep);
-        return m == sp->m;
-    }
+    bool same(const AstNode* samep) const override;
     bool similarDType(const AstNodeDType* samep) const override {
         return type() == samep->type() && same(samep);
     }

src/V3AstNodes.cpp

@@ -233,6 +233,15 @@ int AstBasicDType::widthTotalBytes() const {
     }
 }
 
+bool AstBasicDType::same(const AstNode* samep) const {
+    const AstBasicDType* const sp = static_cast<const AstBasicDType*>(samep);
+    if (!rangep() && !sp->rangep() && m == sp->m) {
+        return true;
+    } else {
+        return m == sp->m && rangep() && rangep()->sameTree(sp->rangep());
+    }
+}
+
 int AstNodeUOrStructDType::widthTotalBytes() const {
     if (width() <= 8) {
         return 1;

src/V3Param.cpp

@@ -342,6 +342,7 @@ class ParamProcessor final {
         // TODO: This parameter value number lookup via a constructed key string is not
         //       particularly robust for type parameters. We should really have a type
         //       equivalence predicate function.
+        if (const AstRefDType* const refp = VN_CAST(nodep, RefDType)) nodep = refp->skipRefp();
         const string key = paramValueKey(nodep);
         // cppcheck-has-bug-suppress unreadVariable
         V3Hash hash = V3Hasher::uncachedHash(nodep);
@@ -705,7 +706,7 @@ class ParamProcessor final {
                               << modvarp->prettyNameQ());
             } else {
                 UINFO(9, "Parameter type assignment expr=" << exprp << " to " << origp << endl);
-                if (exprp->sameTree(origp)) {
+                if (exprp->similarDType(origp)) {
                     // Setting parameter to its default value.  Just ignore it.
                     // This prevents making additional modules, and makes coverage more
                     // obvious as it won't show up under a unique module page name.

test_regress/t/t_class_param_type.v

@@ -18,12 +18,32 @@ class Cls;
    endfunction
 endclass
 
+class ParclsDefaultType #(type T=Cls);
+   static function int get_p;
+     return T::get_p();
+   endfunction
+endclass
+
 typedef Cls cls_t;
 typedef cls_t cls2_t;
 
 module t (/*AUTOARG*/);
 
    initial begin
+      automatic ParclsDefaultType#(Cls) pdt1 = new;
+      automatic ParclsDefaultType#(cls_t) pdt2 = pdt1;
+      automatic ParclsDefaultType#(cls2_t) pdt3 = pdt2;
+      automatic Parcls#(Cls) p1 = new;
+      automatic Parcls#(cls_t) p2 = p1;
+      automatic Parcls#(cls2_t) p3 = p2;
+
+      if (pdt1 != pdt2) $stop;
+      if (pdt2 != pdt3) $stop;
+      if (p1 != p2) $stop;
+      if (p2 != p3) $stop;
+
+      if (p1.get_p() != 20) $stop;
+      if (pdt1.get_p() != 20) $stop;
       if (Parcls#(cls2_t)::get_p() != 20) $stop;
 
       $write("*-* All Finished *-*\n");