Internal cast preparatory cleanups.

src/V3AstNodes.cpp

@@ -1175,6 +1175,7 @@ bool AstClass::isClassExtendedFrom(const AstClass* refClassp, const AstClass* ba
     // TAIL RECURSIVE
     if (!refClassp || !baseClassp) return false;
     if (refClassp == baseClassp) return true;
+    if (!refClassp->extendsp()) return false;
     return isClassExtendedFrom(refClassp->extendsp()->classp(), baseClassp);
 }
 void AstClass::dump(std::ostream& str) const {

src/V3AstNodes.h

@@ -5997,12 +5997,17 @@ public:
 class AstCast final : public AstNode {
     // Cast to appropriate data type - note lhsp is value, to match AstTypedef, AstCCast, etc
 public:
-    AstCast(FileLine* fl, AstNode* lhsp, AstNodeDType* dtp)
+    AstCast(FileLine* fl, AstNode* lhsp, VFlagChildDType, AstNodeDType* dtp)
         : ASTGEN_SUPER(fl) {
         setOp1p(lhsp);
         setOp2p(dtp);
         dtypeFrom(dtp);
     }
+    AstCast(FileLine* fl, AstNode* lhsp, AstNodeDType* dtp)
+        : ASTGEN_SUPER(fl) {
+        setOp1p(lhsp);
+        dtypeFrom(dtp);
+    }
     ASTNODE_NODE_FUNCS(Cast)
     virtual bool hasDType() const override { return true; }
     virtual string emitVerilog() { return "((%d)'(%l))"; }

src/verilog.y

@@ -4255,9 +4255,9 @@ expr<nodep>:			// IEEE: part of expression/constant_expression/primary
 	//
 	//			// IEEE: cast/constant_cast
 	//			// expanded from casting_type
-	|	simple_type yP_TICK '(' expr ')'	{ $$ = new AstCast($1->fileline(), $4, $1); }
+	|	simple_type yP_TICK '(' expr ')'	{ $$ = new AstCast($1->fileline(), $4, VFlagChildDType{}, $1); }
 	|	yTYPE '(' exprOrDataType ')' yP_TICK '(' expr ')'
-			{ $$ = new AstCast($1, $7, new AstRefDType($1, AstRefDType::FlagTypeOfExpr(), $3)); }
+			{ $$ = new AstCast($1, $7, VFlagChildDType(), new AstRefDType($1, AstRefDType::FlagTypeOfExpr(), $3)); }
 	|	ySIGNED yP_TICK '(' expr ')'		{ $$ = new AstSigned($1, $4); }
 	|	yUNSIGNED yP_TICK '(' expr ')'		{ $$ = new AstUnsigned($1, $4); }
 	|	ySTRING yP_TICK '(' expr ')'		{ $$ = new AstCvtPackString($1, $4); }

test_regress/t/t_castdyn_bad.out

@@ -1,9 +0,0 @@
-%Error-UNSUPPORTED: t/t_castdyn_bad.v:20:11: Unsupported: $cast. Suggest try static cast.
-                                           : ... In instance t
-   20 |       i = $cast(c, b);
-      |           ^~~~~
-%Error-UNSUPPORTED: t/t_castdyn_bad.v:23:7: Unsupported: $cast. Suggest try static cast.
-                                          : ... In instance t
-   23 |       $cast(c, b);   
-      |       ^~~~~
-%Error: Exiting due to

test_regress/t/t_castdyn_run_bad.out

@@ -0,0 +1,9 @@
+%Error-UNSUPPORTED: t/t_castdyn_run_bad.v:20:11: Unsupported: $cast. Suggest try static cast.
+                                               : ... In instance t
+   20 |       i = $cast(c, b);
+      |           ^~~~~
+%Error-UNSUPPORTED: t/t_castdyn_run_bad.v:23:7: Unsupported: $cast. Suggest try static cast.
+                                              : ... In instance t
+   23 |       $cast(c, b);   
+      |       ^~~~~
+%Error: Exiting due to