Convert cast tasks to assertions

src/V3AstNodes.h

@@ -5835,6 +5835,10 @@ public:
 };
 
 class AstCastDynamic : public AstNodeBiop {
+    // Verilog $cast used as a function
+    // Task usage of $cast is converted during parse to assert($cast(...))
+    // Parents: MATH
+    // Children: MATH
 public:
     AstCastDynamic(FileLine* fl, AstNode* lhsp, AstNode* rhsp)
         : ASTGEN_SUPER(fl, lhsp, rhsp) {}

src/V3LinkLValue.cpp

@@ -76,6 +76,15 @@ private:
             iterateAndNextNull(nodep->rhsp());
         }
     }
+    virtual void visit(AstCastDynamic* nodep) override {
+        VL_RESTORER(m_setRefLvalue);
+        {
+            m_setRefLvalue = VAccess::WRITE;
+            iterateAndNextNull(nodep->lhsp());
+            m_setRefLvalue = false;
+            iterateAndNextNull(nodep->rhsp());
+        }
+    }
     virtual void visit(AstFOpen* nodep) override {
         VL_RESTORER(m_setRefLvalue);
         {

src/V3Width.cpp

@@ -1599,9 +1599,10 @@ private:
         nodep->widthFromSub(nodep->subDTypep());
     }
     virtual void visit(AstCastDynamic* nodep) override {
+        nodep->dtypeChgWidthSigned(32, 1, VSigning::SIGNED);  // Spec says integer return
         nodep->v3warn(E_UNSUPPORTED, "Unsupported: $cast. Suggest try static cast.");
         AstNode* newp = new AstConst(nodep->fileline(), 1);
-        newp->dtypeSetSigned32();  // Spec says integer return
+        newp->dtypeFrom(nodep);
         nodep->replaceWith(newp);
         VL_DO_DANGLING(pushDeletep(nodep), nodep);
     }

src/verilog.y

@@ -3624,6 +3624,9 @@ system_t_call<nodep>:		// IEEE: system_tf_call (as task)
 	|	yD_WRITEMEMH '(' expr ',' idClassSel ',' expr ')'		{ $$ = new AstWriteMem($1, true,  $3, $5, $7, nullptr); }
 	|	yD_WRITEMEMH '(' expr ',' idClassSel ',' expr ',' expr ')'	{ $$ = new AstWriteMem($1, true,  $3, $5, $7, $9); }
 	//
+	|	yD_CAST '(' expr ',' expr ')'
+			{ $$ = new AstAssert($1, new AstCastDynamic($1, $3, $5), nullptr, nullptr, true); }
+	//
 	// Any system function as a task
 	|	system_f_call_or_t			{ $$ = new AstSysFuncAsTask($<fl>1, $1); }
 	;
@@ -3632,6 +3635,7 @@ system_f_call<nodep>:		// IEEE: system_tf_call (as func)
 		yaD_PLI systemDpiArgsE			{ $$ = new AstFuncRef($<fl>1, *$1, $2); VN_CAST($$, FuncRef)->pli(true); }
 	//
 	|	yD_C '(' cStrList ')'			{ $$ = (v3Global.opt.ignc() ? nullptr : new AstUCFunc($1,$3)); }
+	|	yD_CAST '(' expr ',' expr ')'		{ $$ = new AstCastDynamic($1, $3, $5); }
 	|	yD_SYSTEM  '(' expr ')'			{ $$ = new AstSystemF($1,$3); }
 	//
 	|	system_f_call_or_t			{ $$ = $1; }
@@ -3654,7 +3658,6 @@ system_f_call_or_t<nodep>:	// IEEE: part of system_tf_call (can be task or func)
 	|	yD_BITS '(' exprOrDataType ',' expr ')'	{ $$ = new AstAttrOf($1,AstAttrType::DIM_BITS,$3,$5); }
 	|	yD_BITSTOREAL '(' expr ')'		{ $$ = new AstBitsToRealD($1,$3); }
 	|	yD_BITSTOSHORTREAL '(' expr ')'		{ $$ = new AstBitsToRealD($1,$3); UNSUPREAL($1); }
-	|	yD_CAST '(' expr ',' expr ')'		{ $$ = new AstCastDynamic($1, $3, $5); }
 	|	yD_CEIL '(' expr ')'			{ $$ = new AstCeilD($1,$3); }
 	|	yD_CHANGED '(' expr ')'			{ $$ = new AstLogNot($1, new AstStable($1, $3)); }
 	|	yD_CHANGED '(' expr ',' expr ')'	{ $$ = $3; BBUNSUP($1, "Unsupported: $changed and clock arguments"); }

test_regress/t/t_castdyn.out

@@ -22,8 +22,8 @@
                                        : ... In instance t
    51 |       i = $cast(bbo, b);
       |           ^~~~~
-%Error-UNSUPPORTED: t/t_castdyn.v:57:11: Unsupported: $cast. Suggest try static cast.
+%Error-UNSUPPORTED: t/t_castdyn.v:58:11: Unsupported: $cast. Suggest try static cast.
                                        : ... In instance t
-   57 |       i = $cast(bao, b);
+   58 |       i = $cast(bao, b);
       |           ^~~~~
 %Error: Exiting due to

test_regress/t/t_castdyn.v

@@ -53,9 +53,11 @@ module t (/*AUTOARG*/);
       if (b != bb) $stop;
 
       bb = new;
-      b = b;
+      b = bb;
+      bao = ba;
       i = $cast(bao, b);
       if (i != 0) $stop;
+      if (bao != ba) $stop;  // Unchanged
 
       $write("*-* All Finished *-*\n");
       $finish;