diff --git a/src/V3AstNodeExpr.h b/src/V3AstNodeExpr.h
index 300aea817..1e06fd10c 100644
--- a/src/V3AstNodeExpr.h
+++ b/src/V3AstNodeExpr.h
@@ -4524,6 +4524,7 @@ public:
     void isImplicit(bool flag) { m_isImplicit = flag; }
     bool isScoped() const { return m_isScoped; }
     void isScoped(bool flag) { m_isScoped = flag; }
+    bool isPure() override { return false; }
 };
 class AstTaskRef final : public AstNodeFTaskRef {
     // A reference to a task
diff --git a/src/V3Const.cpp b/src/V3Const.cpp
index 9b5ba8996..2afc17493 100644
--- a/src/V3Const.cpp
+++ b/src/V3Const.cpp
@@ -3241,10 +3241,16 @@ class ConstVisitor final : public VNVisitor {
             } else if (!AstNode::afterCommentp(nodep->thensp())
                        && !AstNode::afterCommentp(nodep->elsesp())) {
                 if (!nodep->condp()->isPure()) {
-                    // Condition has side effect - leave - perhaps in
-                    // future simplify to remove all but side effect terms
+                    // Condition has side effect - leave, but don't need return value
+                    UINFO(4, "IF({x}) ; => STMTEXPR({x}): " << nodep);
+                    nodep->fileline()->warnOff(V3ErrorCode::IGNOREDRETURN, true);
+                    AstNodeStmt* const newp
+                        = new AstStmtExpr{nodep->fileline(), nodep->condp()->unlinkFrBack()};
+                    nodep->replaceWith(newp);
+                    VL_DO_DANGLING(pushDeletep(nodep), nodep);
                 } else {
                     // Empty block, remove it
+                    UINFO(4, "IF({x}) ; => ; : " << nodep);
                     VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
                 }
             } else if (!AstNode::afterCommentp(nodep->thensp())) {
@@ -3498,6 +3504,8 @@ class ConstVisitor final : public VNVisitor {
         }
         // TODO if there's an ExprStmt underneath just keep lower statements
         // (No current test case needs this)
+        // TODO if non-pure, can remove keep removing upper pure-itself
+        // NodeUniOp/NodeBiOp until get to the non-pure child-node expression
     }
 
     // Simplify
diff --git a/src/V3Randomize.cpp b/src/V3Randomize.cpp
index ecf20d1d4..26fb1932d 100644
--- a/src/V3Randomize.cpp
+++ b/src/V3Randomize.cpp
@@ -241,7 +241,8 @@ class RandomizeMarkVisitor final : public VNVisitor {
                     methodHardp->v3fatalSrc("Unknown rand_mode() receiver");
                 }
             }
-            if (!nodep->pinsp() && VN_IS(nodep->backp(), StmtExpr)) {
+            if (!nodep->pinsp() && VN_IS(nodep->backp(), StmtExpr)
+                && !nodep->backp()->fileline()->warnIsOff(V3ErrorCode::IGNOREDRETURN)) {
                 nodep->v3warn(
                     IGNOREDRETURN,
                     "Ignoring return value of non-void function (IEEE 1800-2023 13.4.1)");
@@ -302,7 +303,8 @@ class RandomizeMarkVisitor final : public VNVisitor {
                 nodep->v3error(
                     "'constraint_mode()' with arguments cannot be called as a function");
                 valid = false;
-            } else if (!nodep->pinsp() && VN_IS(nodep->backp(), StmtExpr)) {
+            } else if (!nodep->pinsp() && VN_IS(nodep->backp(), StmtExpr)
+                       && !nodep->backp()->fileline()->warnIsOff(V3ErrorCode::IGNOREDRETURN)) {
                 nodep->v3warn(
                     IGNOREDRETURN,
                     "Ignoring return value of non-void function (IEEE 1800-2023 13.4.1)");
diff --git a/src/V3Task.cpp b/src/V3Task.cpp
index 358811654..b9a00f833 100644
--- a/src/V3Task.cpp
+++ b/src/V3Task.cpp
@@ -1510,7 +1510,8 @@ class TaskVisitor final : public VNVisitor {
             VIsCached::clearCacheTree();
         } else {  // VN_IS(nodep->backp(), StmtExpr)
             insertBeforeStmt(nodep, beginp);
-            if (nodep->taskp()->isFunction()) {
+            if (nodep->taskp()->isFunction()
+                && !nodep->backp()->fileline()->warnIsOff(V3ErrorCode::IGNOREDRETURN)) {
                 nodep->v3warn(
                     IGNOREDRETURN,
                     "Ignoring return value of non-void function (IEEE 1800-2023 13.4.1)");
diff --git a/test_regress/t/t_class_dyn_cast_empty_if.v b/test_regress/t/t_class_dyn_cast_empty_if.v
index f11e35bd4..42a02fc02 100644
--- a/test_regress/t/t_class_dyn_cast_empty_if.v
+++ b/test_regress/t/t_class_dyn_cast_empty_if.v
@@ -7,7 +7,7 @@
 typedef class Derived;
 class Base;
   function Derived cast();
-    if ($cast(cast,this)) begin end
+    if (!$cast(cast, this)) begin end
   endfunction
 endclass