Fix 'case (_) inside' with x wildcards

Found by inspection, case inside used to threat 'x' as a value, not as a
wildcard. Per the standard it should behave as '==?' which treats both
'x' and 'z' as wildcards.

src/V3Case.cpp

@@ -607,8 +607,8 @@ class CaseVisitor final : public VNVisitor {
 
     bool neverItem(const AstCase* casep, const AstConst* itemp) {
         // Xs in case or casez are impossible due to two state simulations
-        if (casep->casex()) {
+        if (casep->casex() || casep->caseInside()) {
-        } else if (casep->casez() || casep->caseInside()) {
+        } else if (casep->casez()) {
             if (itemp->num().isAnyX()) return true;
         } else {
             if (itemp->num().isFourState()) return true;

test_regress/t/t_case_inside_with_x.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of either the GNU Lesser General Public License Version 3
+# or the Perl Artistic License Version 2.0.
+# SPDX-FileCopyrightText: 2026 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('simulator')
+
+test.compile(verilator_flags2=['--binary'])
+
+test.execute()
+
+test.passes()

test_regress/t/t_case_inside_with_x.v

@@ -0,0 +1,35 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain.
+// SPDX-FileCopyrightText: 2026 Wilson Snyder
+// SPDX-License-Identifier: CC0-1.0
+
+// verilog_format: off
+`define stop $stop
+`define checkh(gotv,expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got=%0x exp=%0x (%s !== %s)\n", `__FILE__,`__LINE__, (gotv), (expv), `"gotv`", `"expv`"); `stop; end while(0);
+// verilog_format: on
+
+module top;
+  bit clk = 1'b0;
+  always #1 clk = ~clk;
+
+  logic [2:0] cyc = 3'd0;
+  int count = 0;
+  always @(posedge clk) begin
+    // verilator lint_off CASEWITHX
+    case (cyc) inside
+      3'b000: begin $display("case inside 000"); ++count; end
+      3'b001: begin $display("case inside 001"); ++count; end
+      // Should match z
+      3'b01?: begin $display("case inside 01?"); ++count; end
+      // Should match x
+      3'b1xx: begin $display("case inside 1xx"); ++count; end
+    endcase
+    // verilator lint_on CASEWITHX
+    cyc <= cyc + 3'd1;
+    if (&cyc) begin
+      `checkh(count, 8);
+      $finish;
+    end
+  end
+endmodule