Fix error on illegal nand/nor binary operators (#7353).

Fixes #7353.

Changes

@@ -112,6 +112,7 @@ Verilator 5.047 devel
 * Fix `disable iff` imply-delay statement linking (#7337). [Nick Brereton]
 * Fix lost `$stop` on implied assertion `$error` failures.
 * Fix wait() hang when interface uses process calls and VIF function (#7342). [Yilou Wang]
+* Fix error on illegal nand/nor binary operators (#7353).
 
 
 Verilator 5.046 2026-02-28

src/verilog.y

@@ -27,6 +27,7 @@
 #define YYERROR_VERBOSE 1  // For prior to Bison 3.6
 #define YYINITDEPTH 10000  // Older bisons ignore YYMAXDEPTH
 #define YYMAXDEPTH 10000
+#define YYNEWLINE "\n"
 
 // Pick up new lexer
 #define yylex PARSEP->tokenToBison
@@ -5059,8 +5060,14 @@ expr<nodeExprp>:                // IEEE: part of expression/constant_expression/
         |       ~l~expr '|' ~r~expr                     { $$ = new AstOr{$2, $1, $3}; }
         |       ~l~expr '^' ~r~expr                     { $$ = new AstXor{$2, $1, $3}; }
         |       ~l~expr yP_XNOR ~r~expr                 { $$ = new AstNot{$2, new AstXor{$2, $1, $3}}; }
-        |       ~l~expr yP_NOR ~r~expr                  { $$ = new AstNot{$2, new AstOr{$2, $1, $3}}; }
+        |       ~l~expr yP_NOR ~r~expr
-        |       ~l~expr yP_NAND ~r~expr                 { $$ = new AstNot{$2, new AstAnd{$2, $1, $3}}; }
+                        { $$ = new AstNot{$2, new AstOr{$2, $1, $3}};
+                          $2->v3error("Syntax error: '~|' is not a 'nor' binary operator, but a unary '~ |'"
+                                      << YYNEWLINE << $<fl>1->warnMore() << "... Suggest '~ (... | ...)'"); }
+        |       ~l~expr yP_NAND ~r~expr
+                        { $$ = new AstNot{$2, new AstAnd{$2, $1, $3}};
+                          $2->v3error("Syntax error: '~&' is not a 'nand' binary operator, but a unary '~ &'"
+                                      << YYNEWLINE << $<fl>1->warnMore() << "... Suggest '~ (... & ...)'"); }
         |       ~l~expr yP_SLEFT ~r~expr                { $$ = new AstShiftL{$2, $1, $3}; }
         |       ~l~expr yP_SRIGHT ~r~expr               { $$ = new AstShiftR{$2, $1, $3}; }
         |       ~l~expr yP_SSRIGHT ~r~expr              { $$ = new AstShiftRS{$2, $1, $3}; }

test_regress/t/t_fuzz_nor_bad.out

@@ -0,0 +1,10 @@
+%Error: t/t_fuzz_nor_bad.v:14:21: Syntax error: '~|' is not a 'nor' binary operator, but a unary '~ |'
+                                : ... Suggest '~ (... | ...)'
+   14 |   assign out1 = var1~|var2;   
+      |                     ^~
+        ... See the manual at https://verilator.org/verilator_doc.html?v=latest for more assistance.
+%Error: t/t_fuzz_nor_bad.v:16:21: Syntax error: '~&' is not a 'nand' binary operator, but a unary '~ &'
+                                : ... Suggest '~ (... & ...)'
+   16 |   assign out2 = var1~&var2;   
+      |                     ^~
+%Error: Exiting due to

test_regress/t/t_fuzz_nor_bad.py

@@ -0,0 +1,16 @@
+#!/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: 2024 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('linter')
+
+test.lint(fails=True, expect_filename=test.golden_filename)
+
+test.passes()

test_regress/t/t_fuzz_nor_bad.v

@@ -0,0 +1,20 @@
+// 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
+
+module bug_reduction_nor_binary (
+    input logic [3:0] var1,
+    input logic [3:0] var2,
+    output logic [3:0] out1,
+    output logic [3:0] out2
+);
+
+  assign out1 = var1~|var2;  //< ~| is a unary reduction operator, not a binary infix operator
+
+  assign out2 = var1~&var2;  //< ~& is a unary reduction operator, not a binary infix operator
+
+  // ~^ is legal
+
+endmodule