Add error (vs previous warning) on enum value overflow.

src/V3Width.cpp

@@ -2288,10 +2288,17 @@ private:
         if (nodep->valuep()) {  // else the value will be assigned sequentially
             // Default type is int, but common to assign narrower values, so minwidth from value
             userIterateAndNext(nodep->valuep(), WidthVP{CONTEXT_DET, PRELIM}.p());
+            bool warnOn = true;
+            if (const AstConst* const constp = VN_CAST(nodep->valuep(), Const)) {
+                if (static_cast<int>(constp->num().mostSetBitP1()) > nodep->width()) {
+                    constp->v3error("Enum value exceeds width of enum type (IEEE 1800-2017 6.19)");
+                    warnOn = false;  // Prevent normal WIDTHTRUNC
+                }
+            }
             // Minwidth does not come from value, as spec says set based on parent
             // and if we keep minwidth we'll consider it unsized which is incorrect
             iterateCheck(nodep, "Enum value", nodep->valuep(), CONTEXT_DET, FINAL, nodep->dtypep(),
-                         EXTEND_EXP);
+                         EXTEND_EXP, warnOn);
             // Always create a cast, to avoid later ENUMVALUE warnings
             nodep->valuep(new AstCast{nodep->valuep()->fileline(), nodep->valuep()->unlinkFrBack(),
                                       nodep->dtypep()});

test_regress/t/t_enum_bad_value.out

@@ -0,0 +1,5 @@
+%Error: t/t_enum_bad_value.v:10:19: Enum value exceeds width of enum type (IEEE 1800-2017 6.19)
+                                  : ... In instance t
+   10 |       VALUE_BAD = 8
+      |                   ^
+%Error: Exiting due to

test_regress/t/t_enum_bad_value.pl

@@ -0,0 +1,20 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003 by Wilson Snyder. 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-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+scenarios(linter => 1);
+
+lint(
+    verilator_flags2 => ["--Wno-fatal"],
+    fails => 1,
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;

test_regress/t/t_enum_bad_value.v

@@ -0,0 +1,13 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2023 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+module t();
+
+   typedef enum [2:0] {
+      VALUE_BAD = 8
+   } enum_t;
+
+endmodule