Add enum base type checking per IEEE.

Changes

@@ -15,6 +15,7 @@ Verilator 5.039 devel
 
 * Add ENUMITEMWIDTH error, and apply to X-extended and ranged values.
 * Add NOEFFECT warning, replacing previous `foreach` error.
+* Add enum base type checking per IEEE.
 * Support member-level triggers for virtual interfaces (#5166) (#6148). [Yilou Wang]
 * Support disabling a fork in additional contexts (#5432 partial) (#6174) (#6183). [Ryszard Rozak, Antmicro Ltd.]
 * Support disable dotted references (#6154). [Ryszard Rozak, Antmicro Ltd.]

src/V3Width.cpp

@@ -2483,10 +2483,11 @@ class WidthVisitor final : public VNVisitor {
         UINFO(5, "  ENUMDTYPE " << nodep);
         nodep->refDTypep(iterateEditMoveDTypep(nodep, nodep->subDTypep()));
         nodep->dtypep(nodep);
-        AstBasicDType* basicp = nodep->dtypep()->skipRefp()->basicp();
-        if (!basicp || !basicp->keyword().isIntNumeric()) {
+        AstNodeDType* basicp = nodep->dtypep()->skipRefp()->basicp();
+        if (!dtypeIsIntAtomOrVecRecurse(nodep->subDTypep())) {
             nodep->v3error(
-                "Enum type must be an integer atom or vector type (IEEE 1800-2023 6.19)");
+                "Enum data type must be an integer atom or vector type (IEEE 1800-2023 6.19), not "
+                << nodep->subDTypep()->prettyDTypeNameQ());
             basicp = nodep->findSigned32DType()->basicp();
             nodep->refDTypep(basicp);
         }
@@ -8309,6 +8310,24 @@ class WidthVisitor final : public VNVisitor {
         if (nodep->subDTypep()) return hasOpenArrayIterateDType(nodep->subDTypep()->skipRefp());
         return false;
     }
+    bool dtypeIsIntAtomOrVecRecurse(AstNodeDType* nodep, bool ranged = false) {
+        nodep = nodep->skipRefToEnump();
+        if (AstBasicDType* const dtp = VN_CAST(nodep, BasicDType)) {
+            if (ranged && (!dtp->isBitLogic() || dtp->isRanged())) {
+                UINFO(9, "dtypeIsIntAtomOrVecRecurse false at " << nodep);
+                return false;  // Packed when already packed
+            }
+            if (dtp->keyword().isIntNumeric()) return true;
+        } else if (AstPackArrayDType* const dtp = VN_CAST(nodep, PackArrayDType)) {
+            if (ranged) {
+                UINFO(9, "dtypeIsIntAtomOrVecRecurse false at " << nodep);
+                return false;  // Packed when already packed
+            }
+            return dtypeIsIntAtomOrVecRecurse(nodep->subDTypep(), true);
+        }
+        UINFO(9, "dtypeIsIntAtomOrVecRecurse false at " << nodep);
+        return false;
+    }
 
     //----------------------------------------------------------------------
     // METHODS - special type detection

test_regress/t/t_enum_base.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2025 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
+
+import vltest_bootstrap
+
+test.scenarios('simulator')
+
+test.compile()
+
+test.execute()
+
+test.passes()

test_regress/t/t_enum_base.v

@@ -0,0 +1,18 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2024 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+module t;
+
+  typedef int int_t;
+  typedef enum int_t {INTT_VAL = 1} intt_e;
+  intt_e intte;
+
+  initial begin
+    $write("*-* All Finished *-*\n");
+    $finish;
+  end
+
+endmodule

test_regress/t/t_enum_base_bad.out

@@ -1,6 +1,30 @@
-%Error: t/t_enum_base_bad.v:13:12: Enum type must be an integer atom or vector type (IEEE 1800-2023 6.19)
+%Error: t/t_enum_base_bad.v:11:11: Enum data type must be an integer atom or vector type (IEEE 1800-2023 6.19), not 'struct{}t.s_t'
                                  : ... note: In instance 't'
-   13 |    typedef enum s_t {
-      |            ^~~~
+   11 |   typedef enum s_t {   
+      |           ^~~~
         ... See the manual at https://verilator.org/verilator_doc.html?v=latest for more assistance.
+%Error: t/t_enum_base_bad.v:16:3: Enum data type must be an integer atom or vector type (IEEE 1800-2023 6.19), not 'int[1:0]'
+                                : ... note: In instance 't'
+   16 |   enum int_t [1:0] {   
+      |   ^~~~
+%Error: t/t_enum_base_bad.v:21:3: Enum data type must be an integer atom or vector type (IEEE 1800-2023 6.19), not 'bit[1:0][1:0]'
+                                : ... note: In instance 't'
+   21 |   enum d2_t {   
+      |   ^~~~
+%Error: t/t_enum_base_bad.v:25:3: Enum data type must be an integer atom or vector type (IEEE 1800-2023 6.19), not 'logic[1:0][1:0]'
+                                : ... note: In instance 't'
+   25 |   enum logic [1:0][1:0] {   
+      |   ^~~~
+%Error: t/t_enum_base_bad.v:30:3: Enum data type must be an integer atom or vector type (IEEE 1800-2023 6.19), not 'struct{}t.str_t'
+                                : ... note: In instance 't'
+   30 |   enum str_t {   
+      |   ^~~~
+%Error: t/t_enum_base_bad.v:35:3: Enum data type must be an integer atom or vector type (IEEE 1800-2023 6.19), not 'enum{}t.enum_t'
+                                : ... note: In instance 't'
+   35 |   enum enum_t {   
+      |   ^~~~
+%Error: t/t_enum_base_bad.v:40:3: Enum data type must be an integer atom or vector type (IEEE 1800-2023 6.19), not 'logic$[1:0]'
+                                : ... note: In instance 't'
+   40 |   enum array2_t {   
+      |   ^~~~
 %Error: Exiting due to

test_regress/t/t_enum_base_bad.v

@@ -4,20 +4,43 @@
 // any use, without warranty, 2024 by Wilson Snyder.
 // SPDX-License-Identifier: CC0-1.0
 
-module t(/*AUTOARG*/);
+module t;
 
-   typedef struct {
-      int a;
-   } s_t;
+  typedef struct {int a;} s_t;
 
-   typedef enum s_t {
-                     EN_ZERO } bad_t;
+  typedef enum s_t {  // BAD
+    EN_ZERO
+  } bad_t;
 
-   typedef int int_t;
+  typedef int int_t;
+  enum int_t [1:0] {  // BAD enum type
+    INTRANGE_VAL
+  } intrange_e;
 
-   typedef enum int_t { EN_ONE = 1 } ok1_t;
+  typedef bit [1:0][1:0] d2_t;
+  enum d2_t {  // BAD enum type
+    TD2_VAL
+  } td2_e;
 
-   s_t s;
-   int_t i;
+  enum logic [1:0][1:0] {  // BAD enum type
+    D2_VAL
+  } d2_e;
+
+  typedef struct packed {int x;} str_t;
+  enum str_t {  // BAD enum type
+    STR_VAL
+  } str_e;
+
+  typedef enum {ENUM_VAL} enum_t;
+  enum enum_t {  // BAD enum type
+    ENUMT_VAL
+  } enumt_val;
+
+  typedef logic array2_t[1:0];
+  enum array2_t {  // BAD enum type
+    ARRAY2_VAL
+  } array2_e;
+
+  initial $stop;
 
 endmodule