Lint check for pure virtual in non-virtual class.

src/V3WidthCommit.h

@@ -205,6 +205,15 @@ private:
         nodep->virtRefDTypep(editOneDType(nodep->virtRefDTypep()));
         nodep->virtRefDType2p(editOneDType(nodep->virtRefDType2p()));
     }
+    virtual void visit(AstNodeFTask* nodep) override {
+        iterateChildren(nodep);
+        editDType(nodep);
+        if (nodep->classMethod() && nodep->pureVirtual() && VN_IS(m_modp, Class)
+            && !VN_CAST(m_modp, Class)->isVirtual()) {
+            nodep->v3error(
+                "Illegal to have 'pure virtual' in non-virtual class (IEEE 1800-2017 8.21)");
+        }
+    }
     virtual void visit(AstNodeVarRef* nodep) override {
         iterateChildren(nodep);
         editDType(nodep);

test_regress/t/t_class_virtual_pure.out

@@ -1,7 +0,0 @@
-%Error-UNSUPPORTED: t/t_class_virtual_pure.v:8:22: Unsupported: 'virtual' class method
-    8 |    pure virtual task hello();
-      |                      ^~~~~
-%Error-UNSUPPORTED: t/t_class_virtual_pure.v:7:9: Unsupported: virtual class
-    7 | virtual class VC;
-      |         ^~~~~
-%Error: Exiting due to

test_regress/t/t_class_virtual_pure_bad.out

@@ -0,0 +1,4 @@
+%Error: t/t_class_virtual_pure_bad.v:8:22: Illegal to have 'pure virtual' in non-virtual class (IEEE 1800-2017 8.21)
+    8 |    pure virtual task pure_task;
+      |                      ^~~~~~~~~
+%Error: Exiting due to

test_regress/t/t_class_virtual_pure_bad.pl

@@ -0,0 +1,19 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2020 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(vlt => 1);
+
+lint(
+    fails => 1,
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;

test_regress/t/t_class_virtual_pure_bad.v

@@ -0,0 +1,9 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2019 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+class VBase;
+   pure virtual task pure_task;
+endclass