Fix hang on recursive definition error (#3199).

Changes

@@ -22,6 +22,7 @@ Verilator 4.215 devel
 * Fix array method names with parenthesis (#3181) (#3183). [Teng Huang]
 * Fix split_var assign merging (#3177) (#3179). [Yutetsu TAKATSUKASA]
 * Fix nested generate if genblk naming (#3189). [yanx21]
+* Fix hang on recursive definition error (#3199). [Jonathan Kimmitt]
 * Fix display of signed without format (#3204). [Julie Schwartz]
 * Fix display of empty string constant (#3207). [Julie Schwartz]
 * Fix %0 format on $value$plusargs.

src/V3LinkDot.cpp

@@ -2952,8 +2952,16 @@ private:
                 nodep->classOrPackagep(foundp->classOrPackagep());
             } else if (AstParamTypeDType* defp
                        = foundp ? VN_CAST(foundp->nodep(), ParamTypeDType) : nullptr) {
-                nodep->refDTypep(defp);
+                if (defp == nodep->backp()) {  // Where backp is typically typedef
-                nodep->classOrPackagep(foundp->classOrPackagep());
+                    nodep->v3error("Reference to '" << m_ds.m_dotText
+                                                    << (m_ds.m_dotText == "" ? "" : ".")
+                                                    << nodep->prettyName() << "'"
+                                                    << " type would form a recursive definition");
+                    nodep->refDTypep(nodep->findVoidDType());  // Try to reduce later errors
+                } else {
+                    nodep->refDTypep(defp);
+                    nodep->classOrPackagep(foundp->classOrPackagep());
+                }
             } else if (AstClass* defp = foundp ? VN_AS(foundp->nodep(), Class) : nullptr) {
                 AstNode* paramsp = nodep->paramsp();
                 if (paramsp) paramsp->unlinkFrBackWithNext();

test_regress/t/t_type_param_circ_bad.out

@@ -0,0 +1,4 @@
+%Error: t/t_type_param_circ_bad.v:14:27: Reference to 'SZ' type would form a recursive definition
+   14 |    # (parameter type SZ = SZ)
+      |                           ^~
+%Error: Exiting due to

test_regress/t/t_type_param_circ_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 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(
+    fails => $Self->{vlt_all},
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;

test_regress/t/t_type_param_circ_bad.v

@@ -0,0 +1,20 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2021 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+package pkg;
+   parameter [7:0] WIDTH = 8;
+   typedef logic [WIDTH-1:0] SZ;
+endpackage // pkg
+
+module t
+  import pkg::*;
+   # (parameter type SZ = SZ)
+   (input SZ i,
+    output SZ o);
+
+   always_comb o = i;
+
+endmodule