Fix output with select hitting tristate, bug514.

src/V3Tristate.cpp

@@ -1036,6 +1036,10 @@ class TristateVisitor : public TristateBaseVisitor {
 	    nodep->user2(U2_GRAPHING);
 	    AstVar* enModVarp = (AstVar*) nodep->modVarp()->user1p();
 	    if (!enModVarp) {
+		if (nodep->exprp()) {
+		    // May have an output only that later connects to a tristate, so simplify now.
+		    V3Inst::pinReconnectSimple(nodep, m_cellp, m_modp, false);
+		}
 		iteratePinGuts(nodep);
 		return; // No __en signals on this pin
 	    }

test_regress/t/t_tri_graph.pl

@@ -0,0 +1,15 @@
+#!/usr/bin/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.
+
+# Compile only test
+compile (
+    );
+
+ok(1);
+1;

test_regress/t/t_tri_graph.v

@@ -0,0 +1,27 @@
+// DESCRIPTION: Verilator: Unsupported tristate constructur error
+//
+// This is a compile only regression test of tristate handling for bug514
+//
+// This file ONLY is placed into the Public Domain, for any use,
+// without warranty, 2012 by Jeremy Bennett.
+
+module t (/*AUTOARG*/
+   // Inputs
+   clk
+   );
+   input clk;
+
+   wire [11:0] ck;
+
+   assign ck[1:0] = {1'bz,{1{1'b0}}};
+
+   test i_test (.clk (ck[1:0]));
+
+endmodule
+
+
+module test (clk);
+
+   output wire [1:0] clk;
+
+endmodule // test