Add error on real to non-real output pins (#2690).

Changes

@@ -13,6 +13,8 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 ****  Report UNUSED on parameters, localparam and genvars (#2627). [Charles Eric LaForest]
 
+****  Add error on real to non-real output pins (#2690). [Peter Monsson]
+
 ****  Fix passing parameter type instantiations by position number.
 
 ****  Fix DPI open array handling issues.

src/V3Width.cpp

@@ -4183,6 +4183,8 @@ private:
                                    << conDTypep->prettyDTypeNameQ() << " data type.");
                 } else if (nodep->modVarp()->isTristate()) {
                     if (pinwidth != conwidth) {
+                        // Ideally should call pinReconnectSimple which would tolerate this
+                        // then have a conversion warning
                         nodep->v3warn(E_UNSUPPORTED,
                                       "Unsupported: " << ucfirst(nodep->prettyOperatorName())
                                                       << " to inout signal requires " << pinwidth
@@ -4191,7 +4193,14 @@ private:
                                                       << " generates " << conwidth << " bits.");
                         // otherwise would need some mess to force both sides to proper size
                     }
+                } else if (nodep->modVarp()->direction().isWritable()
+                           && ((conDTypep->isDouble() && !modDTypep->isDouble())
+                               || (!conDTypep->isDouble() && modDTypep->isDouble()))) {
+                    nodep->v3warn(E_UNSUPPORTED,
+                                  "Unsupported: " << ucfirst(nodep->prettyOperatorName())
+                                                  << " connects real to non-real");
                 }
+
                 // Check if an interface is connected to a non-interface and vice versa
                 if ((VN_IS(modDTypep, IfaceRefDType) && !VN_IS(conDTypep, IfaceRefDType))
                     || (VN_IS(conDTypep, IfaceRefDType) && !VN_IS(modDTypep, IfaceRefDType))) {

test_regress/t/t_inst_pin_realnreal.out

@@ -0,0 +1,5 @@
+%Error-UNSUPPORTED: t/t_inst_pin_realnreal.v:51:32: Unsupported: Output port connection 'out' connects real to non-real
+                                                  : ... In instance t.netlist
+   51 |    pga_model pga0(.in, .gain, .out(pga_out));
+      |                                ^~~
+%Error: Exiting due to

test_regress/t/t_inst_pin_realnreal.pl

@@ -0,0 +1,23 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2019 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(simulator => 1);
+
+compile(
+    fails => $Self->{vlt_all},
+    expect_filename => $Self->{golden_filename},
+    );
+
+execute(
+    check_finished => 1,
+    ) if !$Self->{vlt_all};
+
+ok(1);
+1;

test_regress/t/t_inst_pin_realnreal.v

@@ -0,0 +1,76 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed into the Public Domain, for any use,
+// without warranty, 2020 by Peter Monsson.
+// SPDX-License-Identifier: CC0-1.0
+
+module t (/*AUTOARG*/
+   // Inputs
+   clk
+   );
+
+   input clk;
+   integer cyc; initial cyc=1;
+
+   wire    gain = 1'b0;
+   real    in;
+   always_comb in = (cyc-4) * 1.0;
+   wire    cmp;
+
+   adc_netlist netlist(.clk, .in, .gain, .cmp);
+
+   always @ (posedge clk) begin
+      if (cyc!=0) begin
+         cyc <= cyc + 1;
+         $display("cyc=%0d cmp=%d", cyc, cmp);
+         if (cyc == 3) begin
+            if (cmp != 0) $stop;
+         end
+         else if (cyc == 4) begin
+            if (cmp != 1) $stop;
+         end
+         else if (cyc == 5) begin
+            if (cmp != 0) $stop;
+         end
+         else if (cyc == 10) begin
+            $write("*-* All Finished *-*\n");
+            $finish;
+         end
+      end
+   end
+
+endmodule
+
+module adc_netlist(clk, in, gain, cmp);
+   input clk;
+   input real in;
+   input gain;
+   output cmp;
+
+   wire pga_out; //TODO: convert to real or support real
+   pga_model pga0(.in, .gain, .out(pga_out));
+   comparator_model cmp0(.clk, .in(pga_out), .cmp);
+
+endmodule
+
+module pga_model(in, gain, out);
+   input real in;
+   input gain;
+   output real out;
+
+   always_comb begin
+      out = in * 3.0;
+   end
+
+endmodule
+
+module comparator_model(clk, in, cmp);
+   input clk;
+   input real in;
+   output logic cmp;
+
+   always_ff @(posedge clk) begin
+      cmp <= in > 0.0;
+   end
+
+endmodule