Make width violation on function outputs a fatal error

src/V3Width.cpp

@@ -1007,6 +1007,15 @@ private:
 		    } else {
 			// Do PRELIM again, because above accept may have exited early due to node replacement
 			pinp->accept(*this,WidthVP(portp->width(),portp->widthMin(),BOTH).p());
+			if ((portp->isOutput() || portp->isInout())
+			    && pinp->width() != portp->width()) {
+			    pinp->v3error("Unsupported: Function output argument '"<<portp->prettyName()<<"'"
+					  <<" requires "<<pinp->width()
+					  <<" bits, but connection's "<<pinp->prettyTypeName()
+					  <<" generates "<<portp->width()<<" bits.");
+			    // otherwise would need some mess to force both sides to proper size
+			    // (get an ASSIGN with EXTEND on the lhs instead of rhs)
+			}
 			if (portp->basicp() && !portp->basicp()->isOpaque()) {
 			    widthCheck(nodep,"Function Argument",pinp,portp->width(),portp->widthMin());
 			}

test_regress/t/t_func_wide_out_bad.pl

@@ -0,0 +1,19 @@
+#!/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 (
+	 v_flags2 => ["--lint-only"],
+	 fails=>1,
+	 expect=>
+q{%Error: t/t_func_wide_out_bad.v:\d+: Unsupported: Function output argument 'data' requires 4350 bits, but connection's VARREF 'msg' generates 4352 bits.
+%Error: Exiting due to.*},
+	 );
+
+ok(1);
+1;

test_regress/t/t_func_wide_out_bad.v

@@ -0,0 +1,29 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed into the Public Domain, for any use,
+// without warranty, 2003 by Wilson Snyder.
+
+module t ();
+
+   parameter MSG_PORT_WIDTH = 4350;
+   localparam PAYLOAD_MAX_BITS = 4352;
+   
+   reg [MSG_PORT_WIDTH-1:0] 	msg;
+   
+   initial begin
+      // Operator TASKREF 'func' expects 4352 bits on the Function Argument, but Function Argument's VARREF 'msg' generates 4350 bits.
+      // verilator lint_off WIDTH
+      func(msg);
+      // verilator lint_on WIDTH
+      if (msg !== {MSG_PORT_WIDTH{1'b1}}) $stop;
+      $write("*-* All Finished *-*\n");
+      $finish;
+   end
+
+   function integer func (output bit [PAYLOAD_MAX_BITS-1:0] data);
+      /*verilator no_inline_task*/
+      data = {PAYLOAD_MAX_BITS{1'b1}};
+      return (1);
+   endfunction
+
+endmodule