From 801955ffab6ce4d89e1a274aeb34ffce6a771e21 Mon Sep 17 00:00:00 2001
From: Zachary Snow <zach@zachjs.com>
Date: Fri, 21 May 2021 14:02:29 -0400
Subject: [PATCH] support for empty port connections

---
 src/Language/SystemVerilog/Parser/Parse.y | 18 ++++++++++----
 test/basic/unbound_port.sv                | 29 +++++++++++++++++++++++
 test/basic/unbound_port.v                 |  2 ++
 test/lib/functions.sh                     |  1 +
 4 files changed, 45 insertions(+), 5 deletions(-)
 create mode 100644 test/basic/unbound_port.sv
 create mode 100644 test/basic/unbound_port.v

diff --git a/src/Language/SystemVerilog/Parser/Parse.y b/src/Language/SystemVerilog/Parser/Parse.y
index fe6be82..2e58ff7 100644
--- a/src/Language/SystemVerilog/Parser/Parse.y
+++ b/src/Language/SystemVerilog/Parser/Parse.y
@@ -965,11 +965,14 @@ LHSs :: { [LHS] }
   | LHSs "," LHS  { $1 ++ [$3] }
 
 PortBindings :: { [PortBinding] }
-  : "("                    ")" { [] }
-  | "(" PortBindingsInside ")" {% checkPortBindings $2 }
+  : "(" PortBindingsInside ")" {% checkPortBindings $2 }
 PortBindingsInside :: { [PortBinding] }
-  : PortBinding opt(",")               { [$1] }
-  | PortBinding "," PortBindingsInside { $1 : $3}
+  : OptPortBinding                        { [$1] }
+  | OptPortBinding "," PortBindingsInside { $1 : $3}
+OptPortBinding :: { PortBinding }
+  : {- empty -} { ("", Nil) }
+  | PortBinding { $1 }
+
 PortBinding :: { PortBinding }
   : "." Identifier "(" ExprOrNil ")" { ($2, $4) }
   | "." Identifier                   { ($2, Ident $2) }
@@ -1507,7 +1510,12 @@ missingToken expected = do
   throwError $ show p ++ ": Parse error: missing expected `" ++ expected ++ "`"
 
 checkPortBindings :: [PortBinding] -> ParseState [PortBinding]
-checkPortBindings = checkBindings "port connections"
+checkPortBindings [] = return []
+checkPortBindings bindings =
+  checkBindings "port connections" $
+  if last bindings == ("", Nil)
+    then init bindings
+    else bindings
 
 checkParamBindings :: [ParamBinding] -> ParseState [ParamBinding]
 checkParamBindings = checkBindings "parameter overrides"
diff --git a/test/basic/unbound_port.sv b/test/basic/unbound_port.sv
new file mode 100644
index 0000000..9226720
--- /dev/null
+++ b/test/basic/unbound_port.sv
@@ -0,0 +1,29 @@
+`ifndef TRAIL
+`define TRAIL ,
+`endif
+
+module mod #(
+    parameter [23:0] KEY = "INV"
+) (a, b, c);
+    input wire [31:0] a, b, c;
+    initial #1 $display("%s a=%0d b=%0d c=%0d", KEY, a, b, c);
+endmodule
+
+module top;
+    mod #("MA0") MA0(, , );
+    mod #("MA1") MA1(1, , );
+    mod #("MA2") MA2(1, 2, );
+    mod #("MA3") MA3(1, 2, 3);
+    mod #("MA4") MA4(1, , 3);
+    mod #("MA5") MA5(1, , 3);
+    mod #("MA6") MA6(, 2, 3);
+    mod #("MA7") MA7(, , 3);
+    mod #("MB0") MB0(, , `TRAIL);
+    mod #("MB1") MB1(1, , `TRAIL);
+    mod #("MB2") MB2(1, 2, `TRAIL);
+    mod #("MB3") MB3(1, 2, 3 `TRAIL);
+    mod #("MB4") MB4(1, , 3 `TRAIL);
+    mod #("MB5") MB5(1, , 3 `TRAIL);
+    mod #("MB6") MB6(, 2, 3 `TRAIL);
+    mod #("MB7") MB7(, , 3 `TRAIL);
+endmodule
diff --git a/test/basic/unbound_port.v b/test/basic/unbound_port.v
new file mode 100644
index 0000000..a731db9
--- /dev/null
+++ b/test/basic/unbound_port.v
@@ -0,0 +1,2 @@
+`define TRAIL
+`include "unbound_port.sv"
diff --git a/test/lib/functions.sh b/test/lib/functions.sh
index e03eabf..8918418 100644
--- a/test/lib/functions.sh
+++ b/test/lib/functions.sh
@@ -22,6 +22,7 @@ simulate() {
         -Wall \
         -Wno-select-range \
         -Wno-anachronisms \
+        -Wno-portbind \
         -o $sim_prog \
         -g2005 \
         -DTEST_VCD="\"$sim_vcd\"" \