From 08e32c361df46851c4928540f380494257ddc2e8 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Tue, 19 Feb 2019 11:21:28 +0100
Subject: [PATCH 01/37] AST-38: add failing test

---
 test/fail/issue38.as       | 9 +++++++++
 test/fail/ok/issue38.tc.ok | 4 ++++
 2 files changed, 13 insertions(+)
 create mode 100644 test/fail/issue38.as
 create mode 100644 test/fail/ok/issue38.tc.ok

diff --git a/test/fail/issue38.as b/test/fail/issue38.as
new file mode 100644
index 00000000000..c419004f5f8
--- /dev/null
+++ b/test/fail/issue38.as
@@ -0,0 +1,9 @@
+func f() {};
+func g(()) {};
+func h(u:()) {};
+
+let _ : [() -> ()] = [f, g, h];
+
+f();
+g();
+h();
\ No newline at end of file
diff --git a/test/fail/ok/issue38.tc.ok b/test/fail/ok/issue38.tc.ok
new file mode 100644
index 00000000000..32fd767bf43
--- /dev/null
+++ b/test/fail/ok/issue38.tc.ok
@@ -0,0 +1,4 @@
+issue38.as:5.29-5.30: type error, expression of type
+  (()) -> ()
+cannot produce expected type
+  () -> ()

From 921c06a57c716395171d9fdcad8049d668295d49 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Tue, 19 Feb 2019 13:42:37 +0100
Subject: [PATCH 02/37] add Int arguments

---
 test/fail/issue38.as       | 28 +++++++++++++++++++++++++---
 test/fail/ok/issue38.tc.ok |  6 +++---
 2 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/test/fail/issue38.as b/test/fail/issue38.as
index c419004f5f8..151d19688d8 100644
--- a/test/fail/issue38.as
+++ b/test/fail/issue38.as
@@ -2,8 +2,30 @@ func f() {};
 func g(()) {};
 func h(u:()) {};
 
-let _ : [() -> ()] = [f, g, h];
+let _ : [() -> ()] = [f];
+let gh : [(()) -> ()] = [g, h];
 
 f();
-g();
-h();
\ No newline at end of file
+g(); // why is this accepted?
+h(); // dito
+gh[0](); // dito
+gh[1](); // dito
+
+// Correct:
+g(());
+h(());
+gh[0](());
+gh[1](());
+
+
+func j(a:Int) {};
+func k(a:(Int)) {};
+func l(a:((Int))) {};
+
+let jkl : [Int -> ()] = [j, k, l];
+
+j(5);
+k(8);
+l(13);
+jkl[1](21);
+
diff --git a/test/fail/ok/issue38.tc.ok b/test/fail/ok/issue38.tc.ok
index 32fd767bf43..e9bdb45c5d6 100644
--- a/test/fail/ok/issue38.tc.ok
+++ b/test/fail/ok/issue38.tc.ok
@@ -1,4 +1,4 @@
-issue38.as:5.29-5.30: type error, expression of type
-  (()) -> ()
-cannot produce expected type
+issue38.as:6.26-6.27: type error, expression of type
   () -> ()
+cannot produce expected type
+  (()) -> ()

From 7fcb0a5b17d1e7091285ade46fea5949b90fc328 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Wed, 20 Feb 2019 11:16:14 +0100
Subject: [PATCH 03/37] AST-38: introduce ParP to indicate unary function

and guide it through to type checker.

Parser still not done, instead we explicitly
write a 1-ary pattern at toplevel.
---
 src/arrange.ml       | 9 +++++----
 src/coverage.ml      | 3 ++-
 src/definedness.ml   | 3 ++-
 src/desugar.ml       | 1 +
 src/interpret.ml     | 4 ++++
 src/parser.mly       | 7 +++++--
 src/syntax.ml        | 1 +
 src/typing.ml        | 4 +++-
 test/fail/issue38.as | 2 +-
 9 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/src/arrange.ml b/src/arrange.ml
index d2bc40e16c0..bda01e37525 100644
--- a/src/arrange.ml
+++ b/src/arrange.ml
@@ -8,17 +8,17 @@ let rec exp e = match e.it with
   | VarE i              -> "VarE"    $$ [id i]
   | LitE l              -> "LitE"    $$ [lit !l]
   | UnE (ot, uo, e)     -> "UnE"     $$ [operator_type !ot; unop uo; exp e]
-  | BinE (ot, e1, bo, e2) -> "BinE"    $$ [operator_type !ot; exp e1; binop bo; exp e2]
-  | RelE (ot, e1, ro, e2) -> "RelE"    $$ [operator_type !ot; exp e1; relop ro; exp e2]
+  | BinE (ot, e1, bo, e2) -> "BinE"  $$ [operator_type !ot; exp e1; binop bo; exp e2]
+  | RelE (ot, e1, ro, e2) -> "RelE"  $$ [operator_type !ot; exp e1; relop ro; exp e2]
   | TupE es             -> "TupE"    $$ List.map exp es
   | ProjE (e, i)        -> "ProjE"   $$ [exp e; Atom (string_of_int i)]
   | ObjE (s, i, efs)    -> "ObjE"    $$ [obj_sort s; id i] @ List.map exp_field efs
-  | DotE (e, sr, n)         -> "DotE"    $$ [exp e; obj_sort' !sr; name n]
+  | DotE (e, sr, n)     -> "DotE"    $$ [exp e; obj_sort' !sr; name n]
   | AssignE (e1, e2)    -> "AssignE" $$ [exp e1; exp e2]
   | ArrayE (m, es)      -> "ArrayE"  $$ [mut m] @ List.map exp es
   | IdxE (e1, e2)       -> "IdxE"    $$ [exp e1; exp e2]
   | CallE (e1, ts, e2)  -> "CallE"   $$ [exp e1] @ List.map typ ts @ [exp e2]
-  | BlockE (ds, ot)      -> "BlockE"  $$ List.map dec ds @ [operator_type (!ot)]
+  | BlockE (ds, ot)     -> "BlockE"  $$ List.map dec ds @ [operator_type (!ot)]
   | NotE e              -> "NotE"    $$ [exp e]
   | AndE (e1, e2)       -> "AndE"    $$ [exp e1; exp e2]
   | OrE (e1, e2)        -> "OrE"     $$ [exp e1; exp e2]
@@ -48,6 +48,7 @@ and pat p = match p.it with
   | SignP (uo, l) -> "SignP"      $$ [ unop uo ; lit !l ]
   | OptP p        -> "OptP"       $$ [ pat p ]
   | AltP (p1,p2)  -> "AltP"       $$ [ pat p1; pat p2 ]
+  | ParP p        -> "ParP"       $$ [ pat p ]
 
 and lit (l:lit) = match l with
   | NullLit       -> Atom "NullLit"
diff --git a/src/coverage.ml b/src/coverage.ml
index 16d2a2ff54a..930247d8f34 100644
--- a/src/coverage.ml
+++ b/src/coverage.ml
@@ -90,7 +90,8 @@ let rec match_pat ce ctxt desc pat t sets =
   | AltP (pat1, pat2) ->
     sets.alts <- AtSet.add pat1.at (AtSet.add pat2.at sets.alts);
     match_pat ce (InAlt1 (ctxt, pat1.at, pat2, t)) desc pat1 t sets
-  | AnnotP (pat1, _) ->
+  | AnnotP (pat1, _)
+  | ParP pat1 ->
     match_pat ce ctxt desc pat1 t sets
 
 and match_lit ce ctxt desc v t sets =
diff --git a/src/definedness.ml b/src/definedness.ml
index 0214dcb02d5..606280ff195 100644
--- a/src/definedness.ml
+++ b/src/definedness.ml
@@ -126,7 +126,8 @@ and pat msgs p : fd = match p.it with
   | WildP         -> (M.empty, S.empty)
   | VarP i        -> (M.empty, S.singleton i.it)
   | TupP ps       -> pats msgs ps
-  | AnnotP (p, t) -> pat msgs p
+  | AnnotP (p, _)
+  | ParP p        -> pat msgs p
   | LitP l        -> (M.empty, S.empty)
   | SignP (uo, l) -> (M.empty, S.empty)
   | OptP p        -> pat msgs p
diff --git a/src/desugar.ml b/src/desugar.ml
index 7d8af75942f..5c584a6b839 100644
--- a/src/desugar.ml
+++ b/src/desugar.ml
@@ -203,6 +203,7 @@ and pat' = function
   | S.OptP p -> I.OptP (pat p)
   | S.AltP (p1, p2) -> I.AltP (pat p1, pat p2)
   | S.AnnotP (p, _) -> pat' p.it
+  | S.ParP p -> pat' p.it
 
 and prog p = (decs p.it,
   { I.has_await = true
diff --git a/src/interpret.ml b/src/interpret.ml
index a29eb38a2df..d26366369f2 100644
--- a/src/interpret.ml
+++ b/src/interpret.ml
@@ -435,6 +435,7 @@ and declare_pat pat : val_env =
   | OptP pat1 -> declare_pat pat1
   | AltP (pat1, pat2) -> declare_pat pat1
   | AnnotP (pat1, _typ) -> declare_pat pat1
+  | ParP pat1 -> declare_pat pat1
 
 and declare_pats pats ve : val_env =
   match pats with
@@ -464,6 +465,7 @@ and define_pat env pat v =
     | _ -> assert false
     )
   | AnnotP (pat1, _typ) -> define_pat env pat1 v
+  | ParP pat -> define_pat env pat v
 
 and define_pats env pats vs =
   List.iter2 (define_pat env) pats vs
@@ -511,6 +513,8 @@ and match_pat pat v : val_env option =
     )
   | AnnotP (pat1, _typ) ->
     match_pat pat1 v
+  | ParP pat ->
+    match_pat pat v
 
 and match_pats pats vs ve : val_env option =
   match pats, vs with
diff --git a/src/parser.mly b/src/parser.mly
index 3d205e2c8c3..d65246f2923 100644
--- a/src/parser.mly
+++ b/src/parser.mly
@@ -582,8 +582,11 @@ func_dec :
         | (true, e) -> (* body declared as immediate block *)
           match t.it with
           | AsyncT _ -> AsyncE(e) @? e.at
-          | _ -> e
-      in fun s x -> FuncD(s, x, tps, p, t, e) @? at $sloc }
+          | _ -> e in
+      let p2 = match p.it with
+	| TupP [p1] -> (*Printf.printf "Debug: %d\n" (List.length ps);*){ p with it = ParP p1 }
+	| _ -> p
+      in fun s x -> FuncD(s, x, tps, p2, t, e) @? at $sloc }
 
 func_body :
   | EQ e=exp { (false, e) }
diff --git a/src/syntax.ml b/src/syntax.ml
index 01fa40b3ad1..349876db21e 100644
--- a/src/syntax.ml
+++ b/src/syntax.ml
@@ -107,6 +107,7 @@ and pat' =
   | OptP of pat                                (* option *)
   | AltP of pat * pat                          (* disjunctive *)
   | AnnotP of pat * typ                        (* type annotation *)
+  | ParP of pat                                (* toplevel parenthesis *)
 (*
   | AsP of pat * pat                           (* conjunctive *)
   | ObjP of pat_field list                     (* object *)
diff --git a/src/typing.ml b/src/typing.ml
index 0d61df20c8e..0d0fd76e645 100644
--- a/src/typing.ml
+++ b/src/typing.ml
@@ -710,7 +710,8 @@ and gather_pat env ve0 pat : val_env =
     | AltP (pat1, pat2) ->
       go ve pat1
     | OptP pat1
-    | AnnotP (pat1, _) ->
+    | AnnotP (pat1, _)
+    | ParP pat1 ->
       go ve pat1
   in T.Env.adjoin ve0 (go T.Env.empty pat)
 
@@ -761,6 +762,7 @@ and infer_pat' env pat : T.typ * val_env =
   | AnnotP (pat1, typ) ->
     let t = check_typ env typ in
     t, check_pat env t pat1
+  | ParP pat1 -> infer_pat env pat1
 
 and infer_pats at env pats ts ve : T.typ list * val_env =
   match pats with
diff --git a/test/fail/issue38.as b/test/fail/issue38.as
index 151d19688d8..bcecd638f4b 100644
--- a/test/fail/issue38.as
+++ b/test/fail/issue38.as
@@ -1,5 +1,5 @@
 func f() {};
-func g(()) {};
+func g((),) {};
 func h(u:()) {};
 
 let _ : [() -> ()] = [f];

From 67135bebdcf313ab9a002759f71670d55e4a3d06 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Wed, 20 Feb 2019 11:23:33 +0100
Subject: [PATCH 04/37] no more type errors, TODO: non-fail

---
 test/fail/ok/issue38.tc.ok | 4 ----
 1 file changed, 4 deletions(-)
 delete mode 100644 test/fail/ok/issue38.tc.ok

diff --git a/test/fail/ok/issue38.tc.ok b/test/fail/ok/issue38.tc.ok
deleted file mode 100644
index e9bdb45c5d6..00000000000
--- a/test/fail/ok/issue38.tc.ok
+++ /dev/null
@@ -1,4 +0,0 @@
-issue38.as:6.26-6.27: type error, expression of type
-  () -> ()
-cannot produce expected type
-  (()) -> ()

From 3d3ee756ac9b4580bf22ea6eb4f518a4bad9cb8d Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Wed, 20 Feb 2019 12:17:36 +0100
Subject: [PATCH 05/37] fix parser to remember significant parenthesis

---
 src/parser.mly             | 18 ++++++++++++------
 test/fail/issue38.as       |  2 +-
 test/run/empty-tup-args.as |  2 +-
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/src/parser.mly b/src/parser.mly
index d65246f2923..2ec1a324f8d 100644
--- a/src/parser.mly
+++ b/src/parser.mly
@@ -475,6 +475,15 @@ exp_field :
 
 (* Patterns *)
 
+pat_top :
+  | LPAR p=pat RPAR
+    { match p.it with
+      | TupP _ -> { p with it = ParP p }
+      | _ -> p
+    }
+  | p=pat_nullary
+    { p }
+
 pat_nullary :
   | UNDERSCORE
     { WildP @! at $sloc }
@@ -572,7 +581,7 @@ dec :
         LetD(p, ObjE(s, x, efs') @? r) @? r }
 
 func_dec :
-  | tps=typ_params_opt p=pat_nullary rt=return_typ? fb=func_body
+  | tps=typ_params_opt p=pat_top rt=return_typ? fb=func_body
     { let t = Lib.Option.get rt (TupT([]) @! no_region) in
       (* This is a hack to support local func declarations that return a computed async.
          These should be defined using RHS syntax EQ e to avoid the implicit AsyncE introduction
@@ -582,11 +591,8 @@ func_dec :
         | (true, e) -> (* body declared as immediate block *)
           match t.it with
           | AsyncT _ -> AsyncE(e) @? e.at
-          | _ -> e in
-      let p2 = match p.it with
-	| TupP [p1] -> (*Printf.printf "Debug: %d\n" (List.length ps);*){ p with it = ParP p1 }
-	| _ -> p
-      in fun s x -> FuncD(s, x, tps, p2, t, e) @? at $sloc }
+          | _ -> e
+      in fun s x -> FuncD(s, x, tps, p, t, e) @? at $sloc }
 
 func_body :
   | EQ e=exp { (false, e) }
diff --git a/test/fail/issue38.as b/test/fail/issue38.as
index bcecd638f4b..151d19688d8 100644
--- a/test/fail/issue38.as
+++ b/test/fail/issue38.as
@@ -1,5 +1,5 @@
 func f() {};
-func g((),) {};
+func g(()) {};
 func h(u:()) {};
 
 let _ : [() -> ()] = [f];
diff --git a/test/run/empty-tup-args.as b/test/run/empty-tup-args.as
index 1755cf1e22d..1e1f4f43dff 100644
--- a/test/run/empty-tup-args.as
+++ b/test/run/empty-tup-args.as
@@ -2,7 +2,7 @@ func f() {};
 func g(()) {};
 func h(u:()) {};
 let _ = f : () -> ();
-let _ = g : () -> ();
+let _ = g : (()) -> ();
 let _ = h : (()) -> ();
 f();
 g();

From 4fe6e09b153ef419c5acaba844bdde1b7f3df8b7 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Wed, 20 Feb 2019 12:41:05 +0100
Subject: [PATCH 06/37] test successful

---
 test/{fail => run}/issue38.as | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 rename test/{fail => run}/issue38.as (100%)

diff --git a/test/fail/issue38.as b/test/run/issue38.as
similarity index 100%
rename from test/fail/issue38.as
rename to test/run/issue38.as

From 2d8eac1d9d32c864609de3952cacccd36036137c Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Wed, 20 Feb 2019 13:13:49 +0100
Subject: [PATCH 07/37] beef up the testing, discovering a subtle issue in wasm

---
 test/run/issue38.as                | 27 +++++++++++++++++++++++++++
 test/run/ok/issue38.wasm.stderr.ok |  5 +++++
 2 files changed, 32 insertions(+)
 create mode 100644 test/run/ok/issue38.wasm.stderr.ok

diff --git a/test/run/issue38.as b/test/run/issue38.as
index 151d19688d8..69e5dd22866 100644
--- a/test/run/issue38.as
+++ b/test/run/issue38.as
@@ -29,3 +29,30 @@ k(8);
 l(13);
 jkl[1](21);
 
+func m((a:Int, b:Bool)) {};
+func m1((a:Int, b:Bool,)) {};
+let ms : [((Int, Bool)) -> ()] = [m, m1];
+
+func n(a:Int, b:Bool) {};
+func n1(a:Int, b:Bool,) {};
+
+let ns : [(Int, Bool) -> ()] = [n, n1];
+
+func o((a:Int,)) {};
+let os : [((Int,)) -> ()] = [o];
+
+func p((),) {};
+let ps : [((),) -> ()] = [p];
+
+/* the above is a curious case, failing in wasm:
+
+issue38: [tc] [run] [run-low] [run-ir] [wasm]
+--- issue38.wasm.stderr (expected)
++++ issue38.wasm.stderr (actual)
+@@ -0,0 +1,5 @@
++Ill-typed intermediate code (use -v to see dumped IR):
++issue38.as:44.1-44.15: IR type error, subtype violation:
++  (((),)) -> ()
++  (()) -> ()
++
+*/
diff --git a/test/run/ok/issue38.wasm.stderr.ok b/test/run/ok/issue38.wasm.stderr.ok
new file mode 100644
index 00000000000..1cbb20be970
--- /dev/null
+++ b/test/run/ok/issue38.wasm.stderr.ok
@@ -0,0 +1,5 @@
+Ill-typed intermediate code (use -v to see dumped IR):
+issue38.as:44.1-44.15: IR type error, subtype violation:
+  (((),)) -> ()
+  (()) -> ()
+

From 1383827e7541248a6e6ad24c2a7867131f498e9c Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Wed, 20 Feb 2019 13:35:26 +0100
Subject: [PATCH 08/37] review feedback

---
 src/interpret.ml                   | 7 +++----
 src/parser.mly                     | 3 +++
 test/run/issue38.as                | 4 +++-
 test/run/ok/issue38.wasm.stderr.ok | 2 +-
 4 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/src/interpret.ml b/src/interpret.ml
index d26366369f2..4173851845e 100644
--- a/src/interpret.ml
+++ b/src/interpret.ml
@@ -511,10 +511,9 @@ and match_pat pat v : val_env option =
     | None -> match_pat pat2 v
     | some -> some
     )
-  | AnnotP (pat1, _typ) ->
-    match_pat pat1 v
-  | ParP pat ->
-    match_pat pat v
+  | AnnotP (pat1, _)
+  | ParP pat1 ->
+     match_pat pat1 v
 
 and match_pats pats vs ve : val_env option =
   match pats, vs with
diff --git a/src/parser.mly b/src/parser.mly
index 2ec1a324f8d..291bf5e6c0a 100644
--- a/src/parser.mly
+++ b/src/parser.mly
@@ -475,6 +475,9 @@ exp_field :
 
 (* Patterns *)
 
+(* pat_top is needed because top-level parentheses around tuples (unit, 1-ary, pair, etc.)
+   are significant in function arguments, signifying a unary function which matches on a
+   first-class (i.e. consed) tuple *)
 pat_top :
   | LPAR p=pat RPAR
     { match p.it with
diff --git a/test/run/issue38.as b/test/run/issue38.as
index 69e5dd22866..cb15176e322 100644
--- a/test/run/issue38.as
+++ b/test/run/issue38.as
@@ -1,9 +1,11 @@
 func f() {};
 func g(()) {};
+func g1((())) {}; // only top-level parenthesis signifies arity
 func h(u:()) {};
+func h1((u:())) {}; // dito, intermediate parentheses are redundant
 
 let _ : [() -> ()] = [f];
-let gh : [(()) -> ()] = [g, h];
+let gh : [(()) -> ()] = [g, g1, h, h1];
 
 f();
 g(); // why is this accepted?
diff --git a/test/run/ok/issue38.wasm.stderr.ok b/test/run/ok/issue38.wasm.stderr.ok
index 1cbb20be970..469f203b497 100644
--- a/test/run/ok/issue38.wasm.stderr.ok
+++ b/test/run/ok/issue38.wasm.stderr.ok
@@ -1,5 +1,5 @@
 Ill-typed intermediate code (use -v to see dumped IR):
-issue38.as:44.1-44.15: IR type error, subtype violation:
+issue38.as:46.1-46.15: IR type error, subtype violation:
   (((),)) -> ()
   (()) -> ()
 

From 3f2e40567114ff230f2540aae2a7cfcff79f2efe Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Wed, 20 Feb 2019 16:43:49 +0100
Subject: [PATCH 09/37] classes are basically functions and as such inherit the
 top-level arities

---
 src/parser.mly | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/parser.mly b/src/parser.mly
index 291bf5e6c0a..bef8492a537 100644
--- a/src/parser.mly
+++ b/src/parser.mly
@@ -547,7 +547,7 @@ dec_nonvar :
     { (fd s (xf "func" $sloc)).it @? at $sloc }
   | TYPE x=con_id tps=typ_params_opt EQ t=typ
     { TypD(x, tps, t) @? at $sloc }
-  | s=obj_sort_opt CLASS xf=id_opt tps=typ_params_opt p=pat_nullary xefs=class_body
+  | s=obj_sort_opt CLASS xf=id_opt tps=typ_params_opt p=pat_top xefs=class_body
     { let x, efs = xefs in
       let efs' =
         if s.it = Type.Object Type.Local

From da9c08bc8ef924151a6cc9fbf4cde6bebb7e3175 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Wed, 20 Feb 2019 17:20:51 +0100
Subject: [PATCH 10/37] Factor out `pat_simple`

so that `pat_top` and `pat_nullary` can share the common innards.

This avoids the reduce/reduce conflicts reported by `menhir`.

CAVEAT: I am not a grammar expert, so there may be better ways to accomplish this.
Suggestions welcome.
---
 src/parser.mly | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/parser.mly b/src/parser.mly
index bef8492a537..ec920b083eb 100644
--- a/src/parser.mly
+++ b/src/parser.mly
@@ -484,21 +484,25 @@ pat_top :
       | TupP _ -> { p with it = ParP p }
       | _ -> p
     }
-  | p=pat_nullary
+  | p=pat_simple
     { p }
 
-pat_nullary :
+pat_simple :
   | UNDERSCORE
     { WildP @! at $sloc }
   | x=id
     { VarP(x) @! at $sloc }
   | l=lit
     { LitP(ref l) @! at $sloc }
-  | LPAR p=pat RPAR
-    { p }
   | LPAR ps=seplist1(pat_bin, COMMA) RPAR
     { TupP(ps) @! at $sloc }
 
+pat_nullary :
+  | LPAR p=pat RPAR
+    { p }
+  | p=pat_simple
+    { p }
+
 pat_un :
   | p=pat_nullary
     { p }

From 0d797e68a20952a80fe8908276e9c97fcb558717 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Thu, 21 Feb 2019 16:27:36 +0100
Subject: [PATCH 11/37] more tests (classes)

---
 test/run/issue38.as | 39 ++++++++++++++++++++++++---------------
 1 file changed, 24 insertions(+), 15 deletions(-)

diff --git a/test/run/issue38.as b/test/run/issue38.as
index cb15176e322..740fa864317 100644
--- a/test/run/issue38.as
+++ b/test/run/issue38.as
@@ -8,7 +8,8 @@ let _ : [() -> ()] = [f];
 let gh : [(()) -> ()] = [g, g1, h, h1];
 
 f();
-g(); // why is this accepted?
+g(); // accepted, because "At calls there is an implicit coercion
+     //                    between tuples and n-ary arguments"
 h(); // dito
 gh[0](); // dito
 gh[1](); // dito
@@ -19,7 +20,6 @@ h(());
 gh[0](());
 gh[1](());
 
-
 func j(a:Int) {};
 func k(a:(Int)) {};
 func l(a:((Int))) {};
@@ -43,18 +43,27 @@ let ns : [(Int, Bool) -> ()] = [n, n1];
 func o((a:Int,)) {};
 let os : [((Int,)) -> ()] = [o];
 
-func p((),) {};
-let ps : [((),) -> ()] = [p];
+/* TODO
+func q((?(a:Int),)) {};
+func q1((?((a:Int)),)) {};
+func q2(((?((a:Int)),))) {};
+let qs : [((?Int,)) -> ()] = [q, q1, q2]
+*/
+
 
-/* the above is a curious case, failing in wasm:
+// class tests, these have the same argument regime
+class F() {};
+class G(()) {};
+class H(a:()) {};
+class G1((())) {};
+class H1((u:())) {};
+let _ : [() -> F] = [F];
+let _ : [(()) -> G] = [G];
+let _ : [(()) -> G1] = [G1];
+let _ : [(()) -> H] = [H];
+let _ : [(()) -> H1] = [H1];
 
-issue38: [tc] [run] [run-low] [run-ir] [wasm]
---- issue38.wasm.stderr (expected)
-+++ issue38.wasm.stderr (actual)
-@@ -0,0 +1,5 @@
-+Ill-typed intermediate code (use -v to see dumped IR):
-+issue38.as:44.1-44.15: IR type error, subtype violation:
-+  (((),)) -> ()
-+  (()) -> ()
-+
-*/
+func annih<A,B>(f : A -> B) : (A -> ()) { func (a : A) { ignore (f a) } };
+//func annih<A,B>(f : A -> B) : (A -> ()) { func (a : A) { let _ = f a; } };
+// fishy: let _ : [() -> ()] = [annih<(),F> F];
+let _ : [(()) -> ()] = [annih<(),G> G, annih<(),G1> G1, annih<(),H> H, annih<(),H1> H1];

From 53cb2ad8311a6f7cec8f5f659fa95eaae480a914 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Thu, 21 Feb 2019 16:51:47 +0100
Subject: [PATCH 12/37] consolidate tests

---
 test/run/empty-tup-args.as         | 58 ++++++++++++++++++++++++-
 test/run/issue38.as                | 69 ------------------------------
 test/run/ok/issue38.wasm.stderr.ok |  5 ---
 3 files changed, 56 insertions(+), 76 deletions(-)
 delete mode 100644 test/run/issue38.as
 delete mode 100644 test/run/ok/issue38.wasm.stderr.ok

diff --git a/test/run/empty-tup-args.as b/test/run/empty-tup-args.as
index 1e1f4f43dff..78fffad42bf 100644
--- a/test/run/empty-tup-args.as
+++ b/test/run/empty-tup-args.as
@@ -1,9 +1,63 @@
 func f() {};
 func g(()) {};
+func g1((())) {}; // only top-level parenthesis signifies arity
 func h(u:()) {};
+func h1((u:())) {}; // dito, intermediate parentheses are redundant
+
 let _ = f : () -> ();
 let _ = g : (()) -> ();
 let _ = h : (()) -> ();
+
+let _ : [() -> ()] = [f];
+let gh : [(()) -> ()] = [g, g1, h, h1];
+
 f();
-g();
-h();
+g(); // accepted, because "At calls there is an implicit coercion
+     //                    between tuples and n-ary arguments"
+h(); // dito
+gh[0](); // dito
+gh[1](); // dito
+
+// Correct:
+g(());
+h(());
+gh[0](());
+gh[1](());
+
+func j(a:Int) {};
+func k(a:(Int)) {};
+func l(a:((Int))) {};
+
+let jkl : [Int -> ()] = [j, k, l];
+
+j(5);
+k(8);
+l(13);
+jkl[1](21);
+
+func m((a:Int, b:Bool)) {};
+func m1((a:Int, b:Bool,)) {};
+let ms : [((Int, Bool)) -> ()] = [m, m1];
+
+func n(a:Int, b:Bool) {};
+func n1(a:Int, b:Bool,) {};
+
+let ns : [(Int, Bool) -> ()] = [n, n1];
+
+func o((a:Int,)) {};
+let os : [((Int,)) -> ()] = [o];
+
+// class tests, these have the same argument regime
+class F() {};
+class G(()) {};
+class H(a:()) {};
+class G1((())) {};
+class H1((u:())) {};
+let _ : [() -> F] = [F];
+let _ : [(()) -> G] = [G];
+let _ : [(()) -> G1] = [G1];
+let _ : [(()) -> H] = [H];
+let _ : [(()) -> H1] = [H1];
+
+func annih<A,B>(f : A -> B) : (A -> ()) { func (a : A) { ignore (f a) } };
+let _ : [(()) -> ()] = [annih<(),G> G, annih<(),G1> G1, annih<(),H> H, annih<(),H1> H1];
diff --git a/test/run/issue38.as b/test/run/issue38.as
deleted file mode 100644
index 740fa864317..00000000000
--- a/test/run/issue38.as
+++ /dev/null
@@ -1,69 +0,0 @@
-func f() {};
-func g(()) {};
-func g1((())) {}; // only top-level parenthesis signifies arity
-func h(u:()) {};
-func h1((u:())) {}; // dito, intermediate parentheses are redundant
-
-let _ : [() -> ()] = [f];
-let gh : [(()) -> ()] = [g, g1, h, h1];
-
-f();
-g(); // accepted, because "At calls there is an implicit coercion
-     //                    between tuples and n-ary arguments"
-h(); // dito
-gh[0](); // dito
-gh[1](); // dito
-
-// Correct:
-g(());
-h(());
-gh[0](());
-gh[1](());
-
-func j(a:Int) {};
-func k(a:(Int)) {};
-func l(a:((Int))) {};
-
-let jkl : [Int -> ()] = [j, k, l];
-
-j(5);
-k(8);
-l(13);
-jkl[1](21);
-
-func m((a:Int, b:Bool)) {};
-func m1((a:Int, b:Bool,)) {};
-let ms : [((Int, Bool)) -> ()] = [m, m1];
-
-func n(a:Int, b:Bool) {};
-func n1(a:Int, b:Bool,) {};
-
-let ns : [(Int, Bool) -> ()] = [n, n1];
-
-func o((a:Int,)) {};
-let os : [((Int,)) -> ()] = [o];
-
-/* TODO
-func q((?(a:Int),)) {};
-func q1((?((a:Int)),)) {};
-func q2(((?((a:Int)),))) {};
-let qs : [((?Int,)) -> ()] = [q, q1, q2]
-*/
-
-
-// class tests, these have the same argument regime
-class F() {};
-class G(()) {};
-class H(a:()) {};
-class G1((())) {};
-class H1((u:())) {};
-let _ : [() -> F] = [F];
-let _ : [(()) -> G] = [G];
-let _ : [(()) -> G1] = [G1];
-let _ : [(()) -> H] = [H];
-let _ : [(()) -> H1] = [H1];
-
-func annih<A,B>(f : A -> B) : (A -> ()) { func (a : A) { ignore (f a) } };
-//func annih<A,B>(f : A -> B) : (A -> ()) { func (a : A) { let _ = f a; } };
-// fishy: let _ : [() -> ()] = [annih<(),F> F];
-let _ : [(()) -> ()] = [annih<(),G> G, annih<(),G1> G1, annih<(),H> H, annih<(),H1> H1];
diff --git a/test/run/ok/issue38.wasm.stderr.ok b/test/run/ok/issue38.wasm.stderr.ok
deleted file mode 100644
index 469f203b497..00000000000
--- a/test/run/ok/issue38.wasm.stderr.ok
+++ /dev/null
@@ -1,5 +0,0 @@
-Ill-typed intermediate code (use -v to see dumped IR):
-issue38.as:46.1-46.15: IR type error, subtype violation:
-  (((),)) -> ()
-  (()) -> ()
-

From d31dcac67e587b37ef42ba279a2f88043aeae1d7 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Thu, 21 Feb 2019 17:47:57 +0100
Subject: [PATCH 13/37] fix switch syntax in README

---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index a13106b7fa2..dd32911f46b 100644
--- a/README.md
+++ b/README.md
@@ -243,7 +243,7 @@ and open the path printed on the last line of that command.
 * Conditionals and switches
   - `if b ...`
   - `if b ... else ...`
-  - `switch x case 1 ... case 2 ... case _ ...`
+  - `switch x { case 1 ...; case 2 ...; case _ ...}`
 
 * While loops and iterations
   - `while (p()) ...`

From b5b99254d1bf035e978c13b948890becec9861ae Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Thu, 21 Feb 2019 18:41:17 +0100
Subject: [PATCH 14/37] simplify

---
 src/desugar.ml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/desugar.ml b/src/desugar.ml
index 5c584a6b839..dbd59b85e4e 100644
--- a/src/desugar.ml
+++ b/src/desugar.ml
@@ -202,7 +202,7 @@ and pat' = function
   | S.TupP ps -> I.TupP (pats ps)
   | S.OptP p -> I.OptP (pat p)
   | S.AltP (p1, p2) -> I.AltP (pat p1, pat p2)
-  | S.AnnotP (p, _) -> pat' p.it
+  | S.AnnotP (p, _)
   | S.ParP p -> pat' p.it
 
 and prog p = (decs p.it,

From 71ccf02a683e3699a8ac1215b071e9b74421f0b0 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Thu, 21 Feb 2019 18:44:11 +0100
Subject: [PATCH 15/37] tests for redundant parens deeper down in patterns

---
 test/run/empty-tup-args.as | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/test/run/empty-tup-args.as b/test/run/empty-tup-args.as
index 78fffad42bf..ce4fb2ebf8d 100644
--- a/test/run/empty-tup-args.as
+++ b/test/run/empty-tup-args.as
@@ -61,3 +61,24 @@ let _ : [(()) -> H1] = [H1];
 
 func annih<A,B>(f : A -> B) : (A -> ()) { func (a : A) { ignore (f a) } };
 let _ : [(()) -> ()] = [annih<(),G> G, annih<(),G1> G1, annih<(),H> H, annih<(),H1> H1];
+
+
+// test that parens are not significant deeper into the pattern,
+// even around tuples
+
+func p(a:Int,  () ) {};
+func q(a:Int, (())) {};
+func r(a:Int,  (b:Int,) ) {};
+func s(a:Int, ((b:Int,))) {};
+let _ : [(Int, ()) -> ()] = [p, q];
+let _ : [(Int, (Int,)) -> ()] = [r, s];
+
+// redundant parens for anonymous functions
+
+let _ = (func (a:Nat, ()) : Nat { a }) (42, ());
+let _ = (func ((a:Nat, (()))) : Nat { a }) (42, ());
+
+// test that switch expressions are also behave correctly with redundant parens
+
+let _ = switch (42,) { case (3,) 3; case ((5,)) 5; case (a,) a};
+let _ = switch (42,) { case (3,) 3; case ((5,)) 5; case (((a,))) a};

From de8f3a2ed3830ee334d17c3edb4baec4a3e42db3 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Thu, 21 Feb 2019 18:50:01 +0100
Subject: [PATCH 16/37] more simplifications

I smell a bug in declare_pat:
```
| AltP (pat1, pat2) -> declare_pat pat1
```
here the pat2 is not considered.
---
 src/interpret.ml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/interpret.ml b/src/interpret.ml
index 4173851845e..23a04b5ce2a 100644
--- a/src/interpret.ml
+++ b/src/interpret.ml
@@ -434,7 +434,7 @@ and declare_pat pat : val_env =
   | TupP pats -> declare_pats pats V.Env.empty
   | OptP pat1 -> declare_pat pat1
   | AltP (pat1, pat2) -> declare_pat pat1
-  | AnnotP (pat1, _typ) -> declare_pat pat1
+  | AnnotP (pat1, _)
   | ParP pat1 -> declare_pat pat1
 
 and declare_pats pats ve : val_env =
@@ -464,8 +464,8 @@ and define_pat env pat v =
       trap pat.at "value %s does not match pattern" (V.string_of_val v)
     | _ -> assert false
     )
-  | AnnotP (pat1, _typ) -> define_pat env pat1 v
-  | ParP pat -> define_pat env pat v
+  | AnnotP (pat1, _)
+  | ParP pat1 -> define_pat env pat1 v
 
 and define_pats env pats vs =
   List.iter2 (define_pat env) pats vs

From 6f4ee64e1e10e774af8ef53b7746ecfc0c6417ab Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Thu, 21 Feb 2019 19:18:20 +0100
Subject: [PATCH 17/37] roll back parser complications, materialising parens
 around tuples in the AST everywhere

this comes at the slight cost of
- growing the AST when the user inserts redundant parens
- propagating the inference environment inwards of PatP

Both are justified in face of keeping the parsing code cleaner, IMO.
---
 src/parser.mly | 29 ++++++++---------------------
 src/typing.ml  |  1 +
 2 files changed, 9 insertions(+), 21 deletions(-)

diff --git a/src/parser.mly b/src/parser.mly
index ec920b083eb..6772b88597b 100644
--- a/src/parser.mly
+++ b/src/parser.mly
@@ -475,34 +475,21 @@ exp_field :
 
 (* Patterns *)
 
-(* pat_top is needed because top-level parentheses around tuples (unit, 1-ary, pair, etc.)
-   are significant in function arguments, signifying a unary function which matches on a
-   first-class (i.e. consed) tuple *)
-pat_top :
-  | LPAR p=pat RPAR
-    { match p.it with
-      | TupP _ -> { p with it = ParP p }
-      | _ -> p
-    }
-  | p=pat_simple
-    { p }
-
-pat_simple :
+pat_nullary :
   | UNDERSCORE
     { WildP @! at $sloc }
   | x=id
     { VarP(x) @! at $sloc }
   | l=lit
     { LitP(ref l) @! at $sloc }
+  | LPAR p=pat RPAR
+    { match p.it with
+      | TupP _ -> { p with it = ParP p }
+      | _ -> p
+    }
   | LPAR ps=seplist1(pat_bin, COMMA) RPAR
     { TupP(ps) @! at $sloc }
 
-pat_nullary :
-  | LPAR p=pat RPAR
-    { p }
-  | p=pat_simple
-    { p }
-
 pat_un :
   | p=pat_nullary
     { p }
@@ -551,7 +538,7 @@ dec_nonvar :
     { (fd s (xf "func" $sloc)).it @? at $sloc }
   | TYPE x=con_id tps=typ_params_opt EQ t=typ
     { TypD(x, tps, t) @? at $sloc }
-  | s=obj_sort_opt CLASS xf=id_opt tps=typ_params_opt p=pat_top xefs=class_body
+  | s=obj_sort_opt CLASS xf=id_opt tps=typ_params_opt p=pat_nullary xefs=class_body
     { let x, efs = xefs in
       let efs' =
         if s.it = Type.Object Type.Local
@@ -588,7 +575,7 @@ dec :
         LetD(p, ObjE(s, x, efs') @? r) @? r }
 
 func_dec :
-  | tps=typ_params_opt p=pat_top rt=return_typ? fb=func_body
+  | tps=typ_params_opt p=pat_nullary rt=return_typ? fb=func_body
     { let t = Lib.Option.get rt (TupT([]) @! no_region) in
       (* This is a hack to support local func declarations that return a computed async.
          These should be defined using RHS syntax EQ e to avoid the implicit AsyncE introduction
diff --git a/src/typing.ml b/src/typing.ml
index 0d0fd76e645..1023446ecdc 100644
--- a/src/typing.ml
+++ b/src/typing.ml
@@ -829,6 +829,7 @@ and check_pat' env t pat : val_env =
     if ve1 <> T.Env.empty || ve2 <> T.Env.empty then
       error env pat.at "variables are not allowed in pattern alternatives";
     T.Env.empty
+  | ParP pat1 -> check_pat' env t pat1
   | _ ->
     let t', ve = infer_pat env pat in
     if not (T.sub env.cons t t') then

From 0d4844b385275829b9b1731ad9c3c7bfd08702d8 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Thu, 21 Feb 2019 20:24:34 +0100
Subject: [PATCH 18/37] merge snafu

---
 src/coverage.ml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/coverage.ml b/src/coverage.ml
index fee5d13b224..e70a5ae001b 100644
--- a/src/coverage.ml
+++ b/src/coverage.ml
@@ -92,7 +92,7 @@ let rec match_pat ctxt desc pat t sets =
     match_pat (InAlt1 (ctxt, pat1.at, pat2, t)) desc pat1 t sets
   | AnnotP (pat1, _)
   | ParP pat1 ->
-    match_pat ce ctxt desc pat1 t sets
+    match_pat ctxt desc pat1 t sets
 
 and match_lit ctxt desc v t sets =
   let desc_succ = Val v in

From 7daa1601533f43fa6c99107253c07c355357a089 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Fri, 22 Feb 2019 13:47:53 +0100
Subject: [PATCH 19/37] desugar toplevel parentheses as TupP

---
 src/desugar.ml | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/desugar.ml b/src/desugar.ml
index c06f5a84185..004e11fe940 100644
--- a/src/desugar.ml
+++ b/src/desugar.ml
@@ -154,13 +154,17 @@ and decs ds =
       typD :: (phrase' dec' d) :: (decs ds)
     | _ -> (phrase' dec' d) :: (decs ds)
 
-and dec' at n d = match d with
+and dec' at n d =
+  let param p = match p.it with
+    | S.ParP p1 -> pat { p with it = S.TupP [p1] }
+    | _ -> pat p
+  in match d with
   | S.ExpD e -> I.ExpD (exp e)
   | S.LetD (p, e) -> I.LetD (pat p, exp e)
   | S.VarD (i, e) -> I.VarD (i, exp e)
   | S.FuncD (s, i, tbs, p, ty, e) ->
     let cc = Value.call_conv_of_typ n.S.note_typ in
-    I.FuncD (cc, i, typ_binds tbs, pat p, ty.note, exp e)
+    I.FuncD (cc, i, typ_binds tbs, param p, ty.note, exp e)
   | S.TypD (con_id, typ_bind, t) ->
     let c = Lib.Option.value con_id.note in
     I.TypD c
@@ -179,7 +183,7 @@ and dec' at n d = match d with
         T.open_ inst rng
       | _ -> assert false
     in
-    I.FuncD (cc, fun_id, typ_binds tbs, pat p, obj_typ, (* TBR *)
+    I.FuncD (cc, fun_id, typ_binds tbs, param p, obj_typ, (* TBR *)
              { it = obj at s (Some fun_id) self_id es obj_typ;
                at = at;
                note = { S.note_typ = obj_typ; S.note_eff = T.Triv } })

From 82f4f42b5190e2e0d7b069361bb540e33144f0e9 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Fri, 22 Feb 2019 14:12:32 +0100
Subject: [PATCH 20/37] accept IR problems for now

---
 test/run/ok/empty-tup-args.diff-ir.ok     | 13 +++++++++++++
 test/run/ok/empty-tup-args.run-ir.ok      |  4 ++++
 test/run/ok/empty-tup-args.wasm.stderr.ok |  5 +++++
 3 files changed, 22 insertions(+)
 create mode 100644 test/run/ok/empty-tup-args.diff-ir.ok
 create mode 100644 test/run/ok/empty-tup-args.run-ir.ok
 create mode 100644 test/run/ok/empty-tup-args.wasm.stderr.ok

diff --git a/test/run/ok/empty-tup-args.diff-ir.ok b/test/run/ok/empty-tup-args.diff-ir.ok
new file mode 100644
index 00000000000..7a5d2e5e065
--- /dev/null
+++ b/test/run/ok/empty-tup-args.diff-ir.ok
@@ -0,0 +1,13 @@
+--- empty-tup-args.run
++++ empty-tup-args.run-ir
+@@ -0,0 +1,11 @@
++(unknown location): internal error, File "interpret_ir.ml", line 559, characters 9-15: Assertion failed
++
++Last environment:
++
++Called from file "interpret_ir.ml", line 659, characters 8-23
++Called from file "interpret_ir.ml", line 86, characters 8-23
++Re-raised at file "interpret_ir.ml", line 83, characters 19-35
++Called from file "interpret_ir.ml", line 90, characters 36-44
++Called from file "interpret_ir.ml", line 689, characters 2-18
++Called from file "pipeline.ml", line 172, characters 8-48
diff --git a/test/run/ok/empty-tup-args.run-ir.ok b/test/run/ok/empty-tup-args.run-ir.ok
new file mode 100644
index 00000000000..949970c290c
--- /dev/null
+++ b/test/run/ok/empty-tup-args.run-ir.ok
@@ -0,0 +1,4 @@
+(unknown location): internal error, File "interpret_ir.ml", line 559, characters 9-15: Assertion failed
+
+Last environment:
+
diff --git a/test/run/ok/empty-tup-args.wasm.stderr.ok b/test/run/ok/empty-tup-args.wasm.stderr.ok
new file mode 100644
index 00000000000..8ffe2a156f6
--- /dev/null
+++ b/test/run/ok/empty-tup-args.wasm.stderr.ok
@@ -0,0 +1,5 @@
+Ill-typed intermediate code after desugaring (use -v to see dumped IR):
+empty-tup-args.as:2.8-2.10: IR type error, subtype violation:
+  ((),)
+  ()
+

From 922f757fb7e3a7d791efbbd16f42fce647aa9591 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Fri, 22 Feb 2019 15:27:52 +0100
Subject: [PATCH 21/37] WIP: it appears that running non-canonical patterns is
 still a problem

so comment them out for now.
---
 test/run/empty-tup-args.as | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/test/run/empty-tup-args.as b/test/run/empty-tup-args.as
index ce4fb2ebf8d..103afc5fd65 100644
--- a/test/run/empty-tup-args.as
+++ b/test/run/empty-tup-args.as
@@ -12,17 +12,20 @@ let _ : [() -> ()] = [f];
 let gh : [(()) -> ()] = [g, g1, h, h1];
 
 f();
-g(); // accepted, because "At calls there is an implicit coercion
+//g(); // accepted, because "At calls there is an implicit coercion
      //                    between tuples and n-ary arguments"
 h(); // dito
-gh[0](); // dito
-gh[1](); // dito
+//gh[0](); // dito
+//gh[1](); // dito
 
 // Correct:
-g(());
+//g(());
 h(());
-gh[0](());
-gh[1](());
+h1(());
+//gh[0](());
+//gh[1](());
+gh[2](());
+gh[3](());
 
 func j(a:Int) {};
 func k(a:(Int)) {};
@@ -76,7 +79,7 @@ let _ : [(Int, (Int,)) -> ()] = [r, s];
 // redundant parens for anonymous functions
 
 let _ = (func (a:Nat, ()) : Nat { a }) (42, ());
-let _ = (func ((a:Nat, (()))) : Nat { a }) (42, ());
+//let _ = (func ((a:Nat, (()))) : Nat { a }) (42, ());
 
 // test that switch expressions are also behave correctly with redundant parens
 

From 88d6270fd2c1420f3a87e450dc2beb1ddabf3c1d Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Fri, 22 Feb 2019 15:31:35 +0100
Subject: [PATCH 22/37] remove .ok files

---
 test/run/ok/empty-tup-args.diff-ir.ok | 13 -------------
 test/run/ok/empty-tup-args.run-ir.ok  |  4 ----
 2 files changed, 17 deletions(-)
 delete mode 100644 test/run/ok/empty-tup-args.diff-ir.ok
 delete mode 100644 test/run/ok/empty-tup-args.run-ir.ok

diff --git a/test/run/ok/empty-tup-args.diff-ir.ok b/test/run/ok/empty-tup-args.diff-ir.ok
deleted file mode 100644
index 7a5d2e5e065..00000000000
--- a/test/run/ok/empty-tup-args.diff-ir.ok
+++ /dev/null
@@ -1,13 +0,0 @@
---- empty-tup-args.run
-+++ empty-tup-args.run-ir
-@@ -0,0 +1,11 @@
-+(unknown location): internal error, File "interpret_ir.ml", line 559, characters 9-15: Assertion failed
-+
-+Last environment:
-+
-+Called from file "interpret_ir.ml", line 659, characters 8-23
-+Called from file "interpret_ir.ml", line 86, characters 8-23
-+Re-raised at file "interpret_ir.ml", line 83, characters 19-35
-+Called from file "interpret_ir.ml", line 90, characters 36-44
-+Called from file "interpret_ir.ml", line 689, characters 2-18
-+Called from file "pipeline.ml", line 172, characters 8-48
diff --git a/test/run/ok/empty-tup-args.run-ir.ok b/test/run/ok/empty-tup-args.run-ir.ok
deleted file mode 100644
index 949970c290c..00000000000
--- a/test/run/ok/empty-tup-args.run-ir.ok
+++ /dev/null
@@ -1,4 +0,0 @@
-(unknown location): internal error, File "interpret_ir.ml", line 559, characters 9-15: Assertion failed
-
-Last environment:
-

From e646c9c7bda8a87fcd019484321cf20645472785 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Sun, 24 Feb 2019 14:18:04 +0100
Subject: [PATCH 23/37] fix nits

---
 src/interpret.ml | 4 ++--
 src/syntax.ml    | 2 +-
 src/typing.ml    | 6 ++++--
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/interpret.ml b/src/interpret.ml
index 23a04b5ce2a..25f0a05d123 100644
--- a/src/interpret.ml
+++ b/src/interpret.ml
@@ -432,8 +432,8 @@ and declare_pat pat : val_env =
   | WildP | LitP _ | SignP _ ->  V.Env.empty
   | VarP id -> declare_id id
   | TupP pats -> declare_pats pats V.Env.empty
-  | OptP pat1 -> declare_pat pat1
-  | AltP (pat1, pat2) -> declare_pat pat1
+  | OptP pat1
+  | AltP (pat1, _)    (* both have empty binders *)
   | AnnotP (pat1, _)
   | ParP pat1 -> declare_pat pat1
 
diff --git a/src/syntax.ml b/src/syntax.ml
index 30e4c564e14..8b27e931806 100644
--- a/src/syntax.ml
+++ b/src/syntax.ml
@@ -107,7 +107,7 @@ and pat' =
   | OptP of pat                                (* option *)
   | AltP of pat * pat                          (* disjunctive *)
   | AnnotP of pat * typ                        (* type annotation *)
-  | ParP of pat                                (* toplevel parenthesis *)
+  | ParP of pat                                (* parenthesis *)
 (*
   | AsP of pat * pat                           (* conjunctive *)
   | ObjP of pat_field list                     (* object *)
diff --git a/src/typing.ml b/src/typing.ml
index d768f2f6cc9..b7bd37d0abf 100644
--- a/src/typing.ml
+++ b/src/typing.ml
@@ -757,7 +757,8 @@ and infer_pat' env pat : T.typ * val_env =
   | AnnotP (pat1, typ) ->
     let t = check_typ env typ in
     t, check_pat env t pat1
-  | ParP pat1 -> infer_pat env pat1
+  | ParP pat1 ->
+     infer_pat env pat1
 
 and infer_pats at env pats ts ve : T.typ list * val_env =
   match pats with
@@ -824,7 +825,8 @@ and check_pat' env t pat : val_env =
     if ve1 <> T.Env.empty || ve2 <> T.Env.empty then
       error env pat.at "variables are not allowed in pattern alternatives";
     T.Env.empty
-  | ParP pat1 -> check_pat' env t pat1
+  | ParP pat1 ->
+     check_pat' env t pat1
   | _ ->
     let t', ve = infer_pat env pat in
     if not (T.sub t t') then

From 02fd5eea5714bff74d77a0ac86edd5f0cbc1c3c0 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Mon, 25 Feb 2019 20:08:58 +0100
Subject: [PATCH 24/37] apply custom lowering to unary functions, stripping the
 outermost TupP

---
 src/desugar.ml                            |  7 +++++--
 test/run/empty-tup-args.as                | 14 +++++++-------
 test/run/ok/empty-tup-args.wasm.stderr.ok |  5 -----
 3 files changed, 12 insertions(+), 14 deletions(-)
 delete mode 100644 test/run/ok/empty-tup-args.wasm.stderr.ok

diff --git a/src/desugar.ml b/src/desugar.ml
index 80fb1e38ec7..3bade8cfed1 100644
--- a/src/desugar.ml
+++ b/src/desugar.ml
@@ -174,9 +174,12 @@ and decs ds =
 
 and dec d = phrase' dec' d
 and dec' at n d =
+  let fix_unary p = match p.it with
+    | S.TupP [p1] -> { p with it = p1.it }
+    | _ -> p in
   let param p = match p.it with
-    | S.ParP p1 -> pat { p with it = S.TupP [p1] }
-    | _ -> pat p
+    | S.ParP p1 -> pat (fix_unary { p with it = S.TupP [p1] })
+    | _ ->  pat (fix_unary p)
   in match d with
   | S.ExpD e -> I.ExpD (exp e)
   | S.LetD (p, e) -> I.LetD (pat p, exp e)
diff --git a/test/run/empty-tup-args.as b/test/run/empty-tup-args.as
index 103afc5fd65..fbc05c349d3 100644
--- a/test/run/empty-tup-args.as
+++ b/test/run/empty-tup-args.as
@@ -12,18 +12,18 @@ let _ : [() -> ()] = [f];
 let gh : [(()) -> ()] = [g, g1, h, h1];
 
 f();
-//g(); // accepted, because "At calls there is an implicit coercion
+g(); // accepted, because "At calls there is an implicit coercion
      //                    between tuples and n-ary arguments"
 h(); // dito
-//gh[0](); // dito
-//gh[1](); // dito
+gh[0](); // dito
+gh[1](); // dito
 
 // Correct:
-//g(());
+g(());
 h(());
 h1(());
-//gh[0](());
-//gh[1](());
+gh[0](());
+gh[1](());
 gh[2](());
 gh[3](());
 
@@ -79,7 +79,7 @@ let _ : [(Int, (Int,)) -> ()] = [r, s];
 // redundant parens for anonymous functions
 
 let _ = (func (a:Nat, ()) : Nat { a }) (42, ());
-//let _ = (func ((a:Nat, (()))) : Nat { a }) (42, ());
+let _ = (func ((a:Nat, (()))) : Nat { a }) (42, ());
 
 // test that switch expressions are also behave correctly with redundant parens
 
diff --git a/test/run/ok/empty-tup-args.wasm.stderr.ok b/test/run/ok/empty-tup-args.wasm.stderr.ok
deleted file mode 100644
index 8ffe2a156f6..00000000000
--- a/test/run/ok/empty-tup-args.wasm.stderr.ok
+++ /dev/null
@@ -1,5 +0,0 @@
-Ill-typed intermediate code after desugaring (use -v to see dumped IR):
-empty-tup-args.as:2.8-2.10: IR type error, subtype violation:
-  ((),)
-  ()
-

From 10547cbd81805e149a0c302e8c5547cbad84e4c9 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Mon, 25 Feb 2019 23:33:54 +0100
Subject: [PATCH 25/37] typo

---
 src/check_ir.ml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/check_ir.ml b/src/check_ir.ml
index 9b9cf93a8d0..4655505c77f 100644
--- a/src/check_ir.ml
+++ b/src/check_ir.ml
@@ -740,7 +740,7 @@ and check_block_exps env t decs at =
   | [dec] ->
     check_dec env dec;
     check env at (T.is_unit t || T.sub (typ dec) t)
-      "declaration does not produce expect type"
+      "declaration does not produce expected type"
   | dec::decs' ->
     check_dec env dec;
     check_block_exps env t decs' at

From f9ccad9191a963132466e673efdc8e1fd887fdae Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Mon, 25 Feb 2019 23:42:17 +0100
Subject: [PATCH 26/37] transform the type notes like the patterns

---
 src/desugar.ml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/desugar.ml b/src/desugar.ml
index 3bade8cfed1..d1d53440e97 100644
--- a/src/desugar.ml
+++ b/src/desugar.ml
@@ -174,11 +174,11 @@ and decs ds =
 
 and dec d = phrase' dec' d
 and dec' at n d =
-  let fix_unary p = match p.it with
-    | S.TupP [p1] -> { p with it = p1.it }
+  let fix_unary p = match p.it, p.note with
+    | S.TupP [p1], Type.Tup [n] -> { p with it = p1.it; note = n }
     | _ -> p in
   let param p = match p.it with
-    | S.ParP p1 -> pat (fix_unary { p with it = S.TupP [p1] })
+    | S.ParP p1 -> pat (fix_unary { p with it = S.TupP [p1]; note = Type.Tup [p.note] })
     | _ ->  pat (fix_unary p)
   in match d with
   | S.ExpD e -> I.ExpD (exp e)

From 7cbdb577264e5f696cc1368cb1074cbaa7f9f27b Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Mon, 25 Feb 2019 23:44:07 +0100
Subject: [PATCH 27/37] grammar in comment

---
 test/run/empty-tup-args.as | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/run/empty-tup-args.as b/test/run/empty-tup-args.as
index fbc05c349d3..6403ecc783a 100644
--- a/test/run/empty-tup-args.as
+++ b/test/run/empty-tup-args.as
@@ -81,7 +81,7 @@ let _ : [(Int, (Int,)) -> ()] = [r, s];
 let _ = (func (a:Nat, ()) : Nat { a }) (42, ());
 let _ = (func ((a:Nat, (()))) : Nat { a }) (42, ());
 
-// test that switch expressions are also behave correctly with redundant parens
+// test that switch expressions also behave correctly with redundant parens
 
 let _ = switch (42,) { case (3,) 3; case ((5,)) 5; case (a,) a};
 let _ = switch (42,) { case (3,) 3; case ((5,)) 5; case (((a,))) a};

From 9c29a4846541b93e9023653172483eb6b7c07466 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Tue, 26 Feb 2019 11:07:07 +0100
Subject: [PATCH 28/37] more precise Invalid_argument messages

---
 src/operator.ml | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/operator.ml b/src/operator.ml
index 1bdc2c27e4d..a7cbe3afb21 100644
--- a/src/operator.ml
+++ b/src/operator.ml
@@ -14,7 +14,7 @@ let word_unop fword8 fword16 fword32 fword64 = function
   | T.Word16 -> fun v -> Word16 (fword16 (as_word16 v))
   | T.Word32 -> fun v -> Word32 (fword32 (as_word32 v))
   | T.Word64 -> fun v -> Word64 (fword64 (as_word64 v))
-  | _ -> raise (Invalid_argument "unop")
+  | _ -> raise (Invalid_argument "word_unop")
 
 let num_unop fint fword8 fword16 fword32 fword64 ffloat = function
   | T.Int -> fun v -> Int (fint (as_int v))
@@ -37,14 +37,14 @@ let unop t op =
 
 let text_binop ftext = function
   | T.Text -> fun v1 v2 -> Text (ftext (as_text v1) (as_text v2))
-  | _ -> raise (Invalid_argument "binop")
+  | _ -> raise (Invalid_argument "text_binop")
 
 let word_binop fword8 fword16 fword32 fword64 = function
   | T.Word8 -> fun v1 v2 -> Word8 (fword8 (as_word8 v1) (as_word8 v2))
   | T.Word16 -> fun v1 v2 -> Word16 (fword16 (as_word16 v1) (as_word16 v2))
   | T.Word32 -> fun v1 v2 -> Word32 (fword32 (as_word32 v1) (as_word32 v2))
   | T.Word64 -> fun v1 v2 -> Word64 (fword64 (as_word64 v1) (as_word64 v2))
-  | _ -> raise (Invalid_argument "binop")
+  | _ -> raise (Invalid_argument "word_binop")
 
 let num_binop fnat fint fword8 fword16 fword32 fword64 ffloat = function
   | T.Nat -> fun v1 v2 -> Int (fnat (as_int v1) (as_int v2))
@@ -82,7 +82,7 @@ let word_relop fword8 fword16 fword32 fword64 = function
   | T.Word16 -> fun v1 v2 -> Bool (fword16 (as_word16 v1) (as_word16 v2))
   | T.Word32 -> fun v1 v2 -> Bool (fword32 (as_word32 v1) (as_word32 v2))
   | T.Word64 -> fun v1 v2 -> Bool (fword64 (as_word64 v1) (as_word64 v2))
-  | _ -> raise (Invalid_argument "relop")
+  | _ -> raise (Invalid_argument "word_relop")
 
 let num_relop fnat fint fword8 fword16 fword32 fword64 ffloat = function
   | T.Nat -> fun v1 v2 -> Bool (fnat (as_int v1) (as_int v2))

From 2688aeb49f9a094519fdc9b7f84b030a65be5795 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Tue, 26 Feb 2019 12:11:07 +0100
Subject: [PATCH 29/37] use augmented source location

---
 src/parser.mly | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/parser.mly b/src/parser.mly
index 3b98ed953eb..d1ed130cc7d 100644
--- a/src/parser.mly
+++ b/src/parser.mly
@@ -482,7 +482,7 @@ pat_nullary :
     { LitP(ref l) @! at $sloc }
   | LPAR p=pat RPAR
     { match p.it with
-      | TupP _ -> { p with it = ParP p }
+      | TupP _ -> { p with it = ParP p; at = at $sloc }
       | _ -> p
     }
   | LPAR ps=seplist1(pat_bin, COMMA) RPAR

From 0b42e5edcc949ea9ce509014bba6cd72fee4f859 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Tue, 26 Feb 2019 12:12:19 +0100
Subject: [PATCH 30/37] test AST-56

---
 test/run/AST-56.as | 6 ++++++
 1 file changed, 6 insertions(+)
 create mode 100644 test/run/AST-56.as

diff --git a/test/run/AST-56.as b/test/run/AST-56.as
new file mode 100644
index 00000000000..7c246c5d20e
--- /dev/null
+++ b/test/run/AST-56.as
@@ -0,0 +1,6 @@
+func p((),) {};
+func p1(()) {};
+func p2((())) {};
+func p3(((()))) {};
+
+let ps : [((),) -> ()] = [p, p1, p2, p3];

From 92ea6b60e21b15ca1d5e926699cdb87cddb0b03a Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Thu, 28 Feb 2019 13:12:39 +0100
Subject: [PATCH 31/37] review feedback: fold 'fix_unary' into 'param'

and move to toplevel
---
 src/desugar.ml | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/src/desugar.ml b/src/desugar.ml
index d1d53440e97..ebe92c51877 100644
--- a/src/desugar.ml
+++ b/src/desugar.ml
@@ -173,14 +173,13 @@ and decs ds =
     | _ -> (phrase' dec' d) :: (decs ds)
 
 and dec d = phrase' dec' d
+and param p =
+  pat (match p.it, p.note with
+       | S.ParP p1, _ -> p1
+       | S.TupP [p1], Type.Tup [n] -> { p with it = p1.it; note = n }
+       | _ ->  p)
 and dec' at n d =
-  let fix_unary p = match p.it, p.note with
-    | S.TupP [p1], Type.Tup [n] -> { p with it = p1.it; note = n }
-    | _ -> p in
-  let param p = match p.it with
-    | S.ParP p1 -> pat (fix_unary { p with it = S.TupP [p1]; note = Type.Tup [p.note] })
-    | _ ->  pat (fix_unary p)
-  in match d with
+  match d with
   | S.ExpD e -> I.ExpD (exp e)
   | S.LetD (p, e) -> I.LetD (pat p, exp e)
   | S.VarD (i, e) -> I.VarD (i, exp e)

From c67a0121f060eba2d3f3fa7c5fbff51eb88d6922 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Thu, 28 Feb 2019 14:33:28 +0100
Subject: [PATCH 32/37] Revert "more precise Invalid_argument messages"

This reverts commit 9c29a4846541b93e9023653172483eb6b7c07466.
---
 src/operator.ml | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/operator.ml b/src/operator.ml
index a7cbe3afb21..1bdc2c27e4d 100644
--- a/src/operator.ml
+++ b/src/operator.ml
@@ -14,7 +14,7 @@ let word_unop fword8 fword16 fword32 fword64 = function
   | T.Word16 -> fun v -> Word16 (fword16 (as_word16 v))
   | T.Word32 -> fun v -> Word32 (fword32 (as_word32 v))
   | T.Word64 -> fun v -> Word64 (fword64 (as_word64 v))
-  | _ -> raise (Invalid_argument "word_unop")
+  | _ -> raise (Invalid_argument "unop")
 
 let num_unop fint fword8 fword16 fword32 fword64 ffloat = function
   | T.Int -> fun v -> Int (fint (as_int v))
@@ -37,14 +37,14 @@ let unop t op =
 
 let text_binop ftext = function
   | T.Text -> fun v1 v2 -> Text (ftext (as_text v1) (as_text v2))
-  | _ -> raise (Invalid_argument "text_binop")
+  | _ -> raise (Invalid_argument "binop")
 
 let word_binop fword8 fword16 fword32 fword64 = function
   | T.Word8 -> fun v1 v2 -> Word8 (fword8 (as_word8 v1) (as_word8 v2))
   | T.Word16 -> fun v1 v2 -> Word16 (fword16 (as_word16 v1) (as_word16 v2))
   | T.Word32 -> fun v1 v2 -> Word32 (fword32 (as_word32 v1) (as_word32 v2))
   | T.Word64 -> fun v1 v2 -> Word64 (fword64 (as_word64 v1) (as_word64 v2))
-  | _ -> raise (Invalid_argument "word_binop")
+  | _ -> raise (Invalid_argument "binop")
 
 let num_binop fnat fint fword8 fword16 fword32 fword64 ffloat = function
   | T.Nat -> fun v1 v2 -> Int (fnat (as_int v1) (as_int v2))
@@ -82,7 +82,7 @@ let word_relop fword8 fword16 fword32 fword64 = function
   | T.Word16 -> fun v1 v2 -> Bool (fword16 (as_word16 v1) (as_word16 v2))
   | T.Word32 -> fun v1 v2 -> Bool (fword32 (as_word32 v1) (as_word32 v2))
   | T.Word64 -> fun v1 v2 -> Bool (fword64 (as_word64 v1) (as_word64 v2))
-  | _ -> raise (Invalid_argument "word_relop")
+  | _ -> raise (Invalid_argument "relop")
 
 let num_relop fnat fint fword8 fword16 fword32 fword64 ffloat = function
   | T.Nat -> fun v1 v2 -> Bool (fnat (as_int v1) (as_int v2))

From f93ecdc1f364fe8ea207594a24bf9ecbfb467ec8 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Mon, 4 Mar 2019 14:39:47 +0100
Subject: [PATCH 33/37] transform FuncE parameters in exp'

---
 src/desugar.ml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/desugar.ml b/src/desugar.ml
index d552788d42b..652dfb7d6e7 100644
--- a/src/desugar.ml
+++ b/src/desugar.ml
@@ -56,7 +56,7 @@ and exp' at note = function
   | S.IdxE (e1, e2) -> I.IdxE (exp e1, exp e2)
   | S.FuncE (name, s, tbs, p, ty, e) ->
     let cc = Value.call_conv_of_typ note.S.note_typ in
-    I.FuncE (name, cc, typ_binds tbs, pat p, ty.note, exp e)
+    I.FuncE (name, cc, typ_binds tbs, param p, ty.note, exp e)
   | S.CallE (e1, inst, e2) ->
     let cc = Value.call_conv_of_typ e1.Source.note.S.note_typ in
     let inst = List.map (fun t -> t.Source.note) inst in

From bffcea3c9e252e828235b6f4bdd84cd5feffbb44 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Mon, 4 Mar 2019 15:15:44 +0100
Subject: [PATCH 34/37] extend tests to include function expressions

---
 test/run/empty-tup-args.as | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/test/run/empty-tup-args.as b/test/run/empty-tup-args.as
index 6403ecc783a..e3da0a23a6c 100644
--- a/test/run/empty-tup-args.as
+++ b/test/run/empty-tup-args.as
@@ -8,8 +8,8 @@ let _ = f : () -> ();
 let _ = g : (()) -> ();
 let _ = h : (()) -> ();
 
-let _ : [() -> ()] = [f];
-let gh : [(()) -> ()] = [g, g1, h, h1];
+let _ : [() -> ()] = [f, func () {}, func f1 () {}];
+let gh : [(()) -> ()] = [g, g1, h, h1, func (()) {}, func g2 (()) {}];
 
 f();
 g(); // accepted, because "At calls there is an implicit coercion
@@ -31,7 +31,7 @@ func j(a:Int) {};
 func k(a:(Int)) {};
 func l(a:((Int))) {};
 
-let jkl : [Int -> ()] = [j, k, l];
+let jkl : [Int -> ()] = [j, k, l, func l1(a:((Int))) {}];
 
 j(5);
 k(8);

From e4e7268dffa66c8f053f185fdb623f774ffbc057 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Mon, 4 Mar 2019 22:02:24 +0100
Subject: [PATCH 35/37] fix infer_pat' descent into PatP

by calling `infer_pat`, so that the note gets updated for the subpattern
---
 src/typing.ml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/typing.ml b/src/typing.ml
index c18a4592bf3..74e62b2fd37 100644
--- a/src/typing.ml
+++ b/src/typing.ml
@@ -841,7 +841,7 @@ and check_pat' env t pat : val_env =
       error env pat.at "variables are not allowed in pattern alternatives";
     T.Env.empty
   | ParP pat1 ->
-     check_pat' env t pat1
+     check_pat env t pat1
   | _ ->
     let t', ve = infer_pat env pat in
     if not (T.sub t t') then

From c392aded0abd3d1a17a7d09ae653f26fcf385876 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Mon, 4 Mar 2019 22:26:31 +0100
Subject: [PATCH 36/37] experimental: always create ParP

now that we correctly typecheck it.
---
 src/parser.mly | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/parser.mly b/src/parser.mly
index c845d6651ac..7d494ce5a62 100644
--- a/src/parser.mly
+++ b/src/parser.mly
@@ -484,8 +484,8 @@ pat_nullary :
     { LitP(ref l) @! at $sloc }
   | LPAR p=pat RPAR
     { match p.it with
-      | TupP _ -> { p with it = ParP p; at = at $sloc }
-      | _ -> p
+      | TupP _ -> ParP(p) @! at $sloc
+      | _ -> ParP(p) @! p.at
     }
   | LPAR ps=seplist1(pat_bin, COMMA) RPAR
     { TupP(ps) @! at $sloc }

From 81200bbb36cd683a65e16cfd9e054b15cb2a6f29 Mon Sep 17 00:00:00 2001
From: Gabor Greif <gabor@dfinity.org>
Date: Tue, 5 Mar 2019 23:14:44 +0100
Subject: [PATCH 37/37] review feedback: add negative tests

---
 test/fail/ok/one-tuple-ambiguity.tc.ok | 14 ++++++++++++++
 test/fail/one-tuple-ambiguity.as       | 22 ++++++++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 test/fail/ok/one-tuple-ambiguity.tc.ok
 create mode 100644 test/fail/one-tuple-ambiguity.as

diff --git a/test/fail/ok/one-tuple-ambiguity.tc.ok b/test/fail/ok/one-tuple-ambiguity.tc.ok
new file mode 100644
index 00000000000..d81f6ed4b3b
--- /dev/null
+++ b/test/fail/ok/one-tuple-ambiguity.tc.ok
@@ -0,0 +1,14 @@
+one-tuple-ambiguity.as:10.2-10.7: type error, expression of type
+  ((),)
+cannot produce expected type
+  ()
+one-tuple-ambiguity.as:16.3-16.5: type error, literal of type
+  Nat
+does not have expected type
+  (Nat, Bool)
+one-tuple-ambiguity.as:16.1-16.5: type error, expected function type, but expression produces type
+  ()
+one-tuple-ambiguity.as:21.2-21.16: type error, expression of type
+  ((Nat, Bool),)
+cannot produce expected type
+  (Nat, Bool)
diff --git a/test/fail/one-tuple-ambiguity.as b/test/fail/one-tuple-ambiguity.as
new file mode 100644
index 00000000000..170de85d256
--- /dev/null
+++ b/test/fail/one-tuple-ambiguity.as
@@ -0,0 +1,22 @@
+func g(()) {};
+let h = g : ((),) -> ();
+
+// this is accepted
+h(());
+
+// This is rejected, even if it could be seen
+// as passing the single argument which is unit.
+// It is interpreted as passing the one tuple containing unit.
+h((),);
+
+
+func k((a : Nat, b : Bool)) {};
+let l : ((Nat, Bool),) -> () = k;
+
+l 42 false; // rejected, 42 is not of type (Nat, Bool)
+
+l(42, false); // accepted, first-class pair implicitly converted to argument of call
+l((42, false)); // accepted, parenthesis around values is redundant
+
+l((42, false),); // rejected, implicitly converted to passing
+                 // first class one-tuple (enclosing pair) as the sole argument.
\ No newline at end of file