From 6acf91a3f2263854a2c7043caa276ce104d0b6e2 Mon Sep 17 00:00:00 2001
From: Tom Jack <tom@tomjack.co>
Date: Wed, 8 Apr 2020 19:11:01 -0500
Subject: [PATCH] Perform basic eta contraction in Self_mini_c

---
 src/bin/expect_tests/contract_tests.ml   | 10 ++--------
 src/passes/11-self_mini_c/self_mini_c.ml | 20 ++++++++++++++++++++
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/src/bin/expect_tests/contract_tests.ml b/src/bin/expect_tests/contract_tests.ml
index 52c625c2d..1d9ff5c4c 100644
--- a/src/bin/expect_tests/contract_tests.ml
+++ b/src/bin/expect_tests/contract_tests.ml
@@ -10,10 +10,10 @@ let%expect_test _ =
   [%expect {| 1872 bytes |}] ;
 
   run_ligo_good [ "measure-contract" ; contract "multisig.ligo" ; "main" ] ;
-  [%expect {| 1282 bytes |}] ;
+  [%expect {| 1267 bytes |}] ;
 
   run_ligo_good [ "measure-contract" ; contract "multisig-v2.ligo" ; "main" ] ;
-  [%expect {| 2974 bytes |}] ;
+  [%expect {| 2959 bytes |}] ;
 
   run_ligo_good [ "measure-contract" ; contract "vote.mligo" ; "main" ] ;
   [%expect {| 589 bytes |}] ;
@@ -301,9 +301,6 @@ let%expect_test _ =
       storage
         (pair (pair (list %auth key) (nat %counter)) (pair (string %id) (nat %threshold))) ;
       code { DUP ;
-             CAR ;
-             DIP { DUP ; CDR } ;
-             PAIR ;
              DUP ;
              CAR ;
              DIP { DUP } ;
@@ -768,9 +765,6 @@ let%expect_test _ =
                           CAR ;
                           PAIR } ;
                      DUP ;
-                     CAR ;
-                     DIP { DUP ; CDR } ;
-                     PAIR ;
                      DIP { DROP 17 } } ;
                  DIP { DROP } }
                { DUP ;
diff --git a/src/passes/11-self_mini_c/self_mini_c.ml b/src/passes/11-self_mini_c/self_mini_c.ml
index 95e03a661..39a3a4c72 100644
--- a/src/passes/11-self_mini_c/self_mini_c.ml
+++ b/src/passes/11-self_mini_c/self_mini_c.ml
@@ -159,6 +159,25 @@ let betas : bool ref -> expression -> expression =
   fun changed ->
   map_expression (beta changed)
 
+let eta : bool ref -> expression -> expression =
+  fun changed e ->
+  match e.content with
+  | E_constant {cons_name = C_PAIR; arguments = [ { content = E_constant {cons_name = C_CAR; arguments = [ e1 ]} ; type_value = _ } ;
+                                                  { content = E_constant {cons_name = C_CDR; arguments = [ e2 ]} ; type_value = _ }]} ->
+    (match (e1.content, e2.content) with
+     | E_variable x1, E_variable x2 ->
+       if Var.equal x1 x2
+       then
+         (changed := true;
+          { e with content = e1.content })
+       else e
+     | _ -> e)
+  | _ -> e
+
+let etas : bool ref -> expression -> expression =
+  fun changed ->
+  map_expression (eta changed)
+
 let contract_check =
   let all = [Michelson_restrictions.self_in_lambdas] in
   let all_e = List.map Helpers.map_sub_level_expression all in
@@ -169,6 +188,7 @@ let rec all_expression : expression -> expression =
   let changed = ref false in
   let e = inline_lets changed e in
   let e = betas changed e in
+  let e = etas changed e in
   if !changed
   then all_expression e
   else e