Add custom eqWAlizer type checking for maps:to_list

Summary: `maps:to_list` is currently typed as `to_list(#{K => V}) -> [{K, V}]`, which loses type information for shape-like maps. On this diff we're special-handling it in eqWAlizer such that `to_list(#{Ka => Va, Kb => Vb, ...}) -> [{Ka, Va} | {Kb, Vb} | ...]`.

Reviewed By: ilya-klyuchnikov

Differential Revision: D59587052

fbshipit-source-id: 072340ea3a0b406281b52dcd0a91739b72e3958b

Author: ruippeixotog

eqwalizer/src/main/scala/com/whatsapp/eqwalizer/tc/ElabApplyCustom.scala

@@ -38,16 +38,17 @@ class ElabApplyCustom(pipelineContext: PipelineContext) {
       RemoteId("lists", "keysort", 2),
       RemoteId("lists", "keystore", 4),
       RemoteId("maps", "filter", 2),
+      RemoteId("maps", "filtermap", 2),
       RemoteId("maps", "find", 2),
       RemoteId("maps", "fold", 3),
       RemoteId("maps", "get", 2),
       RemoteId("maps", "get", 3),
       RemoteId("maps", "map", 2),
-      RemoteId("maps", "remove", 2),
       RemoteId("maps", "put", 3),
+      RemoteId("maps", "remove", 2),
+      RemoteId("maps", "to_list", 1),
       RemoteId("maps", "with", 2),
       RemoteId("maps", "without", 2),
-      RemoteId("maps", "filtermap", 2),
       RemoteId(CompilerMacro.fake_module, "record_info", 2),
     )
 
@@ -432,6 +433,22 @@ class ElabApplyCustom(pipelineContext: PipelineContext) {
         val ty = remove(narrow.asMapType(mapCoercedTy))
         (ty, env1)
 
+      case RemoteId("maps", "to_list", 1) =>
+        def mapToList(ty: Type): Type = ty match {
+          case ShapeMap(props) =>
+            ListType(UnionType(props.map { prop => TupleType(List(AtomLitType(prop.key), prop.tp)) }.toSet))
+          case DictMap(keysTy, valuesTy) =>
+            ListType(TupleType(List(keysTy, valuesTy)))
+          case UnionType(tys) =>
+            subtype.join(tys.map(mapToList))
+          case NoneType =>
+            NoneType
+          case unexpected =>
+            throw new IllegalStateException(s"unexpected non-map $unexpected")
+        }
+        val pairTys = narrow.asMapType(coerce(args.head, argTys.head, anyMapTy))
+        (mapToList(pairTys), env1)
+
       case RemoteId("maps", "with", 2) =>
         @tailrec
         def toKey(ty: Type)(implicit pos: Pos): Option[String] = ty match {

eqwalizer/test_projects/_cli/otp_funs.cli

@@ -14,10 +14,10 @@ ets  16
 filename  21
 gb_sets  26
 proplists  51
-maps  151
+maps  158
 lists  174
 erlang  410
 Per app stats:
 kernel  21
 erts  410
-stdlib  478
+stdlib  485

eqwalizer/test_projects/check/src/custom.erl

@@ -605,6 +605,30 @@ maps_fold_4_3_neg(M) ->
         M
     ).
 
+-spec maps_to_list_1(#{a => string(), b => number(), c => atom()}) ->
+    [{a, string()} | {b, number()} | {c, atom()}].
+maps_to_list_1(M) -> maps:to_list(M).
+
+-spec maps_to_list_2(#{number() => atom()}) -> [{number(), atom()}].
+maps_to_list_2(M) -> maps:to_list(M).
+
+-spec maps_to_list_3(dynamic()) -> dynamic().
+maps_to_list_3(M) -> maps:to_list(M).
+
+-spec maps_to_list_4(#{a => string(), b => [number()]} | #{b => [atom()], c => atom()}) ->
+    [{a, string()} | {b, [number()] | [atom()]} | {c, atom()}].
+maps_to_list_4(M) -> maps:to_list(M).
+
+-spec maps_to_list_5(#{a => string()} | #{atom() => map()}) ->
+    [{a, string()} | {atom(), map()}].
+maps_to_list_5(M) -> maps:to_list(M).
+
+-spec maps_to_list_6(map()) -> [dynamic()].
+maps_to_list_6(M) -> maps:to_list(M).
+
+-spec maps_to_list_7_neg(number()) -> dynamic().
+maps_to_list_7_neg(Num) -> maps:to_list(Num).
+
 -spec lists_filtermap_1() -> [number()].
 lists_filtermap_1() ->
     lists:filtermap(
@@ -2294,4 +2318,4 @@ maps_fold_keys(M) ->
     ).
 
 -spec process_key(a | b) -> ok.
-process_key(_K) -> ok.
+process_key(_K) -> ok.

eqwalizer/test_projects/check/src/custom.erl.check

@@ -739,6 +739,32 @@ maps_fold_4_3_neg(M) ->                    | ERROR   |
         M                                  |         |
     ).                                     |         |
                                            |         |
+-spec maps_to_list_1(#{a => string(), b =>……         |
+    [{a, string()} | {b, number()} | {c, a……         |
+maps_to_list_1(M) -> maps:to_list(M).      | OK      |
+                                           |         |
+-spec maps_to_list_2(#{number() => atom()}……         |
+maps_to_list_2(M) -> maps:to_list(M).      | OK      |
+                                           |         |
+-spec maps_to_list_3(dynamic()) -> dynamic……         |
+maps_to_list_3(M) -> maps:to_list(M).      | OK      |
+                                           |         |
+-spec maps_to_list_4(#{a => string(), b =>……         |
+    [{a, string()} | {b, [number()] | [ato……         |
+maps_to_list_4(M) -> maps:to_list(M).      | OK      |
+                                           |         |
+-spec maps_to_list_5(#{a => string()} | #{……         |
+    [{a, string()} | {atom(), map()}].     |         |
+maps_to_list_5(M) -> maps:to_list(M).      | OK      |
+                                           |         |
+-spec maps_to_list_6(map()) -> [dynamic()]……         |
+maps_to_list_6(M) -> maps:to_list(M).      | OK      |
+                                           |         |
+-spec maps_to_list_7_neg(number()) -> dyna……         |
+maps_to_list_7_neg(Num) -> maps:to_list(Nu…… ERROR   | Num.
+                                           |         | Expression has type:   number()
+                                           |         | Context expected type: #D{term() => term()}
+                                           |         |
 -spec lists_filtermap_1() -> [number()].   |         |
 lists_filtermap_1() ->                     | OK      |
     lists:filtermap(                       |         |