Add custom eqWAlizer type checking for maps:merge

Summary:
`maps:merge` currently loses all type information of the maps being merged. On this diff I'm adding custom handling of that function to deal with more map manipulation cases in WASERVER.

EqWAlizer already had some nice utilities to merge map types, but the existing implementation was a bit confusing and it the merging logic didn't assume any overwrite behavior (in `maps:merge`, when there are conflicting keys the right-ahnd side map's values are used). I expanded the existing merge logic to support this case, making the code more readable (I hope?) in the process.

Reviewed By: VLanvin

Differential Revision: D59677724

fbshipit-source-id: d0664130eda5e607a92aa110b221d83db95f6a19

eqwalizer/src/main/resources/application.conf

@@ -21,4 +21,6 @@ eqwalizer {
     clause_coverage = ${?EQWALIZER_CLAUSE_COVERAGE}
     overloaded_spec_dynamic_result = false
     overloaded_spec_dynamic_result = ${?EQWALIZER_OVERLOADED_SPEC_DYNAMIC_RESULT}
+    custom_maps_merge = false
+    custom_maps_merge = ${?EQWALIZER_CUSTOM_MAPS_MERGE}
 }

eqwalizer/src/main/scala/com/whatsapp/eqwalizer/package.scala

@@ -48,6 +48,7 @@ package object eqwalizer {
       checkRedundantGuards: Boolean,
       clauseCoverage: Boolean,
       overloadedSpecDynamicResult: Boolean,
+      customMapsMerge: Boolean,
       mode: Mode.Mode,
       errorDepth: Int,
   ) {
@@ -80,6 +81,7 @@ package object eqwalizer {
       checkRedundantGuards = config.getBoolean("check_redundant_guards"),
       clauseCoverage = config.getBoolean("clause_coverage"),
       overloadedSpecDynamicResult = config.getBoolean("overloaded_spec_dynamic_result"),
+      customMapsMerge = config.getBoolean("custom_maps_merge"),
       mode,
       errorDepth = config.getInt("error_depth"),
     )

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

@@ -50,7 +50,11 @@ class ElabApplyCustom(pipelineContext: PipelineContext) {
       RemoteId("maps", "with", 2),
       RemoteId("maps", "without", 2),
       RemoteId(CompilerMacro.fake_module, "record_info", 2),
-    )
+    ) ++ experimentalCustom
+
+  private def experimentalCustom: Set[RemoteId] =
+    if (pipelineContext.customMapsMerge) Set(RemoteId("maps", "merge", 2))
+    else Set()
 
   private lazy val customPredicate: Set[RemoteId] =
     Set(RemoteId("lists", "member", 2))
@@ -458,6 +462,15 @@ class ElabApplyCustom(pipelineContext: PipelineContext) {
         val pairTys = narrow.asMapType(coerce(args.head, argTys.head, anyMapTy))
         (mapToList(pairTys), env1)
 
+      case RemoteId("maps", "merge", 2) =>
+        val List(mapTy1, mapTy2) = args
+          .zip(argTys)
+          .map { case (arg, ty) => narrow.asMapType(coerce(arg, ty, anyMapTy)) }
+        val resMapTys = util
+          .cartesianProduct(mapTy1, mapTy2)
+          .map { case (ty1, ty2) => narrow.joinAndMergeShapes(List(ty1, ty2), true) }
+        (subtype.join(resMapTys), env1)
+
       case RemoteId("maps", "with", 2) =>
         @tailrec
         def toKey(ty: Type)(implicit pos: Pos): Option[String] = ty match {

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

@@ -10,8 +10,6 @@ import com.whatsapp.eqwalizer.ast.Forms.RecDeclTyped
 import com.whatsapp.eqwalizer.ast.{RemoteId, TypeVars}
 import com.whatsapp.eqwalizer.ast.Types._
 
-import scala.collection.mutable
-
 class Narrow(pipelineContext: PipelineContext) {
   private val subtype = pipelineContext.subtype
   private val util = pipelineContext.util
@@ -606,30 +604,32 @@ class Narrow(pipelineContext: PipelineContext) {
       case _ => None
     }
 
-  private def mergeShapes(s1: ShapeMap, s2: ShapeMap): ShapeMap = {
-    var optProps = mutable.HashMap.empty[String, Type]
-    var reqProps = mutable.HashMap.empty[String, Type]
-    val commonReqKeys = s1.props.collect { case ReqProp(key, _) => key }.toSet & s2.props.collect {
-      case ReqProp(key, _) => key
-    }.toSet
-    for (p <- s1.props.toSet ++ s2.props.toSet) {
-      p match {
-        case OptProp(key, tp) => optProps.updateWith(key)(ty => Some(subtype.join(tp, ty.getOrElse(NoneType))))
-        case ReqProp(key, tp) =>
-          if (commonReqKeys.contains(key)) {
-            reqProps.updateWith(key)(ty => Some(subtype.join(tp, ty.getOrElse(NoneType))))
-          } else {
-            optProps.updateWith(key)(ty => Some(subtype.join(tp, ty.getOrElse(NoneType))))
-          }
-      }
+  private def mergeShapes(s1: ShapeMap, s2: ShapeMap, inOrder: Boolean): ShapeMap = {
+    ShapeMap {
+      (s1.props ++ s2.props)
+        .groupBy(_.key)
+        .values
+        .map {
+          // prop is only defined in one of the maps
+          case List(p) if inOrder => p
+          case List(p)            => OptProp(p.key, p.tp)
+          // prop is optional on both sides
+          case List(OptProp(key, tp1), OptProp(_, tp2)) => OptProp(key, subtype.join(tp1, tp2))
+          // prop is required on both sides
+          case List(ReqProp(key, tp1), ReqProp(_, tp2)) if inOrder => ReqProp(key, tp2)
+          case List(ReqProp(key, tp1), ReqProp(_, tp2))            => ReqProp(key, subtype.join(tp1, tp2))
+          // prop is required on one side and optional on the other
+          case List(OptProp(key, tp1), ReqProp(_, tp2)) if inOrder => ReqProp(key, tp2)
+          case List(ReqProp(key, tp1), OptProp(_, tp2)) if inOrder => ReqProp(key, subtype.join(tp1, tp2))
+          case List(p1, p2)                                        => OptProp(p1.key, subtype.join(p1.tp, p2.tp))
+
+          case _ => throw new IllegalStateException()
+        }
+        .toList
     }
-    val allProps = optProps.map { case (k, t) => OptProp(k, t) }.toList ++ reqProps.map { case (k, t) =>
-      ReqProp(k, t)
-    }.toList
-    ShapeMap(allProps)
   }
 
-  def joinAndMergeShapes(tys: Iterable[Type]): Type = {
+  def joinAndMergeShapes(tys: Iterable[Type], inOrder: Boolean = false): Type = {
     val (shapes, notShapes) = tys.partition {
       case s: ShapeMap => true
       case _           => false
@@ -640,7 +640,7 @@ class Narrow(pipelineContext: PipelineContext) {
       joinedNotShapes
     } else {
       subtype.join(
-        shapesCoerced.tail.foldLeft(shapesCoerced.head)((acc, shape) => mergeShapes(acc, shape)),
+        shapesCoerced.tail.foldLeft(shapesCoerced.head)((acc, shape) => mergeShapes(acc, shape, inOrder)),
         joinedNotShapes,
       )
     }

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

@@ -139,4 +139,12 @@ class Util(pipelineContext: PipelineContext) {
     case BoundedDynamicType(_) => true
     case _                     => false
   }
+
+  def cartesianProduct(ty1: Type, ty2: Type): List[(Type, Type)] = {
+    def expand(ty: Type): List[Type] = ty match {
+      case UnionType(tys) => tys.toList.flatMap(expand)
+      case ty             => List(ty)
+    }
+    for (t1 <- expand(ty1); t2 <- expand(ty2)) yield (t1, t2)
+  }
 }

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

@@ -74,5 +74,6 @@ package object tc {
       options.errorDepth.getOrElse(config.errorDepth)
     val clauseCoverage: Boolean = config.clauseCoverage
     val overloadedSpecDynamicResult: Boolean = config.overloadedSpecDynamicResult
+    val customMapsMerge: Boolean = config.customMapsMerge
   }
 }

eqwalizer/src/test/resources/application.conf

@@ -17,4 +17,6 @@ eqwalizer {
     clause_coverage = ${?EQWALIZER_CLAUSE_COVERAGE}
     overloaded_spec_dynamic_result = false
     overloaded_spec_dynamic_result = ${?EQWALIZER_OVERLOADED_SPEC_DYNAMIC_RESULT}
+    custom_maps_merge = true
+    custom_maps_merge = ${?EQWALIZER_CUSTOM_MAPS_MERGE}
 }

eqwalizer/test_projects/check/src/custom.erl

@@ -646,6 +646,36 @@ 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 maps_merge_1(#{a => string(), b => number()}, #{b => number(), c => atom()}) ->
+    #{a => string(), b => number(), c => atom()}.
+maps_merge_1(M1, M2) -> maps:merge(M1, M2).
+
+-spec maps_merge_2(#{a => string(), b => number()}, #{b => boolean(), c => atom()}) ->
+    #{a => string(), b => number() | boolean(), c => atom()}.
+maps_merge_2(M1, M2) -> maps:merge(M1, M2).
+
+-spec maps_merge_3(#{a := string(), b => number()}, #{b := boolean(), c => atom()}) ->
+    #{a := string(), b := boolean(), c => atom()}.
+maps_merge_3(M1, M2) -> maps:merge(M1, M2).
+
+-spec maps_merge_4(#{a => string(), b => number()}, #{atom() => boolean()}) ->
+    #{atom() => boolean() | string() | number()}.
+maps_merge_4(M1, M2) -> maps:merge(M1, M2).
+
+-spec maps_merge_5(#{string() => number()}, #{atom() => boolean()}) ->
+    #{string() | atom() => boolean() | number()}.
+maps_merge_5(M1, M2) -> maps:merge(M1, M2).
+
+-spec maps_merge_6(#{a => binary()}, map()) -> map().
+maps_merge_6(M1, M2) -> maps:merge(M1, M2).
+
+-spec maps_merge_7_neg(#{a => binary()}, number()) -> term().
+maps_merge_7_neg(M1, M2) -> maps:merge(M1, M2).
+
+-spec maps_merge_8(#{a := atom()}, #{b := number()} | #{}) ->
+    #{a := atom(), b := number()} | #{a := atom()}.
+maps_merge_8(M1, M2) -> maps:merge(M1, M2).
+
 -spec lists_filtermap_1() -> [number()].
 lists_filtermap_1() ->
     lists:filtermap(

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

@@ -787,6 +787,38 @@ maps_to_list_7_neg(Num) -> maps:to_list(Nu…… ERROR   | Num.
                                            |         | Expression has type:   number()
                                            |         | Context expected type: #D{term() => term()}
                                            |         |
+-spec maps_merge_1(#{a => string(), b => n……         |
+    #{a => string(), b => number(), c => a……         |
+maps_merge_1(M1, M2) -> maps:merge(M1, M2)…… OK      |
+                                           |         |
+-spec maps_merge_2(#{a => string(), b => n……         |
+    #{a => string(), b => number() | boole……         |
+maps_merge_2(M1, M2) -> maps:merge(M1, M2)…… OK      |
+                                           |         |
+-spec maps_merge_3(#{a := string(), b => n……         |
+    #{a := string(), b := boolean(), c => ……         |
+maps_merge_3(M1, M2) -> maps:merge(M1, M2)…… OK      |
+                                           |         |
+-spec maps_merge_4(#{a => string(), b => n……         |
+    #{atom() => boolean() | string() | num……         |
+maps_merge_4(M1, M2) -> maps:merge(M1, M2)…… OK      |
+                                           |         |
+-spec maps_merge_5(#{string() => number()}……         |
+    #{string() | atom() => boolean() | num……         |
+maps_merge_5(M1, M2) -> maps:merge(M1, M2)…… OK      |
+                                           |         |
+-spec maps_merge_6(#{a => binary()}, map()……         |
+maps_merge_6(M1, M2) -> maps:merge(M1, M2)…… OK      |
+                                           |         |
+-spec maps_merge_7_neg(#{a => binary()}, n……         |
+maps_merge_7_neg(M1, M2) -> maps:merge(M1,…… ERROR   | M2.
+                                           |         | Expression has type:   number()
+                                           |         | Context expected type: #D{term() => term()}
+                                           |         |
+-spec maps_merge_8(#{a := atom()}, #{b := ……         |
+    #{a := atom(), b := number()} | #{a :=……         |
+maps_merge_8(M1, M2) -> maps:merge(M1, M2)…… OK      |
+                                           |         |
 -spec lists_filtermap_1() -> [number()].   |         |
 lists_filtermap_1() ->                     | OK      |
     lists:filtermap(                       |         |