Renamed class for SubTypers and added to Context

2 files changed, 16 insertions, 4 deletions

diff --git a/src/dotty/tools/dotc/core/Contexts.scala b/src/dotty/tools/dotc/core/Contexts.scala
index bdec812bf..873bbf377 100644
--- a/src/dotty/tools/dotc/core/Contexts.scala
+++ b/src/dotty/tools/dotc/core/Contexts.scala
@@ -16,6 +16,7 @@ object Contexts {
     val underlying: Context
     val root: RootContext
     val period: Period
+    def constraints: Constraints
     def subTyper: SubTyper
     def names: NameTable
     def phase: Phase = ???
@@ -26,8 +27,11 @@ object Contexts {
   abstract class SubContext(val underlying: Context) extends Context {
     val root: RootContext = underlying.root
     val period: Period = underlying.period
-    val subTyper = underlying.subTyper
+    val constraints = underlying.constraints
     def names: NameTable = root.names
+    lazy val subTyper =
+      if (constraints eq underlying.constraints) underlying.subTyper
+      else new SubTyper(this)
   }
 
   class RootContext extends Context
@@ -37,6 +41,7 @@ object Contexts {
                        with Types {
 
     val underlying: Context = throw new UnsupportedOperationException("RootContext.underlying")
+    def subTyper: SubTyper = ???
 
     val root: RootContext = this
     val period = periodOf(NoRunId, NoPhaseId)
@@ -46,7 +51,7 @@ object Contexts {
     var lastPhaseId: Int = NoPhaseId
     lazy val definitions = new Definitions()(this)
 
-    val subTyper = new SubTyper(Map())(this)
+    val constraints: Constraints = Map()
   }
 
   private final val initialUniquesCapacity = 4096
diff --git a/src/dotty/tools/dotc/core/SubTyper.scala b/src/dotty/tools/dotc/core/SubTypers.scala
index 52e8f7ece..602b380f4 100644
--- a/src/dotty/tools/dotc/core/SubTyper.scala
+++ b/src/dotty/tools/dotc/core/SubTypers.scala
@@ -11,9 +11,13 @@ object SubTypers {
     private final val LogPendingSubTypesThreshold = 50
   }
 
-  class SubTyper(var constraints: Constraints)(implicit ctx: Context) extends DotClass {
+  class SubTyper(_ctx: Context) extends DotClass {
     import SubTyper._
 
+    implicit val ctx = _ctx
+
+    var constraints = ctx.constraints
+
     private var pendingSubTypes: mutable.Set[(Type, Type)] = null
     private var recCount = 0
 
@@ -215,6 +219,9 @@ object SubTypers {
         }
     }
 
-    def isSameType(tp1: Type, tp2: Type): Boolean = ???
+    def isSameType(tp1: Type, tp2: Type): Boolean =
+      if (tp1 == NoType || tp2 == NoType) false
+      else if (tp1 eq tp2) true
+      else isSubType(tp1, tp2) && isSubType(tp2, tp1)
   }
 }
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