Use eq-based map for constraints

This makes the logic in ProtoTypes#constrained independent of whether we
type lambdas are cached or uncached.

Author: odersky

compiler/src/dotty/tools/dotc/core/Constraint.scala

@@ -3,7 +3,6 @@ package dotc
 package core
 
 import Types._, Contexts._, Symbols._
-import util.SimpleMap
 import collection.mutable
 import printing.{Printer, Showable}
 import printing.Texts._

compiler/src/dotty/tools/dotc/core/OrderingConstraint.scala

@@ -3,7 +3,7 @@ package dotc
 package core
 
 import Types._, Contexts._, Symbols._, Decorators._
-import util.SimpleMap
+import util.SimpleEqMap
 import collection.mutable
 import printing.{Printer, Showable}
 import printing.Texts._
@@ -14,7 +14,7 @@ import annotation.tailrec
 
 object OrderingConstraint {
 
-  type ArrayValuedMap[T] = SimpleMap[TypeLambda, Array[T]]
+  type ArrayValuedMap[T] = SimpleEqMap[TypeLambda, Array[T]]
 
   /** The type of `OrderingConstraint#boundsMap` */
   type ParamBounds = ArrayValuedMap[Type]

compiler/src/dotty/tools/dotc/core/TyperState.scala

@@ -5,7 +5,7 @@ package core
 import Types._
 import Flags._
 import Contexts._
-import util.{SimpleMap, DotClass}
+import util.{SimpleEqMap, DotClass}
 import reporting._
 import printing.{Showable, Printer}
 import printing.Texts._
@@ -24,7 +24,7 @@ class TyperState(previous: TyperState /* | Null */) extends DotClass with Showab
   def setReporter(reporter: Reporter): this.type = { myReporter = reporter; this }
 
   private var myConstraint: Constraint =
-    if (previous == null) new OrderingConstraint(SimpleMap.Empty, SimpleMap.Empty, SimpleMap.Empty)
+    if (previous == null) new OrderingConstraint(SimpleEqMap.Empty, SimpleEqMap.Empty, SimpleEqMap.Empty)
     else previous.constraint
 
   def constraint = myConstraint