Rename Empty -> empty in SimpleIdentityMap

It is already `empty` in SimpleIdentitySet. That way
we use the same convention as in the stdlib.

# Conflicts:
#	compiler/src/dotty/tools/dotc/util/LinearIdentityMap.scala

Author: odersky

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

@@ -289,7 +289,7 @@ object Contexts {
     private def lookup(key: Phase | SourceFile): Context =
       util.Stats.record("Context.related.lookup")
       if related == null then
-        related = SimpleIdentityMap.Empty
+        related = SimpleIdentityMap.empty
         null
       else
         related(key)

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

@@ -1603,7 +1603,7 @@ class Definitions {
     valueTypeEnc(sym2.asClass.name) % valueTypeEnc(sym1.asClass.name) == 0
 
   @tu lazy val specialErasure: SimpleIdentityMap[Symbol, ClassSymbol] =
-    SimpleIdentityMap.Empty[Symbol]
+    SimpleIdentityMap.empty[Symbol]
       .updated(AnyClass, ObjectClass)
       .updated(AnyValClass, ObjectClass)
       .updated(SingletonClass, ObjectClass)

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

@@ -65,9 +65,9 @@ final class ProperGadtConstraint private(
   import dotty.tools.dotc.config.Printers.{gadts, gadtsConstr}
 
   def this() = this(
-    myConstraint = new OrderingConstraint(SimpleIdentityMap.Empty, SimpleIdentityMap.Empty, SimpleIdentityMap.Empty),
-    mapping = SimpleIdentityMap.Empty,
-    reverseMapping = SimpleIdentityMap.Empty
+    myConstraint = new OrderingConstraint(SimpleIdentityMap.empty, SimpleIdentityMap.empty, SimpleIdentityMap.empty),
+    mapping = SimpleIdentityMap.empty,
+    reverseMapping = SimpleIdentityMap.empty
   )
 
   /** Exposes ConstraintHandling.subsumes */

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

@@ -105,7 +105,7 @@ object OrderingConstraint {
   }
 
   @sharable
-  val empty = new OrderingConstraint(SimpleIdentityMap.Empty, SimpleIdentityMap.Empty, SimpleIdentityMap.Empty)
+  val empty = new OrderingConstraint(SimpleIdentityMap.empty, SimpleIdentityMap.empty, SimpleIdentityMap.empty)
 }
 
 import OrderingConstraint._

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

@@ -1569,7 +1569,7 @@ object SymDenotations {
     // ----- caches -------------------------------------------------------
 
     private var myTypeParams: List[TypeSymbol] = null
-    private var fullNameCache: SimpleIdentityMap[QualifiedNameKind, Name] = SimpleIdentityMap.Empty
+    private var fullNameCache: SimpleIdentityMap[QualifiedNameKind, Name] = SimpleIdentityMap.empty
 
     private var myMemberCache: IdentityHashMap[Name, PreDenotation] = null
     private var myMemberCachePeriod: Period = Nowhere
@@ -2606,7 +2606,7 @@ object SymDenotations {
   }
 
   private class MemberNamesImpl(createdAt: Period) extends InheritedCacheImpl(createdAt) with MemberNames {
-    private var cache: SimpleIdentityMap[NameFilter, Set[Name]] = SimpleIdentityMap.Empty
+    private var cache: SimpleIdentityMap[NameFilter, Set[Name]] = SimpleIdentityMap.empty
 
     final def isValid(using Context): Boolean =
       cache != null && isValidAt(ctx.phase)
@@ -2619,7 +2619,7 @@ object SymDenotations {
      */
     def invalidate(): Unit =
       if (cache != null)
-        if (locked) cache = SimpleIdentityMap.Empty
+        if (locked) cache = SimpleIdentityMap.empty
         else {
           cache = null
           invalidateDependents()

compiler/src/dotty/tools/dotc/typer/ImportInfo.scala

@@ -99,8 +99,8 @@ class ImportInfo(symf: Context ?=> Symbol,
   /** Compute info relating to the selector list */
   private def ensureInitialized(): Unit = if myExcluded == null then
     myExcluded = Set()
-    myForwardMapping = SimpleIdentityMap.Empty
-    myReverseMapping = SimpleIdentityMap.Empty
+    myForwardMapping = SimpleIdentityMap.empty
+    myReverseMapping = SimpleIdentityMap.empty
     for sel <- selectors do
       if sel.isWildcard then
         myWildcardImport = true
@@ -180,7 +180,7 @@ class ImportInfo(symf: Context ?=> Symbol,
   private var myUnimported: Symbol = _
 
   private var myOwner: Symbol = null
-  private var myResults: SimpleIdentityMap[TermName, java.lang.Boolean] = SimpleIdentityMap.Empty
+  private var myResults: SimpleIdentityMap[TermName, java.lang.Boolean] = SimpleIdentityMap.empty
 
   /** Does this import clause or a preceding import clause import `owner.feature`? */
   def featureImported(feature: TermName, owner: Symbol)(using Context): Boolean =

compiler/src/dotty/tools/dotc/typer/Inferencing.scala

@@ -438,7 +438,7 @@ object Inferencing {
       if (vmap1 eq vmap) vmap else propagate(vmap1)
     }
 
-    propagate(accu(SimpleIdentityMap.Empty, tp))
+    propagate(accu(SimpleIdentityMap.empty, tp))
   }
 }
 

compiler/src/dotty/tools/dotc/typer/Inliner.scala

@@ -1040,7 +1040,7 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(using Context) {
             }
           }
 
-          extractBindVariance(SimpleIdentityMap.Empty, tpt.tpe)
+          extractBindVariance(SimpleIdentityMap.empty, tpt.tpe)
         }
 
         def addTypeBindings(typeBinds: TypeBindsMap)(using Context): Unit =

compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala

@@ -246,7 +246,7 @@ object ProtoTypes {
     var typedArgs: List[Tree] = Nil
 
     /** A map in which typed arguments can be stored to be later integrated in `typedArgs`. */
-    var typedArg: SimpleIdentityMap[untpd.Tree, Tree] = SimpleIdentityMap.Empty
+    var typedArg: SimpleIdentityMap[untpd.Tree, Tree] = SimpleIdentityMap.empty
 
     /** The tupled or untupled version of this prototype, if it has been computed */
     var tupledDual: Type = NoType

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -2594,7 +2594,7 @@ class Typer extends Namer
 
   def typedStats(stats: List[untpd.Tree], exprOwner: Symbol)(using Context): (List[Tree], Context) = {
     val buf = new mutable.ListBuffer[Tree]
-    var enumContexts: SimpleIdentityMap[Symbol, Context] = SimpleIdentityMap.Empty
+    var enumContexts: SimpleIdentityMap[Symbol, Context] = SimpleIdentityMap.empty
     val initialNotNullInfos = ctx.notNullInfos
       // A map from `enum` symbols to the contexts enclosing their definitions
     @tailrec def traverse(stats: List[untpd.Tree])(using Context): (List[Tree], Context) = stats match {