Use descriptive name for SelfInfo type

Author: odersky

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

@@ -3373,6 +3373,8 @@ object Types {
 
   // ------ ClassInfo, Type Bounds ------------------------------------------------------------
 
+  type TypeOrSymbol = AnyRef /* should be: Type | Symbol */
+
   /** Roughly: the info of a class during a period.
    *  @param prefix       The prefix on which parents, decls, and selfType need to be rebased.
    *  @param cls          The class symbol.
@@ -3389,7 +3391,7 @@ object Types {
       cls: ClassSymbol,
       classParents: List[Type],
       decls: Scope,
-      selfInfo: DotClass /* should be: Type | Symbol */) extends CachedGroundType with TypeType {
+      selfInfo: TypeOrSymbol) extends CachedGroundType with TypeType {
 
     private[this] var selfTypeCache: Type = null
     private[this] var appliedRefCache: Type = null
@@ -3437,7 +3439,7 @@ object Types {
       if (prefix eq this.prefix) this
       else ClassInfo(prefix, cls, classParents, decls, selfInfo)
 
-    def derivedClassInfo(prefix: Type = this.prefix, classParents: List[Type] = this.classParents, decls: Scope = this.decls, selfInfo: DotClass = this.selfInfo)(implicit ctx: Context) =
+    def derivedClassInfo(prefix: Type = this.prefix, classParents: List[Type] = this.classParents, decls: Scope = this.decls, selfInfo: TypeOrSymbol = this.selfInfo)(implicit ctx: Context) =
       if ((prefix eq this.prefix) && (classParents eq this.classParents) && (decls eq this.decls) && (selfInfo eq this.selfInfo)) this
       else ClassInfo(prefix, cls, classParents, decls, selfInfo)
 
@@ -3456,11 +3458,11 @@ object Types {
     override def toString = s"ClassInfo($prefix, $cls, $classParents)"
   }
 
-  class CachedClassInfo(prefix: Type, cls: ClassSymbol, classParents: List[Type], decls: Scope, selfInfo: DotClass)
+  class CachedClassInfo(prefix: Type, cls: ClassSymbol, classParents: List[Type], decls: Scope, selfInfo: TypeOrSymbol)
     extends ClassInfo(prefix, cls, classParents, decls, selfInfo)
 
   /** A class for temporary class infos where `parents` are not yet known */
-  final class TempClassInfo(prefix: Type, cls: ClassSymbol, decls: Scope, selfInfo: DotClass)
+  final class TempClassInfo(prefix: Type, cls: ClassSymbol, decls: Scope, selfInfo: TypeOrSymbol)
   extends CachedClassInfo(prefix, cls, Nil, decls, selfInfo) {
 
     /** Install classinfo with known parents in `denot` s */
@@ -3475,7 +3477,7 @@ object Types {
   }
 
   object ClassInfo {
-    def apply(prefix: Type, cls: ClassSymbol, classParents: List[Type], decls: Scope, selfInfo: DotClass = NoType)(implicit ctx: Context) =
+    def apply(prefix: Type, cls: ClassSymbol, classParents: List[Type], decls: Scope, selfInfo: TypeOrSymbol = NoType)(implicit ctx: Context) =
       unique(new CachedClassInfo(prefix, cls, classParents, decls, selfInfo))
   }