move admitsNull to Types.scala

Author: olhotak

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

@@ -50,17 +50,6 @@ object NullOpsDecorator:
       val stripped = self.stripNull()
       stripped ne self
     }
-
-    def admitsNull(using Context): Boolean = {
-      self.isNullType || self.isAny || (self match
-        case OrType(l, r) => r.admitsNull || l.admitsNull
-        case AndType(l, r) => r.admitsNull && l.admitsNull
-        case TypeBounds(lo, hi) => lo.admitsNull
-        case FlexibleType(lo, hi) => true
-        case tp: TypeProxy => tp.underlying.admitsNull
-        case _ => false
-      )
-    }
   end extension
 
   import ast.tpd.*

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

@@ -382,6 +382,17 @@ object Types extends TypeUtils {
       case _ => false
     }
 
+    /** Is it possible that `null` is a value of this type? */
+    def admitsNull(using Context): Boolean =
+      isNullType || isAny || (this match
+        case OrType(l, r) => r.admitsNull || l.admitsNull
+        case AndType(l, r) => r.admitsNull && l.admitsNull
+        case TypeBounds(lo, hi) => lo.admitsNull
+        case FlexibleType(lo, hi) => true
+        case tp: TypeProxy => tp.underlying.admitsNull
+        case _ => false
+      )
+
     /** Is this type produced as a repair for an error? */
     final def isError(using Context): Boolean = stripTypeVar.isInstanceOf[ErrorType]