Fix usage of ctx

Author: liufengyun

compiler/src/dotty/tools/dotc/transform/TreeChecker.scala

@@ -435,7 +435,7 @@ class TreeChecker extends Phase with SymTransformer {
       def isNonMagicalMember(x: Symbol) =
         !x.isValueClassConvertMethod &&
         !x.name.is(DocArtifactName) &&
-        !(ctx.phase.id >= ctx.genBCodePhase.id && x.name == str.MODULE_INSTANCE_FIELD.toTermName)
+        !(ctx.phase.id >= genBCodePhase.id && x.name == str.MODULE_INSTANCE_FIELD.toTermName)
 
       val decls   = cls.classInfo.decls.toList.toSet.filter(isNonMagicalMember)
       val defined = impl.body.map(_.symbol)