diff --git a/core/shared/src/main/scala/sigma/SigmaDsl.scala b/core/shared/src/main/scala/sigma/SigmaDsl.scala
index 5e647cad0e..9cf632cc59 100644
--- a/core/shared/src/main/scala/sigma/SigmaDsl.scala
+++ b/core/shared/src/main/scala/sigma/SigmaDsl.scala
@@ -155,6 +155,9 @@ trait BigInt {
   def or(that: BigInt): BigInt
   def |(that: BigInt): BigInt = or(that)
 
+  /**
+    * @return a big integer whose value is `this xor that`
+    */
   def xor(that: BigInt): BigInt
 
   def shiftLeft(bits: Int): BigInt
diff --git a/core/shared/src/main/scala/sigma/serialization/TypeSerializer.scala b/core/shared/src/main/scala/sigma/serialization/TypeSerializer.scala
index c21a3458c0..1936bbcd9a 100644
--- a/core/shared/src/main/scala/sigma/serialization/TypeSerializer.scala
+++ b/core/shared/src/main/scala/sigma/serialization/TypeSerializer.scala
@@ -4,7 +4,6 @@ import debox.cfor
 import sigma.VersionContext
 import sigma.ast.SCollectionType.{CollectionTypeCode, NestedCollectionTypeCode}
 import sigma.ast._
-import sigma.serialization.{CoreByteReader, CoreByteWriter, InvalidTypePrefix}
 import sigma.util.safeNewArray
 import sigma.validation.ValidationRules.{CheckPrimitiveTypeCode, CheckTypeCode}
 
@@ -215,7 +214,6 @@ class TypeSerializer {
             STypeParam(ident.asInstanceOf[STypeVar])
           }
           SFunc(tDom, tRange, tpeParams)
-        // todo: serialize tParams
         case _ =>
           // todo: 6.0: replace 1008 check with identical behavior but other opcode, to activate
           //  ReplacedRule(1008 -> new opcode) during 6.0 activation
diff --git a/data/shared/src/main/scala/sigma/ast/methods.scala b/data/shared/src/main/scala/sigma/ast/methods.scala
index b40cdca79c..67bb1c74fb 100644
--- a/data/shared/src/main/scala/sigma/ast/methods.scala
+++ b/data/shared/src/main/scala/sigma/ast/methods.scala
@@ -5,7 +5,6 @@ import org.ergoplatform.validation._
 import sigma._
 import sigma.ast.SCollection.{SBooleanArray, SBoxArray, SByteArray, SByteArray2, SHeaderArray}
 import sigma.ast.SMethod.{MethodCallIrBuilder, MethodCostFunc, javaMethodOf}
-import sigma.ast.SNumericTypeMethods.BitwiseAndMethod
 import sigma.ast.SType.TypeCode
 import sigma.ast.syntax.{SValue, ValueOps}
 import sigma.data.ExactIntegral.{ByteIsExactIntegral, IntIsExactIntegral, LongIsExactIntegral, ShortIsExactIntegral}
diff --git a/data/shared/src/main/scala/sigma/data/ExactNumeric.scala b/data/shared/src/main/scala/sigma/data/ExactNumeric.scala
index 90d28e5370..9612cccc34 100644
--- a/data/shared/src/main/scala/sigma/data/ExactNumeric.scala
+++ b/data/shared/src/main/scala/sigma/data/ExactNumeric.scala
@@ -1,12 +1,8 @@
 package sigma.data
 
 import debox.cfor
-import sigma.Evaluation.stypeToRType
-import sigma.{BigInt, Coll, Colls}
+import sigma.{Coll, Colls}
 import sigma.data.ExactIntegral._
-import sigma.data.RType.SomeType
-
-import scala.collection.mutable
 
 /** Numeric operations with overflow checks.
   * Raise exception when overflow is detected.