Added comments

idea/src/org/jetbrains/kotlin/idea/intentions/loopToCallChain/baseTransformations.kt

@@ -23,7 +23,10 @@ import org.jetbrains.kotlin.psi.KtForExpression
 import org.jetbrains.kotlin.psi.KtPsiFactory
 import org.jetbrains.kotlin.psi.psiUtil.PsiChildRange
 
-abstract class ReplaceLoopResultTransformation(final override val loop: KtForExpression): ResultTransformation {
+/**
+ * Base class for [ResultTransformation]'s that replaces the loop-expression with the result call chain
+ */
+abstract class ReplaceLoopResultTransformation(final override val loop: KtForExpression) : ResultTransformation {
 
     override val commentSavingRange = PsiChildRange.singleElement(loop.unwrapIfLabeled())
 
@@ -35,6 +38,9 @@ abstract class ReplaceLoopResultTransformation(final override val loop: KtForExp
     }
 }
 
+/**
+ * Base class for [ResultTransformation]'s that replaces initialization of a variable with the result call chain
+ */
 abstract class AssignToVariableResultTransformation(
         final override val loop: KtForExpression,
         protected val initialization: VariableInitialization
@@ -88,6 +94,9 @@ abstract class AssignToVariableResultTransformation(
     }
 }
 
+/**
+ * [ResultTransformation] that replaces initialization of a variable with the call chain produced by the given [SequenceTransformation]
+ */
 class AssignSequenceResultTransformation(
         private val sequenceTransformation: SequenceTransformation,
         initialization: VariableInitialization

idea/src/org/jetbrains/kotlin/idea/intentions/loopToCallChain/sequence/IntroduceIndexMatcher.kt

@@ -29,6 +29,10 @@ import org.jetbrains.kotlin.psi.psiUtil.collectDescendantsOfType
 import org.jetbrains.kotlin.psi.psiUtil.isAncestor
 import java.util.*
 
+/**
+ * Analyzes the rest of the loop and detects index variable manually incremented inside.
+ * So it does not produce any transformation in its result but adds an index variable.
+ */
 object IntroduceIndexMatcher : TransformationMatcher {
     override val indexVariableAllowed: Boolean
         get() = false // old index variable is still needed - cannot introduce another one