Remove redundant API from ColumnSelectionDsl.

Author: nikitinas

src/main/kotlin/org/jetbrains/kotlinx/dataframe/ColumnsContainer.kt

@@ -16,7 +16,7 @@ import kotlin.reflect.KProperty
 /**
  * Provides access to [columns][DataColumn].
  *
- * Base interface for [DataFrame] and [column selection DSLs][ColumnSelectionDsl]
+ * Base interface for [DataFrame] and [ColumnSelectionDsl]
  *
  * @param T Schema marker. Used to generate extension properties for typed column access.
  */

src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/ColumnsSelectionDsl.kt

@@ -17,7 +17,6 @@ import org.jetbrains.kotlinx.dataframe.columns.UnresolvedColumnsPolicy
 import org.jetbrains.kotlinx.dataframe.columns.renamedReference
 import org.jetbrains.kotlinx.dataframe.impl.DataFrameReceiver
 import org.jetbrains.kotlinx.dataframe.impl.columnName
-import org.jetbrains.kotlinx.dataframe.impl.columns.ColumnAccessorImpl
 import org.jetbrains.kotlinx.dataframe.impl.columns.ColumnsList
 import org.jetbrains.kotlinx.dataframe.impl.columns.DistinctColumnSet
 import org.jetbrains.kotlinx.dataframe.impl.columns.allColumnsExcept
@@ -36,19 +35,11 @@ import kotlin.reflect.typeOf
 
 public interface ColumnSelectionDsl<out T> : ColumnsContainer<T> {
 
-    public operator fun <C> ColumnReference<C>.invoke(): DataColumn<C> = get(this)
-
-    public operator fun <T> ColumnReference<DataRow<T>>.invoke(): ColumnGroup<T> = get(this)
-
-    public operator fun <C> ColumnReference<C>.invoke(newName: String): ColumnReference<C> = renamedReference(newName)
-
     public operator fun <C> ColumnPath.invoke(): DataColumn<C> = getColumn(this).cast()
 
     public operator fun <C> String.invoke(): DataColumn<C> = getColumn(this).cast()
 
     public operator fun String.get(column: String): ColumnPath = pathOf(this, column)
-
-    public fun <C> String.cast(): ColumnAccessor<C> = ColumnAccessorImpl(this)
 }
 
 public interface ColumnsSelectionDsl<out T> : ColumnSelectionDsl<T>, SingleColumn<DataRow<T>> {

src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/sort.kt

@@ -23,13 +23,13 @@ import kotlin.reflect.KProperty
 public interface SortDsl<out T> : ColumnsSelectionDsl<T> {
 
     public fun <C> ColumnSet<C>.desc(): ColumnSet<C> = addFlag(SortFlag.Reversed)
-    public fun String.desc(): ColumnSet<Comparable<*>?> = cast<Comparable<*>>().desc()
+    public fun String.desc(): ColumnSet<Comparable<*>?> = invoke<Comparable<*>>().desc()
     public fun <C> KProperty<C>.desc(): ColumnSet<C> = toColumnAccessor().desc()
 
     public fun <C> ColumnSet<C?>.nullsLast(flag: Boolean = true): ColumnSet<C?> =
         if (flag) addFlag(SortFlag.NullsLast) else this
 
-    public fun String.nullsLast(flag: Boolean = true): ColumnSet<Comparable<*>?> = cast<Comparable<*>>().nullsLast(flag)
+    public fun String.nullsLast(flag: Boolean = true): ColumnSet<Comparable<*>?> = invoke<Comparable<*>>().nullsLast(flag)
     public fun <C> KProperty<C?>.nullsLast(flag: Boolean = true): ColumnSet<C?> = toColumnAccessor().nullsLast(flag)
 }
 

src/test/kotlin/org/jetbrains/kotlinx/dataframe/testSets/person/DataFrameTests.kt

@@ -451,7 +451,7 @@ class DataFrameTests : BaseTest() {
 
         df.sortBy { Person::name and Person::age.desc() }.check()
 
-        df.sortBy { "name".cast<String>() and "age".desc() }.check()
+        df.sortBy { "name"<String>() and "age".desc() }.check()
     }
 
     @Test