Deprecate sequence implementations in favor of sequence operations.

libraries/tools/kotlin-stdlib-gen/src/templates/Filtering.kt

@@ -351,7 +351,7 @@ fun filtering(): List<GenericFunction> {
         returns(Sequences) { "Sequence<T>" }
         body(Sequences) {
             """
-            return FilteringSequence(this, false, { it == null }) as Sequence<T>
+            return filterNot { it == null } as Sequence<T>
             """
         }
     }

libraries/tools/kotlin-stdlib-gen/src/templates/Generators.kt

@@ -21,7 +21,7 @@ fun generators(): List<GenericFunction> {
         returns(Sequences) { "Sequence<T>" }
         body(Sequences) {
             """
-            return MultiSequence(sequenceOf(this, sequenceOf(element)))
+            return sequenceOf(this, sequenceOf(element)).flatten()
             """
         }
     }
@@ -58,7 +58,7 @@ fun generators(): List<GenericFunction> {
         returns("Sequence<T>")
         body {
             """
-            return MultiSequence(sequenceOf(this, collection.sequence()))
+            return sequenceOf(this, collection.sequence()).flatten()
             """
         }
     }
@@ -69,7 +69,7 @@ fun generators(): List<GenericFunction> {
         returns("Sequence<T>")
         body {
             """
-            return MultiSequence(sequenceOf(this, sequence))
+            return sequenceOf(this, sequence).flatten()
             """
         }
     }

libraries/tools/kotlin-stdlib-gen/src/templates/Guards.kt

@@ -27,12 +27,7 @@ fun guards(): List<GenericFunction> {
         }
         body(Sequences) {
             """
-            return FilteringSequence(this) {
-                if (it == null) {
-                    throw IllegalArgumentException("null element found in $THIS")
-                }
-                true
-            } as Sequence<T>
+            return map { it ?: throw IllegalArgumentException("null element found in $THIS") }
             """
         }
     }

libraries/tools/kotlin-stdlib-gen/src/templates/SpecialJVM.kt

@@ -106,7 +106,7 @@ fun specialJVM(): List<GenericFunction> {
         returns(Sequences) { "Sequence<R>" }
         body(Sequences) {
             """
-            return FilteringSequence(this, true, { klass.isInstance(it) }) as Sequence<R>
+            return filter { klass.isInstance(it) } as Sequence<R>
             """
         }
     }
@@ -146,7 +146,7 @@ fun specialJVM(): List<GenericFunction> {
         receiverAsterisk(true)
         body(Sequences) {
             """
-            return FilteringSequence(this, true, { it is R }) as Sequence<R>
+            return filter { it is R } as Sequence<R>
             """
         }
     }