Merge pull request #12390 from moiseev/strides

[stdlib] Implement customization points for StrideTo, StrideThrough, and LazyFilterX

Author: moiseev

stdlib/public/core/Filter.swift.gyb

@@ -84,6 +84,19 @@ public struct LazyFilterSequence<Base : Sequence>
       _base: base.makeIterator(), _include)
   }
 
+  @_inlineable
+  public func _customContainsEquatableElement(
+    _ element: Element
+  ) -> Bool? {
+    if !_include(element) {
+      return false
+    }
+    if let baseContains = base._customContainsEquatableElement(element) {
+      return baseContains
+    }
+    return nil
+  }
+
   /// Creates an instance consisting of the elements `x` of `base` for
   /// which `isIncluded(x) == true`.
   @_inlineable // FIXME(sil-serialize-all)
@@ -152,6 +165,19 @@ public struct ${Self}<
     self._predicate = isIncluded
   }
 
+  @_inlineable
+  public func _customContainsEquatableElement(
+    _ element: Element
+  ) -> Bool? {
+    if !_predicate(element) {
+      return false
+    }
+    if let baseContains = _base._customContainsEquatableElement(element) {
+      return baseContains
+    }
+    return nil
+  }
+
   /// The position of the first element in a non-empty collection.
   ///
   /// In an empty collection, `startIndex == endIndex`.

stdlib/public/core/Stride.swift.gyb

@@ -233,6 +233,23 @@ public struct StrideTo<Element : Strideable> : Sequence, CustomReflectable {
     return StrideToIterator(_start: _start, end: _end, stride: _stride)
   }
 
+  @_inlineable
+  public func _preprocessingPass<R>(
+    _ preprocess: () throws -> R
+  ) rethrows -> R? {
+    return try preprocess()
+  }
+
+  @_inlineable
+  public func _customContainsEquatableElement(
+    _ element: Element
+  ) -> Bool? {
+    if element < _start || _end <= element {
+      return false
+    }
+    return nil
+  }
+
   @_inlineable
   @_versioned
   internal init(_start: Element, end: Element, stride: Element.Stride) {
@@ -333,6 +350,23 @@ public struct StrideThrough<
     return StrideThroughIterator(_start: _start, end: _end, stride: _stride)
   }
 
+  @_inlineable
+  public func _preprocessingPass<R>(
+    _ preprocess: () throws -> R
+  ) rethrows -> R? {
+    return try preprocess()
+  }
+
+  @_inlineable
+  public func _customContainsEquatableElement(
+    _ element: Element
+  ) -> Bool? {
+    if element < _start || _end < element {
+      return false
+    }
+    return nil
+  }
+
   @_inlineable
   @_versioned
   internal init(_start: Element, end: Element, stride: Element.Stride) {