Allow AsyncSequence operators to be inlined in their construction (#38310)

Author: phausler

stdlib/public/Concurrency/AsyncCompactMapSequence.swift

@@ -56,14 +56,15 @@ extension AsyncSequence {
 /// An asynchronous sequence that maps a given closure over the asynchronous
 /// sequence’s elements, omitting results that don't return a value.
 @available(SwiftStdlib 5.5, *)
+@frozen
 public struct AsyncCompactMapSequence<Base: AsyncSequence, ElementOfResult> {
   @usableFromInline
   let base: Base
 
   @usableFromInline
   let transform: (Base.Element) async -> ElementOfResult?
 
-  @usableFromInline
+  @inlinable
   init(
     _ base: Base, 
     transform: @escaping (Base.Element) async -> ElementOfResult?
@@ -84,6 +85,7 @@ extension AsyncCompactMapSequence: AsyncSequence {
   public typealias AsyncIterator = Iterator
 
   /// The iterator that produces elements of the compact map sequence.
+  @frozen
   public struct Iterator: AsyncIteratorProtocol {
     public typealias Element = ElementOfResult
 
@@ -93,7 +95,7 @@ extension AsyncCompactMapSequence: AsyncSequence {
     @usableFromInline
     let transform: (Base.Element) async -> ElementOfResult?
 
-    @usableFromInline
+    @inlinable
     init(
       _ baseIterator: Base.AsyncIterator, 
       transform: @escaping (Base.Element) async -> ElementOfResult?

stdlib/public/Concurrency/AsyncDropFirstSequence.swift

@@ -49,14 +49,15 @@ extension AsyncSequence {
 /// An asynchronous sequence which omits a specified number of elements from the
 /// base asynchronous sequence, then passes through all remaining elements.
 @available(SwiftStdlib 5.5, *)
+@frozen
 public struct AsyncDropFirstSequence<Base: AsyncSequence> {
   @usableFromInline
   let base: Base
 
   @usableFromInline
   let count: Int
 
-  @usableFromInline 
+  @inlinable 
   init(_ base: Base, dropping count: Int) {
     self.base = base
     self.count = count
@@ -74,14 +75,15 @@ extension AsyncDropFirstSequence: AsyncSequence {
   public typealias AsyncIterator = Iterator
 
   /// The iterator that produces elements of the drop-first sequence.
+  @frozen
   public struct Iterator: AsyncIteratorProtocol {
     @usableFromInline
     var baseIterator: Base.AsyncIterator
 
     @usableFromInline
     var count: Int
 
-    @usableFromInline
+    @inlinable
     init(_ baseIterator: Base.AsyncIterator, count: Int) {
       self.baseIterator = baseIterator
       self.count = count

stdlib/public/Concurrency/AsyncDropWhileSequence.swift

@@ -53,14 +53,15 @@ extension AsyncSequence {
 /// given closure returns false, after which it passes through all remaining
 /// elements.
 @available(SwiftStdlib 5.5, *)
+@frozen
 public struct AsyncDropWhileSequence<Base: AsyncSequence> {
   @usableFromInline
   let base: Base
 
   @usableFromInline
   let predicate: (Base.Element) async -> Bool
 
-  @usableFromInline
+  @inlinable
   init(
     _ base: Base, 
     predicate: @escaping (Base.Element) async -> Bool
@@ -82,14 +83,15 @@ extension AsyncDropWhileSequence: AsyncSequence {
   public typealias AsyncIterator = Iterator
 
   /// The iterator that produces elements of the drop-while sequence.
+  @frozen
   public struct Iterator: AsyncIteratorProtocol {
     @usableFromInline
     var baseIterator: Base.AsyncIterator
 
     @usableFromInline
     var predicate: ((Base.Element) async -> Bool)?
 
-    @usableFromInline
+    @inlinable
     init(
       _ baseIterator: Base.AsyncIterator, 
       predicate: @escaping (Base.Element) async -> Bool

stdlib/public/Concurrency/AsyncFilterSequence.swift

@@ -44,14 +44,15 @@ extension AsyncSequence {
 /// An asynchronous sequence that contains, in order, the elements of
 /// the base sequence that satisfy a given predicate.
 @available(SwiftStdlib 5.5, *)
+@frozen
 public struct AsyncFilterSequence<Base: AsyncSequence> {
   @usableFromInline
   let base: Base
 
   @usableFromInline
   let isIncluded: (Element) async -> Bool
 
-  @usableFromInline
+  @inlinable
   init(
     _ base: Base, 
     isIncluded: @escaping (Base.Element) async -> Bool
@@ -72,14 +73,15 @@ extension AsyncFilterSequence: AsyncSequence {
   public typealias AsyncIterator = Iterator
 
   /// The iterator that produces elements of the filter sequence.
+  @frozen
   public struct Iterator: AsyncIteratorProtocol {
     @usableFromInline
     var baseIterator: Base.AsyncIterator
 
     @usableFromInline
     let isIncluded: (Base.Element) async -> Bool
 
-    @usableFromInline
+    @inlinable
     init(
       _ baseIterator: Base.AsyncIterator,
       isIncluded: @escaping (Base.Element) async -> Bool

stdlib/public/Concurrency/AsyncFlatMapSequence.swift

@@ -50,14 +50,15 @@ extension AsyncSequence {
 /// An asynchronous sequence that concatenates the results of calling a given
 /// transformation with each element of this sequence.
 @available(SwiftStdlib 5.5, *)
+@frozen
 public struct AsyncFlatMapSequence<Base: AsyncSequence, SegmentOfResult: AsyncSequence> {
   @usableFromInline
   let base: Base
 
   @usableFromInline
   let transform: (Base.Element) async -> SegmentOfResult
 
-  @usableFromInline
+  @inlinable
   init(
     _ base: Base,
     transform: @escaping (Base.Element) async -> SegmentOfResult
@@ -78,6 +79,7 @@ extension AsyncFlatMapSequence: AsyncSequence {
   public typealias AsyncIterator = Iterator
 
   /// The iterator that produces elements of the flat map sequence.
+  @frozen
   public struct Iterator: AsyncIteratorProtocol {
     @usableFromInline
     var baseIterator: Base.AsyncIterator
@@ -91,7 +93,7 @@ extension AsyncFlatMapSequence: AsyncSequence {
     @usableFromInline
     var finished = false
 
-    @usableFromInline
+    @inlinable
     init(
       _ baseIterator: Base.AsyncIterator,
       transform: @escaping (Base.Element) async -> SegmentOfResult

stdlib/public/Concurrency/AsyncMapSequence.swift

@@ -54,14 +54,15 @@ extension AsyncSequence {
 /// An asynchronous sequence that maps the given closure over the asynchronous
 /// sequence’s elements.
 @available(SwiftStdlib 5.5, *)
+@frozen
 public struct AsyncMapSequence<Base: AsyncSequence, Transformed> {
   @usableFromInline
   let base: Base
 
   @usableFromInline
   let transform: (Base.Element) async -> Transformed
 
-  @usableFromInline
+  @inlinable
   init(
     _ base: Base, 
     transform: @escaping (Base.Element) async -> Transformed
@@ -82,14 +83,15 @@ extension AsyncMapSequence: AsyncSequence {
   public typealias AsyncIterator = Iterator
 
   /// The iterator that produces elements of the map sequence.
+  @frozen
   public struct Iterator: AsyncIteratorProtocol {
     @usableFromInline
     var baseIterator: Base.AsyncIterator
 
     @usableFromInline
     let transform: (Base.Element) async -> Transformed
 
-    @usableFromInline
+    @inlinable
     init(
       _ baseIterator: Base.AsyncIterator, 
       transform: @escaping (Base.Element) async -> Transformed

stdlib/public/Concurrency/AsyncPrefixSequence.swift

@@ -49,14 +49,15 @@ extension AsyncSequence {
 /// An asynchronous sequence, up to a specified maximum length,
 /// containing the initial elements of a base asynchronous sequence.
 @available(SwiftStdlib 5.5, *)
+@frozen
 public struct AsyncPrefixSequence<Base: AsyncSequence> {
   @usableFromInline
   let base: Base
 
   @usableFromInline
   let count: Int
 
-  @usableFromInline
+  @inlinable
   init(_ base: Base, count: Int) {
     self.base = base
     self.count = count
@@ -74,14 +75,15 @@ extension AsyncPrefixSequence: AsyncSequence {
   public typealias AsyncIterator = Iterator
 
   /// The iterator that produces elements of the prefix sequence.
+  @frozen
   public struct Iterator: AsyncIteratorProtocol {
     @usableFromInline
     var baseIterator: Base.AsyncIterator
 
     @usableFromInline
     var remaining: Int
 
-    @usableFromInline
+    @inlinable
     init(_ baseIterator: Base.AsyncIterator, count: Int) {
       self.baseIterator = baseIterator
       self.remaining = count

stdlib/public/Concurrency/AsyncPrefixWhileSequence.swift

@@ -49,14 +49,15 @@ extension AsyncSequence {
 /// An asynchronous sequence, containing the initial, consecutive
 /// elements of the base sequence that satisfy a given predicate.
 @available(SwiftStdlib 5.5, *)
+@frozen
 public struct AsyncPrefixWhileSequence<Base: AsyncSequence> {
   @usableFromInline
   let base: Base
 
   @usableFromInline
   let predicate: (Base.Element) async -> Bool
 
-  @usableFromInline
+  @inlinable
   init(
     _ base: Base, 
     predicate: @escaping (Base.Element) async -> Bool
@@ -77,6 +78,7 @@ extension AsyncPrefixWhileSequence: AsyncSequence {
   public typealias AsyncIterator = Iterator
 
   /// The iterator that produces elements of the prefix-while sequence.
+  @frozen
   public struct Iterator: AsyncIteratorProtocol {
     @usableFromInline
     var predicateHasFailed = false
@@ -87,7 +89,7 @@ extension AsyncPrefixWhileSequence: AsyncSequence {
     @usableFromInline
     let predicate: (Base.Element) async -> Bool
 
-    @usableFromInline
+    @inlinable
     init(
       _ baseIterator: Base.AsyncIterator, 
       predicate: @escaping (Base.Element) async -> Bool

stdlib/public/Concurrency/AsyncThrowingCompactMapSequence.swift

@@ -68,14 +68,15 @@ extension AsyncSequence {
 /// An asynchronous sequence that maps an error-throwing closure over the base
 /// sequence’s elements, omitting results that don't return a value.
 @available(SwiftStdlib 5.5, *)
+@frozen
 public struct AsyncThrowingCompactMapSequence<Base: AsyncSequence, ElementOfResult> {
   @usableFromInline
   let base: Base
 
   @usableFromInline
   let transform: (Base.Element) async throws -> ElementOfResult?
 
-  @usableFromInline
+  @inlinable
   init(
     _ base: Base, 
     transform: @escaping (Base.Element) async throws -> ElementOfResult?
@@ -96,6 +97,7 @@ extension AsyncThrowingCompactMapSequence: AsyncSequence {
   public typealias AsyncIterator = Iterator
 
   /// The iterator that produces elements of the compact map sequence.
+  @frozen
   public struct Iterator: AsyncIteratorProtocol {
     public typealias Element = ElementOfResult
 
@@ -108,7 +110,7 @@ extension AsyncThrowingCompactMapSequence: AsyncSequence {
     @usableFromInline
     var finished = false
 
-    @usableFromInline
+    @inlinable
     init(
       _ baseIterator: Base.AsyncIterator, 
       transform: @escaping (Base.Element) async throws -> ElementOfResult?

stdlib/public/Concurrency/AsyncThrowingDropWhileSequence.swift

@@ -66,14 +66,15 @@ extension AsyncSequence {
 /// given error-throwing closure returns false, after which it passes through
 /// all remaining elements.
 @available(SwiftStdlib 5.5, *)
+@frozen
 public struct AsyncThrowingDropWhileSequence<Base: AsyncSequence> {
   @usableFromInline
   let base: Base
 
   @usableFromInline
   let predicate: (Base.Element) async throws -> Bool
 
-  @usableFromInline
+  @inlinable
   init(
     _ base: Base, 
     predicate: @escaping (Base.Element) async throws -> Bool
@@ -94,6 +95,7 @@ extension AsyncThrowingDropWhileSequence: AsyncSequence {
   public typealias AsyncIterator = Iterator
 
   /// The iterator that produces elements of the drop-while sequence.
+  @frozen
   public struct Iterator: AsyncIteratorProtocol {
     @usableFromInline
     var baseIterator: Base.AsyncIterator
@@ -107,7 +109,7 @@ extension AsyncThrowingDropWhileSequence: AsyncSequence {
     @usableFromInline
     var doneDropping = false
 
-    @usableFromInline
+    @inlinable
     init(
       _ baseIterator: Base.AsyncIterator, 
       predicate: @escaping (Base.Element) async throws -> Bool