Merge pull request #15120 from airspeedswift/only-yoouuuuuuuuu (#16225)

Author: airspeedswift

stdlib/public/core/SequenceAlgorithms.swift

@@ -488,6 +488,21 @@ extension Sequence {
     }
     return false
   }
+
+  /// Returns a Boolean value indicating whether every element of a sequence
+  /// satisfies a given predicate.
+  ///
+  /// - Parameter predicate: A closure that takes an element of the sequence
+  ///   as its argument and returns a Boolean value that indicates whether
+  ///   the passed element satisfies a condition.
+  /// - Returns: `true` if the sequence contains only elements that satisfy
+  ///   `predicate`; otherwise, `false`.
+  @inlinable
+  public func allSatisfy(
+    _ predicate: (Element) throws -> Bool
+  ) rethrows -> Bool {
+    return try !contains { try !predicate($0) }
+  }
 }
 
 extension Sequence where Element : Equatable {

validation-test/stdlib/SequenceType.swift.gyb

@@ -614,6 +614,20 @@ SequenceTypeTests.test("contains/Predicate") {
   }
 }
 
+SequenceTypeTests.test("allSatisfy/Predicate") {
+  for test in findTests {
+    let s = MinimalSequence<OpaqueValue<Int>>(
+      elements: test.sequence.map { OpaqueValue($0.value) })
+    expectEqual(
+      test.expected == nil,
+      s.allSatisfy { $0.value != test.element.value },
+      stackTrace: SourceLocStack().with(test.loc))
+    expectEqual(
+      test.expectedLeftoverSequence.map { $0.value }, s.map { $0.value },
+      stackTrace: SourceLocStack().with(test.loc))
+  }
+}
+
 //===----------------------------------------------------------------------===//
 // reduce()
 //===----------------------------------------------------------------------===//