Mop up remaining "better expressed as a where clause" warnings

Author: airspeedswift

benchmark/single-source/PopFrontGeneric.swift

@@ -19,8 +19,6 @@ let arrayCount = 1024
 // being really slow).
 @_versioned
 protocol MyArrayBufferProtocol : MutableCollection, RandomAccessCollection {
-  associatedtype Element
-
   mutating func myReplace<C>(
     _ subRange: Range<Int>,
     with newValues: C

stdlib/public/core/ArrayBufferProtocol.swift

@@ -21,9 +21,6 @@ internal protocol _ArrayBufferProtocol
   : RandomAccessCollection 
     = CountableRange<Int>
 
-  /// The type of elements stored in the buffer.
-  associatedtype Element
-
   /// Create an empty buffer.
   init()
 

stdlib/public/core/SetAlgebra.swift

@@ -409,28 +409,6 @@ extension SetAlgebra {
     for e in sequence { insert(e) }
   }
 
-  /// Creates a set containing the elements of the given array literal.
-  ///
-  /// Do not call this initializer directly. It is used by the compiler when
-  /// you use an array literal. Instead, create a new set using an array
-  /// literal as its value by enclosing a comma-separated list of values in
-  /// square brackets. You can use an array literal anywhere a set is expected
-  /// by the type context.
-  ///
-  /// Here, a set of strings is created from an array literal holding only
-  /// strings:
-  ///
-  ///     let ingredients: Set = ["cocoa beans", "sugar", "cocoa butter", "salt"]
-  ///     if ingredients.isSuperset(of: ["sugar", "salt"]) {
-  ///         print("Whatever it is, it's bound to be delicious!")
-  ///     }
-  ///     // Prints "Whatever it is, it's bound to be delicious!"
-  ///
-  /// - Parameter arrayLiteral: A list of elements of the new set.
-  public init(arrayLiteral: Element...) {
-    self.init(arrayLiteral)
-  }
-
   /// Removes the elements of the given set from this set.
   ///
   /// In the following example, the elements of the `employees` set that are
@@ -571,6 +549,30 @@ extension SetAlgebra {
   }
 }
 
+extension SetAlgebra where Element == ArrayLiteralElement {
+  /// Creates a set containing the elements of the given array literal.
+  ///
+  /// Do not call this initializer directly. It is used by the compiler when
+  /// you use an array literal. Instead, create a new set using an array
+  /// literal as its value by enclosing a comma-separated list of values in
+  /// square brackets. You can use an array literal anywhere a set is expected
+  /// by the type context.
+  ///
+  /// Here, a set of strings is created from an array literal holding only
+  /// strings:
+  ///
+  ///     let ingredients: Set = ["cocoa beans", "sugar", "cocoa butter", "salt"]
+  ///     if ingredients.isSuperset(of: ["sugar", "salt"]) {
+  ///         print("Whatever it is, it's bound to be delicious!")
+  ///     }
+  ///     // Prints "Whatever it is, it's bound to be delicious!"
+  ///
+  /// - Parameter arrayLiteral: A list of elements of the new set.
+  public init(arrayLiteral: Element...) {
+    self.init(arrayLiteral)
+  }  
+}
+
 @available(*, unavailable, renamed: "SetAlgebra")
 public typealias SetAlgebraType = SetAlgebra