stdlib: simplify the '+=' singature for arrays

Author: gribozavr

stdlib/public/core/Arrays.swift.gyb

@@ -1014,10 +1014,8 @@ extension ${Self} {
 // a `+=` operator on `RangeReplaceableCollection`.
 /// Append the contents of `rhs` to `lhs`.
 public func += <
-  Element, S : Sequence
-  where
-  S.Iterator.Element == Element
->(lhs: inout ${Self}<Element>, rhs: S) {
+  S : Sequence
+>(lhs: inout ${Self}<S.Iterator.Element>, rhs: S) {
   let oldCount = lhs.count
   let capacity = lhs.capacity
   let newCount = oldCount + rhs.underestimatedCount
@@ -1033,10 +1031,8 @@ public func += <
 // a `+=` operator on `RangeReplaceableCollection`.
 /// Append the contents of `rhs` to `lhs`.
 public func += <
-  Element, C : Collection
-  where
-  C.Iterator.Element == Element
->(lhs: inout ${Self}<Element>, rhs: C) {
+  C : Collection
+>(lhs: inout ${Self}<C.Iterator.Element>, rhs: C) {
   let rhsCount = numericCast(rhs.count) as Int
 
   let oldCount = lhs.count

test/Misc/misc_diagnostics.swift

@@ -99,14 +99,11 @@ func test17875634() {
   var col = 2
   var coord = (row, col)
 
-  match += (1, 2) // expected-error{{binary operator '+=' cannot be applied to operands of type '[(Int, Int)]' and '(Int, Int)'}}
-  // expected-note @-1 {{overloads for '+=' exist with these partially matching parameter lists:}}
-  
-  match += (row, col) // expected-error{{binary operator '+=' cannot be applied to operands of type '[(Int, Int)]' and '(Int, Int)'}}
-  // expected-note @-1 {{overloads for '+=' exist with these partially matching parameter lists:}}
-
-  match += coord // expected-error{{binary operator '+=' cannot be applied to operands of type '[(Int, Int)]' and '(Int, Int)'}}
-  // expected-note @-1 {{overloads for '+=' exist with these partially matching parameter lists:}}
+  match += (1, 2) // expected-error{{argument type '(Int, Int)' does not conform to expected type 'Sequence'}}
+
+  match += (row, col) // expected-error{{argument type '(@lvalue Int, @lvalue Int)' does not conform to expected type 'Sequence'}}
+
+  match += coord // expected-error{{argument type '@lvalue (Int, Int)' does not conform to expected type 'Sequence'}}
 
   match.append(row, col) // expected-error{{extra argument in call}}