[ABI] [stdlib] Remove magnitude-based overload of abs(_:).

stdlib/public/core/Integers.swift

@@ -318,17 +318,6 @@ extension SignedNumeric {
   }
 }
 
-
-/// Returns the absolute value of the given number.
-///
-/// - Parameter x: A signed number.
-/// - Returns: The absolute value of `x`.
-@inlinable
-public func abs<T : SignedNumeric>(_ x: T) -> T
-  where T.Magnitude == T {
-  return x.magnitude
-}
-
 /// Returns the absolute value of the given number.
 ///
 /// The absolute value of `x` must be representable in the same type. In
@@ -344,6 +333,10 @@ public func abs<T : SignedNumeric>(_ x: T) -> T
 /// - Returns: The absolute value of `x`.
 @inlinable
 public func abs<T : SignedNumeric & Comparable>(_ x: T) -> T {
+  if T.self == T.Magnitude.self {
+    return unsafeBitCast(x.magnitude, to: T.self)
+  }
+
   return x < (0 as T) ? -x : x
 }
 

test/SourceKit/CodeComplete/complete_moduleimportdepth.swift

@@ -23,18 +23,6 @@ func test() {
 // CHECK:        key.modulename: "Swift"
 // CHECK-NEXT: },
 
-// CHECK-LABEL:  key.name: "abs(:)",
-// CHECK-NEXT:   key.sourcetext: "abs(<#T##x: Comparable & SignedNumeric##Comparable & SignedNumeric#>)",
-// CHECK-NEXT:   key.description: "abs(x: Comparable & SignedNumeric)",
-// CHECK-NEXT:   key.typename: "Comparable & SignedNumeric",
-// CHECK-NEXT:   key.doc.brief: "Returns the absolute value of the given number.",
-// CHECK-NEXT:   key.context: source.codecompletion.context.othermodule,
-// CHECK-NEXT:   key.moduleimportdepth: 1,
-// CHECK-NEXT:   key.num_bytes_to_erase: 0,
-// CHECK-NOT:    key.modulename
-// CHECK:        key.modulename: "Swift"
-// CHECK-NEXT: },
-
 // FooHelper.FooHelperExplicit == 1
 // CHECK-LABEL:  key.name: "fooHelperExplicitFrameworkFunc1(:)",
 // CHECK-NEXT:   key.sourcetext: "fooHelperExplicitFrameworkFunc1(<#T##a: Int32##Int32#>)",

test/api-digester/Outputs/stability-stdlib-abi.swift.expected

@@ -17,6 +17,7 @@ Func _int64ToStringImpl(_:_:_:_:_:) has been removed
 Func _uint64ToStringImpl(_:_:_:_:_:) has been removed
 Func _typeByMangledName(_:substitutions:) has been removed
 Func _withUninitializedString(_:) has been removed
+Func abs(_:) has been removed
 
 Func Optional.unwrappedOrError() has been removed
 Struct _UnwrappingFailed has been removed

test/api-digester/Outputs/stability-stdlib-source.swift.expected

@@ -97,6 +97,7 @@ Func UnsafeMutableRawPointer.copyBytes(from:count:) has been removed (deprecated
 Func UnsafeMutableRawPointer.deallocate(bytes:alignedTo:) has been removed (deprecated)
 Func UnsafeMutableRawPointer.initializeMemory(as:at:count:to:) has been removed (deprecated)
 Func UnsafeMutableRawPointer.initializeMemory(as:from:) has been removed (deprecated)
+Func abs(_:) has been removed
 Protocol Collection has generic signature change from <Self : Sequence, Self.Index : Comparable, Self.Index == Self.Indices.Element, Self.Indices : Collection, Self.Indices == Self.Indices.SubSequence, Self.SubSequence : Collection, Self.Indices.Element == Self.Indices.Index, Self.Indices.Index == Self.SubSequence.Index, Self.SubSequence.Index == Self.Indices.Indices.Element, Self.Indices.Indices.Element == Self.Indices.Indices.Index, Self.Indices.Indices.Index == Self.SubSequence.Indices.Element, Self.SubSequence.Indices.Element == Self.SubSequence.Indices.Index, Self.SubSequence.Indices.Index == Self.SubSequence.Indices.Indices.Element, Self.SubSequence.Indices.Indices.Element == Self.SubSequence.Indices.Indices.Index> to <Self : Sequence, Self.Element == Self.SubSequence.Element, Self.Index : Comparable, Self.Index == Self.Indices.Element, Self.Indices : Collection, Self.Indices == Self.Indices.SubSequence, Self.SubSequence : Collection, Self.SubSequence == Self.SubSequence.SubSequence, Self.Indices.Element == Self.Indices.Index, Self.Indices.Index == Self.SubSequence.Index, Self.SubSequence.Index == Self.Indices.Indices.Element, Self.Indices.Indices.Element == Self.Indices.Indices.Index, Self.Indices.Indices.Index == Self.SubSequence.Indices.Element, Self.SubSequence.Indices.Element == Self.SubSequence.Indices.Index, Self.SubSequence.Indices.Index == Self.SubSequence.Indices.Indices.Element, Self.SubSequence.Indices.Indices.Element == Self.SubSequence.Indices.Indices.Index>
 Protocol Sequence has generic signature change from <Self.Element == Self.Iterator.Element, Self.Iterator : IteratorProtocol, Self.SubSequence : Sequence, Self.SubSequence == Self.SubSequence.SubSequence, Self.Iterator.Element == Self.SubSequence.Element, Self.SubSequence.Element == Self.SubSequence.Iterator.Element> to <Self.Element == Self.Iterator.Element, Self.Iterator : IteratorProtocol>
 Protocol _SequenceWrapper has been removed

test/stdlib/FloatingPoint.swift.gyb

@@ -413,6 +413,11 @@ extension FloatingPoint {
   public var isQuietNaN: Bool { return isNaN && !isSignalingNaN }
 }
 
+func genericAbs<T: SignedNumeric & Comparable>(_ x: T) -> T {
+  return abs(x)
+}
+
+
 %for Self in ['Float', 'Double', 'Float80']:
 % if Self == 'Float80':
 #if !os(Windows) && (arch(i386) || arch(x86_64))
@@ -533,6 +538,12 @@ FloatingPoint.test("${Self}.significandWidth") {
   expectEqual(0, ${Self}(2).significandWidth)
   expectEqual(1, ${Self}(3).significandWidth)
 }
+
+FloatingPoint.test("${Self}.absNegativeZero") {
+  expectEqual(abs(${Self}(-0.0)), ${Self}(0.0))
+  expectEqual(genericAbs(${Self}(-0.0)), ${Self}(0.0))
+}
+
 % if Self == 'Float80':
 #endif
 % end

test/stdlib/IntegerCompatibility.swift

@@ -55,3 +55,9 @@ func sr5176(description: String = "unambiguous Int32.init(bitPattern:)") {
 func sr6634(x: UnsafeBufferPointer<UInt8>) -> Int {
   return x.lazy.filter { $0 > 127 || $0 == 0 }.count // should be unambiguous
 }
+
+// abs of an integer literal
+func returnIntAbs() -> Int {
+  let x = abs(-8)
+  return x
+}