stdlib: Adopt @_disallowFeatureSuppression(NoncopyableGenerics2).

This prevents some re-declaration errors when building the standard library
from its `.swiftinterface` with older compilers.

Author: tshortli

stdlib/public/core/Optional.swift

@@ -213,20 +213,22 @@ extension Optional where Wrapped: ~Copyable {
     }
   }
 
-#if hasFeature(BorrowingSwitch)
   // FIXME(NCG): Make this public.
   @_alwaysEmitIntoClient
   public borrowing func _borrowingMap<U: ~Copyable, E: Error>(
     _ transform: (borrowing Wrapped) throws(E) -> U
   ) throws(E) -> U? {
+    #if $NoncopyableGenerics2
     switch self {
     case .some(_borrowing y):
       return .some(try transform(y))
     case .none:
       return .none
     }
+    #else
+    fatalError("unsupported compiler")
+    #endif
   }
-#endif
 }
 
 extension Optional {
@@ -263,6 +265,7 @@ extension Optional {
   }
 }
 
+@_disallowFeatureSuppression(NoncopyableGenerics2)
 extension Optional where Wrapped: ~Copyable {
   // FIXME(NCG): Make this public.
   @_alwaysEmitIntoClient
@@ -277,7 +280,6 @@ extension Optional where Wrapped: ~Copyable {
     }
   }
 
-#if hasFeature(BorrowingSwitch)
   // FIXME(NCG): Make this public.
   @_alwaysEmitIntoClient
   public func _borrowingFlatMap<U: ~Copyable, E: Error>(
@@ -290,7 +292,6 @@ extension Optional where Wrapped: ~Copyable {
       return .none
     }
   }
-#endif
 }
 
 extension Optional {
@@ -546,7 +547,6 @@ public struct _OptionalNilComparisonType: ExpressibleByNilLiteral {
   }
 }
 
-#if hasFeature(BorrowingSwitch)
 extension Optional where Wrapped: ~Copyable {
   /// Returns a Boolean value indicating whether an argument matches `nil`.
   ///
@@ -735,9 +735,6 @@ extension Optional where Wrapped: ~Copyable {
     }
   }
 }
-#else
-#error("FIXME(NCG): Fill this out.")
-#endif
 
 /// Performs a nil-coalescing operation, returning the wrapped value of an
 /// `Optional` instance or a default value.

stdlib/public/core/Result.swift

@@ -61,6 +61,7 @@ extension Result {
   }
 }
 
+@_disallowFeatureSuppression(NoncopyableGenerics2)
 extension Result where Success: ~Copyable {
   // FIXME(NCG): Make this public.
   @_alwaysEmitIntoClient
@@ -75,7 +76,6 @@ extension Result where Success: ~Copyable {
     }
   }
 
-#if $BorrowingSwitch
   // FIXME(NCG): Make this public.
   @_alwaysEmitIntoClient
   public borrowing func _borrowingMap<NewSuccess: ~Copyable>(
@@ -88,7 +88,6 @@ extension Result where Success: ~Copyable {
       return .failure(failure)
     }
   }
-#endif
 }
 
 extension Result where Success: ~Copyable {
@@ -131,6 +130,7 @@ extension Result where Success: ~Copyable {
   }
 }
 
+@_disallowFeatureSuppression(NoncopyableGenerics2)
 extension Result {
   @_spi(SwiftStdlibLegacyABI) @available(swift, obsoleted: 1)
   @usableFromInline
@@ -186,6 +186,7 @@ extension Result {
   }
 }
 
+@_disallowFeatureSuppression(NoncopyableGenerics2)
 extension Result where Success: ~Copyable {
   // FIXME(NCG): Make this public.
   @_alwaysEmitIntoClient
@@ -200,7 +201,6 @@ extension Result where Success: ~Copyable {
     }
   }
 
-#if $BorrowingSwitch
   // FIXME(NCG): Make this public.
   @_alwaysEmitIntoClient
   public borrowing func _borrowingFlatMap<NewSuccess: ~Copyable>(
@@ -213,7 +213,6 @@ extension Result where Success: ~Copyable {
       return .failure(failure)
     }
   }
-#endif
 }
 
 extension Result {

stdlib/public/core/UnsafeBufferPointer.swift.gyb

@@ -456,6 +456,7 @@ extension Unsafe${Mutable}BufferPointer where Element: ~Copyable {
 
 }
 
+@_disallowFeatureSuppression(NoncopyableGenerics2)
 extension Unsafe${Mutable}BufferPointer {
   /// Accesses the element at the specified position.
   ///

stdlib/public/core/UnsafePointer.swift

@@ -286,6 +286,7 @@ extension UnsafePointer where Pointee: ~Copyable {
   }
 }
 
+@_disallowFeatureSuppression(NoncopyableGenerics2)
 extension UnsafePointer {
   // This preserves the ABI of the original (pre-6.0) `pointee` property that
   // used to export a getter. The current one above would export a read
@@ -315,6 +316,7 @@ extension UnsafePointer where Pointee: ~Copyable {
   }
 }
 
+@_disallowFeatureSuppression(NoncopyableGenerics2)
 extension UnsafePointer {
   // This preserves the ABI of the original (pre-6.0) subscript that used to
   // export a getter. The current one above would export a read accessor, if it
@@ -843,6 +845,7 @@ extension UnsafeMutablePointer where Pointee: ~Copyable {
   }
 }
 
+@_disallowFeatureSuppression(NoncopyableGenerics2)
 extension UnsafeMutablePointer {
   // This preserves the ABI of the original (pre-6.0) `pointee` property that
   // used to export a getter. The current one above would export a read
@@ -1300,6 +1303,7 @@ extension UnsafeMutablePointer where Pointee: ~Copyable {
   }
 }
 
+@_disallowFeatureSuppression(NoncopyableGenerics2)
 extension UnsafeMutablePointer {
   // This preserves the ABI of the original (pre-6.0) subscript that used to
   // export a getter. The current one above would export a read accessor, if it

test/ModuleInterface/Inputs/NoncopyableGenerics_Misc.swift

@@ -109,3 +109,6 @@ public func old_swap<T: ~Copyable>(_ a: inout T, _ b: inout T) {}
 
 @_preInverseGenerics
 public func borrowsNoncopyable<T: ~Copyable>(_ t: borrowing T) {}
+
+@_disallowFeatureSuppression(NoncopyableGenerics2)
+public func suppressesNoncopyableGenerics<T: ~Copyable>(_ t: borrowing T) {}

test/ModuleInterface/noncopyable_generics.swift

@@ -156,6 +156,11 @@ import NoncopyableGenerics_Misc
 // CHECK-MISC-NEXT: public func borrowsNoncopyable<T>(_ t: T)
 // CHECK-MISC-NEXT: #endif
 
+// CHECK-MISC: #if compiler(>=5.3) && $NoncopyableGenerics2
+// CHECK-MISC-NEXT: public func suppressesNoncopyableGenerics<T>(_ t: borrowing T) where T : ~Copyable
+// CHECK-MISC-NEXT: #endif
+
+
 import Swiftskell
 
 // CHECK: #if compiler(>=5.3) && $NoncopyableGenerics2