Merge pull request #81289 from DougGregor/mutablespan-older-compilers

Fix issue with older compilers not handling MutableSpan code

Author: DougGregor

stdlib/public/core/Span/MutableRawSpan.swift

@@ -588,10 +588,14 @@ extension MutableRawSpan {
   @_alwaysEmitIntoClient
   @lifetime(&self)
   mutating public func extracting(first maxLength: Int) -> Self {
+#if compiler(>=5.3) && hasFeature(SendableCompletionHandlers)
     _precondition(maxLength >= 0, "Can't have a prefix of negative length")
     let newCount = min(maxLength, byteCount)
     let newSpan = unsafe Self(_unchecked: _pointer, byteCount: newCount)
     return unsafe _overrideLifetime(newSpan, mutating: &self)
+#else
+    fatalError("Unsupported compiler")
+#endif
   }
 
   /// Returns a span over all but the given number of trailing elements.
@@ -611,11 +615,15 @@ extension MutableRawSpan {
   @_alwaysEmitIntoClient
   @lifetime(&self)
   mutating public func extracting(droppingLast k: Int) -> Self {
+#if compiler(>=5.3) && hasFeature(SendableCompletionHandlers)
     _precondition(k >= 0, "Can't drop a negative number of elements")
     let droppedCount = min(k, byteCount)
     let newCount = byteCount &- droppedCount
     let newSpan = unsafe Self(_unchecked: _pointer, byteCount: newCount)
     return unsafe _overrideLifetime(newSpan, mutating: &self)
+#else
+    fatalError("Unsupported compiler")
+#endif
   }
 
   /// Returns a span containing the final elements of the span,
@@ -660,11 +668,15 @@ extension MutableRawSpan {
   @_alwaysEmitIntoClient
   @lifetime(&self)
   mutating public func extracting(droppingFirst k: Int) -> Self {
+#if compiler(>=5.3) && hasFeature(SendableCompletionHandlers)
     _precondition(k >= 0, "Can't drop a negative number of bytes")
     let droppedCount = min(k, byteCount)
     let newStart = unsafe _pointer?.advanced(by: droppedCount)
     let newCount = byteCount &- droppedCount
     let newSpan = unsafe Self(_unchecked: newStart, byteCount: newCount)
     return unsafe _overrideLifetime(newSpan, mutating: &self)
+#else
+    fatalError("Unsupported compiler")
+#endif
   }
 }

stdlib/public/core/Span/MutableSpan.swift

@@ -825,10 +825,14 @@ extension MutableSpan where Element: ~Copyable {
   @_alwaysEmitIntoClient
   @lifetime(&self)
   mutating public func extracting(first maxLength: Int) -> Self {
+#if compiler(>=5.3) && hasFeature(SendableCompletionHandlers)
     _precondition(maxLength >= 0, "Can't have a prefix of negative length")
     let newCount = min(maxLength, count)
     let newSpan = unsafe Self(_unchecked: _pointer, count: newCount)
     return unsafe _overrideLifetime(newSpan, mutating: &self)
+#else
+    fatalError("Unsupported compiler")
+#endif
   }
 
   /// Returns a span over all but the given number of trailing elements.
@@ -848,11 +852,15 @@ extension MutableSpan where Element: ~Copyable {
   @_alwaysEmitIntoClient
   @lifetime(&self)
   mutating public func extracting(droppingLast k: Int) -> Self {
+#if compiler(>=5.3) && hasFeature(SendableCompletionHandlers)
     _precondition(k >= 0, "Can't drop a negative number of elements")
     let droppedCount = min(k, count)
     let newCount = count &- droppedCount
     let newSpan = unsafe Self(_unchecked: _pointer, count: newCount)
     return unsafe _overrideLifetime(newSpan, mutating: &self)
+#else
+    fatalError("Unsupported compiler")
+#endif
   }
 
   /// Returns a span containing the final elements of the span,
@@ -873,12 +881,16 @@ extension MutableSpan where Element: ~Copyable {
   @_alwaysEmitIntoClient
   @lifetime(&self)
   mutating public func extracting(last maxLength: Int) -> Self {
+#if compiler(>=5.3) && hasFeature(SendableCompletionHandlers)
     _precondition(maxLength >= 0, "Can't have a suffix of negative length")
     let newCount = min(maxLength, count)
     let offset = (count &- newCount) * MemoryLayout<Element>.stride
     let newStart = unsafe _pointer?.advanced(by: offset)
     let newSpan = unsafe Self(_unchecked: newStart, count: newCount)
     return unsafe _overrideLifetime(newSpan, mutating: &self)
+#else
+    fatalError("Unsupported compiler")
+#endif
   }
 
   /// Returns a span over all but the given number of initial elements.
@@ -898,12 +910,16 @@ extension MutableSpan where Element: ~Copyable {
   @_alwaysEmitIntoClient
   @lifetime(&self)
   mutating public func extracting(droppingFirst k: Int) -> Self {
+#if compiler(>=5.3) && hasFeature(SendableCompletionHandlers)
     _precondition(k >= 0, "Can't drop a negative number of elements")
     let droppedCount = min(k, count)
     let offset = droppedCount * MemoryLayout<Element>.stride
     let newStart = unsafe _pointer?.advanced(by: offset)
     let newCount = count &- droppedCount
     let newSpan = unsafe Self(_unchecked: newStart, count: newCount)
     return unsafe _overrideLifetime(newSpan, mutating: &self)
+#else
+    fatalError("Unsupported compiler")
+#endif
   }
 }