[stdlib] Unchecked bounds are unsafe

stdlib/public/core/ClosedRange.swift

@@ -70,6 +70,7 @@ public struct ClosedRange<Bound: Comparable> {
 
   // This works around _debugPrecondition() impacting the performance of
   // optimized code. (rdar://72246338)
+  @unsafe
   @_alwaysEmitIntoClient @inline(__always)
   internal init(_uncheckedBounds bounds: (lower: Bound, upper: Bound)) {
     self.lowerBound = bounds.lower
@@ -89,7 +90,9 @@ public struct ClosedRange<Bound: Comparable> {
   public init(uncheckedBounds bounds: (lower: Bound, upper: Bound)) {
     _debugPrecondition(bounds.lower <= bounds.upper,
       "ClosedRange requires lowerBound <= upperBound")
-    self.init(_uncheckedBounds: (lower: bounds.lower, upper: bounds.upper))
+    unsafe self.init(
+      _uncheckedBounds: (lower: bounds.lower, upper: bounds.upper)
+    )
   }
 }
 
@@ -109,7 +112,7 @@ extension ClosedRange: RangeExpression {
   @inlinable // trivial-implementation
   public func relative<C: Collection>(to collection: C) -> Range<Bound>
   where C.Index == Bound {
-    return Range(
+    return unsafe Range(
       _uncheckedBounds: (
         lower: lowerBound,
         upper: collection.index(after: self.upperBound)))
@@ -405,7 +408,7 @@ extension Comparable {
   public static func ... (minimum: Self, maximum: Self) -> ClosedRange<Self> {
     _precondition(
       minimum <= maximum, "Range requires lowerBound <= upperBound")
-    return ClosedRange(_uncheckedBounds: (lower: minimum, upper: maximum))
+    return unsafe ClosedRange(_uncheckedBounds: (lower: minimum, upper: maximum))
   }
 }
 
@@ -496,7 +499,7 @@ extension ClosedRange {
       limits.upperBound < self.upperBound ? limits.upperBound
           : limits.lowerBound > self.upperBound ? limits.lowerBound
           : self.upperBound
-    return ClosedRange(_uncheckedBounds: (lower: lower, upper: upper))
+    return unsafe ClosedRange(_uncheckedBounds: (lower: lower, upper: upper))
   }
 }
 
@@ -512,7 +515,9 @@ extension ClosedRange where Bound: Strideable, Bound.Stride: SignedInteger {
   public init(_ other: Range<Bound>) {
     _precondition(!other.isEmpty, "Can't form an empty closed range")
     let upperBound = other.upperBound.advanced(by: -1)
-    self.init(_uncheckedBounds: (lower: other.lowerBound, upper: upperBound))
+    unsafe self.init(
+      _uncheckedBounds: (lower: other.lowerBound, upper: upperBound)
+    )
   }
 }
 
@@ -581,7 +586,7 @@ extension ClosedRange: Decodable where Bound: Decodable {
           codingPath: decoder.codingPath,
           debugDescription: "Cannot initialize \(ClosedRange.self) with a lowerBound (\(lowerBound)) greater than upperBound (\(upperBound))"))
     }
-    self.init(_uncheckedBounds: (lower: lowerBound, upper: upperBound))
+    unsafe self.init(_uncheckedBounds: (lower: lowerBound, upper: upperBound))
   }
 }
 

stdlib/public/core/InlineArray.swift

@@ -294,7 +294,7 @@ extension InlineArray where Element: ~Copyable {
   @_alwaysEmitIntoClient
   @_transparent
   public var indices: Range<Int> {
-    Range(_uncheckedBounds: (0, count))
+    unsafe Range(_uncheckedBounds: (0, count))
   }
 
   /// Returns the position immediately after the given index.

stdlib/public/core/Range.swift

@@ -159,6 +159,7 @@ public struct Range<Bound: Comparable> {
 
   // This works around _debugPrecondition() impacting the performance of
   // optimized code. (rdar://72246338)
+  @unsafe
   @_alwaysEmitIntoClient @inline(__always)
   internal init(_uncheckedBounds bounds: (lower: Bound, upper: Bound)) {
     self.lowerBound = bounds.lower
@@ -178,7 +179,9 @@ public struct Range<Bound: Comparable> {
   public init(uncheckedBounds bounds: (lower: Bound, upper: Bound)) {
     _debugPrecondition(bounds.lower <= bounds.upper,
       "Range requires lowerBound <= upperBound")
-    self.init(_uncheckedBounds: (lower: bounds.lower, upper: bounds.upper))
+    unsafe self.init(
+      _uncheckedBounds: (lower: bounds.lower, upper: bounds.upper)
+    )
   }
 
   /// Returns a Boolean value indicating whether the given element is contained
@@ -321,7 +324,9 @@ extension Range where Bound: Strideable, Bound.Stride: SignedInteger {
   @inlinable // trivial-implementation
   public init(_ other: ClosedRange<Bound>) {
     let upperBound = other.upperBound.advanced(by: 1)
-    self.init(_uncheckedBounds: (lower: other.lowerBound, upper: upperBound))
+    unsafe self.init(
+      _uncheckedBounds: (lower: other.lowerBound, upper: upperBound)
+    )
   }
 }
 
@@ -372,7 +377,7 @@ extension Range {
       limits.upperBound < self.upperBound ? limits.upperBound
           : limits.lowerBound > self.upperBound ? limits.lowerBound
           : self.upperBound
-    return Range(_uncheckedBounds: (lower: lower, upper: upper))
+    return unsafe Range(_uncheckedBounds: (lower: lower, upper: upper))
   }
 }
 
@@ -453,7 +458,7 @@ extension Range: Decodable where Bound: Decodable {
           codingPath: decoder.codingPath,
           debugDescription: "Cannot initialize \(Range.self) with a lowerBound (\(lowerBound)) greater than upperBound (\(upperBound))"))
     }
-    self.init(_uncheckedBounds: (lower: lowerBound, upper: upperBound))
+    unsafe self.init(_uncheckedBounds: (lower: lowerBound, upper: upperBound))
   }
 }
 
@@ -754,7 +759,7 @@ extension Comparable {
   public static func ..< (minimum: Self, maximum: Self) -> Range<Self> {
     _precondition(minimum <= maximum,
       "Range requires lowerBound <= upperBound")
-    return Range(_uncheckedBounds: (lower: minimum, upper: maximum))
+    return unsafe Range(_uncheckedBounds: (lower: minimum, upper: maximum))
   }
 
   /// Returns a partial range up to, but not including, its upper bound.
@@ -1123,7 +1128,7 @@ extension Range where Bound == String.Index {
     _internalInvariant(
       (lowerBound._canBeUTF8 && upperBound._canBeUTF8)
       || (lowerBound._canBeUTF16 && upperBound._canBeUTF16))
-    return Range<Int>(
+    return unsafe Range<Int>(
       _uncheckedBounds: (lowerBound._encodedOffset, upperBound._encodedOffset))
   }
 }

stdlib/public/core/Slice.swift

@@ -138,7 +138,7 @@ public struct Slice<Base: Collection> {
 
   @_alwaysEmitIntoClient @inline(__always)
   internal var _bounds: Range<Base.Index> {
-    Range(_uncheckedBounds: (_startIndex, _endIndex))
+    unsafe Range(_uncheckedBounds: (_startIndex, _endIndex))
   }
 }
 

stdlib/public/core/Span/RawSpan.swift

@@ -322,7 +322,7 @@ extension RawSpan {
   /// - Complexity: O(1)
   @_alwaysEmitIntoClient
   public var byteOffsets: Range<Int> {
-    .init(_uncheckedBounds: (0, byteCount))
+    unsafe Range(_uncheckedBounds: (0, byteCount))
   }
 }
 
@@ -629,13 +629,13 @@ extension RawSpan {
   public func byteOffsets(of other: borrowing Self) -> Range<Int>? {
     if other._count > _count { return nil }
     guard let spanStart = other._pointer, _count > 0 else {
-      return unsafe _pointer == other._pointer ? Range(_uncheckedBounds: (0, 0)) : nil
+      return unsafe _pointer == other._pointer ? 0..<0 : nil
     }
     let start = _start()
     let spanEnd = unsafe spanStart + other._count
     if unsafe spanStart < start || (start + _count) < spanEnd { return nil }
     let lower = unsafe start.distance(to: spanStart)
-    return Range(_uncheckedBounds: (lower, lower &+ other._count))
+    return unsafe Range(_uncheckedBounds: (lower, lower &+ other._count))
   }
 }
 

stdlib/public/core/Span/Span.swift

@@ -395,7 +395,7 @@ extension Span where Element: ~Copyable {
   /// - Complexity: O(1)
   @_alwaysEmitIntoClient
   public var indices: Range<Index> {
-    Range(_uncheckedBounds: (0, _count))
+    unsafe Range(_uncheckedBounds: (0, _count))
   }
 }
 
@@ -679,7 +679,7 @@ extension Span where Element: ~Copyable {
   public func indices(of other: borrowing Self) -> Range<Index>? {
     if other._count > _count { return nil }
     guard let spanStart = other._pointer, _count > 0 else {
-      return unsafe _pointer == other._pointer ? Range(_uncheckedBounds: (0, 0)) : nil
+      return unsafe _pointer == other._pointer ? 0..<0 : nil
     }
     let start = _start()
     let stride = MemoryLayout<Element>.stride
@@ -688,7 +688,7 @@ extension Span where Element: ~Copyable {
     let byteOffset = unsafe start.distance(to: spanStart)
     let (lower, r) = byteOffset.quotientAndRemainder(dividingBy: stride)
     guard r == 0 else { return nil }
-    return Range(_uncheckedBounds: (lower, lower &+ other._count))
+    return unsafe Range(_uncheckedBounds: (lower, lower &+ other._count))
   }
 }
 

stdlib/public/core/StringGraphemeBreaking.swift

@@ -599,7 +599,7 @@ extension Unicode {
       while i < buffer.endIndex {
         let (next, n) = unsafe _decodeScalar(buffer, startingAt: i)
         if hasBreak(before: next) {
-          return Range(_uncheckedBounds: (i, i &+ n))
+          return unsafe Range(_uncheckedBounds: (i, i &+ n))
         }
         i &+= n
       }

stdlib/public/core/StringGutsRangeReplaceable.swift

@@ -367,7 +367,7 @@ extension _StringGuts {
     let j = result._guts.count
     result.append(contentsOf: selfStr[bounds.upperBound...])
     self = result._guts
-    return Range(_uncheckedBounds: (i, j))
+    return unsafe Range(_uncheckedBounds: (i, j))
   }
 
   // - Returns: The encoded offset range of the replaced contents in the result.
@@ -421,7 +421,7 @@ extension _StringGuts {
     let j = result._guts.count
     result.append(contentsOf: selfStr[bounds.upperBound...])
     self = result._guts
-    return Range(_uncheckedBounds: (i, j))
+    return unsafe Range(_uncheckedBounds: (i, j))
   }
 
   // - Returns: The encoded offset range of the replaced contents in the result.
@@ -443,7 +443,7 @@ extension _StringGuts {
     updateNativeStorage {
       unsafe $0.replace(from: start, to: end, with: codeUnits)
     }
-    return Range(_uncheckedBounds: (start, start + codeUnits.count))
+    return unsafe Range(_uncheckedBounds: (start, start + codeUnits.count))
   }
 
   // - Returns: The encoded offset range of the replaced contents in the result.
@@ -468,7 +468,7 @@ extension _StringGuts {
       $0.replace(
         from: start, to: end, with: codeUnits, replacementCount: replCount)
     }
-    return Range(_uncheckedBounds: (start, start + replCount))
+    return unsafe Range(_uncheckedBounds: (start, start + replCount))
   }
 
   /// Run `body` to mutate the given `subrange` of this string within
@@ -540,9 +540,9 @@ extension _StringGuts {
     let oldRange = subrange._encodedOffsetRange
     let newRange = body(&self)
 
-    let oldBounds = Range(
+    let oldBounds = unsafe Range(
       _uncheckedBounds: (startIndex._encodedOffset, endIndex._encodedOffset))
-    let newBounds = Range(_uncheckedBounds: (
+    let newBounds = unsafe Range(_uncheckedBounds: (
         oldBounds.lowerBound,
         oldBounds.upperBound &+ newRange.count &- oldRange.count))
 

stdlib/public/core/StringGutsSlice.swift

@@ -24,7 +24,7 @@ internal struct _StringGutsSlice {
   @inline(__always)
   internal init(_ guts: _StringGuts) {
     self._guts = guts
-    self._offsetRange = Range(_uncheckedBounds: (0, guts.count))
+    self._offsetRange = unsafe Range(_uncheckedBounds: (0, guts.count))
   }
 
   @inline(__always)
@@ -74,7 +74,7 @@ internal struct _StringGutsSlice {
         ._scalarAligned
       let higher = String.Index(_encodedOffset: _offsetRange.upperBound)
         ._scalarAligned
-      return Range(_uncheckedBounds: (lower, higher))
+      return unsafe Range(_uncheckedBounds: (lower, higher))
     }
   }
 

stdlib/public/core/StringIndexValidation.swift

@@ -80,7 +80,7 @@ extension _StringGuts {
     _precondition(upper <= endIndex && lower <= upper,
       "String index range is out of bounds")
 
-    return Range(_uncheckedBounds: (lower, upper))
+    return unsafe Range(_uncheckedBounds: (lower, upper))
   }
 
   @_alwaysEmitIntoClient
@@ -102,7 +102,7 @@ extension _StringGuts {
       && upper <= bounds.upperBound,
       "Substring index range is out of bounds")
 
-    return Range(_uncheckedBounds: (lower, upper))
+    return unsafe Range(_uncheckedBounds: (lower, upper))
   }
 }
 
@@ -213,7 +213,7 @@ extension _StringGuts {
     }
 
     let r = validateSubscalarRange(range)
-    return Range(
+    return unsafe Range(
       _uncheckedBounds: (scalarAlign(r.lowerBound), scalarAlign(r.upperBound)))
   }
 
@@ -243,7 +243,7 @@ extension _StringGuts {
     let r = validateSubscalarRange(range, in: bounds)
     let upper = scalarAlign(r.upperBound)
     let lower = scalarAlign(r.lowerBound)
-    return Range(_uncheckedBounds: (lower, upper))
+    return unsafe Range(_uncheckedBounds: (lower, upper))
   }
 }
 
@@ -356,7 +356,7 @@ extension _StringGuts {
     _precondition(upper <= endIndex && lower <= upper,
       "String index range is out of bounds")
 
-    return Range(_uncheckedBounds: (lower, upper))
+    return unsafe Range(_uncheckedBounds: (lower, upper))
   }
 
   /// A version of `validateScalarRange` that only traps if the main executable
@@ -377,7 +377,7 @@ extension _StringGuts {
     }
 
     let r = validateSubscalarRange_5_7(range)
-    return Range(
+    return unsafe Range(
       _uncheckedBounds: (scalarAlign(r.lowerBound), scalarAlign(r.upperBound)))
   }
 

stdlib/public/core/StringProtocol.swift

@@ -153,7 +153,9 @@ extension StringProtocol {
       let end = endIndex
       _internalInvariant(
         start.transcodedOffset == 0 && end.transcodedOffset == 0)
-      return Range(_uncheckedBounds: (start._encodedOffset, end._encodedOffset))
+      return unsafe Range(
+        _uncheckedBounds: (start._encodedOffset, end._encodedOffset)
+      )
     }
   }
 

stdlib/public/core/StringRangeReplaceableCollection.swift

@@ -218,7 +218,7 @@ extension String: RangeReplaceableCollection {
   /// - Complexity: O(*n*), where *n* is the length of the string.
   public mutating func insert(_ newElement: Character, at i: Index) {
     let i = _guts.validateInclusiveScalarIndex(i)
-    let range = Range(_uncheckedBounds: (i, i))
+    let range = unsafe Range(_uncheckedBounds: (i, i))
     _guts.replaceSubrange(range, with: newElement._str)
   }
 
@@ -243,7 +243,7 @@ extension String: RangeReplaceableCollection {
     contentsOf newElements: S, at i: Index
   ) where S.Element == Character {
     let i = _guts.validateInclusiveScalarIndex(i)
-    let range = Range(_uncheckedBounds: (i, i))
+    let range = unsafe Range(_uncheckedBounds: (i, i))
     _guts.replaceSubrange(range, with: newElements)
   }
 

stdlib/public/core/StringStorageBridge.swift

@@ -54,7 +54,7 @@ extension _AbstractStringStorage {
     _precondition(aRange.location + aRange.length <= Int(count),
                   "Range out of bounds")
 
-    let range = Range(
+    let range = unsafe Range(
       _uncheckedBounds: (aRange.location, aRange.location+aRange.length))
     let str = asString
     unsafe str._copyUTF16CodeUnits(