[temporary] disable small-string support

Author: glessard

stdlib/public/core/StringUTF8View.swift

@@ -89,7 +89,6 @@ extension String {
   ///     print(String(s1.utf8.prefix(15))!)
   ///     // Prints "They call me 'B"
   @frozen
-  @_addressableForDependencies
   public struct UTF8View: Sendable {
     @usableFromInline
     internal var _guts: _StringGuts
@@ -341,10 +340,7 @@ extension String.UTF8View {
 #endif
       let count = _guts.count
       if _guts.isSmall {
-        let a = Builtin.addressOfBorrow(self)
-        let address = unsafe UnsafePointer<UTF8.CodeUnit>(a)
-        let span = unsafe Span(_unsafeStart: address, count: count)
-        return unsafe _overrideLifetime(span, borrowing: self)
+        fatalError("Span over the small string form is not supported yet.")
       }
       _precondition(_guts.isFastUTF8)
       let buffer = unsafe _guts._object.fastUTF8

stdlib/public/core/Substring.swift

@@ -630,7 +630,6 @@ extension Substring: LosslessStringConvertible {
 
 extension Substring {
   @frozen
-  @_addressableForDependencies
   public struct UTF8View: Sendable {
     @usableFromInline
     internal var _slice: Slice<String.UTF8View>
@@ -771,11 +770,7 @@ extension Substring.UTF8View {
       let first = _slice._startIndex._encodedOffset
       let end = _slice._endIndex._encodedOffset
       if _wholeGuts.isSmall {
-        let a = Builtin.addressOfBorrow(self)
-        let offset = first &+ (2 &* MemoryLayout<String.Index>.stride)
-        let start = unsafe UnsafePointer<UTF8.CodeUnit>(a).advanced(by: offset)
-        let span = unsafe Span(_unsafeStart: start, count: end &- first)
-        return unsafe _overrideLifetime(span, borrowing: self)
+        fatalError("Span over the small string form is not supported yet.")
       }
       _internalInvariant(_wholeGuts.isFastUTF8)
       let buffer = unsafe _wholeGuts._object.fastUTF8.extracting(

test/stdlib/Span/StringUTF8SpanProperty.swift

@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-// RUN: %target-run-stdlib-swift(-enable-experimental-feature LifetimeDependence -enable-experimental-feature Span -enable-experimental-feature AddressableTypes)
+// RUN: %target-run-stdlib-swift(-enable-experimental-feature LifetimeDependence -enable-experimental-feature AddressableTypes)
 
 // REQUIRES: executable_test
 
@@ -25,6 +25,7 @@ suite.test("Span from Small String")
 
   let s = "A small string.".utf8
   let u = Array(s)
+  expectCrashLater()
   let span = s.span
 
   let count = span.count
@@ -57,6 +58,7 @@ suite.test("Span from Small String's Substring")
 
   let s = "A small string.".dropFirst(8).utf8
   let u = Array("string.".utf8)
+  expectCrashLater()
   let span = s.span
 
   let count = span.count