Revert "Copy the code units into a temporary buffer in the invalid UTF8 handling path of String(unsafeUninitializedCapacity:initializingWith:) before calling a function which might invalidate the String's buffer. rdar://80379070"

This reverts commit 4bdc8e3.

Author: Catfish-Man

stdlib/public/core/StringCreate.swift

@@ -120,15 +120,8 @@ extension String {
       )
       return result.asString
     case .error(let initialRange):
-      // repairUTF8 will call reserveCapacity, invalidating result.codeUnits if
-      // we use it directly. This could be a little faster, but this error path
-      // shouldn't be perf-sensitive anyway.
-      let temporaryCodeUnits = Array(result.codeUnits)
-      defer { _fixLifetime(temporaryCodeUnits) }
-      return temporaryCodeUnits.withContiguousStorageIfAvailable {
-        //This could be optimized to use excess tail capacity
-        return repairUTF8($0, firstKnownBrokenRange: initialRange)
-      }!
+      //This could be optimized to use excess tail capacity
+      return repairUTF8(result.codeUnits, firstKnownBrokenRange: initialRange)
     }
   }
 

test/stdlib/StringCreate.swift

@@ -57,33 +57,22 @@ if #available(macOS 10.16, iOS 14.0, watchOS 7.0, tvOS 14.0, *) {
       }
       expectEqual(expected, actual)
     }
-        
+
     let validUTF8: [UInt8] = [0x43, 0x61, 0x66, 0xC3, 0xA9]
     let invalidUTF8: [UInt8] = [0x43, 0x61, 0x66, 0xC3]
-    let longerValidUTF8: [UInt8] = [0x21, 0x21, 0x21, 0x21, 0x21, 0x21, 0x21, 0x21, 0x21, 0x21, 0x43, 0x61, 0x66, 0xC3, 0xA9]
-    let longerInvalidUTF8: [UInt8] = [0x21, 0x21, 0x43, 0x61, 0x66, 0xC3, 0x43, 0x61, 0x66, 0xC3, 0x43, 0x61, 0x66, 0xC3]
-    
-    func test(bufferSize: Int, input: [UInt8], expected: String) {
-      let strs = (0..<100).map { _ in
-        String(unsafeUninitializedCapacity: bufferSize) { buffer in
-          _ = buffer.initialize(from: input)
-          return input.count
-        }
-      }
-      for str in strs {
-        expectEqual(expected, str)
-      }
+
+    let cafe1 = String(unsafeUninitializedCapacity: validUTF8.count) {
+      _ = $0.initialize(from: validUTF8)
+      return validUTF8.count
     }
-    
-    test(bufferSize: validUTF8.count, input: validUTF8, expected: "Café")
-    test(bufferSize: invalidUTF8.count, input: invalidUTF8, expected: "Caf�")
-    // Force non-smol strings by using a larger capacity
-    test(bufferSize: 16, input: validUTF8, expected: "Café")
-    test(bufferSize: 16, input: invalidUTF8, expected: "Caf�")
-    test(bufferSize: longerValidUTF8.count, input: longerValidUTF8, expected: "!!!!!!!!!!Café")
-    test(bufferSize: longerInvalidUTF8.count, input: longerInvalidUTF8, expected: "!!Caf�Caf�Caf�")
-    test(bufferSize: 16, input: longerValidUTF8, expected: "!!!!!!!!!!Café")
-    test(bufferSize: 16, input: longerInvalidUTF8, expected: "!!Caf�Caf�Caf�")
+    expectEqual("Café", cafe1)
+
+    let cafe2 = String(unsafeUninitializedCapacity: invalidUTF8.count) {
+      _ = $0.initialize(from: invalidUTF8)
+      return invalidUTF8.count
+    }
+    expectEqual("Caf�", cafe2)
+
     let empty = String(unsafeUninitializedCapacity: 16) { _ in
       // Can't initialize the buffer (e.g. the capacity is too small).
       return 0