Remove unsafe modifier from Memory<T>.Span

Author: xtqqczze

src/libraries/System.Private.CoreLib/src/System/Memory.cs

@@ -263,7 +263,7 @@ public Memory<T> Slice(int start, int length)
         /// <summary>
         /// Returns a span from the memory.
         /// </summary>
-        public unsafe Span<T> Span
+        public Span<T> Span
         {
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
             get
@@ -343,7 +343,7 @@ public unsafe Span<T> Span
                     }
 #endif
 
-                    refToReturn = ref Unsafe.Add(ref refToReturn, (IntPtr)(void*)desiredStartIndex);
+                    refToReturn = ref Unsafe.Add(ref refToReturn, (nint)desiredStartIndex);
                     lengthOfUnderlyingSpan = desiredLength;
                 }
 

src/libraries/System.Private.CoreLib/src/System/ReadOnlyMemory.cs

@@ -192,7 +192,7 @@ public ReadOnlyMemory<T> Slice(int start, int length)
         /// <summary>
         /// Returns a span from the memory.
         /// </summary>
-        public unsafe ReadOnlySpan<T> Span
+        public ReadOnlySpan<T> Span
         {
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
             get
@@ -265,7 +265,7 @@ public unsafe ReadOnlySpan<T> Span
                     }
 #endif
 
-                    refToReturn = ref Unsafe.Add(ref refToReturn, (IntPtr)(void*)desiredStartIndex);
+                    refToReturn = ref Unsafe.Add(ref refToReturn, (nint)desiredStartIndex);
                     lengthOfUnderlyingSpan = desiredLength;
                 }