Fix undefined behaviour in Array.cs (#83116)

Fixes #83115

diff --git a/src/libraries/System.Private.CoreLib/src/System/Array.cs b/src/libraries/System.Private.CoreLib/src/System/Array.cs
index a937f69..9772545 100644 (file)
--- a/src/libraries/System.Private.CoreLib/src/System/Array.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Array.cs
@@ -1332,7 +1332,7 @@ namespace System
                 if (sizeof(T) == sizeof(byte))
                 {
                     int result = SpanHelpers.IndexOfValueType(
-                        ref Unsafe.Add(ref MemoryMarshal.GetArrayDataReference(Unsafe.As<byte[]>(array)), startIndex),
+                        ref Unsafe.Add(ref Unsafe.As<T, byte>(ref MemoryMarshal.GetArrayDataReference(array)), startIndex),
                         Unsafe.As<T, byte>(ref value),
                         count);
                     return (result >= 0 ? startIndex : 0) + result;
@@ -1340,7 +1340,7 @@ namespace System
                 else if (sizeof(T) == sizeof(short))
                 {
                     int result = SpanHelpers.IndexOfValueType(
-                        ref Unsafe.Add(ref MemoryMarshal.GetArrayDataReference(Unsafe.As<short[]>(array)), startIndex),
+                        ref Unsafe.Add(ref Unsafe.As<T, short>(ref MemoryMarshal.GetArrayDataReference(array)), startIndex),
                         Unsafe.As<T, short>(ref value),
                         count);
                     return (result >= 0 ? startIndex : 0) + result;
@@ -1348,7 +1348,7 @@ namespace System
                 else if (sizeof(T) == sizeof(int))
                 {
                     int result = SpanHelpers.IndexOfValueType(
-                        ref Unsafe.Add(ref MemoryMarshal.GetArrayDataReference(Unsafe.As<int[]>(array)), startIndex),
+                        ref Unsafe.Add(ref Unsafe.As<T, int>(ref MemoryMarshal.GetArrayDataReference(array)), startIndex),
                         Unsafe.As<T, int>(ref value),
                         count);
                     return (result >= 0 ? startIndex : 0) + result;
@@ -1356,7 +1356,7 @@ namespace System
                 else if (sizeof(T) == sizeof(long))
                 {
                     int result = SpanHelpers.IndexOfValueType(
-                        ref Unsafe.Add(ref MemoryMarshal.GetArrayDataReference(Unsafe.As<long[]>(array)), startIndex),
+                        ref Unsafe.Add(ref Unsafe.As<T, long>(ref MemoryMarshal.GetArrayDataReference(array)), startIndex),
                         Unsafe.As<T, long>(ref value),
                         count);
                     return (result >= 0 ? startIndex : 0) + result;
@@ -1580,7 +1580,7 @@ namespace System
                 {
                     int endIndex = startIndex - count + 1;
                     int result = SpanHelpers.LastIndexOfValueType(
-                        ref Unsafe.Add(ref MemoryMarshal.GetArrayDataReference(Unsafe.As<byte[]>(array)), endIndex),
+                        ref Unsafe.Add(ref Unsafe.As<T, byte>(ref MemoryMarshal.GetArrayDataReference(array)), endIndex),
                         Unsafe.As<T, byte>(ref value),
                         count);
 
@@ -1590,7 +1590,7 @@ namespace System
                 {
                     int endIndex = startIndex - count + 1;
                     int result = SpanHelpers.LastIndexOfValueType(
-                        ref Unsafe.Add(ref MemoryMarshal.GetArrayDataReference(Unsafe.As<short[]>(array)), endIndex),
+                        ref Unsafe.Add(ref Unsafe.As<T, short>(ref MemoryMarshal.GetArrayDataReference(array)), endIndex),
                         Unsafe.As<T, short>(ref value),
                         count);
 
@@ -1600,7 +1600,7 @@ namespace System
                 {
                     int endIndex = startIndex - count + 1;
                     int result = SpanHelpers.LastIndexOfValueType(
-                        ref Unsafe.Add(ref MemoryMarshal.GetArrayDataReference(Unsafe.As<int[]>(array)), endIndex),
+                        ref Unsafe.Add(ref Unsafe.As<T, int>(ref MemoryMarshal.GetArrayDataReference(array)), endIndex),
                         Unsafe.As<T, int>(ref value),
                         count);
 
@@ -1610,7 +1610,7 @@ namespace System
                 {
                     int endIndex = startIndex - count + 1;
                     int result = SpanHelpers.LastIndexOfValueType(
-                        ref Unsafe.Add(ref MemoryMarshal.GetArrayDataReference(Unsafe.As<long[]>(array)), endIndex),
+                        ref Unsafe.Add(ref Unsafe.As<T, long>(ref MemoryMarshal.GetArrayDataReference(array)), endIndex),
                         Unsafe.As<T, long>(ref value),
                         count);