Use ICollection<T> check instead of IList<T> in TryCopyTo

src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableExtensions.Minimal.cs

@@ -102,8 +102,8 @@ internal static bool TryCopyTo<T>(this IEnumerable<T> sequence, T[] array, int a
             Debug.Assert(array != null);
             Debug.Assert(arrayIndex >= 0 && arrayIndex <= array.Length);
 
-            // IList is the GCD of what the following types implement.
-            if (sequence is IList<T>)
+            // ICollection is the GCD of what the following types implement.
+            if (sequence is ICollection<T>)
             {
                 if (sequence is List<T> list)
                 {
@@ -126,6 +126,18 @@ internal static bool TryCopyTo<T>(this IEnumerable<T> sequence, T[] array, int a
                     Array.Copy(immutable.array!, 0, array, arrayIndex, immutable.Length);
                     return true;
                 }
+
+#if !NET
+                // On .NET Framework, if 'sequence' is actually a covariant array (for example, string[] used as ICollection<object>),
+                // its ICollection<T>.CopyTo implementation may call Array.Copy and throw an ArrayTypeMismatchException when copying into a T[].
+                if (sequence is Array)
+                {
+                    return false;
+                }
+#endif
+
+                ((ICollection<T>)sequence).CopyTo(array, arrayIndex);
+                return true;
             }
 
             return false;

src/libraries/System.Collections.Immutable/tests/ImmutableArrayTest.cs

@@ -1438,6 +1438,8 @@ public static IEnumerable<object[]> InsertRangeData()
             yield return new object[] { s_empty, 0, new uint[] { 1, 2, 3 } };
             yield return new object[] { s_manyElements, 0, new uint[] { 4, 5, 6 } };
             yield return new object[] { s_manyElements, 3, new uint[] { 4, 5, 6 } };
+            yield return new object[] { s_manyElements, 0, new Dictionary<int, int> { [4] = 0, [5] = 0 }.Keys };
+            yield return new object[] { s_manyElements, 3, new Dictionary<int, int> { [4] = 0, [5] = 0 }.Keys };
         }
 
         [Theory]