Merge pull request #2 from ledjon-behluli/fix-concurrent-tuple-to-string

Fix concurrent tuple ToString & GetEnumerator
ledjon-behluli · Jul 22, 2023 · e707fd8 · e707fd8
2 parents 11289a6 + 2b628eb
commit e707fd8
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Showing 42 changed files with 420 additions and 88 deletions.
diff --git a/src/OrleanSpaces/Helpers/TemplateHelpers.cs b/src/OrleanSpaces/Helpers/TemplateHelpers.cs
@@ -58,5 +58,5 @@ public static bool Matches<T, TTuple, TTemplate>(this TTemplate template, TTuple
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static string ToString<T>(T?[] fields) where T : unmanaged
-        => $"({string.Join(", ", fields.Select(field => field is null ? "{NULL}" : field.ToString()))})";
+        => fields is null ? "()" : $"({string.Join(", ", fields.Select(field => field is null ? "{NULL}" : field.ToString()))})";
 }
diff --git a/src/OrleanSpaces/Helpers/TupleHelpers.cs b/src/OrleanSpaces/Helpers/TupleHelpers.cs
@@ -244,5 +244,5 @@ static int GetCharCount(int tupleLength, int maxFieldCharLength)
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static string ToString<T>(T[] fields) where T : unmanaged
-        => $"({string.Join(", ", fields)})";
+        => fields is null ? "()" : $"({string.Join(", ", fields)})";
 }
diff --git a/src/OrleanSpaces/Tuples/SpaceTuple.cs b/src/OrleanSpaces/Tuples/SpaceTuple.cs
@@ -102,13 +102,14 @@ public bool Equals(SpaceTuple other)
         return true;
     }
 
-    public override int GetHashCode() => fields.GetHashCode();
-    public override string ToString() => $"({string.Join(", ", fields)})";
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
+    public override string ToString() => $"({string.Join(", ", fields ?? Array.Empty<object>())})";
 
     /// <summary>
     /// Returns an enumerator to enumerate over the fields of this tuple.
     /// </summary>
-    public ReadOnlySpan<object>.Enumerator GetEnumerator() => new ReadOnlySpan<object>(fields).GetEnumerator();
+    public ReadOnlySpan<object>.Enumerator GetEnumerator() =>
+        (fields is null ? ReadOnlySpan<object>.Empty : new ReadOnlySpan<object>(fields)).GetEnumerator();
 }
 
 /// <summary>
@@ -224,11 +225,12 @@ public bool Equals(SpaceTemplate other)
         return true;
     }
 
-    public override int GetHashCode() => fields.GetHashCode();
-    public override string ToString() => $"({string.Join(", ", fields.Select(field => field ?? "{NULL}"))})";
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
+    public override string ToString() => fields is null ? "()" : $"({string.Join(", ", fields.Select(field => field ?? "{NULL}"))})";
 
     /// <summary>
     /// Returns an enumerator to enumerate over the fields of this tuple.
     /// </summary>
-    public ReadOnlySpan<object?>.Enumerator GetEnumerator() => new ReadOnlySpan<object?>(fields).GetEnumerator();
+    public ReadOnlySpan<object?>.Enumerator GetEnumerator() =>
+        (fields is null ? ReadOnlySpan<object?>.Empty : new ReadOnlySpan<object?>(fields)).GetEnumerator();
 }
diff --git a/src/OrleanSpaces/Tuples/Specialized/BoolTuple.cs b/src/OrleanSpaces/Tuples/Specialized/BoolTuple.cs
@@ -55,12 +55,13 @@ public bool Equals(BoolTuple other)
         return marshaller.TryParallelEquals(out bool result) ? result : this.SequentialEquals<bool, BoolTuple>(other);
     }
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TupleHelpers.ToString(fields);
 
     static BoolTuple ISpaceFactory<bool, BoolTuple>.Create(bool[] fields) => new(fields);
 
-    public ReadOnlySpan<bool>.Enumerator GetEnumerator() => new ReadOnlySpan<bool>(fields).GetEnumerator();
+    public ReadOnlySpan<bool>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<bool>.Empty : new ReadOnlySpan<bool>(fields)).GetEnumerator();
 
     public ReadOnlySpan<char> AsSpan()
     {
@@ -131,8 +132,9 @@ public BoolTemplate([AllowNull] params bool?[] fields)
     public bool Matches(BoolTuple tuple) => this.Matches<bool, BoolTuple, BoolTemplate>(tuple);
     public bool Equals(BoolTemplate other) => this.SequentialEquals<bool, BoolTemplate>(other);
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TemplateHelpers.ToString(fields);
 
-    public ReadOnlySpan<bool?>.Enumerator GetEnumerator() => new ReadOnlySpan<bool?>(fields).GetEnumerator();
+    public ReadOnlySpan<bool?>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<bool?>.Empty : new ReadOnlySpan<bool?>(fields)).GetEnumerator();
 }
diff --git a/src/OrleanSpaces/Tuples/Specialized/ByteTuple.cs b/src/OrleanSpaces/Tuples/Specialized/ByteTuple.cs
@@ -55,13 +55,14 @@ public bool Equals(ByteTuple other)
         => this.TryParallelEquals<byte, ByteTuple>(other, out bool result) ? 
                result : this.SequentialEquals<byte, ByteTuple>(other);
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TupleHelpers.ToString(fields);
 
     static ByteTuple ISpaceFactory<byte, ByteTuple>.Create(byte[] fields) => new(fields);
 
     public ReadOnlySpan<char> AsSpan() => this.AsSpan<byte, ByteTuple>(Constants.MaxFieldCharLength_Byte);
-    public ReadOnlySpan<byte>.Enumerator GetEnumerator() => new ReadOnlySpan<byte>(fields).GetEnumerator();
+    public ReadOnlySpan<byte>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<byte>.Empty : new ReadOnlySpan<byte>(fields)).GetEnumerator();
 }
 
 /// <summary>
@@ -98,8 +99,9 @@ public ByteTemplate([AllowNull] params byte?[] fields)
     public bool Matches(ByteTuple tuple) => this.Matches<byte, ByteTuple, ByteTemplate>(tuple);
     public bool Equals(ByteTemplate other) => this.SequentialEquals<byte, ByteTemplate>(other);
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TemplateHelpers.ToString(fields);
 
-    public ReadOnlySpan<byte?>.Enumerator GetEnumerator() => new ReadOnlySpan<byte?>(fields).GetEnumerator();
+    public ReadOnlySpan<byte?>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<byte?>.Empty : new ReadOnlySpan<byte?>(fields)).GetEnumerator();
 }
diff --git a/src/OrleanSpaces/Tuples/Specialized/CharTuple.cs b/src/OrleanSpaces/Tuples/Specialized/CharTuple.cs
@@ -66,13 +66,14 @@ public bool Equals(CharTuple other)
                    result : this.SequentialEquals<char, CharTuple>(other);
     }
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TupleHelpers.ToString(fields);
 
     static CharTuple ISpaceFactory<char, CharTuple>.Create(char[] fields) => new(fields);
 
     public ReadOnlySpan<char> AsSpan() => this.AsSpan<char, CharTuple>(Constants.MaxFieldCharLength_Char);
-    public ReadOnlySpan<char>.Enumerator GetEnumerator() => new ReadOnlySpan<char>(fields).GetEnumerator();
+    public ReadOnlySpan<char>.Enumerator GetEnumerator() =>
+        (fields is null ? ReadOnlySpan<char>.Empty : new ReadOnlySpan<char>(fields)).GetEnumerator();
 }
 
 /// <summary>
@@ -109,8 +110,9 @@ public CharTemplate([AllowNull] params char?[] fields)
     public bool Matches(CharTuple tuple) => this.Matches<char, CharTuple, CharTemplate>(tuple);
     public bool Equals(CharTemplate other) => this.SequentialEquals<char, CharTemplate>(other);
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TemplateHelpers.ToString(fields);
 
-    public ReadOnlySpan<char?>.Enumerator GetEnumerator() => new ReadOnlySpan<char?>(fields).GetEnumerator();
+    public ReadOnlySpan<char?>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<char?>.Empty : new ReadOnlySpan<char?>(fields)).GetEnumerator();
 }
diff --git a/src/OrleanSpaces/Tuples/Specialized/DateTimeOffsetTuple.cs b/src/OrleanSpaces/Tuples/Specialized/DateTimeOffsetTuple.cs
@@ -56,13 +56,14 @@ public bool Equals(DateTimeOffsetTuple other)
                    result : this.SequentialEquals<DateTimeOffset, DateTimeOffsetTuple>(other);
     }
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TupleHelpers.ToString(fields);
 
     static DateTimeOffsetTuple ISpaceFactory<DateTimeOffset, DateTimeOffsetTuple>.Create(DateTimeOffset[] fields) => new(fields);
 
     public ReadOnlySpan<char> AsSpan() => this.AsSpan<DateTimeOffset, DateTimeOffsetTuple>(Constants.MaxFieldCharLength_DateTimeOffset);
-    public ReadOnlySpan<DateTimeOffset>.Enumerator GetEnumerator() => new ReadOnlySpan<DateTimeOffset>(fields).GetEnumerator();
+    public ReadOnlySpan<DateTimeOffset>.Enumerator GetEnumerator() =>
+        (fields is null ? ReadOnlySpan<DateTimeOffset>.Empty : new ReadOnlySpan<DateTimeOffset>(fields)).GetEnumerator();
 }
 
 /// <summary>
@@ -99,8 +100,9 @@ public DateTimeOffsetTemplate([AllowNull] params DateTimeOffset?[] fields) =>
     public bool Matches(DateTimeOffsetTuple tuple) => this.Matches<DateTimeOffset, DateTimeOffsetTuple, DateTimeOffsetTemplate>(tuple);
     public bool Equals(DateTimeOffsetTemplate other) => this.SequentialEquals<DateTimeOffset, DateTimeOffsetTemplate>(other);
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TemplateHelpers.ToString(fields);
 
-    public ReadOnlySpan<DateTimeOffset?>.Enumerator GetEnumerator() => new ReadOnlySpan<DateTimeOffset?>(fields).GetEnumerator();
+    public ReadOnlySpan<DateTimeOffset?>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<DateTimeOffset?>.Empty : new ReadOnlySpan<DateTimeOffset?>(fields)).GetEnumerator();
 }
diff --git a/src/OrleanSpaces/Tuples/Specialized/DateTimeTuple.cs b/src/OrleanSpaces/Tuples/Specialized/DateTimeTuple.cs
@@ -56,13 +56,14 @@ public bool Equals(DateTimeTuple other)
                    result : this.SequentialEquals<DateTime, DateTimeTuple>(other);
     }
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TupleHelpers.ToString(fields);
 
     static DateTimeTuple ISpaceFactory<DateTime, DateTimeTuple>.Create(DateTime[] fields) => new(fields);
 
     public ReadOnlySpan<char> AsSpan() => this.AsSpan<DateTime, DateTimeTuple>(Constants.MaxFieldCharLength_DateTime);
-    public ReadOnlySpan<DateTime>.Enumerator GetEnumerator() => new ReadOnlySpan<DateTime>(fields).GetEnumerator();
+    public ReadOnlySpan<DateTime>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<DateTime>.Empty : new ReadOnlySpan<DateTime>(fields)).GetEnumerator();
 }
 
 /// <summary>
@@ -99,8 +100,9 @@ public DateTimeTemplate([AllowNull] params DateTime?[] fields) =>
     public bool Matches(DateTimeTuple tuple) => this.Matches<DateTime, DateTimeTuple, DateTimeTemplate>(tuple);
     public bool Equals(DateTimeTemplate other) => this.SequentialEquals<DateTime, DateTimeTemplate>(other);
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TemplateHelpers.ToString(fields);
 
-    public ReadOnlySpan<DateTime?>.Enumerator GetEnumerator() => new ReadOnlySpan<DateTime?>(fields).GetEnumerator();
+    public ReadOnlySpan<DateTime?>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<DateTime?>.Empty : new ReadOnlySpan<DateTime?>(fields)).GetEnumerator();
 }
diff --git a/src/OrleanSpaces/Tuples/Specialized/DecimalTuple.cs b/src/OrleanSpaces/Tuples/Specialized/DecimalTuple.cs
@@ -79,13 +79,14 @@ public bool Equals(DecimalTuple other)
         return new Comparer(this, other).AllocateAndExecute<int, Comparer>(8 * Length); // 8 x Length, because each decimal will be decomposed into 4 ints, and we have 2 tuples to compare.
     }
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TupleHelpers.ToString(fields);
 
     static DecimalTuple ISpaceFactory<decimal, DecimalTuple>.Create(decimal[] fields) => new(fields);
 
     public ReadOnlySpan<char> AsSpan() => this.AsSpan<decimal, DecimalTuple>(Constants.MaxFieldCharLength_Decimal);
-    public ReadOnlySpan<decimal>.Enumerator GetEnumerator() => new ReadOnlySpan<decimal>(fields).GetEnumerator();
+    public ReadOnlySpan<decimal>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<decimal>.Empty : new ReadOnlySpan<decimal>(fields)).GetEnumerator();
 
     readonly struct Comparer : IBufferConsumer<int>
     {
@@ -151,8 +152,9 @@ public DecimalTemplate([AllowNull] params decimal?[] fields)
     public bool Matches(DecimalTuple tuple) => this.Matches<decimal, DecimalTuple, DecimalTemplate>(tuple);
     public bool Equals(DecimalTemplate other) => this.SequentialEquals<decimal, DecimalTemplate>(other);
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TemplateHelpers.ToString(fields);
 
-    public ReadOnlySpan<decimal?>.Enumerator GetEnumerator() => new ReadOnlySpan<decimal?>(fields).GetEnumerator();
+    public ReadOnlySpan<decimal?>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<decimal?>.Empty : new ReadOnlySpan<decimal?>(fields)).GetEnumerator();
 }
diff --git a/src/OrleanSpaces/Tuples/Specialized/DoubleTuple.cs b/src/OrleanSpaces/Tuples/Specialized/DoubleTuple.cs
@@ -55,13 +55,14 @@ public bool Equals(DoubleTuple other)
         => this.TryParallelEquals<double, DoubleTuple>(other, out bool result) ? 
                result : this.SequentialEquals<double, DoubleTuple>(other);
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TupleHelpers.ToString(fields);
 
     static DoubleTuple ISpaceFactory<double, DoubleTuple>.Create(double[] fields) => new(fields);
 
     public ReadOnlySpan<char> AsSpan() => this.AsSpan<double, DoubleTuple>(Constants.MaxFieldCharLength_Double);
-    public ReadOnlySpan<double>.Enumerator GetEnumerator() => new ReadOnlySpan<double>(fields).GetEnumerator();
+    public ReadOnlySpan<double>.Enumerator GetEnumerator() =>
+        (fields is null ? ReadOnlySpan<double>.Empty : new ReadOnlySpan<double>(fields)).GetEnumerator();
 }
 
 /// <summary>
@@ -98,8 +99,9 @@ public DoubleTemplate([AllowNull] params double?[] fields)
     public bool Matches(DoubleTuple tuple) => this.Matches<double, DoubleTuple, DoubleTemplate>(tuple);
     public bool Equals(DoubleTemplate other) => this.SequentialEquals<double, DoubleTemplate>(other);
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TemplateHelpers.ToString(fields);
 
-    public ReadOnlySpan<double?>.Enumerator GetEnumerator() => new ReadOnlySpan<double?>(fields).GetEnumerator();
+    public ReadOnlySpan<double?>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<double?>.Empty : new ReadOnlySpan<double?>(fields)).GetEnumerator();
 }
diff --git a/src/OrleanSpaces/Tuples/Specialized/FloatTuple.cs b/src/OrleanSpaces/Tuples/Specialized/FloatTuple.cs
@@ -55,13 +55,14 @@ public bool Equals(FloatTuple other)
         => this.TryParallelEquals<float, FloatTuple>(other, out bool result) ?
                 result : this.SequentialEquals<float, FloatTuple>(other);
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TupleHelpers.ToString(fields);
 
     static FloatTuple ISpaceFactory<float, FloatTuple>.Create(float[] fields) => new(fields);
 
     public ReadOnlySpan<char> AsSpan() => this.AsSpan<float, FloatTuple>(Constants.MaxFieldCharLength_Float);
-    public ReadOnlySpan<float>.Enumerator GetEnumerator() => new ReadOnlySpan<float>(fields).GetEnumerator();
+    public ReadOnlySpan<float>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<float>.Empty : new ReadOnlySpan<float>(fields)).GetEnumerator();
 }
 
 /// <summary>
@@ -98,8 +99,9 @@ public FloatTemplate([AllowNull] params float?[] fields)
     public bool Matches(FloatTuple tuple) => this.Matches<float, FloatTuple, FloatTemplate>(tuple);
     public bool Equals(FloatTemplate other) => this.SequentialEquals<float, FloatTemplate>(other);
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TemplateHelpers.ToString(fields);
 
-    public ReadOnlySpan<float?>.Enumerator GetEnumerator() => new ReadOnlySpan<float?>(fields).GetEnumerator();
+    public ReadOnlySpan<float?>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<float?>.Empty : new ReadOnlySpan<float?>(fields)).GetEnumerator();
 }
diff --git a/src/OrleanSpaces/Tuples/Specialized/GuidTuple.cs b/src/OrleanSpaces/Tuples/Specialized/GuidTuple.cs
@@ -80,13 +80,14 @@ public bool Equals(GuidTuple other)
         return true;
     }
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TupleHelpers.ToString(fields);
 
     static GuidTuple ISpaceFactory<Guid, GuidTuple>.Create(Guid[] fields) => new(fields);
 
     public ReadOnlySpan<char> AsSpan() => this.AsSpan<Guid, GuidTuple>(Constants.MaxFieldCharLength_Guid);
-    public ReadOnlySpan<Guid>.Enumerator GetEnumerator() => new ReadOnlySpan<Guid>(fields).GetEnumerator();
+    public ReadOnlySpan<Guid>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<Guid>.Empty : new ReadOnlySpan<Guid>(fields)).GetEnumerator();
 }
 
 /// <summary>
@@ -123,8 +124,9 @@ public GuidTemplate([AllowNull] params Guid?[] fields)
     public bool Matches(GuidTuple tuple) => this.Matches<Guid, GuidTuple, GuidTemplate>(tuple);
     public bool Equals(GuidTemplate other) => this.SequentialEquals<Guid, GuidTemplate>(other);
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TemplateHelpers.ToString(fields);
 
-    public ReadOnlySpan<Guid?>.Enumerator GetEnumerator() => new ReadOnlySpan<Guid?>(fields).GetEnumerator();
+    public ReadOnlySpan<Guid?>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<Guid?>.Empty : new ReadOnlySpan<Guid?>(fields)).GetEnumerator();
 }
diff --git a/src/OrleanSpaces/Tuples/Specialized/HugeTuple.cs b/src/OrleanSpaces/Tuples/Specialized/HugeTuple.cs
@@ -68,13 +68,14 @@ public bool Equals(HugeTuple other)
         return new Comparer(this, other).AllocateAndExecute<byte, Comparer>(2 * Constants.ByteCount_Int128 * Length);
     }
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TupleHelpers.ToString(fields);
 
     static HugeTuple ISpaceFactory<Int128, HugeTuple>.Create(Int128[] fields) => new(fields);
 
     public ReadOnlySpan<char> AsSpan() => this.AsSpan<Int128, HugeTuple>(Constants.MaxFieldCharLength_Huge);
-    public ReadOnlySpan<Int128>.Enumerator GetEnumerator() => new ReadOnlySpan<Int128>(fields).GetEnumerator();
+    public ReadOnlySpan<Int128>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<Int128>.Empty : new ReadOnlySpan<Int128>(fields)).GetEnumerator();
 
     readonly struct Comparer : IBufferConsumer<byte>
     {
@@ -147,8 +148,9 @@ public HugeTemplate([AllowNull] params Int128?[] fields)
     public bool Matches(HugeTuple tuple) => this.Matches<Int128, HugeTuple, HugeTemplate>(tuple);
     public bool Equals(HugeTemplate other) => this.SequentialEquals<Int128, HugeTemplate>(other);
 
-    public override int GetHashCode() => fields.GetHashCode();
+    public override int GetHashCode() => fields?.GetHashCode() ?? 0;
     public override string ToString() => TemplateHelpers.ToString(fields);
 
-    public ReadOnlySpan<Int128?>.Enumerator GetEnumerator() => new ReadOnlySpan<Int128?>(fields).GetEnumerator();
+    public ReadOnlySpan<Int128?>.Enumerator GetEnumerator() => 
+        (fields is null ? ReadOnlySpan<Int128?>.Empty : new ReadOnlySpan<Int128?>(fields)).GetEnumerator();
 }