clockworklabs/SpacetimeDB · error · InvalidOperationException

Unsupported special type

Error message

Unsupported special type {type} ({type.SpecialType})

What it means

GetTypeInfo maps a type symbol's SpecialType to a BSATN name; bool, the numeric types and string are handled explicitly. Any other Roslyn 'special' type — char (System_Char), decimal (System_Decimal), DateTime/DateTimeOffset (System_DateTime), nint/IntPtr — hits the default arm and throws InvalidOperationException, printing the symbol and its SpecialType.

Solutions

1. Map to supported primitives: DateTime/DateTimeOffset -> long (unix µs) or the SDK timestamp type if available; decimal -> scaled long or double; char -> string or byte
2. Replace nint/IntPtr with long
3. Rebuild — the error is compile-time, so replacing the type clears it immediately

Example fix

// before
[SpacetimeDB.Table(Name = "player", Public = true)]
public partial struct Player {
    public DateTime CreatedAt;
    public decimal Balance;
    public char Rank;
}

// after
[SpacetimeDB.Table(Name = "player", Public = true)]
public partial struct Player {
    public long CreatedAtMicros;  // unix microseconds
    public long BalanceMicros;    // scaled fixed-point
    public string Rank;
}

// Compile-time by design: `dotnet build` fails while any schema type is unsupported.
// Checklist to apply to every table/reducer member:
//   DateTime/DateTimeOffset -> long micros
//   decimal -> long (scaled) or double
//   char -> string | byte
//   nint/IntPtr -> long

// compile-time error: nothing to catch. Replace the type and rebuild.

When it happens

Trigger: Using char, decimal, DateTime, DateTimeOffset, nint/IntPtr (or other non-None special types) in a table column, reducer argument, or [SpacetimeDB.Type] member of a C# project processed by the BSATN generator.

Common situations: C# developers defaulting to DateTime for timestamps and decimal for money; EF/LINQ-style domain models pasted into SpacetimeDB schema types; char fields for single-letter codes.

Related errors

• Unsupported system type
• Unsupported type
• Unsupported type
• Enum does not have a [SpacetimeDB.Type] attribute
• Argument must be a I128

AI-assisted analysis of clockworklabs/SpacetimeDB@6dee26c6ef (2026-08-20). Data as JSON: /api/errors/0b00830812a88d59. Report an issue: GitHub.

Appendix: source

Thrown at crates/bindings-csharp/BSATN.Codegen/Utils.cs:138

        return type switch
        {
            ITypeParameterSymbol typeParameter => MakeRwTypeParam(typeParameter.Name),
            INamedTypeSymbol namedType => type.SpecialType switch
            {
                SpecialType.System_Boolean => "SpacetimeDB.BSATN.Bool",
                SpecialType.System_SByte => "SpacetimeDB.BSATN.I8",
                SpecialType.System_Byte => "SpacetimeDB.BSATN.U8",
                SpecialType.System_Int16 => "SpacetimeDB.BSATN.I16",
                SpecialType.System_UInt16 => "SpacetimeDB.BSATN.U16",
                SpecialType.System_Int32 => "SpacetimeDB.BSATN.I32",
                SpecialType.System_UInt32 => "SpacetimeDB.BSATN.U32",
                SpecialType.System_Int64 => "SpacetimeDB.BSATN.I64",
                SpecialType.System_UInt64 => "SpacetimeDB.BSATN.U64",
                SpecialType.System_Single => "SpacetimeDB.BSATN.F32",
                SpecialType.System_Double => "SpacetimeDB.BSATN.F64",
                SpecialType.System_String => "SpacetimeDB.BSATN.String",
                SpecialType.None => GetTypeInfoForNamedType(namedType),
                _ => throw new InvalidOperationException(
                    $"Unsupported special type {type} ({type.SpecialType})"
                ),
            },
            IArrayTypeSymbol { ElementType: var elementType } => elementType.SpecialType
            == SpecialType.System_Byte
                ? "SpacetimeDB.BSATN.ByteArray"
                : $"SpacetimeDB.BSATN.Array<{elementType}, {GetTypeInfo(elementType)}>",
            _ => throw new InvalidOperationException($"Unsupported type {type}"),
        };

        static string GetTypeInfoForNamedType(INamedTypeSymbol type)
        {
            if (type.TypeKind == Microsoft.CodeAnalysis.TypeKind.Error)
            {
                throw new UnresolvedTypeException(type);
            }
            if (type.TypeKind == Microsoft.CodeAnalysis.TypeKind.Enum)
            {

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