SDK generation fails when the value type of the enum is `integer`

[welovej]

Hi team,

We encountered a generation failure in the SDK pipeline when typespec defines the following extensible enum:

/**
 * The minute element of the time. Allowed values are 0 and 30. If not specified, its value defaults to 0.
 */
union Minute {
  integer,
  #suppress "@azure-tools/typespec-azure-core/documentation-required" "For backward compatibility"
  `0`: 0,
  #suppress "@azure-tools/typespec-azure-core/documentation-required" "For backward compatibility"
  `30`: 30,
}

This schema causes a failure during SDK generation due to a mismatch in the type resolution logic. The code that fails looks like this:
Location

InputEnumTypeValue enumValue = valueType.Kind switch
{
    InputPrimitiveTypeKind.String => new InputEnumTypeStringValue(name, rawValue.Value.GetString() ?? throw new JsonException(), valueType, enumType, summary, doc) { Decorators = decorators ?? [] },
    InputPrimitiveTypeKind.Int32 => new InputEnumTypeIntegerValue(name, rawValue.Value.GetInt32(), valueType, enumType, summary, doc) { Decorators = decorators ?? [] },
    InputPrimitiveTypeKind.Float32 => new InputEnumTypeFloatValue(name, rawValue.Value.GetSingle(), valueType, enumType, summary, doc) { Decorators = decorators ?? [] },
    _ => throw new JsonException()
};

Problem

In this case, valueType.Kind is InputPrimitiveTypeKind.Integer, which does not match any of the expected InputPrimitiveTypeKind.Int32, String, or Float32, causing the fallback _ => throw new JsonException() to be triggered.

This happens because the typespec int32 union does not explicitly indicate a format, and the generator attempts to map it to InputPrimitiveTypeKind.Integer, which is not handled in the switch statement.

Related TCGC issue

Link

Thanks!

[ArcturusZhang]

We currently only support the enum value type to be string, int32, and float32.
The spec author could write anything they want therefore maybe we need to expand this.