Some documentation

README.md

@@ -603,9 +603,13 @@ func projected(to newProjection: Projection) -> GeometryCollection
 A `Feature` is sort of a container for exactly one GeoJSON geometry (`Point`, `MultiPoint`, `LineString`, `MultiLineString`, `Polygon`, `MultiPolygon`, `GeometryCollection`) together with some `properties` and an optional `id`:
 ```swift
 /// A GeoJSON identifier that can either be a string or number.
+/// Any parsed integer value `Int64.min ⪬ i ⪬ Int64.max`  will be cast to `Int`
+/// (or `Int64` on 32-bit platforms), values above `Int64.max` will be cast to `UInt`
+/// (or `UInt64` on 32-bit platforms).
 enum Identifier: Equatable, Hashable, CustomStringConvertible {
     case string(String)
     case int(Int)
+    case uint(UInt)
     case double(Double)
 }
 

Sources/GISTools/GeoJson/Feature.swift

@@ -4,6 +4,10 @@ import Foundation
 public struct Feature: GeoJson {
 
     /// A GeoJSON identifier that can either be a string or number.
+    ///
+    /// Any parsed integer value `Int64.min ⪬ i ⪬ Int64.max`  will be cast to `Int`
+    /// (or `Int64` on 32-bit platforms), values above `Int64.max` will be cast to `UInt`
+    /// (or `UInt64` on 32-bit platforms).
     public enum Identifier: Equatable, Hashable, CustomStringConvertible, Sendable {
 
 #if _pointerBitWidth(_32)

Tests/GISToolsTests/GeoJson/FeatureTests.swift

@@ -106,19 +106,23 @@ final class FeatureTests: XCTestCase {
     }
 
     func testFeatureIds() throws {
+        XCTAssertEqual(Feature.Identifier(value: 1234), .int(1234))
         XCTAssertEqual(Feature.Identifier(value: Int8(32)), .int(32))
         XCTAssertEqual(Feature.Identifier(value: Int8(32))?.int64Value, 32)
         XCTAssertEqual(Feature.Identifier(value: Int8(32))?.uint64Value, 32)
 
-        // UInt -> Int
-        XCTAssertEqual(Feature.Identifier(value: UInt64(32)), .int(32))
-
+        XCTAssertEqual(Feature.Identifier(value: -1234), .int(-1234))
         XCTAssertEqual(Feature.Identifier(value: Int8(-32)), .int(-32))
         XCTAssertEqual(Feature.Identifier(value: Int8(-32))?.int64Value, -32)
         XCTAssertNil(Feature.Identifier(value: Int8(-32))?.uint64Value)
 
+        // UInt -> Int
+        XCTAssertEqual(Feature.Identifier(value: UInt64(32)), .int(32))
+
         XCTAssertEqual(Feature.Identifier(value: Int64.max), .int(9223372036854775807))
         XCTAssertEqual(Feature.Identifier(value: Int64.max)?.int64Value, 9223372036854775807)
+        XCTAssertEqual(Feature.Identifier(value: Int64.min), .int(-9223372036854775808))
+        XCTAssertEqual(Feature.Identifier(value: Int64.min)?.int64Value, -9223372036854775808)
 
         // 9223372036854775808 is Int64.max+1
         XCTAssertEqual(Feature.Identifier(value: UInt64(9223372036854775808)), .uint(9223372036854775808))