fix: correct hierarchical style resolution and level conversion

Sources/OpenSwiftUICore/Shape/ShapeStyle/ContentStyle.swift

@@ -2,7 +2,7 @@
 //  ContentStyle.swift
 //  OpenSwiftUICore
 //
-//  Audited for 6.0.87
+//  Audited for 6.5.4
 //  Status: Complete
 //  ID: BE30CA4BBA5F98638AD9D34F1557FB4D (SwiftUICore)
 
@@ -286,17 +286,15 @@ extension ContentStyle.ID: ColorProvider {
     }
 
     package init?(level: Int) {
-        self.init(rawValue: Int8(level & 0xFF))
+        guard (0..<5).contains(level) else {
+            return nil
+        }
+        self.init(rawValue: Int8(level))
     }
 
     package init(truncatingLevel level: Int) {
-        switch level {
-        case 0: self = .primary
-        case 1: self = .secondary
-        case 2: self = .tertiary
-        case 3: self = .quaternary
-        default: self = .quinary
-        }
+        let rawValue = Int8(truncatingIfNeeded: min(level, 4))
+        self = Self(rawValue: rawValue)!
     }
 }
 
@@ -345,7 +343,7 @@ public struct HierarchicalShapeStyleModifier<Base>: ShapeStyle where Base: Shape
     }
 
     public func _apply(to shape: inout _ShapeStyle_Shape) {
-        if let primaryStyle = primaryStyle(in: shape.environment) {
+        if let primaryStyle = base.primaryStyle(in: shape.environment) {
             primaryStyle.offset(by: level)._apply(to: &shape)
         } else {
             base.offset(by: level)._apply(to: &shape)

Tests/OpenSwiftUICoreTests/Shape/ShapeStyle/ContentStyleTests.swift

@@ -0,0 +1,43 @@
+//
+//  ContentStyleTests.swift
+//  OpenSwiftUICoreTests
+
+import OpenSwiftUICore
+import OpenSwiftUITestsSupport
+import Testing
+
+@Suite(.tags(.aigc))
+struct ContentStyleTests {
+    @Test(arguments: [
+        (0, ContentStyle.ID.primary),
+        (1, .secondary),
+        (2, .tertiary),
+        (3, .quaternary),
+        (4, .quinary),
+    ])
+    func levelSelectsStyle(level: Int, expected: ContentStyle.ID) {
+        #expect(ContentStyle.ID(level: level) == expected)
+    }
+
+    @Test(arguments: [Int.min, -256, -1, 5, 127, 128, 255, 256, 260, Int.max])
+    func invalidLevelReturnsNil(level: Int) {
+        #expect(ContentStyle.ID(level: level) == nil)
+    }
+
+    @Test(arguments: [
+        (0, ContentStyle.ID.primary),
+        (1, .secondary),
+        (2, .tertiary),
+        (3, .quaternary),
+        (4, .quinary),
+        (5, .quinary),
+        (256, .quinary),
+        (Int.max, .quinary),
+        (-256, .primary),
+        (-255, .secondary),
+        (-252, .quinary),
+    ])
+    func truncatingLevelSelectsStyle(level: Int, expected: ContentStyle.ID) {
+        #expect(ContentStyle.ID(truncatingLevel: level) == expected)
+    }
+}

Tests/OpenSwiftUICoreTests/Shape/ShapeStyle/HierarchicalShapeStyleTests.swift

@@ -0,0 +1,46 @@
+//
+//  HierarchicalShapeStyleTests.swift
+//  OpenSwiftUICoreTests
+
+@testable import OpenSwiftUICore
+import OpenSwiftUITestsSupport
+import Testing
+
+@Suite(.tags(.aigc))
+struct HierarchicalShapeStyleTests {
+    @Test
+    func secondaryColorUsesBaseColor() {
+        var environment = EnvironmentValues()
+        environment.setTestSystemColorDefinition()
+        var shape = _ShapeStyle_Shape(
+            operation: .fallbackColor(level: 0),
+            environment: environment
+        )
+
+        Color.red.secondary._apply(to: &shape)
+
+        guard case let .color(color) = shape.result else {
+            Issue.record("Expected secondary fallback color")
+            return
+        }
+        #expect(color == .red.opacity(0.75))
+    }
+
+    @Test
+    func nestedStyleUsesPrimaryBaseColor() {
+        var environment = EnvironmentValues()
+        environment.setTestSystemColorDefinition()
+        var shape = _ShapeStyle_Shape(
+            operation: .fallbackColor(level: 0),
+            environment: environment
+        )
+
+        Color.red.tertiary.secondary._apply(to: &shape)
+
+        guard case let .color(color) = shape.result else {
+            Issue.record("Expected secondary fallback color")
+            return
+        }
+        #expect(color == .red.opacity(0.75))
+    }
+}