Merge pull request #43 from wickwirew/nested-struct-crash

check the flags to check whether the type is generic or not

Author: wickwirew

Sources/Runtime/Layouts/StructTypeDescriptor.swift

@@ -28,7 +28,7 @@ struct StructTypeDescriptor: TypeDescriptor {
     var flags: ContextDescriptorFlags
     var parent: Int32
     var mangledName: RelativePointer<Int32, CChar>
-    var unknown3: Int32
+    var accessFunctionPtr: RelativePointer<Int32, UnsafeRawPointer>
     var fieldDescriptor: RelativePointer<Int32, FieldDescriptor>
     var numberOfFields: Int32
     var offsetToTheFieldOffsetVector: RelativeVectorPointer<Int32, Int32>

Sources/Runtime/Layouts/TypeDescriptor.swift

@@ -26,6 +26,7 @@ protocol TypeDescriptor {
     /// e.g. Struct are an Int32 and classes are an Int
     associatedtype FieldOffsetVectorOffsetType: IntegerConvertible
 
+    var flags: ContextDescriptorFlags { get set }
     var mangledName: RelativePointer<Int32, CChar> { get set }
     var fieldDescriptor: RelativePointer<Int32, FieldDescriptor> { get set }
     var numberOfFields: Int32 { get set }

Sources/Runtime/Metadata/NominalMetadataType.swift

@@ -35,6 +35,10 @@ extension NominalMetadataType {
         return 2
     }
 
+    var isGeneric: Bool {
+        return (pointer.pointee.typeDescriptor.pointee.flags & 0x80) != 0
+    }
+    
     mutating func mangledName() -> String {
         return String(cString: pointer.pointee.typeDescriptor.pointee.mangledName.advanced())
     }
@@ -78,11 +82,18 @@ extension NominalMetadataType {
     }
 
     func genericArguments() -> [Any.Type] {
-        let n = pointer.pointee.typeDescriptor.pointee.genericContextHeader.base.numberOfParams
-        guard n > 0 else { return [] }
+        guard isGeneric else { return [] }
+        
+        let genericHeader = pointer.pointee
+            .typeDescriptor
+            .pointee
+            .genericContextHeader
+        
+        guard genericHeader.base.numberOfParams > 0 else { return [] }
 
         let vector = genericArgumentVector()
-        return (0..<Int(pointer.pointee.typeDescriptor.pointee.genericContextHeader.base.numberOfParams)).map { i in
+        
+        return (0..<Int(genericHeader.base.numberOfParams)).map { i in
             return vector.pointee.element(at: i).pointee
         }
     }

Tests/RuntimeTests/MetadataTests.swift

@@ -79,6 +79,7 @@ class MetadataTests: XCTestCase {
 
         var md = StructMetadata(type: A.self)
         let info = md.toTypeInfo()
+        XCTAssert(info.genericTypes.count == 0)
         XCTAssert(info.kind == .struct)
         XCTAssert(info.type == A.self)
         XCTAssert(info.properties.count == 5)
@@ -89,6 +90,32 @@ class MetadataTests: XCTestCase {
         XCTAssert(info.properties[4].isVar)
     }
 
+    // https://github.com/wickwirew/Runtime/issues/42
+    func testNestedStruct() {
+        
+        let nest: () -> Void = {
+            
+            struct NestedA {
+                let a, b, c, d: Int
+                var e: Int
+            }
+            
+            var md = StructMetadata(type: NestedA.self)
+            let info = md.toTypeInfo()
+            XCTAssert(info.genericTypes.count == 0)
+            XCTAssert(info.kind == .struct)
+            XCTAssert(info.type == NestedA.self)
+            XCTAssert(info.properties.count == 5)
+            XCTAssert(info.size == MemoryLayout<NestedA>.size)
+            XCTAssert(info.alignment == MemoryLayout<NestedA>.alignment)
+            XCTAssert(info.stride == MemoryLayout<NestedA>.stride)
+            XCTAssert(!info.properties[0].isVar)
+            XCTAssert(info.properties[4].isVar)
+        }
+        
+        nest()
+    }
+    
     func testProtocol() {
         var md = ProtocolMetadata(type: MyProtocol.self)
         let info = md.toTypeInfo()