swiftwasm · krodak · Jan 21, 2026 · Jan 21, 2026
diff --git a/Examples/PlayBridgeJS/Sources/PlayBridgeJS/Generated/BridgeJS.Macros.swift b/Examples/PlayBridgeJS/Sources/PlayBridgeJS/Generated/BridgeJS.Macros.swift
@@ -8,6 +8,6 @@
 
 @JSFunction func createTS2Swift() throws (JSException) -> TS2Swift
 
-@JSClass struct TS2Swift: _JSBridgedClass {
+@JSClass struct TS2Swift {
     @JSFunction func convert(_ ts: String) throws (JSException) -> String
 }
diff --git a/Plugins/BridgeJS/Sources/BridgeJSMacros/JSClassMacro.swift b/Plugins/BridgeJS/Sources/BridgeJSMacros/JSClassMacro.swift
@@ -9,6 +9,7 @@ extension JSClassMacro: MemberMacro {
     public static func expansion(
         of node: AttributeSyntax,
         providingMembersOf declaration: some DeclGroupSyntax,
+        conformingTo protocols: [TypeSyntax],
         in context: some MacroExpansionContext
     ) throws -> [DeclSyntax] {
         var members: [DeclSyntax] = []
@@ -49,3 +50,20 @@ extension JSClassMacro: MemberMacro {
         return members
     }
 }
+
+extension JSClassMacro: ExtensionMacro {
+    public static func expansion(
+        of node: AttributeSyntax,
+        attachedTo declaration: some DeclGroupSyntax,
+        providingExtensionsOf type: some TypeSyntaxProtocol,
+        conformingTo protocols: [TypeSyntax],
+        in context: some MacroExpansionContext
+    ) throws -> [ExtensionDeclSyntax] {
+        guard !protocols.isEmpty else { return [] }
+
+        let conformanceList = protocols.map { $0.trimmed.description }.joined(separator: ", ")
+        return [
+            try ExtensionDeclSyntax("extension \(type.trimmed): \(raw: conformanceList) {}")
+        ]
+    }
+}
diff --git a/Plugins/BridgeJS/Sources/TS2Swift/JavaScript/src/processor.js b/Plugins/BridgeJS/Sources/TS2Swift/JavaScript/src/processor.js
@@ -213,7 +213,7 @@ export class TypeProcessor {
         if (!node.name) return;
 
         const className = this.renderIdentifier(node.name.text);
-        this.swiftLines.push(`@JSClass struct ${className}: _JSBridgedClass {`);
+        this.swiftLines.push(`@JSClass struct ${className} {`);
 
         // Process members in declaration order
         for (const member of node.members) {
@@ -268,7 +268,7 @@ export class TypeProcessor {
      */
     visitStructuredType(name, members) {
         const typeName = this.renderIdentifier(name);
-        this.swiftLines.push(`@JSClass struct ${typeName}: _JSBridgedClass {`);
+        this.swiftLines.push(`@JSClass struct ${typeName} {`);
 
         // Collect all declarations with their positions to preserve order
         /** @type {Array<{ decl: ts.Node, symbol: ts.Symbol, position: number }>} */

diff --git a/Plugins/BridgeJS/Tests/BridgeJSMacrosTests/JSClassMacroTests.swift b/Plugins/BridgeJS/Tests/BridgeJSMacrosTests/JSClassMacroTests.swift
@@ -1,12 +1,16 @@
 import SwiftDiagnostics
 import SwiftSyntax
+import SwiftSyntaxMacroExpansion
 import SwiftSyntaxMacros
 import SwiftSyntaxMacrosTestSupport
 import Testing
 import BridgeJSMacros
 
 @Suite struct JSClassMacroTests {
     private let indentationWidth: Trivia = .spaces(4)
+    private let macroSpecs: [String: MacroSpec] = [
+        "JSClass": MacroSpec(type: JSClassMacro.self, conformances: ["_JSBridgedClass"])
+    ]
 
     @Test func emptyStruct() {
         assertMacroExpansion(
@@ -23,8 +27,11 @@ import BridgeJSMacros
                         self.jsObject = jsObject
                     }
                 }
+
+                extension MyClass: _JSBridgedClass {
+                }
                 """,
-            macros: ["JSClass": JSClassMacro.self],
+            macroSpecs: macroSpecs,
             indentationWidth: indentationWidth
         )
     }
@@ -45,8 +52,11 @@ import BridgeJSMacros
                         self.jsObject = jsObject
                     }
                 }
+
+                extension MyClass: _JSBridgedClass {
+                }
                 """,
-            macros: ["JSClass": JSClassMacro.self],
+            macroSpecs: macroSpecs,
             indentationWidth: indentationWidth
         )
     }
@@ -69,8 +79,11 @@ import BridgeJSMacros
                         self.jsObject = jsObject
                     }
                 }
+
+                extension MyClass: _JSBridgedClass {
+                }
                 """,
-            macros: ["JSClass": JSClassMacro.self],
+            macroSpecs: macroSpecs,
             indentationWidth: indentationWidth
         )
     }
@@ -95,8 +108,11 @@ import BridgeJSMacros
                         self.jsObject = jsObject
                     }
                 }
+
+                extension MyClass: _JSBridgedClass {
+                }
                 """,
-            macros: ["JSClass": JSClassMacro.self],
+            macroSpecs: macroSpecs,
             indentationWidth: indentationWidth
         )
     }
@@ -119,8 +135,11 @@ import BridgeJSMacros
                         self.jsObject = jsObject
                     }
                 }
+
+                extension MyClass: _JSBridgedClass {
+                }
                 """,
-            macros: ["JSClass": JSClassMacro.self],
+            macroSpecs: macroSpecs,
             indentationWidth: indentationWidth
         )
     }
@@ -140,8 +159,11 @@ import BridgeJSMacros
                         self.jsObject = jsObject
                     }
                 }
+
+                extension MyClass: _JSBridgedClass {
+                }
                 """,
-            macros: ["JSClass": JSClassMacro.self],
+            macroSpecs: macroSpecs,
             indentationWidth: indentationWidth
         )
     }
@@ -161,8 +183,11 @@ import BridgeJSMacros
                         self.jsObject = jsObject
                     }
                 }
+
+                extension MyEnum: _JSBridgedClass {
+                }
                 """,
-            macros: ["JSClass": JSClassMacro.self],
+            macroSpecs: macroSpecs,
             indentationWidth: indentationWidth
         )
     }
@@ -182,8 +207,11 @@ import BridgeJSMacros
                         self.jsObject = jsObject
                     }
                 }
+
+                extension MyActor: _JSBridgedClass {
+                }
                 """,
-            macros: ["JSClass": JSClassMacro.self],
+            macroSpecs: macroSpecs,
             indentationWidth: indentationWidth
         )
     }
@@ -206,8 +234,11 @@ import BridgeJSMacros
                         self.jsObject = jsObject
                     }
                 }
+
+                extension MyClass: _JSBridgedClass {
+                }
                 """,
-            macros: ["JSClass": JSClassMacro.self],
+            macroSpecs: macroSpecs,
             indentationWidth: indentationWidth
         )
     }
@@ -232,8 +263,11 @@ import BridgeJSMacros
                         self.jsObject = jsObject
                     }
                 }
+
+                extension MyClass: _JSBridgedClass {
+                }
                 """,
-            macros: ["JSClass": JSClassMacro.self],
+            macroSpecs: macroSpecs,
             indentationWidth: indentationWidth
         )
     }
@@ -258,8 +292,11 @@ import BridgeJSMacros
                         self.jsObject = jsObject
                     }
                 }
+
+                extension MyClass: _JSBridgedClass {
+                }
                 """,
-            macros: ["JSClass": JSClassMacro.self],
+            macroSpecs: macroSpecs,
             indentationWidth: indentationWidth
         )
     }
@@ -281,8 +318,32 @@ import BridgeJSMacros
                         self.jsObject = jsObject
                     }
                 }
+
+                extension MyClass: _JSBridgedClass {
+                }
+                """,
+            macroSpecs: macroSpecs,
+            indentationWidth: indentationWidth
+        )
+    }
+
+    @Test func structAlreadyConforms() {
+        assertMacroExpansion(
+            """
+            @JSClass
+            struct MyClass: _JSBridgedClass {
+            }
+            """,
+            expandedSource: """
+                struct MyClass: _JSBridgedClass {
+                    let jsObject: JSObject
+
+                    init(unsafelyWrapping jsObject: JSObject) {
+                        self.jsObject = jsObject
+                    }
+                }
                 """,
-            macros: ["JSClass": JSClassMacro.self],
+            macroSpecs: macroSpecs,
             indentationWidth: indentationWidth
         )
     }

diff --git a/Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/ImportTSTests/Interface.Macros.swift b/Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/ImportTSTests/Interface.Macros.swift
@@ -8,7 +8,7 @@
 
 @JSFunction func returnAnimatable() throws (JSException) -> Animatable
 
-@JSClass struct Animatable: _JSBridgedClass {
+@JSClass struct Animatable {
     @JSFunction func animate(_ keyframes: JSObject, _ options: JSObject) throws (JSException) -> JSObject
     @JSFunction func getAnimations(_ options: JSObject) throws (JSException) -> JSObject
 }
diff --git a/...eJS/Tests/BridgeJSToolTests/__Snapshots__/ImportTSTests/InvalidPropertyNames.Macros.swift b/...eJS/Tests/BridgeJSToolTests/__Snapshots__/ImportTSTests/InvalidPropertyNames.Macros.swift
@@ -8,14 +8,14 @@
 
 @JSFunction func createArrayBuffer() throws (JSException) -> ArrayBufferLike
 
-@JSClass struct ArrayBufferLike: _JSBridgedClass {
+@JSClass struct ArrayBufferLike {
     @JSGetter var byteLength: Double
     @JSFunction func slice(_ begin: Double, _ end: Double) throws (JSException) -> ArrayBufferLike
 }
 
 @JSFunction func createWeirdObject() throws (JSException) -> WeirdNaming
 
-@JSClass struct WeirdNaming: _JSBridgedClass {
+@JSClass struct WeirdNaming {
     @JSGetter var normalProperty: String
     @JSSetter func setNormalProperty(_ value: String) throws (JSException)
     @JSGetter var `for`: String

diff --git a/...JS/Tests/BridgeJSToolTests/__Snapshots__/ImportTSTests/MultipleImportedTypes.Macros.swift b/...JS/Tests/BridgeJSToolTests/__Snapshots__/ImportTSTests/MultipleImportedTypes.Macros.swift
@@ -8,7 +8,7 @@
 
 @JSFunction func createDatabaseConnection(_ config: JSObject) throws (JSException) -> DatabaseConnection
 
-@JSClass struct DatabaseConnection: _JSBridgedClass {
+@JSClass struct DatabaseConnection {
     @JSFunction func connect(_ url: String) throws (JSException) -> Void
     @JSFunction func execute(_ query: String) throws (JSException) -> JSObject
     @JSGetter var isConnected: Bool
@@ -18,15 +18,15 @@
 
 @JSFunction func createLogger(_ level: String) throws (JSException) -> Logger
 
-@JSClass struct Logger: _JSBridgedClass {
+@JSClass struct Logger {
     @JSFunction func log(_ message: String) throws (JSException) -> Void
     @JSFunction func error(_ message: String, _ error: JSObject) throws (JSException) -> Void
     @JSGetter var level: String
 }
 
 @JSFunction func getConfigManager() throws (JSException) -> ConfigManager
 
-@JSClass struct ConfigManager: _JSBridgedClass {
+@JSClass struct ConfigManager {
     @JSFunction func get(_ key: String) throws (JSException) -> JSObject
     @JSFunction func set(_ key: String, _ value: JSObject) throws (JSException) -> Void
     @JSGetter var configPath: String

diff --git a/...BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/ImportTSTests/TS2SkeletonLike.Macros.swift b/...BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/ImportTSTests/TS2SkeletonLike.Macros.swift
@@ -8,15 +8,15 @@
 
 @JSFunction func createTS2Skeleton() throws (JSException) -> TypeScriptProcessor
 
-@JSClass struct TypeScriptProcessor: _JSBridgedClass {
+@JSClass struct TypeScriptProcessor {
     @JSFunction func convert(_ ts: String) throws (JSException) -> String
     @JSFunction func validate(_ ts: String) throws (JSException) -> Bool
     @JSGetter var version: String
 }
 
 @JSFunction func createCodeGenerator(_ format: String) throws (JSException) -> CodeGenerator
 
-@JSClass struct CodeGenerator: _JSBridgedClass {
+@JSClass struct CodeGenerator {
     @JSFunction func generate(_ input: JSObject) throws (JSException) -> String
     @JSGetter var outputFormat: String
 }
diff --git a/...BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/ImportTSTests/TypeScriptClass.Macros.swift b/...BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/ImportTSTests/TypeScriptClass.Macros.swift
@@ -6,7 +6,7 @@
 
 @_spi(Experimental) import JavaScriptKit
 
-@JSClass struct Greeter: _JSBridgedClass {
+@JSClass struct Greeter {
     @JSGetter var name: String
     @JSSetter func setName(_ value: String) throws (JSException)
     @JSGetter var age: Double

diff --git a/Sources/JavaScriptKit/JSBridgedType.swift b/Sources/JavaScriptKit/JSBridgedType.swift
@@ -15,7 +15,7 @@ extension JSBridgedType {
 
 /// A protocol that Swift classes that are exposed to JavaScript via `@JS class` conform to.
 ///
-/// The conformance is automatically synthesized by the BridgeJS code generator.
+/// The conformance is automatically synthesized by `@JSClass` for BridgeJS-generated declarations.
 public protocol _JSBridgedClass {
     /// The JavaScript object wrapped by this instance.
     /// You may assume that `jsObject instanceof Self.constructor == true`

diff --git a/Sources/JavaScriptKit/Macros.swift b/Sources/JavaScriptKit/Macros.swift
@@ -174,14 +174,15 @@ public macro JSFunction() =
 /// @_spi(Experimental) import JavaScriptKit
 ///
 /// @JSClass
-/// struct JsGreeter: _JSBridgedClass {
+/// struct JsGreeter {
 ///     @JSGetter var name: String
 ///     @JSSetter func setName(_ value: String) throws (JSException)
 ///     @JSFunction init(_ name: String) throws (JSException)
 ///     @JSFunction func greet() throws (JSException) -> String
 /// }
 /// ```
 @attached(member, names: arbitrary)
+@attached(extension, conformances: _JSBridgedClass)
 @_spi(Experimental)
 public macro JSClass() =
     #externalMacro(module: "BridgeJSMacros", type: "JSClassMacro")
diff --git a/Tests/BridgeJSRuntimeTests/Generated/BridgeJS.Macros.swift b/Tests/BridgeJSRuntimeTests/Generated/BridgeJS.Macros.swift
@@ -22,7 +22,7 @@
 
 @JSFunction func jsThrowOrString(_ shouldThrow: Bool) throws (JSException) -> String
 
-@JSClass struct JsGreeter: _JSBridgedClass {
+@JSClass struct JsGreeter {
     @JSGetter var name: String
     @JSSetter func setName(_ value: String) throws (JSException)
     @JSGetter var `prefix`: String