diff --git a/bind/genclasses.go b/bind/genclasses.go
index 30f375d..465a0c8 100644
--- a/bind/genclasses.go
+++ b/bind/genclasses.go
@@ -302,7 +302,7 @@
 		g.Printf(", _a%d", i)
 	}
 	g.Printf(");\n")
-	g.Printf("jobject _exc = go_seq_wrap_exception(env);\n")
+	g.Printf("jobject _exc = go_seq_get_exception(env);\n")
 	g.Printf("int32_t _exc_ref = go_seq_to_refnum(env, _exc);\n")
 	if f.Ret != nil {
 		g.genJavaToC("res", f.Ret)
@@ -370,7 +370,7 @@
 			g.Printf(", _a%d", i)
 		}
 		g.Printf(");\n")
-		g.Printf("jobject _exc = go_seq_wrap_exception(env);\n")
+		g.Printf("jobject _exc = go_seq_get_exception(env);\n")
 		g.Printf("int32_t _exc_ref = go_seq_to_refnum(env, _exc);\n")
 		if f.Ret != nil {
 			g.genJavaToC("res", f.Ret)
diff --git a/bind/genjava.go b/bind/genjava.go
index 589af2f..ee5d65a 100644
--- a/bind/genjava.go
+++ b/bind/genjava.go
@@ -120,6 +120,15 @@
 	return nil
 }
 
+func (g *JavaGen) genProxyImpl(name string) {
+	g.Printf("private final Seq.Ref ref;\n\n")
+	g.Printf("@Override public final int incRefnum() {\n")
+	g.Printf("      int refnum = ref.refnum;\n")
+	g.Printf("      Seq.incGoRef(refnum);\n")
+	g.Printf("      return refnum;\n")
+	g.Printf("}\n\n")
+}
+
 func (g *JavaGen) genStruct(s structInfo) {
 	pkgPath := ""
 	if g.Pkg != nil {
@@ -140,6 +149,8 @@
 				impls = append(impls, cls.Name)
 			}
 		}
+	} else {
+		impls = append(impls, "Seq.Proxy")
 	}
 
 	pT := types.NewPointer(s.obj.Type())
@@ -158,8 +169,6 @@
 		if jinf.extends != nil {
 			g.Printf(" extends %s", jinf.extends.Name)
 		}
-	} else {
-		g.Printf(" extends Seq.Proxy")
 	}
 	if len(impls) > 0 {
 		g.Printf(" implements %s", strings.Join(impls, ", "))
@@ -168,8 +177,8 @@
 	g.Indent()
 
 	g.Printf("static { %s.touch(); }\n\n", g.className())
+	g.genProxyImpl(n)
 	if jinf != nil {
-		g.Printf("private final Seq.Ref ref;\n\n")
 		for _, f := range jinf.cons {
 			if !g.isSigSupported(f.Type()) {
 				g.Printf("// skipped constructor %s.%s with unsupported parameter or return types\n\n", n, f.Name())
@@ -184,13 +193,8 @@
 			g.Printf("public %s() { this.ref = __New(); }\n\n", n)
 			g.Printf("private static native Seq.Ref __New();\n\n")
 		}
-		g.Printf("@Override public final int incRefnum() {\n")
-		g.Printf("	int refnum = ref.refnum;\n")
-		g.Printf("	Seq.incGoRef(refnum);\n")
-		g.Printf("	return refnum;\n")
-		g.Printf("}\n\n")
 	} else {
-		g.Printf("%s(Seq.Ref ref) { super(ref); }\n\n", n)
+		g.Printf("%s(Seq.Ref ref) { this.ref = ref; }\n\n", n)
 	}
 
 	for _, f := range fields {
@@ -1090,7 +1094,7 @@
 			rets = append(rets, retName)
 		}
 		if res.Len() == 2 || isErrorType(t) {
-			g.Printf("jobject exc = go_seq_wrap_exception(env);\n")
+			g.Printf("jobject exc = go_seq_get_exception(env);\n")
 			errType := types.Universe.Lookup("error").Type()
 			g.genJavaToC("exc", errType, modeRetained)
 			retName = "_exc"
@@ -1288,6 +1292,13 @@
 		g.Printf("clazz = (*env)->FindClass(env, %q);\n", g.jniClassSigPrefix(pkg)+className(pkg)+"$proxy"+iface.obj.Name())
 		g.Printf("proxy_class_%s_%s = (*env)->NewGlobalRef(env, clazz);\n", g.pkgPrefix, iface.obj.Name())
 		g.Printf("proxy_class_%s_%s_cons = (*env)->GetMethodID(env, clazz, \"<init>\", \"(Lgo/Seq$Ref;)V\");\n", g.pkgPrefix, iface.obj.Name())
+		if isErrorType(iface.obj.Type()) {
+			// As a special case, Java Exceptions are passed to Go pretending to implement the Go error interface.
+			// To complete the illusion, use the Throwable.getMessage method for proxied calls to the error.Error method.
+			g.Printf("clazz = (*env)->FindClass(env, \"java/lang/Throwable\");\n")
+			g.Printf("mid_error_Error = (*env)->GetMethodID(env, clazz, \"getMessage\", \"()Ljava/lang/String;\");\n")
+			continue
+		}
 		g.Printf("clazz = (*env)->FindClass(env, %q);\n", g.jniClassSigPrefix(pkg)+iface.obj.Name())
 		for _, m := range iface.summary.callable {
 			if !g.isSigSupported(m.Type()) {
@@ -1390,12 +1401,22 @@
 	g.Printf("private static native void _init();\n\n")
 
 	for _, iface := range g.interfaces {
-		g.Printf(javaProxyPreamble, iface.obj.Name())
+		n := iface.obj.Name()
+		g.Printf("private static final class proxy%s", n)
+		if isErrorType(iface.obj.Type()) {
+			g.Printf(" extends Exception")
+		}
+		g.Printf(" implements Seq.Proxy, %s {\n", n)
 		g.Indent()
+		g.genProxyImpl("proxy" + n)
+		g.Printf("proxy%s(Seq.Ref ref) { this.ref = ref; }\n\n", n)
 
+		if isErrorType(iface.obj.Type()) {
+			g.Printf("@Override public String getMessage() { return error(); }\n\n")
+		}
 		for _, m := range iface.summary.callable {
 			if !g.isSigSupported(m.Type()) {
-				g.Printf("// skipped method %s.%s with unsupported parameter or return types\n\n", iface.obj.Name(), m.Name())
+				g.Printf("// skipped method %s.%s with unsupported parameter or return types\n\n", n, m.Name())
 				continue
 			}
 			g.Printf("public native ")
@@ -1461,10 +1482,6 @@
 }
 
 const (
-	javaProxyPreamble = `private static final class proxy%[1]s extends Seq.Proxy implements %[1]s {
-	proxy%[1]s(Seq.Ref ref) { super(ref); }
-
-`
 	javaPreamble = `// Java class %[1]s.%[2]s is a proxy for talking to a Go program.
 //   gobind %[3]s %[4]s
 //
diff --git a/bind/genobjc.go b/bind/genobjc.go
index 49467f0..b1ab0ff 100644
--- a/bind/genobjc.go
+++ b/bind/genobjc.go
@@ -193,12 +193,8 @@
 
 func (g *objcGen) genM() error {
 	var pkgPath string
-	var errDomain string
 	if g.Pkg != nil {
 		pkgPath = g.Pkg.Path()
-		errDomain = "go." + pkgPath
-	} else {
-		errDomain = "go"
 	}
 	g.Printf(objcPreamble, pkgPath, g.gobindOpts(), pkgPath)
 	g.Printf("#include <Foundation/Foundation.h>\n")
@@ -206,8 +202,6 @@
 	g.Printf("#include \"_cgo_export.h\"\n")
 	g.Printf("#include %q\n", g.namePrefix+".h")
 	g.Printf("\n")
-	g.Printf("static NSString* errDomain = @%q;\n", errDomain)
-	g.Printf("\n")
 
 	// struct
 	for _, s := range g.structs {
@@ -676,7 +670,7 @@
 			if isErrorType(p.typ) {
 				g.Printf("if (_%s != nil && %s != nil) {\n", p.name, p.name)
 				g.Indent()
-				g.Printf("*%s = go_seq_to_nserror(_%s, errDomain);\n", p.name, p.name)
+				g.Printf("*%s = _%s;\n", p.name, p.name)
 				g.Outdent()
 				g.Printf("}\n")
 			} else {
@@ -696,14 +690,19 @@
 }
 
 func (g *objcGen) genInterfaceInterface(obj *types.TypeName, summary ifaceSummary, isProtocol bool) {
-	g.Printf("@interface %[1]s%[2]s : NSObject", g.namePrefix, obj.Name())
+	g.Printf("@interface %[1]s%[2]s : ", g.namePrefix, obj.Name())
+	if isErrorType(obj.Type()) {
+		g.Printf("NSError")
+	} else {
+		g.Printf("NSObject")
+	}
 	if isProtocol {
 		g.Printf(" <%[1]s%[2]s>", g.namePrefix, obj.Name())
 	}
 	g.Printf(" {\n}\n")
 	g.Printf("@property(strong, readonly) id _ref;\n")
 	g.Printf("\n")
-	g.Printf("- (id)initWithRef:(id)ref;\n")
+	g.Printf("- (instancetype)initWithRef:(id)ref;\n")
 	for _, m := range summary.callable {
 		if !g.isSigSupported(m.Type()) {
 			g.Printf("// skipped method %s.%s with unsupported parameter or return types\n\n", obj.Name(), m.Name())
@@ -740,10 +739,17 @@
 	g.Printf("@implementation %s%s {\n", g.namePrefix, obj.Name())
 	g.Printf("}\n")
 	g.Printf("\n")
-	g.Printf("- (id)initWithRef:(id)ref {\n")
+	g.Printf("- (instancetype)initWithRef:(id)ref {\n")
 	g.Indent()
-	g.Printf("self = [super init];\n")
-	g.Printf("if (self) { __ref = ref; }\n")
+	if isErrorType(obj.Type()) {
+		g.Printf("if (self) {\n")
+		g.Printf("	__ref = ref;\n")
+		g.Printf("	self = [super initWithDomain:@\"go\" code:1 userInfo:@{NSLocalizedDescriptionKey: [self error]}];\n")
+		g.Printf("}\n")
+	} else {
+		g.Printf("self = [super init];\n")
+		g.Printf("if (self) { __ref = ref; }\n")
+	}
 	g.Printf("return self;\n")
 	g.Outdent()
 	g.Printf("}\n")
@@ -790,10 +796,16 @@
 		}
 	}
 
-	if s.ret == "void" {
-		g.Printf("[o %s];\n", s.callMethod(g))
+	if isErrorType(obj.Type()) && m.Name() == "Error" {
+		// As a special case, ObjC NSErrors are passed to Go pretending to implement the Go error interface.
+		// They don't actually have an Error method, so calls to to it needs to be rerouted.
+		g.Printf("NSString *returnVal = [o localizedDescription];\n")
 	} else {
-		g.Printf("%s returnVal = [o %s];\n", s.ret, s.callMethod(g))
+		if s.ret == "void" {
+			g.Printf("[o %s];\n", s.callMethod(g))
+		} else {
+			g.Printf("%s returnVal = [o %s];\n", s.ret, s.callMethod(g))
+		}
 	}
 
 	if len(s.retParams) > 0 {
@@ -812,7 +824,7 @@
 						g.Printf("if (%s != nil) {\n", p.name)
 					}
 					g.Indent()
-					g.Printf("_%[1]s = [[goSeqErrorWrapper alloc] initWithError:%[1]s];\n", p.name)
+					g.Printf("_%[1]s = %[1]s;\n", p.name)
 					g.Outdent()
 					g.Printf("}\n")
 					g.genWrite("_"+p.name, p.typ, modeRetained)
diff --git a/bind/java/Seq.java b/bind/java/Seq.java
index 2d636a9..b421a93 100644
--- a/bind/java/Seq.java
+++ b/bind/java/Seq.java
@@ -9,7 +9,6 @@
 import java.util.logging.Logger;
 
 import go.Universe;
-import go.error;
 
 // Seq is a sequence of machine-dependent encoded values.
 // Used by automatically generated language bindings to talk to Go.
@@ -48,18 +47,6 @@
 	private Seq() {
 	}
 
-	private static void throwException(error err) throws Exception {
-		throw new Exception(err.error());
-	}
-
-	private static error wrapThrowable(final Throwable t) {
-		return new error() {
-			@Override public String error() {
-				return t.getMessage();
-			}
-		};
-	}
-
 	// ctx is an android.context.Context.
 	static native void setContext(java.lang.Object ctx);
 
@@ -105,23 +92,10 @@
 		// invalidating it before being translated on the Go side.
 		int incRefnum();
 	}
-
 	// A Proxy is a Java object that proxies a Go object. Proxies, unlike
 	// GoObjects, are unwrapped to their Go counterpart when deserialized
 	// in Go.
-	public static abstract class Proxy implements GoObject {
-		private final Ref ref;
-
-		protected Proxy(Ref ref) {
-			this.ref = ref;
-		}
-
-		@Override public final int incRefnum() {
-			int refnum = ref.refnum;
-			Seq.incGoRef(refnum);
-			return refnum;
-		}
-	}
+	public interface Proxy extends GoObject {}
 
 	// A Ref is an object tagged with an integer for passing back and
 	// forth across the language boundary.
diff --git a/bind/java/SeqTest.java b/bind/java/SeqTest.java
index 6348e01..5e6af55 100644
--- a/bind/java/SeqTest.java
+++ b/bind/java/SeqTest.java
@@ -416,11 +416,19 @@
   }
 
   public void testErrorField() {
-    final String want = "an error message";
     Node n = Testpkg.newNode("ErrTest");
-    n.setErr(new Exception(want));
+    Exception want = new Exception("an error message");
+    n.setErr(want);
     Exception got = n.getErr();
-    assertEquals("want back the error message we set", want, got.getMessage());
+    assertTrue("want back the error we set", want == got);
+    String msg = Testpkg.errorMessage(want);
+    assertEquals("the error message must match", want.getMessage(), msg);
+  }
+
+  public void testErrorDup() {
+    Exception err = Testpkg.getGlobalErr();
+    assertTrue("the Go error instance must preserve its identity", Testpkg.isGlobalErr(err));
+    assertEquals("the Go error message must be preserved", "global err", err.getMessage());
   }
 
   //test if we have JNI local reference table overflow error
diff --git a/bind/java/seq.h b/bind/java/seq.h
index 6c0ae58..363056d 100644
--- a/bind/java/seq.h
+++ b/bind/java/seq.h
@@ -39,9 +39,8 @@
 extern jobject go_seq_from_refnum(JNIEnv *env, int32_t refnum, jclass proxy_class, jmethodID proxy_cons);
 
 extern void go_seq_maybe_throw_exception(JNIEnv *env, jobject msg);
-// go_seq_wrap_exception wraps a pending exception in a Java object implementing the
-// golang/x/mobile/bind/errors.Error interface. If there is no pending exception, it returns NULL.
-extern jobject go_seq_wrap_exception(JNIEnv *env);
+// go_seq_get_exception returns any pending exception and clears the exception status.
+extern jobject go_seq_get_exception(JNIEnv *env);
 
 extern jbyteArray go_seq_to_java_bytearray(JNIEnv *env, nbyteslice s, int copy);
 extern nbyteslice go_seq_from_java_bytearray(JNIEnv *env, jbyteArray s, int copy);
diff --git a/bind/java/seq_android.c.support b/bind/java/seq_android.c.support
index 19a57d3..495b9e2 100644
--- a/bind/java/seq_android.c.support
+++ b/bind/java/seq_android.c.support
@@ -25,13 +25,11 @@
 static pthread_key_t jnienvs;
 
 static jclass seq_class;
-static jmethodID seq_throw_exc;
 static jmethodID seq_getRef;
 static jmethodID seq_decRef;
 static jmethodID seq_incRef;
 static jmethodID seq_incGoObjectRef;
 static jmethodID seq_incRefnum;
-static jmethodID seq_wrapThrowable;
 
 static jfieldID ref_objField;
 
@@ -60,23 +58,19 @@
 	return env;
 }
 
-void go_seq_maybe_throw_exception(JNIEnv *env, jobject msg) {
-	if (msg != NULL) {
-		if ((*env)->IsInstanceOf(env, msg, throwable_class)) {
-			(*env)->Throw(env, msg);
-		} else {
-			(*env)->CallStaticVoidMethod(env, seq_class, seq_throw_exc, msg);
-		}
+void go_seq_maybe_throw_exception(JNIEnv *env, jobject exc) {
+	if (exc != NULL) {
+		(*env)->Throw(env, exc);
 	}
 }
 
-jobject go_seq_wrap_exception(JNIEnv *env) {
+jobject go_seq_get_exception(JNIEnv *env) {
 	jthrowable exc = (*env)->ExceptionOccurred(env);
 	if (!exc) {
 		return NULL;
 	}
 	(*env)->ExceptionClear(env);
-	return (*env)->CallStaticObjectMethod(env, seq_class, seq_wrapThrowable, exc);
+	return exc;
 }
 
 jbyteArray go_seq_to_java_bytearray(JNIEnv *env, nbyteslice s, int copy) {
@@ -310,11 +304,6 @@
 	}
 
 	seq_class = (*env)->NewGlobalRef(env, clazz);
-	seq_throw_exc = (*env)->GetStaticMethodID(env, seq_class, "throwException", "(Lgo/error;)V");
-	if (seq_throw_exc == NULL) {
-		LOG_FATAL("failed to find method Seq.throwException");
-	}
-
 	seq_getRef = (*env)->GetStaticMethodID(env, seq_class, "getRef", "(I)Lgo/Seq$Ref;");
 	if (seq_getRef == NULL) {
 		LOG_FATAL("failed to find method Seq.getRef");
@@ -335,15 +324,6 @@
 	if (seq_incGoObjectRef == NULL) {
 		LOG_FATAL("failed to find method Seq.incGoObjectRef");
 	}
-	seq_wrapThrowable = (*env)->GetStaticMethodID(env, seq_class, "wrapThrowable", "(Ljava/lang/Throwable;)Lgo/error;");
-	if (seq_wrapThrowable == NULL) {
-		LOG_FATAL("failed to find method Seq.wrapThrowable");
-	}
-	throwable_class = (*env)->FindClass(env, "java/lang/Throwable");
-	if (throwable_class == NULL) {
-		LOG_FATAL("failed to find Throwable class");
-	}
-	throwable_class = (*env)->NewGlobalRef(env, throwable_class);
 	jclass ref_class = (*env)->FindClass(env, "go/Seq$Ref");
 	if (ref_class == NULL) {
 		LOG_FATAL("failed to find the Seq.Ref class");
diff --git a/bind/objc/SeqTest.m b/bind/objc/SeqTest.m
index 7709131..8fd15cf 100644
--- a/bind/objc/SeqTest.m
+++ b/bind/objc/SeqTest.m
@@ -35,6 +35,7 @@
        }
        return true;
    }
+   *error = [NSError errorWithDomain:@"SeqTest" code:1 userInfo:@{NSLocalizedDescriptionKey: @"NumberError"}];
    return false;
 }
 
@@ -295,12 +296,20 @@
 }
 
 - (void)testErrorField {
-	NSString *want = @"an error message";
+	NSString *wantMsg = @"an error message";
+	NSError *want = [NSError errorWithDomain:@"SeqTest" code:1 userInfo:@{NSLocalizedDescriptionKey: wantMsg}];
 	GoTestpkgNode *n = GoTestpkgNewNode(@"ErrTest");
-	n.err = [NSError errorWithDomain:@"SeqTest" code:1 userInfo:@{NSLocalizedDescriptionKey: want}];
+	n.err = want;
 	NSError *got = n.err;
-	NSString *gotMsg = [got.userInfo valueForKey:NSLocalizedDescriptionKey];
-	XCTAssertEqualObjects(gotMsg, want, @"err = %@, want %@", gotMsg, want);
+	XCTAssertEqual(got, want, @"got different objects efter roundtrip");
+	NSString *gotMsg = GoTestpkgErrorMessage(want);
+	XCTAssertEqualObjects(gotMsg, wantMsg, @"err = %@, want %@", gotMsg, wantMsg);
+}
+
+- (void)testErrorDup {
+	NSError *err = GoTestpkg.globalErr;
+	XCTAssertTrue(GoTestpkgIsGlobalErr(err), @"A Go error must preserve its identity across the boundary");
+	XCTAssertEqualObjects([err localizedDescription], @"global err", "A Go error message must be preserved");
 }
 
 - (void)testVar {
@@ -343,6 +352,8 @@
 	NSString *ret;
 	NSError *error;
 	XCTAssertFalse(GoTestpkgCallIStringError(num, @"alphabet", &ret, &error), @"GoTestpkgCallIStringError(Number, 'alphabet') succeeded; want error");
+	NSString *desc = [error localizedDescription];
+	XCTAssertEqualObjects(desc, @"NumberError", @"GoTestpkgCallIStringError(Number, 'alphabet') returned unexpected error message %@", desc);
 	NSError *error2;
 	XCTAssertTrue(GoTestpkgCallIStringError(num, @"number", &ret, &error2), @"GoTestpkgCallIStringError(Number, 'number') failed(%@); want success", error2);
 	XCTAssertEqualObjects(ret, @"OK", @"GoTestpkgCallIStringError(Number, 'number') returned unexpected results %@", ret);
diff --git a/bind/objc/seq.h b/bind/objc/seq.h
index 8941760..f1f2e95 100644
--- a/bind/objc/seq.h
+++ b/bind/objc/seq.h
@@ -24,14 +24,6 @@
                               userInfo:NULL];                                  \
   }
 
-// goErrorWrapper is a adapter between an NSError * and the bind Error interface
-@interface goSeqErrorWrapper : NSObject<GoUniverseerror> {
-}
-@property NSError *err;
-
-- (id)initWithError:(NSError *)err;
-@end
-
 // GoSeqRef is an object tagged with an integer for passing back and
 // forth across the language boundary. A GoSeqRef may represent either
 // an instance of a Go object, or an Objective-C object passed to Go.
@@ -92,6 +84,5 @@
 
 extern NSData *go_seq_to_objc_bytearray(nbyteslice, int copy);
 extern NSString *go_seq_to_objc_string(nstring str);
-extern NSError *go_seq_to_nserror(id<GoUniverseerror> err, NSString *errDomain);
 
 #endif // __GO_SEQ_HDR__
diff --git a/bind/objc/seq_darwin.m.support b/bind/objc/seq_darwin.m.support
index 933a35f..917a4ef 100644
--- a/bind/objc/seq_darwin.m.support
+++ b/bind/objc/seq_darwin.m.support
@@ -49,22 +49,6 @@
 // Note that this file is copied into and compiled with the generated
 // bindings.
 
-@implementation goSeqErrorWrapper {
-}
-@synthesize err;
-
-- (id)initWithError:(NSError *)e {
-  if (!(self = [super init]))
-    return nil;
-  self.err = e;
-  return self;
-}
-
-- (NSString *)error {
-  return [self.err localizedDescription];
-}
-@end
-
 // A simple thread-safe mutable dictionary.
 @interface goSeqDictionary : NSObject {
 }
@@ -250,13 +234,6 @@
   return res;
 }
 
-NSError *go_seq_to_nserror(id<GoUniverseerror> err, NSString *errDomain) {
-	NSString *errStr = [err error];
-	NSMutableDictionary* details = [NSMutableDictionary dictionary];
-	[details setValue:errStr forKey:NSLocalizedDescriptionKey];
-	return [NSError errorWithDomain:errDomain code:1 userInfo:details];
-}
-
 @implementation GoSeqRef {
 }
 
diff --git a/bind/testdata/basictypes.objc.m.golden b/bind/testdata/basictypes.objc.m.golden
index 2f8bff7..3dbe443 100644
--- a/bind/testdata/basictypes.objc.m.golden
+++ b/bind/testdata/basictypes.objc.m.golden
@@ -8,8 +8,6 @@
 #include "_cgo_export.h"
 #include "GoBasictypes.h"
 
-static NSString* errDomain = @"go.basictypes";
-
 const BOOL GoBasictypesABool = YES;
 const double GoBasictypesAFloat = 0.2015;
 NSString* const GoBasictypesALongString = @"LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString,LongString";
@@ -47,7 +45,7 @@
 		}
 	}
 	if (_error != nil && error != nil) {
-		*error = go_seq_to_nserror(_error, errDomain);
+		*error = _error;
 	}
 	return (_error == nil);
 }
@@ -65,7 +63,7 @@
 	}
 	*ret0_ = _ret0_;
 	if (_error != nil && error != nil) {
-		*error = go_seq_to_nserror(_error, errDomain);
+		*error = _error;
 	}
 	return (_error == nil);
 }
diff --git a/bind/testdata/classes.java.c.golden b/bind/testdata/classes.java.c.golden
index 41942e1..c8c6a73 100644
--- a/bind/testdata/classes.java.c.golden
+++ b/bind/testdata/classes.java.c.golden
@@ -39,7 +39,7 @@
 	// Must be a Java object
 	jobject _this = go_seq_from_refnum(env, this, NULL, NULL);
 	(*env)->CallVoidMethod(env, _this, m_java_lang_Runnable_run);
-	jobject _exc = go_seq_wrap_exception(env);
+	jobject _exc = go_seq_get_exception(env);
 	int32_t _exc_ref = go_seq_to_refnum(env, _exc);
 	go_seq_pop_local_frame(env);
 	return _exc_ref;
@@ -50,7 +50,7 @@
 	// Must be a Java object
 	jobject _this = go_seq_from_refnum(env, this, NULL, NULL);
 	jint res = (*env)->CallIntMethod(env, _this, m_java_io_InputStream_read__);
-	jobject _exc = go_seq_wrap_exception(env);
+	jobject _exc = go_seq_get_exception(env);
 	int32_t _exc_ref = go_seq_to_refnum(env, _exc);
 	jint _res = res;
 	go_seq_pop_local_frame(env);
@@ -63,7 +63,7 @@
 	// Must be a Java object
 	jobject _this = go_seq_from_refnum(env, this, NULL, NULL);
 	jint res = (*env)->CallNonvirtualIntMethod(env, _this, class_java_io_InputStream, m_java_io_InputStream_read__);
-	jobject _exc = go_seq_wrap_exception(env);
+	jobject _exc = go_seq_get_exception(env);
 	int32_t _exc_ref = go_seq_to_refnum(env, _exc);
 	jint _res = res;
 	go_seq_pop_local_frame(env);
@@ -76,7 +76,7 @@
 	// Must be a Java object
 	jobject _this = go_seq_from_refnum(env, this, NULL, NULL);
 	jobject res = (*env)->CallObjectMethod(env, _this, m_java_util_concurrent_Future_get__);
-	jobject _exc = go_seq_wrap_exception(env);
+	jobject _exc = go_seq_get_exception(env);
 	int32_t _exc_ref = go_seq_to_refnum(env, _exc);
 	jint _res = go_seq_to_refnum(env, res);
 	go_seq_pop_local_frame(env);
@@ -91,7 +91,7 @@
 	jlong _a0 = a0;
 	jobject _a1 = go_seq_from_refnum(env, a1, NULL, NULL);
 	jobject res = (*env)->CallObjectMethod(env, _this, m_java_util_concurrent_Future_get__JLjava_util_concurrent_TimeUnit_2, _a0, _a1);
-	jobject _exc = go_seq_wrap_exception(env);
+	jobject _exc = go_seq_get_exception(env);
 	int32_t _exc_ref = go_seq_to_refnum(env, _exc);
 	jint _res = go_seq_to_refnum(env, res);
 	go_seq_pop_local_frame(env);
diff --git a/bind/testdata/classes.java.golden b/bind/testdata/classes.java.golden
index 2716ec9..40d4999 100644
--- a/bind/testdata/classes.java.golden
+++ b/bind/testdata/classes.java.golden
@@ -11,18 +11,18 @@
     
     private final Seq.Ref ref;
     
+    @Override public final int incRefnum() {
+          int refnum = ref.refnum;
+          Seq.incGoRef(refnum);
+          return refnum;
+    }
+    
     Future(Seq.Ref ref) { this.ref = ref; }
     
     public Future() { this.ref = __New(); }
     
     private static native Seq.Ref __New();
     
-    @Override public final int incRefnum() {
-    	int refnum = ref.refnum;
-    	Seq.incGoRef(refnum);
-    	return refnum;
-    }
-    
     public final native java.util.concurrent.Future getFuture();
     public final native void setFuture(java.util.concurrent.Future v);
     
@@ -43,6 +43,12 @@
     
     private final Seq.Ref ref;
     
+    @Override public final int incRefnum() {
+          int refnum = ref.refnum;
+          Seq.incGoRef(refnum);
+          return refnum;
+    }
+    
     public InputStream() {
         super();
         this.ref = __NewInputStream();
@@ -50,12 +56,6 @@
     
     private static native Seq.Ref __NewInputStream();
     
-    @Override public final int incRefnum() {
-    	int refnum = ref.refnum;
-    	Seq.incGoRef(refnum);
-    	return refnum;
-    }
-    
     public final native java.io.InputStream getInputStream();
     public final native void setInputStream(java.io.InputStream v);
     
@@ -75,18 +75,18 @@
     
     private final Seq.Ref ref;
     
+    @Override public final int incRefnum() {
+          int refnum = ref.refnum;
+          Seq.incGoRef(refnum);
+          return refnum;
+    }
+    
     Object(Seq.Ref ref) { this.ref = ref; }
     
     public Object() { this.ref = __New(); }
     
     private static native Seq.Ref __New();
     
-    @Override public final int incRefnum() {
-    	int refnum = ref.refnum;
-    	Seq.incGoRef(refnum);
-    	return refnum;
-    }
-    
     public final native java.lang.Object getObject();
     public final native void setObject(java.lang.Object v);
     
@@ -105,18 +105,18 @@
     
     private final Seq.Ref ref;
     
+    @Override public final int incRefnum() {
+          int refnum = ref.refnum;
+          Seq.incGoRef(refnum);
+          return refnum;
+    }
+    
     Runnable(Seq.Ref ref) { this.ref = ref; }
     
     public Runnable() { this.ref = __New(); }
     
     private static native Seq.Ref __New();
     
-    @Override public final int incRefnum() {
-    	int refnum = ref.refnum;
-    	Seq.incGoRef(refnum);
-    	return refnum;
-    }
-    
     public final native java.lang.Runnable getRunnable();
     public final native void setRunnable(java.lang.Runnable v);
     
diff --git a/bind/testdata/customprefix.objc.m.golden b/bind/testdata/customprefix.objc.m.golden
index f8f7425..5eae706 100644
--- a/bind/testdata/customprefix.objc.m.golden
+++ b/bind/testdata/customprefix.objc.m.golden
@@ -8,8 +8,6 @@
 #include "_cgo_export.h"
 #include "EXCustomprefix.h"
 
-static NSString* errDomain = @"go.customprefix";
-
 
 void EXCustomprefixF() {
 	proxycustomprefix__F();
diff --git a/bind/testdata/ignore.java.golden b/bind/testdata/ignore.java.golden
index b273056..7a90fde 100644
--- a/bind/testdata/ignore.java.golden
+++ b/bind/testdata/ignore.java.golden
@@ -6,10 +6,18 @@
 
 import go.Seq;
 
-public final class S extends Seq.Proxy implements I {
+public final class S implements Seq.Proxy, I {
     static { Ignore.touch(); }
     
-    S(Seq.Ref ref) { super(ref); }
+    private final Seq.Ref ref;
+    
+    @Override public final int incRefnum() {
+          int refnum = ref.refnum;
+          Seq.incGoRef(refnum);
+          return refnum;
+    }
+    
+    S(Seq.Ref ref) { this.ref = ref; }
     
     // skipped field S.F with unsupported type: *types.Interface
     
@@ -75,9 +83,17 @@
     
     private static native void _init();
     
-    private static final class proxyI extends Seq.Proxy implements I {
-    	proxyI(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyI implements Seq.Proxy, I {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyI(Seq.Ref ref) { this.ref = ref; }
+        
         // skipped method I.Argument with unsupported parameter or return types
         
         // skipped method I.Result with unsupported parameter or return types
diff --git a/bind/testdata/ignore.objc.h.golden b/bind/testdata/ignore.objc.h.golden
index 3515ac5..a47b512 100644
--- a/bind/testdata/ignore.objc.h.golden
+++ b/bind/testdata/ignore.objc.h.golden
@@ -55,7 +55,7 @@
 }
 @property(strong, readonly) id _ref;
 
-- (id)initWithRef:(id)ref;
+- (instancetype)initWithRef:(id)ref;
 // skipped method I.Argument with unsupported parameter or return types
 
 // skipped method I.Result with unsupported parameter or return types
diff --git a/bind/testdata/ignore.objc.m.golden b/bind/testdata/ignore.objc.m.golden
index 57f1ba2..ed46739 100644
--- a/bind/testdata/ignore.objc.m.golden
+++ b/bind/testdata/ignore.objc.m.golden
@@ -8,8 +8,6 @@
 #include "_cgo_export.h"
 #include "GoIgnore.h"
 
-static NSString* errDomain = @"go.ignore";
-
 
 @implementation GoIgnoreS {
 }
@@ -31,7 +29,7 @@
 @implementation GoIgnoreI {
 }
 
-- (id)initWithRef:(id)ref {
+- (instancetype)initWithRef:(id)ref {
 	self = [super init];
 	if (self) { __ref = ref; }
 	return self;
diff --git a/bind/testdata/interfaces.java.c.golden b/bind/testdata/interfaces.java.c.golden
index 71b12b5..1295730 100644
--- a/bind/testdata/interfaces.java.c.golden
+++ b/bind/testdata/interfaces.java.c.golden
@@ -124,7 +124,7 @@
     JNIEnv *env = go_seq_push_local_frame(0);
     jobject o = go_seq_from_refnum(env, refnum, proxy_class_interfaces_Error, proxy_class_interfaces_Error_cons);
     (*env)->CallVoidMethod(env, o, mid_Error_Err);
-    jobject exc = go_seq_wrap_exception(env);
+    jobject exc = go_seq_get_exception(env);
     int32_t _exc = go_seq_to_refnum(env, exc);
     go_seq_pop_local_frame(env);
     return _exc;
diff --git a/bind/testdata/interfaces.java.golden b/bind/testdata/interfaces.java.golden
index 5c49ed0..8164d15 100644
--- a/bind/testdata/interfaces.java.golden
+++ b/bind/testdata/interfaces.java.golden
@@ -124,45 +124,109 @@
     
     private static native void _init();
     
-    private static final class proxyError extends Seq.Proxy implements Error {
-    	proxyError(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyError implements Seq.Proxy, Error {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyError(Seq.Ref ref) { this.ref = ref; }
+        
         public native void err() throws Exception;
     }
-    private static final class proxyI extends Seq.Proxy implements I {
-    	proxyI(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyI implements Seq.Proxy, I {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyI(Seq.Ref ref) { this.ref = ref; }
+        
         public native int rand();
     }
-    private static final class proxyI1 extends Seq.Proxy implements I1 {
-    	proxyI1(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyI1 implements Seq.Proxy, I1 {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyI1(Seq.Ref ref) { this.ref = ref; }
+        
         public native void j();
     }
-    private static final class proxyI2 extends Seq.Proxy implements I2 {
-    	proxyI2(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyI2 implements Seq.Proxy, I2 {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyI2(Seq.Ref ref) { this.ref = ref; }
+        
         public native void g();
     }
-    private static final class proxyI3 extends Seq.Proxy implements I3 {
-    	proxyI3(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyI3 implements Seq.Proxy, I3 {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyI3(Seq.Ref ref) { this.ref = ref; }
+        
         public native I1 f();
     }
-    private static final class proxyLargerI extends Seq.Proxy implements LargerI {
-    	proxyLargerI(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyLargerI implements Seq.Proxy, LargerI {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyLargerI(Seq.Ref ref) { this.ref = ref; }
+        
         public native void anotherFunc();
         public native int rand();
     }
-    private static final class proxySameI extends Seq.Proxy implements SameI {
-    	proxySameI(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxySameI implements Seq.Proxy, SameI {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxySameI(Seq.Ref ref) { this.ref = ref; }
+        
         public native int rand();
     }
-    private static final class proxyWithParam extends Seq.Proxy implements WithParam {
-    	proxyWithParam(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyWithParam implements Seq.Proxy, WithParam {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyWithParam(Seq.Ref ref) { this.ref = ref; }
+        
         public native void hasParam(boolean p0);
     }
     
diff --git a/bind/testdata/interfaces.objc.h.golden b/bind/testdata/interfaces.objc.h.golden
index 4464d81..171c519 100644
--- a/bind/testdata/interfaces.objc.h.golden
+++ b/bind/testdata/interfaces.objc.h.golden
@@ -36,7 +36,7 @@
 }
 @property(strong, readonly) id _ref;
 
-- (id)initWithRef:(id)ref;
+- (instancetype)initWithRef:(id)ref;
 - (void)j;
 @end
 
@@ -44,7 +44,7 @@
 }
 @property(strong, readonly) id _ref;
 
-- (id)initWithRef:(id)ref;
+- (instancetype)initWithRef:(id)ref;
 - (void)g;
 @end
 
@@ -87,7 +87,7 @@
 }
 @property(strong, readonly) id _ref;
 
-- (id)initWithRef:(id)ref;
+- (instancetype)initWithRef:(id)ref;
 - (BOOL)err:(NSError**)error;
 @end
 
@@ -95,7 +95,7 @@
 }
 @property(strong, readonly) id _ref;
 
-- (id)initWithRef:(id)ref;
+- (instancetype)initWithRef:(id)ref;
 - (int32_t)rand;
 @end
 
@@ -103,7 +103,7 @@
 }
 @property(strong, readonly) id _ref;
 
-- (id)initWithRef:(id)ref;
+- (instancetype)initWithRef:(id)ref;
 - (GoInterfacesI1*)f;
 @end
 
@@ -111,7 +111,7 @@
 }
 @property(strong, readonly) id _ref;
 
-- (id)initWithRef:(id)ref;
+- (instancetype)initWithRef:(id)ref;
 - (void)anotherFunc;
 - (int32_t)rand;
 @end
@@ -120,7 +120,7 @@
 }
 @property(strong, readonly) id _ref;
 
-- (id)initWithRef:(id)ref;
+- (instancetype)initWithRef:(id)ref;
 - (int32_t)rand;
 @end
 
@@ -128,7 +128,7 @@
 }
 @property(strong, readonly) id _ref;
 
-- (id)initWithRef:(id)ref;
+- (instancetype)initWithRef:(id)ref;
 - (void)hasParam:(BOOL)p0;
 @end
 
diff --git a/bind/testdata/interfaces.objc.m.golden b/bind/testdata/interfaces.objc.m.golden
index 47ccc23..4b7d5d4 100644
--- a/bind/testdata/interfaces.objc.m.golden
+++ b/bind/testdata/interfaces.objc.m.golden
@@ -8,12 +8,10 @@
 #include "_cgo_export.h"
 #include "GoInterfaces.h"
 
-static NSString* errDomain = @"go.interfaces";
-
 @implementation GoInterfacesError {
 }
 
-- (id)initWithRef:(id)ref {
+- (instancetype)initWithRef:(id)ref {
 	self = [super init];
 	if (self) { __ref = ref; }
 	return self;
@@ -31,7 +29,7 @@
 		}
 	}
 	if (_error != nil && error != nil) {
-		*error = go_seq_to_nserror(_error, errDomain);
+		*error = _error;
 	}
 	return (_error == nil);
 }
@@ -42,7 +40,7 @@
 @implementation GoInterfacesI {
 }
 
-- (id)initWithRef:(id)ref {
+- (instancetype)initWithRef:(id)ref {
 	self = [super init];
 	if (self) { __ref = ref; }
 	return self;
@@ -61,7 +59,7 @@
 @implementation GoInterfacesI1 {
 }
 
-- (id)initWithRef:(id)ref {
+- (instancetype)initWithRef:(id)ref {
 	self = [super init];
 	if (self) { __ref = ref; }
 	return self;
@@ -78,7 +76,7 @@
 @implementation GoInterfacesI2 {
 }
 
-- (id)initWithRef:(id)ref {
+- (instancetype)initWithRef:(id)ref {
 	self = [super init];
 	if (self) { __ref = ref; }
 	return self;
@@ -95,7 +93,7 @@
 @implementation GoInterfacesI3 {
 }
 
-- (id)initWithRef:(id)ref {
+- (instancetype)initWithRef:(id)ref {
 	self = [super init];
 	if (self) { __ref = ref; }
 	return self;
@@ -121,7 +119,7 @@
 @implementation GoInterfacesLargerI {
 }
 
-- (id)initWithRef:(id)ref {
+- (instancetype)initWithRef:(id)ref {
 	self = [super init];
 	if (self) { __ref = ref; }
 	return self;
@@ -145,7 +143,7 @@
 @implementation GoInterfacesSameI {
 }
 
-- (id)initWithRef:(id)ref {
+- (instancetype)initWithRef:(id)ref {
 	self = [super init];
 	if (self) { __ref = ref; }
 	return self;
@@ -164,7 +162,7 @@
 @implementation GoInterfacesWithParam {
 }
 
-- (id)initWithRef:(id)ref {
+- (instancetype)initWithRef:(id)ref {
 	self = [super init];
 	if (self) { __ref = ref; }
 	return self;
@@ -211,7 +209,7 @@
 		}
 	}
 	if (_error != nil && error != nil) {
-		*error = go_seq_to_nserror(_error, errDomain);
+		*error = _error;
 	}
 	return (_error == nil);
 }
@@ -236,7 +234,7 @@
 		BOOL returnVal = [o err:&error];
 		id<GoUniverseerror> _error = nil;
 		if (!returnVal) {
-			_error = [[goSeqErrorWrapper alloc] initWithError:error];
+			_error = error;
 		}
 		int32_t __error;
 		if ([(id<NSObject>)(_error) isKindOfClass:[GoUniverseerror class]]) {
diff --git a/bind/testdata/issue10788.java.golden b/bind/testdata/issue10788.java.golden
index 4f23190..08d15f6 100644
--- a/bind/testdata/issue10788.java.golden
+++ b/bind/testdata/issue10788.java.golden
@@ -6,10 +6,18 @@
 
 import go.Seq;
 
-public final class TestStruct extends Seq.Proxy {
+public final class TestStruct implements Seq.Proxy {
     static { Issue10788.touch(); }
     
-    TestStruct(Seq.Ref ref) { super(ref); }
+    private final Seq.Ref ref;
+    
+    @Override public final int incRefnum() {
+          int refnum = ref.refnum;
+          Seq.incGoRef(refnum);
+          return refnum;
+    }
+    
+    TestStruct(Seq.Ref ref) { this.ref = ref; }
     
     public final native String getValue();
     public final native void setValue(String v);
@@ -78,9 +86,17 @@
     
     private static native void _init();
     
-    private static final class proxyTestInterface extends Seq.Proxy implements TestInterface {
-    	proxyTestInterface(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyTestInterface implements Seq.Proxy, TestInterface {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyTestInterface(Seq.Ref ref) { this.ref = ref; }
+        
         public native void doSomeWork(TestStruct s);
         public native void multipleUnnamedParams(long p0, String p1, long p2);
     }
diff --git a/bind/testdata/issue10788.objc.h.golden b/bind/testdata/issue10788.objc.h.golden
index 7ef26c0..25c2e7d 100644
--- a/bind/testdata/issue10788.objc.h.golden
+++ b/bind/testdata/issue10788.objc.h.golden
@@ -33,7 +33,7 @@
 }
 @property(strong, readonly) id _ref;
 
-- (id)initWithRef:(id)ref;
+- (instancetype)initWithRef:(id)ref;
 - (void)doSomeWork:(GoIssue10788TestStruct*)s;
 - (void)multipleUnnamedParams:(long)p0 p1:(NSString*)p1 p2:(int64_t)p2;
 @end
diff --git a/bind/testdata/issue10788.objc.m.golden b/bind/testdata/issue10788.objc.m.golden
index dfdf093..80fc8a5 100644
--- a/bind/testdata/issue10788.objc.m.golden
+++ b/bind/testdata/issue10788.objc.m.golden
@@ -8,8 +8,6 @@
 #include "_cgo_export.h"
 #include "GoIssue10788.h"
 
-static NSString* errDomain = @"go.issue10788";
-
 
 @implementation GoIssue10788TestStruct {
 }
@@ -38,7 +36,7 @@
 @implementation GoIssue10788TestInterface {
 }
 
-- (id)initWithRef:(id)ref {
+- (instancetype)initWithRef:(id)ref {
 	self = [super init];
 	if (self) { __ref = ref; }
 	return self;
diff --git a/bind/testdata/issue12328.java.golden b/bind/testdata/issue12328.java.golden
index 1afcc1d..3dd20f9 100644
--- a/bind/testdata/issue12328.java.golden
+++ b/bind/testdata/issue12328.java.golden
@@ -6,10 +6,18 @@
 
 import go.Seq;
 
-public final class T extends Seq.Proxy {
+public final class T implements Seq.Proxy {
     static { Issue12328.touch(); }
     
-    T(Seq.Ref ref) { super(ref); }
+    private final Seq.Ref ref;
+    
+    @Override public final int incRefnum() {
+          int refnum = ref.refnum;
+          Seq.incGoRef(refnum);
+          return refnum;
+    }
+    
+    T(Seq.Ref ref) { this.ref = ref; }
     
     public final native java.lang.Exception getErr();
     public final native void setErr(java.lang.Exception v);
diff --git a/bind/testdata/issue12328.objc.m.golden b/bind/testdata/issue12328.objc.m.golden
index 66969f4..7c5b8c0 100644
--- a/bind/testdata/issue12328.objc.m.golden
+++ b/bind/testdata/issue12328.objc.m.golden
@@ -8,8 +8,6 @@
 #include "_cgo_export.h"
 #include "GoIssue12328.h"
 
-static NSString* errDomain = @"go.issue12328";
-
 
 @implementation GoIssue12328T {
 }
diff --git a/bind/testdata/issue12403.java.c.golden b/bind/testdata/issue12403.java.c.golden
index cbb99ff..b641ba9 100644
--- a/bind/testdata/issue12403.java.c.golden
+++ b/bind/testdata/issue12403.java.c.golden
@@ -60,7 +60,7 @@
     jobject o = go_seq_from_refnum(env, refnum, proxy_class_issue12403_Parsable, proxy_class_issue12403_Parsable_cons);
     jstring res = (*env)->CallObjectMethod(env, o, mid_Parsable_ToJSON);
     nstring _res = go_seq_from_java_string(env, res);
-    jobject exc = go_seq_wrap_exception(env);
+    jobject exc = go_seq_get_exception(env);
     int32_t _exc = go_seq_to_refnum(env, exc);
     cproxyissue12403_Parsable_ToJSON_return sres = {
     	_res, _exc
diff --git a/bind/testdata/issue12403.java.golden b/bind/testdata/issue12403.java.golden
index 30976be..50c81af 100644
--- a/bind/testdata/issue12403.java.golden
+++ b/bind/testdata/issue12403.java.golden
@@ -33,9 +33,17 @@
     
     private static native void _init();
     
-    private static final class proxyParsable extends Seq.Proxy implements Parsable {
-    	proxyParsable(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyParsable implements Seq.Proxy, Parsable {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyParsable(Seq.Ref ref) { this.ref = ref; }
+        
         public native String fromJSON(String jstr);
         public native String toJSON() throws Exception;
     }
diff --git a/bind/testdata/issue12403.objc.h.golden b/bind/testdata/issue12403.objc.h.golden
index 5b9f310..14c7dad 100644
--- a/bind/testdata/issue12403.objc.h.golden
+++ b/bind/testdata/issue12403.objc.h.golden
@@ -23,7 +23,7 @@
 }
 @property(strong, readonly) id _ref;
 
-- (id)initWithRef:(id)ref;
+- (instancetype)initWithRef:(id)ref;
 - (NSString*)fromJSON:(NSString*)jstr;
 - (BOOL)toJSON:(NSString**)ret0_ error:(NSError**)error;
 @end
diff --git a/bind/testdata/issue12403.objc.m.golden b/bind/testdata/issue12403.objc.m.golden
index 4a06e15..c453a52 100644
--- a/bind/testdata/issue12403.objc.m.golden
+++ b/bind/testdata/issue12403.objc.m.golden
@@ -8,12 +8,10 @@
 #include "_cgo_export.h"
 #include "GoIssue12403.h"
 
-static NSString* errDomain = @"go.issue12403";
-
 @implementation GoIssue12403Parsable {
 }
 
-- (id)initWithRef:(id)ref {
+- (instancetype)initWithRef:(id)ref {
 	self = [super init];
 	if (self) { __ref = ref; }
 	return self;
@@ -41,7 +39,7 @@
 	}
 	*ret0_ = _ret0_;
 	if (_error != nil && error != nil) {
-		*error = go_seq_to_nserror(_error, errDomain);
+		*error = _error;
 	}
 	return (_error == nil);
 }
@@ -69,7 +67,7 @@
 		nstring _ret0_ = go_seq_from_objc_string(ret0_);
 		id<GoUniverseerror> _error = nil;
 		if (!returnVal) {
-			_error = [[goSeqErrorWrapper alloc] initWithError:error];
+			_error = error;
 		}
 		int32_t __error;
 		if ([(id<NSObject>)(_error) isKindOfClass:[GoUniverseerror class]]) {
diff --git a/bind/testdata/java.java.golden b/bind/testdata/java.java.golden
index 3948a2b..74d9694 100644
--- a/bind/testdata/java.java.golden
+++ b/bind/testdata/java.java.golden
@@ -71,23 +71,55 @@
     
     private static native void _init();
     
-    private static final class proxyF extends Seq.Proxy implements F {
-    	proxyF(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyF implements Seq.Proxy, F {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyF(Seq.Ref ref) { this.ref = ref; }
+        
     }
-    private static final class proxyO extends Seq.Proxy implements O {
-    	proxyO(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyO implements Seq.Proxy, O {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyO(Seq.Ref ref) { this.ref = ref; }
+        
         // skipped method O.Super with unsupported parameter or return types
         
     }
-    private static final class proxyR extends Seq.Proxy implements R {
-    	proxyR(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyR implements Seq.Proxy, R {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyR(Seq.Ref ref) { this.ref = ref; }
+        
     }
-    private static final class proxyS extends Seq.Proxy implements S {
-    	proxyS(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyS implements Seq.Proxy, S {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyS(Seq.Ref ref) { this.ref = ref; }
+        
         // skipped method S.Super with unsupported parameter or return types
         
     }
diff --git a/bind/testdata/keywords.java.golden b/bind/testdata/keywords.java.golden
index b7f5ea1..04e7cb4 100644
--- a/bind/testdata/keywords.java.golden
+++ b/bind/testdata/keywords.java.golden
@@ -84,9 +84,17 @@
     
     private static native void _init();
     
-    private static final class proxyKeywordCaller extends Seq.Proxy implements KeywordCaller {
-    	proxyKeywordCaller(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyKeywordCaller implements Seq.Proxy, KeywordCaller {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyKeywordCaller(Seq.Ref ref) { this.ref = ref; }
+        
         public native void abstract_();
         public native void assert_();
         public native void boolean_();
diff --git a/bind/testdata/keywords.objc.h.golden b/bind/testdata/keywords.objc.h.golden
index df4c914..1cbdf7d 100644
--- a/bind/testdata/keywords.objc.h.golden
+++ b/bind/testdata/keywords.objc.h.golden
@@ -74,7 +74,7 @@
 }
 @property(strong, readonly) id _ref;
 
-- (id)initWithRef:(id)ref;
+- (instancetype)initWithRef:(id)ref;
 - (void)abstract;
 - (void)assert;
 - (void)boolean;
diff --git a/bind/testdata/keywords.objc.m.golden b/bind/testdata/keywords.objc.m.golden
index d4f9d73..837ce6d 100644
--- a/bind/testdata/keywords.objc.m.golden
+++ b/bind/testdata/keywords.objc.m.golden
@@ -8,12 +8,10 @@
 #include "_cgo_export.h"
 #include "GoKeywords.h"
 
-static NSString* errDomain = @"go.keywords";
-
 @implementation GoKeywordsKeywordCaller {
 }
 
-- (id)initWithRef:(id)ref {
+- (instancetype)initWithRef:(id)ref {
 	self = [super init];
 	if (self) { __ref = ref; }
 	return self;
diff --git a/bind/testdata/structs.java.golden b/bind/testdata/structs.java.golden
index 61402a3..306f597 100644
--- a/bind/testdata/structs.java.golden
+++ b/bind/testdata/structs.java.golden
@@ -6,10 +6,18 @@
 
 import go.Seq;
 
-public final class S extends Seq.Proxy {
+public final class S implements Seq.Proxy {
     static { Structs.touch(); }
     
-    S(Seq.Ref ref) { super(ref); }
+    private final Seq.Ref ref;
+    
+    @Override public final int incRefnum() {
+          int refnum = ref.refnum;
+          Seq.incGoRef(refnum);
+          return refnum;
+    }
+    
+    S(Seq.Ref ref) { this.ref = ref; }
     
     public final native double getX();
     public final native void setX(double v);
@@ -58,10 +66,18 @@
 
 import go.Seq;
 
-public final class S2 extends Seq.Proxy implements I {
+public final class S2 implements Seq.Proxy, I {
     static { Structs.touch(); }
     
-    S2(Seq.Ref ref) { super(ref); }
+    private final Seq.Ref ref;
+    
+    @Override public final int incRefnum() {
+          int refnum = ref.refnum;
+          Seq.incGoRef(refnum);
+          return refnum;
+    }
+    
+    S2(Seq.Ref ref) { this.ref = ref; }
     
     public native void m();
     public native String string();
@@ -116,9 +132,17 @@
     
     private static native void _init();
     
-    private static final class proxyI extends Seq.Proxy implements I {
-    	proxyI(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyI implements Seq.Proxy, I {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyI(Seq.Ref ref) { this.ref = ref; }
+        
         public native void m();
     }
     
diff --git a/bind/testdata/structs.objc.h.golden b/bind/testdata/structs.objc.h.golden
index 1512cf7..8a911bc 100644
--- a/bind/testdata/structs.objc.h.golden
+++ b/bind/testdata/structs.objc.h.golden
@@ -50,7 +50,7 @@
 }
 @property(strong, readonly) id _ref;
 
-- (id)initWithRef:(id)ref;
+- (instancetype)initWithRef:(id)ref;
 - (void)m;
 @end
 
diff --git a/bind/testdata/structs.objc.m.golden b/bind/testdata/structs.objc.m.golden
index e48173e..b66a3e3 100644
--- a/bind/testdata/structs.objc.m.golden
+++ b/bind/testdata/structs.objc.m.golden
@@ -8,8 +8,6 @@
 #include "_cgo_export.h"
 #include "GoStructs.h"
 
-static NSString* errDomain = @"go.structs";
-
 
 @implementation GoStructsS {
 }
@@ -67,7 +65,7 @@
 	}
 	*ret0_ = _ret0_;
 	if (_error != nil && error != nil) {
-		*error = go_seq_to_nserror(_error, errDomain);
+		*error = _error;
 	}
 	return (_error == nil);
 }
@@ -108,7 +106,7 @@
 @implementation GoStructsI {
 }
 
-- (id)initWithRef:(id)ref {
+- (instancetype)initWithRef:(id)ref {
 	self = [super init];
 	if (self) { __ref = ref; }
 	return self;
@@ -170,7 +168,7 @@
 	}
 	*ret0_ = _ret0_;
 	if (_error != nil && error != nil) {
-		*error = go_seq_to_nserror(_error, errDomain);
+		*error = _error;
 	}
 	return (_error == nil);
 }
diff --git a/bind/testdata/try.objc.m.golden b/bind/testdata/try.objc.m.golden
index 9750654..0a0c03c 100644
--- a/bind/testdata/try.objc.m.golden
+++ b/bind/testdata/try.objc.m.golden
@@ -8,8 +8,6 @@
 #include "_cgo_export.h"
 #include "GoTry.h"
 
-static NSString* errDomain = @"go.try";
-
 
 NSString* GoTryThis() {
 	nstring r0 = proxytry__This();
diff --git a/bind/testdata/vars.java.golden b/bind/testdata/vars.java.golden
index 665910c..c66da14 100644
--- a/bind/testdata/vars.java.golden
+++ b/bind/testdata/vars.java.golden
@@ -6,10 +6,18 @@
 
 import go.Seq;
 
-public final class S extends Seq.Proxy implements I {
+public final class S implements Seq.Proxy, I {
     static { Vars.touch(); }
     
-    S(Seq.Ref ref) { super(ref); }
+    private final Seq.Ref ref;
+    
+    @Override public final int incRefnum() {
+          int refnum = ref.refnum;
+          Seq.incGoRef(refnum);
+          return refnum;
+    }
+    
+    S(Seq.Ref ref) { this.ref = ref; }
     
     @Override public boolean equals(Object o) {
         if (o == null || !(o instanceof S)) {
@@ -63,9 +71,17 @@
     
     private static native void _init();
     
-    private static final class proxyI extends Seq.Proxy implements I {
-    	proxyI(Seq.Ref ref) { super(ref); }
-    
+    private static final class proxyI implements Seq.Proxy, I {
+        private final Seq.Ref ref;
+        
+        @Override public final int incRefnum() {
+              int refnum = ref.refnum;
+              Seq.incGoRef(refnum);
+              return refnum;
+        }
+        
+        proxyI(Seq.Ref ref) { this.ref = ref; }
+        
     }
     
     
diff --git a/bind/testdata/vars.objc.h.golden b/bind/testdata/vars.objc.h.golden
index e1f45b8..4f15bc7 100644
--- a/bind/testdata/vars.objc.h.golden
+++ b/bind/testdata/vars.objc.h.golden
@@ -68,7 +68,7 @@
 }
 @property(strong, readonly) id _ref;
 
-- (id)initWithRef:(id)ref;
+- (instancetype)initWithRef:(id)ref;
 @end
 
 #endif
diff --git a/bind/testdata/vars.objc.m.golden b/bind/testdata/vars.objc.m.golden
index 7331d71..8a69fb3 100644
--- a/bind/testdata/vars.objc.m.golden
+++ b/bind/testdata/vars.objc.m.golden
@@ -8,8 +8,6 @@
 #include "_cgo_export.h"
 #include "GoVars.h"
 
-static NSString* errDomain = @"go.vars";
-
 
 @implementation GoVarsS {
 }
@@ -25,7 +23,7 @@
 @implementation GoVarsI {
 }
 
-- (id)initWithRef:(id)ref {
+- (instancetype)initWithRef:(id)ref {
 	self = [super init];
 	if (self) { __ref = ref; }
 	return self;
diff --git a/bind/testpkg/testpkg.go b/bind/testpkg/testpkg.go
index a812e9e..091b640 100644
--- a/bind/testpkg/testpkg.go
+++ b/bind/testpkg/testpkg.go
@@ -537,3 +537,13 @@
 type Issue17073 interface {
 	OnError(err error)
 }
+
+func ErrorMessage(err error) string {
+	return err.Error()
+}
+
+var GlobalErr error = errors.New("global err")
+
+func IsGlobalErr(err error) bool {
+	return GlobalErr == err
+}