f.walk(&n.Type, ctxType, visit)
		}
	case *ast.FieldList:
		for _, field := range n.List {
			f.walk(field, context, visit)
		}
	case *ast.BadExpr:
	case *ast.Ident:
	case *ast.Ellipsis:
		f.walk(&n.Elt, ctxType, visit)
	case *ast.BasicLit:
	case *ast.FuncLit:
		f.walk(n.Type, ctxType, visit)
		f.walk(n.Body, ctxStmt, visit)
	case *ast.CompositeLit:
		f.walk(&n.Type, ctxType, visit)

	callbackMutex.Lock()
	callbackToken++
	i := callbackToken
	callbackFuncs[i] = f
	callbackMutex.Unlock()

	// Pass the address of i because the C function was written to
	// take a pointer.  We could pass an int if we felt like
	// rewriting the C code.
	C.callback(unsafe.Pointer(&i))

	callbackMutex.Lock()
	delete(callbackFuncs, i)
	callbackMutex.Unlock()
}

//export goCallback
func goCallback(p unsafe.Pointer) {

		// this is created by code in this file.
		if t.Name == "unsafe.Pointer" {
			return ast.NewIdent("_cgo_unsafe.Pointer")
		}
	case *ast.ArrayType:
		t1 := p.rewriteUnsafe(t.Elt)
		if t1 != t.Elt {
			r := *t
			r.Elt = t1
			return &r
		}
	case *ast.StructType:
		changed := false
		fields := *t.Fields
		fields.List = nil
		for _, f := range t.Fields.List {