build: use typepatch.Pkg merge patches of a standard library

internal/typepatch/patch.go

@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package typepatch
+
+import (
+	"go/token"
+	"go/types"
+	"unsafe"
+)
+
+type typesScope struct {
+	parent   *types.Scope
+	children []*types.Scope
+	number   int
+	elems    map[string]types.Object // TODO(xsw): ensure offset of elems
+	pos, end token.Pos
+	comment  string
+	isFunc   bool
+}
+
+type object struct {
+	parent *types.Scope
+	pos    token.Pos
+	pkg    *types.Package // TODO(xsw): ensure offset of pkg
+	unused [8]byte
+}
+
+type iface struct {
+	tab  unsafe.Pointer
+	data unsafe.Pointer
+}
+
+func setPkg(o types.Object, pkg *types.Package) {
+	data := (*iface)(unsafe.Pointer(&o)).data
+	(*object)(data).pkg = pkg
+}
+
+func setObject(scope *types.Scope, name string, o types.Object) {
+	s := (*typesScope)(unsafe.Pointer(scope))
+	s.elems[name] = o
+}
+
+func Pkg(pkg, alt *types.Package) *types.Package {
+	scope := pkg.Scope()
+	altScope := alt.Scope()
+	for _, name := range altScope.Names() {
+		o := altScope.Lookup(name)
+		setPkg(o, pkg)
+		setObject(scope, name, o)
+	}
+	return pkg
+}