*: enable deadcode

DEPS.bzl

@@ -934,6 +934,13 @@ def go_deps():
         sum = "h1:iR3fYXUjHCR97qWS8ch1y9zPNsgXThGwjKPrYfqMPks=",
         version = "v0.0.0-20190930125516-244bba706f1a",
     )
+    go_repository(
+        name = "com_github_golangci_go_misc",
+        build_file_proto_mode = "disable",
+        importpath = "github.com/golangci/go-misc",
+        sum = "h1:6RGUuS7EGotKx6J5HIP8ZtyMdiDscjMLfRBSPuzVVeo=",
+        version = "v0.0.0-20220329215616-d24fe342adfe",
+    )
 
     go_repository(
         name = "com_github_golangci_prealloc",
@@ -2049,6 +2056,28 @@ def go_deps():
         sum = "h1:OdAsTTz6OkFY5QxjkYwrChwuRruF69c169dPK26NUlk=",
         version = "v0.0.0-20200410134404-eec4a21b6bb0",
     )
+    go_repository(
+        name = "com_github_remyoudompheng_go_dbus",
+        build_file_proto_mode = "disable",
+        importpath = "github.com/remyoudompheng/go-dbus",
+        sum = "h1:CvqZS4QYHBRvx7AeFdimd16HCbLlYsvQMcKDACpJW/c=",
+        version = "v0.0.0-20121104212943-b7232d34b1d5",
+    )
+    go_repository(
+        name = "com_github_remyoudompheng_go_liblzma",
+        build_file_proto_mode = "disable",
+        importpath = "github.com/remyoudompheng/go-liblzma",
+        sum = "h1:J8J/cgLDRuqXJnwIrRDBvtl+LLsdg7De74znW/BRRq4=",
+        version = "v0.0.0-20190506200333-81bf2d431b96",
+    )
+    go_repository(
+        name = "com_github_remyoudompheng_go_misc",
+        build_file_proto_mode = "disable",
+        importpath = "github.com/remyoudompheng/go-misc",
+        sum = "h1:eTWZyPUnHcuGRDiryS/l2I7FfKjbU3IBx3IjqHPxuKU=",
+        version = "v0.0.0-20190427085024-2d6ac652a50e",
+    )
+
     go_repository(
         name = "com_github_rivo_uniseg",
         build_file_proto_mode = "disable_global",
@@ -3009,8 +3038,8 @@ def go_deps():
         name = "org_golang_x_net",
         build_file_proto_mode = "disable_global",
         importpath = "golang.org/x/net",
-        sum = "h1:O7DYs+zxREGLKzKoMQrtrEacpb0ZVXA5rIwylE2Xchk=",
-        version = "v0.0.0-20220127200216-cd36cc0744dd",
+        sum = "h1:pZB1TWnKi+o4bENlbzAgLrEbY4RMYmUIRobMcSmfeYc=",
+        version = "v0.0.0-20220325170049-de3da57026de",
     )
     go_repository(
         name = "org_golang_x_oauth2",

build/BUILD.bazel

@@ -81,6 +81,7 @@ nogo(
         "@org_golang_x_tools//go/analysis/passes/unreachable:go_default_library",
         "@org_golang_x_tools//go/analysis/passes/unsafeptr:go_default_library",
         "@org_golang_x_tools//go/analysis/passes/unusedresult:go_default_library",
+        "//build/linter/deadcode:deadcode",
         "//build/linter/durationcheck:durationcheck",
         "//build/linter/exportloopref:exportloopref",
         "//build/linter/gofmt:gofmt",

build/linter/deadcode/BUILD.bazel

@@ -0,0 +1,14 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "deadcode",
+    srcs = ["analyzer.go"],
+    importpath = "github.com/pingcap/tidb/build/linter/deadcode",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//build/linter/util",
+        "@com_github_golangci_go_misc//deadcode:go_default_library",
+        "@org_golang_x_tools//go/analysis",
+        "@org_golang_x_tools//go/loader",
+    ],
+)

build/linter/deadcode/analyzer.go

@@ -0,0 +1,63 @@
+// Copyright 2022 PingCAP, Inc.
+//
+// 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 deadcode
+
+import (
+	"go/token"
+	"go/types"
+
+	deadcodeAPI "github.com/golangci/go-misc/deadcode"
+	"github.com/pingcap/tidb/build/linter/util"
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/loader"
+)
+
+// Name is the name of the analyzer.
+const Name = "deadcode"
+
+// Analyzer is the analyzer struct of deadcode.
+var Analyzer = &analysis.Analyzer{
+	Name: Name,
+	Doc:  "Finds unused code",
+	Run:  run,
+}
+
+func run(pass *analysis.Pass) (interface{}, error) {
+	var createdPkgs []*loader.PackageInfo
+	createdPkgs = append(createdPkgs, util.MakeFakeLoaderPackageInfo(pass))
+	allPkgs := map[*types.Package]*loader.PackageInfo{}
+	for _, pkg := range createdPkgs {
+		pkg := pkg
+		allPkgs[pkg.Pkg] = pkg
+	}
+	prog := &loader.Program{
+		Fset:        pass.Fset,
+		Imported:    nil,         // not used without .Created in any linter
+		Created:     createdPkgs, // all initial packages
+		AllPackages: allPkgs,     // all initial packages and their depndencies
+	}
+	issues, err := deadcodeAPI.Run(prog)
+	if err != nil {
+		return nil, err
+	}
+	for _, i := range issues {
+		pass.Reportf(token.Pos(i.Pos.Offset), "[%s] %s is unused", Name, util.FormatCode(i.UnusedIdentName))
+	}
+	return nil, nil
+}
+
+func init() {
+	util.SkipAnalyzer(Analyzer)
+}

build/linter/util/BUILD.bazel

@@ -8,5 +8,6 @@ go_library(
     deps = [
         "@co_honnef_go_tools//analysis/report",
         "@org_golang_x_tools//go/analysis",
+        "@org_golang_x_tools//go/loader",
     ],
 )

build/linter/util/util.go

@@ -22,6 +22,7 @@ import (
 	"strings"
 
 	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/loader"
 	"honnef.co/go/tools/analysis/report"
 )
 
@@ -147,3 +148,22 @@ func FormatCode(code string) string {
 
 	return fmt.Sprintf("`%s`", code)
 }
+
+// MakeFakeLoaderPackageInfo creates a fake loader.PackageInfo for a given package.
+func MakeFakeLoaderPackageInfo(pass *analysis.Pass) *loader.PackageInfo {
+	var errs []error
+
+	typeInfo := pass.TypesInfo
+
+	return &loader.PackageInfo{
+		Pkg:                   pass.Pkg,
+		Importable:            true, // not used
+		TransitivelyErrorFree: true, // not used
+
+		// use compiled (preprocessed) go files AST;
+		// AST linters use not preprocessed go files AST
+		Files:  pass.Files,
+		Errors: errs,
+		Info:   *typeInfo,
+	}
+}

build/nogo_config.json

@@ -74,6 +74,15 @@
       ".*_generated\\.go$": "ignore generated code"
     }
   },
+  "deadcode": {
+    "exclude_files": {
+      "/external/": "no need to vet third party code",
+      ".*_generated\\.go$": "ignore generated code",
+      "/cgo/": "no need to vet third party code for cgo",
+      "br/pkg/lightning/manual/allocator.go": "ignore code",
+      "parser/": "ignore code"
+    }
+  },
   "deepequalerrors": {
     "exclude_files": {
       "/external/": "no need to vet third party code",

go.mod

@@ -80,7 +80,7 @@ require (
 	go.uber.org/multierr v1.8.0
 	go.uber.org/zap v1.21.0
 	golang.org/x/exp v0.0.0-20220426173459-3bcf042a4bf5
-	golang.org/x/net v0.0.0-20220127200216-cd36cc0744dd
+	golang.org/x/net v0.0.0-20220325170049-de3da57026de
 	golang.org/x/oauth2 v0.0.0-20211104180415-d3ed0bb246c8
 	golang.org/x/sync v0.0.0-20220513210516-0976fa681c29
 	golang.org/x/sys v0.0.0-20220408201424-a24fb2fb8a0f
@@ -98,6 +98,7 @@ require (
 require (
 	github.com/aliyun/alibaba-cloud-sdk-go v1.61.1581
 	github.com/charithe/durationcheck v0.0.9
+	github.com/golangci/go-misc v0.0.0-20220329215616-d24fe342adfe
 	github.com/golangci/gofmt v0.0.0-20190930125516-244bba706f1a
 	github.com/gordonklaus/ineffassign v0.0.0-20210914165742-4cc7213b9bc8
 	github.com/kyoh86/exportloopref v0.1.8

go.sum

@@ -343,6 +343,8 @@ github.com/golang/snappy v0.0.2-0.20190904063534-ff6b7dc882cf/go.mod h1:/XxbfmMg
 github.com/golang/snappy v0.0.3/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/golang/snappy v0.0.4 h1:yAGX7huGHXlcLOEtBnF4w7FQwA26wojNCwOYAEhLjQM=
 github.com/golang/snappy v0.0.4/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
+github.com/golangci/go-misc v0.0.0-20220329215616-d24fe342adfe h1:6RGUuS7EGotKx6J5HIP8ZtyMdiDscjMLfRBSPuzVVeo=
+github.com/golangci/go-misc v0.0.0-20220329215616-d24fe342adfe/go.mod h1:gjqyPShc/m8pEMpk0a3SeagVb0kaqvhscv+i9jI5ZhQ=
 github.com/golangci/gofmt v0.0.0-20190930125516-244bba706f1a h1:iR3fYXUjHCR97qWS8ch1y9zPNsgXThGwjKPrYfqMPks=
 github.com/golangci/gofmt v0.0.0-20190930125516-244bba706f1a/go.mod h1:9qCChq59u/eW8im404Q2WWTrnBUQKjpNYKMbU4M7EFU=
 github.com/golangci/prealloc v0.0.0-20180630174525-215b22d4de21 h1:leSNB7iYzLYSSx3J/s5sVf4Drkc68W2wm4Ixh/mr0us=
@@ -1019,8 +1021,9 @@ golang.org/x/net v0.0.0-20210525063256-abc453219eb5/go.mod h1:9nx3DQGgdP8bBQD5qx
 golang.org/x/net v0.0.0-20210610132358-84b48f89b13b/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
 golang.org/x/net v0.0.0-20210805182204-aaa1db679c0d/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
 golang.org/x/net v0.0.0-20211015210444-4f30a5c0130f/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
-golang.org/x/net v0.0.0-20220127200216-cd36cc0744dd h1:O7DYs+zxREGLKzKoMQrtrEacpb0ZVXA5rIwylE2Xchk=
 golang.org/x/net v0.0.0-20220127200216-cd36cc0744dd/go.mod h1:CfG3xpIq0wQ8r1q4Su4UZFWDARRcnwPjda9FqA0JpMk=
+golang.org/x/net v0.0.0-20220325170049-de3da57026de h1:pZB1TWnKi+o4bENlbzAgLrEbY4RMYmUIRobMcSmfeYc=
+golang.org/x/net v0.0.0-20220325170049-de3da57026de/go.mod h1:CfG3xpIq0wQ8r1q4Su4UZFWDARRcnwPjda9FqA0JpMk=
 golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
 golang.org/x/oauth2 v0.0.0-20190226205417-e64efc72b421/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
 golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=

parser/ast/ddl.go

@@ -2508,6 +2508,7 @@ func (n *ColumnPosition) Accept(v Visitor) (Node, bool) {
 type AlterTableType int
 
 // AlterTable types.
+//nolint: deadcode
 const (
 	AlterTableOption AlterTableType = iota + 1
 	AlterTableAddColumns