Add staticcheck tool

vendor/honnef.co/go/tools/simple/s1023/s1023.go

@@ -0,0 +1,79 @@
+package s1023
+
+import (
+	"go/ast"
+	"go/token"
+
+	"honnef.co/go/tools/analysis/code"
+	"honnef.co/go/tools/analysis/facts/generated"
+	"honnef.co/go/tools/analysis/lint"
+	"honnef.co/go/tools/analysis/report"
+
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/analysis/passes/inspect"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "S1023",
+		Run:      run,
+		Requires: []*analysis.Analyzer{inspect.Analyzer, generated.Analyzer},
+	},
+	Doc: &lint.RawDocumentation{
+		Title: `Omit redundant control flow`,
+		Text: `Functions that have no return value do not need a return statement as
+the final statement of the function.
+
+Switches in Go do not have automatic fallthrough, unlike languages
+like C. It is not necessary to have a break statement as the final
+statement in a case block.`,
+		Since:   "2017.1",
+		MergeIf: lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+func run(pass *analysis.Pass) (any, error) {
+	fn1 := func(node ast.Node) {
+		clause := node.(*ast.CaseClause)
+		if len(clause.Body) < 2 {
+			return
+		}
+		branch, ok := clause.Body[len(clause.Body)-1].(*ast.BranchStmt)
+		if !ok || branch.Tok != token.BREAK || branch.Label != nil {
+			return
+		}
+		report.Report(pass, branch, "redundant break statement", report.FilterGenerated())
+	}
+	fn2 := func(node ast.Node) {
+		var ret *ast.FieldList
+		var body *ast.BlockStmt
+		switch x := node.(type) {
+		case *ast.FuncDecl:
+			ret = x.Type.Results
+			body = x.Body
+		case *ast.FuncLit:
+			ret = x.Type.Results
+			body = x.Body
+		default:
+			lint.ExhaustiveTypeSwitch(node)
+		}
+		// if the func has results, a return can't be redundant.
+		// similarly, if there are no statements, there can be
+		// no return.
+		if ret != nil || body == nil || len(body.List) < 1 {
+			return
+		}
+		rst, ok := body.List[len(body.List)-1].(*ast.ReturnStmt)
+		if !ok {
+			return
+		}
+		// we don't need to check rst.Results as we already
+		// checked x.Type.Results to be nil.
+		report.Report(pass, rst, "redundant return statement", report.FilterGenerated())
+	}
+	code.Preorder(pass, fn1, (*ast.CaseClause)(nil))
+	code.Preorder(pass, fn2, (*ast.FuncDecl)(nil), (*ast.FuncLit)(nil))
+	return nil, nil
+}