Add staticcheck tool

vendor/honnef.co/go/tools/staticcheck/sa4009/sa4009.go

@@ -0,0 +1,106 @@
+package sa4009
+
+import (
+	"fmt"
+	"go/ast"
+
+	"honnef.co/go/tools/analysis/lint"
+	"honnef.co/go/tools/analysis/report"
+	"honnef.co/go/tools/go/ir"
+	"honnef.co/go/tools/go/ir/irutil"
+	"honnef.co/go/tools/internal/passes/buildir"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "SA4009",
+		Run:      run,
+		Requires: []*analysis.Analyzer{buildir.Analyzer},
+	},
+	Doc: &lint.RawDocumentation{
+		Title:    `A function argument is overwritten before its first use`,
+		Since:    "2017.1",
+		Severity: lint.SeverityWarning,
+		MergeIf:  lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+func run(pass *analysis.Pass) (any, error) {
+	for _, fn := range pass.ResultOf[buildir.Analyzer].(*buildir.IR).SrcFuncs {
+		cb := func(node ast.Node) bool {
+			var typ *ast.FuncType
+			var body *ast.BlockStmt
+			switch fn := node.(type) {
+			case *ast.FuncDecl:
+				typ = fn.Type
+				body = fn.Body
+			case *ast.FuncLit:
+				typ = fn.Type
+				body = fn.Body
+			}
+			if body == nil {
+				return true
+			}
+			if len(typ.Params.List) == 0 {
+				return true
+			}
+			for _, field := range typ.Params.List {
+				for _, arg := range field.Names {
+					obj := pass.TypesInfo.ObjectOf(arg)
+					var irobj *ir.Parameter
+					for _, param := range fn.Params {
+						if param.Object() == obj {
+							irobj = param
+							break
+						}
+					}
+					if irobj == nil {
+						continue
+					}
+					refs := irobj.Referrers()
+					if refs == nil {
+						continue
+					}
+					if len(irutil.FilterDebug(*refs)) != 0 {
+						continue
+					}
+
+					var assignment ast.Node
+					ast.Inspect(body, func(node ast.Node) bool {
+						if assignment != nil {
+							return false
+						}
+						assign, ok := node.(*ast.AssignStmt)
+						if !ok {
+							return true
+						}
+						for _, lhs := range assign.Lhs {
+							ident, ok := lhs.(*ast.Ident)
+							if !ok {
+								continue
+							}
+							if pass.TypesInfo.ObjectOf(ident) == obj {
+								assignment = assign
+								return false
+							}
+						}
+						return true
+					})
+					if assignment != nil {
+						report.Report(pass, arg, fmt.Sprintf("argument %s is overwritten before first use", arg),
+							report.Related(assignment, fmt.Sprintf("assignment to %s", arg)))
+					}
+				}
+			}
+			return true
+		}
+		if source := fn.Source(); source != nil {
+			ast.Inspect(source, cb)
+		}
+	}
+	return nil, nil
+}