Add staticcheck tool

vendor/honnef.co/go/tools/stylecheck/st1008/st1008.go

@@ -0,0 +1,58 @@
+package st1008
+
+import (
+	"go/types"
+
+	"honnef.co/go/tools/analysis/lint"
+	"honnef.co/go/tools/analysis/report"
+	"honnef.co/go/tools/internal/passes/buildir"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "ST1008",
+		Run:      run,
+		Requires: []*analysis.Analyzer{buildir.Analyzer},
+	},
+	Doc: &lint.RawDocumentation{
+		Title:   `A function's error value should be its last return value`,
+		Text:    `A function's error value should be its last return value.`,
+		Since:   `2019.1`,
+		MergeIf: lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+func run(pass *analysis.Pass) (any, error) {
+fnLoop:
+	for _, fn := range pass.ResultOf[buildir.Analyzer].(*buildir.IR).SrcFuncs {
+		sig := fn.Type().(*types.Signature)
+		rets := sig.Results()
+		if rets == nil || rets.Len() < 2 {
+			continue
+		}
+
+		if types.Unalias(rets.At(rets.Len()-1).Type()) == types.Universe.Lookup("error").Type() {
+			// Last return type is error. If the function also returns
+			// errors in other positions, that's fine.
+			continue
+		}
+
+		if rets.Len() >= 2 &&
+			types.Unalias(rets.At(rets.Len()-1).Type()) == types.Universe.Lookup("bool").Type() &&
+			types.Unalias(rets.At(rets.Len()-2).Type()) == types.Universe.Lookup("error").Type() {
+			// Accept (..., error, bool) and assume it's a comma-ok function. It's not clear whether the bool should come last or not for these kinds of functions.
+			continue
+		}
+		for i := rets.Len() - 2; i >= 0; i-- {
+			if types.Unalias(rets.At(i).Type()) == types.Universe.Lookup("error").Type() {
+				report.Report(pass, rets.At(i), "error should be returned as the last argument", report.ShortRange())
+				continue fnLoop
+			}
+		}
+	}
+	return nil, nil
+}