Add staticcheck tool

vendor/honnef.co/go/tools/staticcheck/sa5004/sa5004.go

@@ -0,0 +1,49 @@
+package sa5004
+
+import (
+	"go/ast"
+
+	"honnef.co/go/tools/analysis/code"
+	"honnef.co/go/tools/analysis/edit"
+	"honnef.co/go/tools/analysis/lint"
+	"honnef.co/go/tools/analysis/report"
+	"honnef.co/go/tools/pattern"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "SA5004",
+		Run:      run,
+		Requires: code.RequiredAnalyzers,
+	},
+	Doc: &lint.RawDocumentation{
+		Title:    `\"for { select { ...\" with an empty default branch spins`,
+		Since:    "2017.1",
+		Severity: lint.SeverityWarning,
+		MergeIf:  lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+var query = pattern.MustParse(`(ForStmt nil nil nil (SelectStmt body))`)
+
+func run(pass *analysis.Pass) (any, error) {
+	for _, m := range code.Matches(pass, query) {
+		for _, c := range m.State["body"].([]ast.Stmt) {
+			// FIXME this leaves behind an empty line, and possibly
+			// comments in the default branch. We can't easily fix
+			// either.
+			if comm, ok := c.(*ast.CommClause); ok && comm.Comm == nil && len(comm.Body) == 0 {
+				report.Report(pass, comm,
+					"should not have an empty default case in a for+select loop; the loop will spin",
+					report.Fixes(edit.Fix("Remove empty default branch", edit.Delete(comm))))
+				// there can only be one default case
+				break
+			}
+		}
+	}
+	return nil, nil
+}