Add staticcheck tool

vendor/honnef.co/go/tools/staticcheck/sa5002/sa5002.go

@@ -0,0 +1,74 @@
+package sa5002
+
+import (
+	"go/ast"
+	"go/constant"
+	"go/types"
+
+	"honnef.co/go/tools/analysis/code"
+	"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:     "SA5002",
+		Run:      run,
+		Requires: []*analysis.Analyzer{inspect.Analyzer},
+	},
+	Doc: &lint.RawDocumentation{
+		Title:    `The empty for loop (\"for {}\") spins and can block the scheduler`,
+		Since:    "2017.1",
+		Severity: lint.SeverityWarning,
+		MergeIf:  lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+func run(pass *analysis.Pass) (any, error) {
+	fn := func(node ast.Node) {
+		loop := node.(*ast.ForStmt)
+		if len(loop.Body.List) != 0 || loop.Post != nil {
+			return
+		}
+
+		if loop.Init != nil {
+			// TODO(dh): this isn't strictly necessary, it just makes
+			// the check easier.
+			return
+		}
+		// An empty loop is bad news in two cases: 1) The loop has no
+		// condition. In that case, it's just a loop that spins
+		// forever and as fast as it can, keeping a core busy. 2) The
+		// loop condition only consists of variable or field reads and
+		// operators on those. The only way those could change their
+		// value is with unsynchronised access, which constitutes a
+		// data race.
+		//
+		// If the condition contains any function calls, its behaviour
+		// is dynamic and the loop might terminate. Similarly for
+		// channel receives.
+
+		if loop.Cond != nil {
+			if code.MayHaveSideEffects(pass, loop.Cond, nil) {
+				return
+			}
+			if ident, ok := loop.Cond.(*ast.Ident); ok {
+				if k, ok := pass.TypesInfo.ObjectOf(ident).(*types.Const); ok {
+					if !constant.BoolVal(k.Val()) {
+						// don't flag `for false {}` loops. They're a debug aid.
+						return
+					}
+				}
+			}
+			report.Report(pass, loop, "loop condition never changes or has a race condition")
+		}
+		report.Report(pass, loop, "this loop will spin, using 100% CPU", report.ShortRange())
+	}
+	code.Preorder(pass, fn, (*ast.ForStmt)(nil))
+	return nil, nil
+}