Add staticcheck tool

vendor/honnef.co/go/tools/simple/s1036/s1036.go

@@ -0,0 +1,88 @@
+package s1036
+
+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:     "S1036",
+		Run:      run,
+		Requires: code.RequiredAnalyzers,
+	},
+	Doc: &lint.RawDocumentation{
+		Title: `Unnecessary guard around map access`,
+
+		Text: `
+When accessing a map key that doesn't exist yet, one receives a zero
+value. Often, the zero value is a suitable value, for example when
+using append or doing integer math.
+
+The following
+
+    if _, ok := m["foo"]; ok {
+        m["foo"] = append(m["foo"], "bar")
+    } else {
+        m["foo"] = []string{"bar"}
+    }
+
+can be simplified to
+
+    m["foo"] = append(m["foo"], "bar")
+
+and
+
+    if _, ok := m2["k"]; ok {
+        m2["k"] += 4
+    } else {
+        m2["k"] = 4
+    }
+
+can be simplified to
+
+    m["k"] += 4
+`,
+		Since:   "2020.1",
+		MergeIf: lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+var checkUnnecessaryGuardQ = pattern.MustParse(`
+	(Or
+		(IfStmt
+			(AssignStmt [(Ident "_") ok@(Ident _)] ":=" indexexpr@(IndexExpr _ _))
+			ok
+			set@(AssignStmt indexexpr "=" (CallExpr (Builtin "append") indexexpr:values))
+			(AssignStmt indexexpr "=" (CompositeLit _ values)))
+		(IfStmt
+			(AssignStmt [(Ident "_") ok] ":=" indexexpr@(IndexExpr _ _))
+			ok
+			set@(AssignStmt indexexpr "+=" value)
+			(AssignStmt indexexpr "=" value))
+		(IfStmt
+			(AssignStmt [(Ident "_") ok] ":=" indexexpr@(IndexExpr _ _))
+			ok
+			set@(IncDecStmt indexexpr "++")
+			(AssignStmt indexexpr "=" (IntegerLiteral "1"))))`)
+
+func run(pass *analysis.Pass) (any, error) {
+	for node, m := range code.Matches(pass, checkUnnecessaryGuardQ) {
+		if code.MayHaveSideEffects(pass, m.State["indexexpr"].(ast.Expr), nil) {
+			continue
+		}
+		report.Report(pass, node, "unnecessary guard around map access",
+			report.ShortRange(),
+			report.Fixes(edit.Fix("Simplify map access", edit.ReplaceWithNode(pass.Fset, node, m.State["set"].(ast.Node)))))
+	}
+	return nil, nil
+}