Add staticcheck tool

vendor/honnef.co/go/tools/staticcheck/sa4027/sa4027.go

@@ -0,0 +1,57 @@
+package sa4027
+
+import (
+	"go/ast"
+
+	"honnef.co/go/tools/analysis/code"
+	"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:     "SA4027",
+		Run:      run,
+		Requires: code.RequiredAnalyzers,
+	},
+	Doc: &lint.RawDocumentation{
+		Title: `\'(*net/url.URL).Query\' returns a copy, modifying it doesn't change the URL`,
+		Text: `\'(*net/url.URL).Query\' parses the current value of \'net/url.URL.RawQuery\'
+and returns it as a map of type \'net/url.Values\'. Subsequent changes to
+this map will not affect the URL unless the map gets encoded and
+assigned to the URL's \'RawQuery\'.
+
+As a consequence, the following code pattern is an expensive no-op:
+\'u.Query().Add(key, value)\'.`,
+		Since:    "2021.1",
+		Severity: lint.SeverityWarning,
+		MergeIf:  lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+var ineffectiveURLQueryAddQ = pattern.MustParse(`(CallExpr (SelectorExpr (CallExpr (SelectorExpr recv (Ident "Query")) []) (Ident meth)) _)`)
+
+func run(pass *analysis.Pass) (any, error) {
+	// TODO(dh): We could make this check more complex and detect
+	// pointless modifications of net/url.Values in general, but that
+	// requires us to get the state machine correct, else we'll cause
+	// false positives.
+
+	for node, m := range code.Matches(pass, ineffectiveURLQueryAddQ) {
+		if !code.IsOfPointerToTypeWithName(pass, m.State["recv"].(ast.Expr), "net/url.URL") {
+			continue
+		}
+		switch m.State["meth"].(string) {
+		case "Add", "Del", "Set":
+		default:
+			continue
+		}
+		report.Report(pass, node, "(*net/url.URL).Query returns a copy, modifying it doesn't change the URL")
+	}
+	return nil, nil
+}