Add staticcheck tool

vendor/honnef.co/go/tools/simple/s1030/s1030.go

@@ -0,0 +1,87 @@
+package s1030
+
+import (
+	"fmt"
+	"go/ast"
+	"go/types"
+
+	"honnef.co/go/tools/analysis/code"
+	"honnef.co/go/tools/analysis/edit"
+	"honnef.co/go/tools/analysis/facts/generated"
+	"honnef.co/go/tools/analysis/lint"
+	"honnef.co/go/tools/analysis/report"
+	"honnef.co/go/tools/pattern"
+
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/analysis/passes/inspect"
+	"golang.org/x/tools/go/ast/inspector"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "S1030",
+		Run:      run,
+		Requires: []*analysis.Analyzer{inspect.Analyzer, generated.Analyzer},
+	},
+	Doc: &lint.RawDocumentation{
+		Title: `Use \'bytes.Buffer.String\' or \'bytes.Buffer.Bytes\'`,
+		Text: `\'bytes.Buffer\' has both a \'String\' and a \'Bytes\' method. It is almost never
+necessary to use \'string(buf.Bytes())\' or \'[]byte(buf.String())\' – simply
+use the other method.
+
+The only exception to this are map lookups. Due to a compiler optimization,
+\'m[string(buf.Bytes())]\' is more efficient than \'m[buf.String()]\'.
+`,
+		Since:   "2017.1",
+		MergeIf: lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+var (
+	checkBytesBufferConversionsQ  = pattern.MustParse(`(CallExpr _ [(CallExpr sel@(SelectorExpr recv _) [])])`)
+	checkBytesBufferConversionsRs = pattern.MustParse(`(CallExpr (SelectorExpr recv (Ident "String")) [])`)
+	checkBytesBufferConversionsRb = pattern.MustParse(`(CallExpr (SelectorExpr recv (Ident "Bytes")) [])`)
+)
+
+func run(pass *analysis.Pass) (any, error) {
+	if pass.Pkg.Path() == "bytes" || pass.Pkg.Path() == "bytes_test" {
+		// The bytes package can use itself however it wants
+		return nil, nil
+	}
+	fn := func(c inspector.Cursor) {
+		node := c.Node()
+		m, ok := code.Match(pass, checkBytesBufferConversionsQ, node)
+		if !ok {
+			return
+		}
+		call := node.(*ast.CallExpr)
+		sel := m.State["sel"].(*ast.SelectorExpr)
+
+		typ := pass.TypesInfo.TypeOf(call.Fun)
+		if types.Unalias(typ) == types.Universe.Lookup("string").Type() && code.IsCallTo(pass, call.Args[0], "(*bytes.Buffer).Bytes") {
+			if _, ok := c.Parent().Node().(*ast.IndexExpr); ok {
+				// Don't flag m[string(buf.Bytes())] – thanks to a
+				// compiler optimization, this is actually faster than
+				// m[buf.String()]
+				return
+			}
+
+			report.Report(pass, call, fmt.Sprintf("should use %v.String() instead of %v", report.Render(pass, sel.X), report.Render(pass, call)),
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("Simplify conversion", edit.ReplaceWithPattern(pass.Fset, node, checkBytesBufferConversionsRs, m.State))))
+		} else if typ, ok := types.Unalias(typ).(*types.Slice); ok &&
+			types.Unalias(typ.Elem()) == types.Universe.Lookup("byte").Type() &&
+			code.IsCallTo(pass, call.Args[0], "(*bytes.Buffer).String") {
+			report.Report(pass, call, fmt.Sprintf("should use %v.Bytes() instead of %v", report.Render(pass, sel.X), report.Render(pass, call)),
+				report.FilterGenerated(),
+				report.Fixes(edit.Fix("Simplify conversion", edit.ReplaceWithPattern(pass.Fset, node, checkBytesBufferConversionsRb, m.State))))
+		}
+
+	}
+	for c := range code.Cursor(pass).Preorder((*ast.CallExpr)(nil)) {
+		fn(c)
+	}
+	return nil, nil
+}