go/analysis/passes/tests/tests.go - tools - Git at Google

 // Copyright 2015 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package tests

 import (
 	_ "embed"
 	"fmt"
 	"go/ast"
 	"go/token"
 	"go/types"
 	"regexp"
 	"strings"
 	"unicode"
 	"unicode/utf8"

 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
 	"golang.org/x/tools/internal/typeparams"
 )

 //go:embed doc.go
 var doc string

 var Analyzer = &analysis.Analyzer{
 	Name: "tests",
 	Doc:  analysisutil.MustExtractDoc(doc, "tests"),
 	URL:  "https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/tests",
 	Run:  run,
 }

 var acceptedFuzzTypes = []types.Type{
 	types.Typ[types.String],
 	types.Typ[types.Bool],
 	types.Typ[types.Float32],
 	types.Typ[types.Float64],
 	types.Typ[types.Int],
 	types.Typ[types.Int8],
 	types.Typ[types.Int16],
 	types.Typ[types.Int32],
 	types.Typ[types.Int64],
 	types.Typ[types.Uint],
 	types.Typ[types.Uint8],
 	types.Typ[types.Uint16],
 	types.Typ[types.Uint32],
 	types.Typ[types.Uint64],
 	types.NewSlice(types.Universe.Lookup("byte").Type()),
 }

 func run(pass *analysis.Pass) (interface{}, error) {
 	for _, f := range pass.Files {
 		if !strings.HasSuffix(pass.Fset.File(f.Pos()).Name(), "_test.go") {
 			continue
 		}
 		for _, decl := range f.Decls {
 			fn, ok := decl.(*ast.FuncDecl)
 			if !ok || fn.Recv != nil {
 				// Ignore non-functions or functions with receivers.
 				continue
 			}
 			switch {
 			case strings.HasPrefix(fn.Name.Name, "Example"):
 				checkExampleName(pass, fn)
 				checkExampleOutput(pass, fn, f.Comments)
 			case strings.HasPrefix(fn.Name.Name, "Test"):
 				checkTest(pass, fn, "Test")
 			case strings.HasPrefix(fn.Name.Name, "Benchmark"):
 				checkTest(pass, fn, "Benchmark")
 			case strings.HasPrefix(fn.Name.Name, "Fuzz"):
 				checkTest(pass, fn, "Fuzz")
 				checkFuzz(pass, fn)
 			}
 		}
 	}
 	return nil, nil
 }

 // checkFuzz checks the contents of a fuzz function.
 func checkFuzz(pass *analysis.Pass, fn *ast.FuncDecl) {
 	params := checkFuzzCall(pass, fn)
 	if params != nil {
 		checkAddCalls(pass, fn, params)
 	}
 }

 // checkFuzzCall checks the arguments of f.Fuzz() calls:
 //
 //  1. f.Fuzz() should call a function and it should be of type (*testing.F).Fuzz().
 //  2. The called function in f.Fuzz(func(){}) should not return result.
 //  3. First argument of func() should be of type *testing.T
 //  4. Second argument onwards should be of type []byte, string, bool, byte,
 //     rune, float32, float64, int, int8, int16, int32, int64, uint, uint8, uint16,
 //     uint32, uint64
 //  5. func() must not call any *F methods, e.g. (*F).Log, (*F).Error, (*F).Skip
 //     The only *F methods that are allowed in the (*F).Fuzz function are (*F).Failed and (*F).Name.
 //
 // Returns the list of parameters to the fuzz function, if they are valid fuzz parameters.
 func checkFuzzCall(pass *analysis.Pass, fn *ast.FuncDecl) (params *types.Tuple) {
 	ast.Inspect(fn, func(n ast.Node) bool {
 		call, ok := n.(*ast.CallExpr)
 		if ok {
 			if !isFuzzTargetDotFuzz(pass, call) {
 				return true
 			}

 			// Only one argument (func) must be passed to (*testing.F).Fuzz.
 			if len(call.Args) != 1 {
 				return true
 			}
 			expr := call.Args[0]
 			if pass.TypesInfo.Types[expr].Type == nil {
 				return true
 			}
 			t := pass.TypesInfo.Types[expr].Type.Underlying()
 			tSign, argOk := t.(*types.Signature)
 			// Argument should be a function
 			if !argOk {
 				pass.ReportRangef(expr, "argument to Fuzz must be a function")
 				return false
 			}
 			// ff Argument function should not return
 			if tSign.Results().Len() != 0 {
 				pass.ReportRangef(expr, "fuzz target must not return any value")
 			}
 			// ff Argument function should have 1 or more argument
 			if tSign.Params().Len() == 0 {
 				pass.ReportRangef(expr, "fuzz target must have 1 or more argument")
 				return false
 			}
 			ok := validateFuzzArgs(pass, tSign.Params(), expr)
 			if ok && params == nil {
 				params = tSign.Params()
 			}
 			// Inspect the function that was passed as an argument to make sure that
 			// there are no calls to *F methods, except for Name and Failed.
 			ast.Inspect(expr, func(n ast.Node) bool {
 				if call, ok := n.(*ast.CallExpr); ok {
 					if !isFuzzTargetDot(pass, call, "") {
 						return true
 					}
 					if !isFuzzTargetDot(pass, call, "Name") && !isFuzzTargetDot(pass, call, "Failed") {
 						pass.ReportRangef(call, "fuzz target must not call any *F methods")
 					}
 				}
 				return true
 			})
 			// We do not need to look at any calls to f.Fuzz inside of a Fuzz call,
 			// since they are not allowed.
 			return false
 		}
 		return true
 	})
 	return params
 }

 // checkAddCalls checks that the arguments of f.Add calls have the same number and type of arguments as
 // the signature of the function passed to (*testing.F).Fuzz
 func checkAddCalls(pass *analysis.Pass, fn *ast.FuncDecl, params *types.Tuple) {
 	ast.Inspect(fn, func(n ast.Node) bool {
 		call, ok := n.(*ast.CallExpr)
 		if ok {
 			if !isFuzzTargetDotAdd(pass, call) {
 				return true
 			}

 			// The first argument to function passed to (*testing.F).Fuzz is (*testing.T).
 			if len(call.Args) != params.Len()-1 {
 				pass.ReportRangef(call, "wrong number of values in call to (*testing.F).Add: %d, fuzz target expects %d", len(call.Args), params.Len()-1)
 				return true
 			}
 			var mismatched []int
 			for i, expr := range call.Args {
 				if pass.TypesInfo.Types[expr].Type == nil {
 					return true
 				}
 				t := pass.TypesInfo.Types[expr].Type
 				if !types.Identical(t, params.At(i+1).Type()) {
 					mismatched = append(mismatched, i)
 				}
 			}
 			// If just one of the types is mismatched report for that
 			// type only. Otherwise report for the whole call to (*testing.F).Add
 			if len(mismatched) == 1 {
 				i := mismatched[0]
 				expr := call.Args[i]
 				t := pass.TypesInfo.Types[expr].Type
 				pass.ReportRangef(expr, fmt.Sprintf("mismatched type in call to (*testing.F).Add: %v, fuzz target expects %v", t, params.At(i+1).Type()))
 			} else if len(mismatched) > 1 {
 				var gotArgs, wantArgs []types.Type
 				for i := 0; i < len(call.Args); i++ {
 					gotArgs, wantArgs = append(gotArgs, pass.TypesInfo.Types[call.Args[i]].Type), append(wantArgs, params.At(i+1).Type())
 				}
 				pass.ReportRangef(call, fmt.Sprintf("mismatched types in call to (*testing.F).Add: %v, fuzz target expects %v", gotArgs, wantArgs))
 			}
 		}
 		return true
 	})
 }

 // isFuzzTargetDotFuzz reports whether call is (*testing.F).Fuzz().
 func isFuzzTargetDotFuzz(pass *analysis.Pass, call *ast.CallExpr) bool {
 	return isFuzzTargetDot(pass, call, "Fuzz")
 }

 // isFuzzTargetDotAdd reports whether call is (*testing.F).Add().
 func isFuzzTargetDotAdd(pass *analysis.Pass, call *ast.CallExpr) bool {
 	return isFuzzTargetDot(pass, call, "Add")
 }

 // isFuzzTargetDot reports whether call is (*testing.F).<name>().
 func isFuzzTargetDot(pass *analysis.Pass, call *ast.CallExpr, name string) bool {
 	if selExpr, ok := call.Fun.(*ast.SelectorExpr); ok {
 		if !isTestingType(pass.TypesInfo.Types[selExpr.X].Type, "F") {
 			return false
 		}
 		if name == "" || selExpr.Sel.Name == name {
 			return true
 		}
 	}
 	return false
 }

 // Validate the arguments of fuzz target.
 func validateFuzzArgs(pass *analysis.Pass, params *types.Tuple, expr ast.Expr) bool {
 	fLit, isFuncLit := expr.(*ast.FuncLit)
 	exprRange := expr
 	ok := true
 	if !isTestingType(params.At(0).Type(), "T") {
 		if isFuncLit {
 			exprRange = fLit.Type.Params.List[0].Type
 		}
 		pass.ReportRangef(exprRange, "the first parameter of a fuzz target must be *testing.T")
 		ok = false
 	}
 	for i := 1; i < params.Len(); i++ {
 		if !isAcceptedFuzzType(params.At(i).Type()) {
 			if isFuncLit {
 				curr := 0
 				for _, field := range fLit.Type.Params.List {
 					curr += len(field.Names)
 					if i < curr {
 						exprRange = field.Type
 						break
 					}
 				}
 			}
 			pass.ReportRangef(exprRange, "fuzzing arguments can only have the following types: "+formatAcceptedFuzzType())
 			ok = false
 		}
 	}
 	return ok
 }

 func isTestingType(typ types.Type, testingType string) bool {
 	ptr, ok := typ.(*types.Pointer)
 	if !ok {
 		return false
 	}
 	return analysisutil.IsNamedType(ptr.Elem(), "testing", testingType)
 }

 // Validate that fuzz target function's arguments are of accepted types.
 func isAcceptedFuzzType(paramType types.Type) bool {
 	for _, typ := range acceptedFuzzTypes {
 		if types.Identical(typ, paramType) {
 			return true
 		}
 	}
 	return false
 }

 func formatAcceptedFuzzType() string {
 	var acceptedFuzzTypesStrings []string
 	for _, typ := range acceptedFuzzTypes {
 		acceptedFuzzTypesStrings = append(acceptedFuzzTypesStrings, typ.String())
 	}
 	acceptedFuzzTypesMsg := strings.Join(acceptedFuzzTypesStrings, ", ")
 	return acceptedFuzzTypesMsg
 }

 func isExampleSuffix(s string) bool {
 	r, size := utf8.DecodeRuneInString(s)
 	return size > 0 && unicode.IsLower(r)
 }

 func isTestSuffix(name string) bool {
 	if len(name) == 0 {
 		// "Test" is ok.
 		return true
 	}
 	r, _ := utf8.DecodeRuneInString(name)
 	return !unicode.IsLower(r)
 }

 func isTestParam(typ ast.Expr, wantType string) bool {
 	ptr, ok := typ.(*ast.StarExpr)
 	if !ok {
 		// Not a pointer.
 		return false
 	}
 	// No easy way of making sure it's a *testing.T or *testing.B:
 	// ensure the name of the type matches.
 	if name, ok := ptr.X.(*ast.Ident); ok {
 		return name.Name == wantType
 	}
 	if sel, ok := ptr.X.(*ast.SelectorExpr); ok {
 		return sel.Sel.Name == wantType
 	}
 	return false
 }

 func lookup(pkg *types.Package, name string) []types.Object {
 	if o := pkg.Scope().Lookup(name); o != nil {
 		return []types.Object{o}
 	}

 	var ret []types.Object
 	// Search through the imports to see if any of them define name.
 	// It's hard to tell in general which package is being tested, so
 	// for the purposes of the analysis, allow the object to appear
 	// in any of the imports. This guarantees there are no false positives
 	// because the example needs to use the object so it must be defined
 	// in the package or one if its imports. On the other hand, false
 	// negatives are possible, but should be rare.
 	for _, imp := range pkg.Imports() {
 		if obj := imp.Scope().Lookup(name); obj != nil {
 			ret = append(ret, obj)
 		}
 	}
 	return ret
 }

 // This pattern is taken from /go/src/go/doc/example.go
 var outputRe = regexp.MustCompile(`(?i)^[[:space:]]*(unordered )?output:`)

 type commentMetadata struct {
 	isOutput bool
 	pos      token.Pos
 }

 func checkExampleOutput(pass *analysis.Pass, fn *ast.FuncDecl, fileComments []*ast.CommentGroup) {
 	commentsInExample := []commentMetadata{}
 	numOutputs := 0

 	// Find the comment blocks that are in the example. These comments are
 	// guaranteed to be in order of appearance.
 	for _, cg := range fileComments {
 		if cg.Pos() < fn.Pos() {
 			continue
 		} else if cg.End() > fn.End() {
 			break
 		}

 		isOutput := outputRe.MatchString(cg.Text())
 		if isOutput {
 			numOutputs++
 		}

 		commentsInExample = append(commentsInExample, commentMetadata{
 			isOutput: isOutput,
 			pos:      cg.Pos(),
 		})
 	}

 	// Change message based on whether there are multiple output comment blocks.
 	msg := "output comment block must be the last comment block"
 	if numOutputs > 1 {
 		msg = "there can only be one output comment block per example"
 	}

 	for i, cg := range commentsInExample {
 		// Check for output comments that are not the last comment in the example.
 		isLast := (i == len(commentsInExample)-1)
 		if cg.isOutput && !isLast {
 			pass.Report(
 				analysis.Diagnostic{
 					Pos:     cg.pos,
 					Message: msg,
 				},
 			)
 		}
 	}
 }

 func checkExampleName(pass *analysis.Pass, fn *ast.FuncDecl) {
 	fnName := fn.Name.Name
 	if params := fn.Type.Params; len(params.List) != 0 {
 		pass.Reportf(fn.Pos(), "%s should be niladic", fnName)
 	}
 	if results := fn.Type.Results; results != nil && len(results.List) != 0 {
 		pass.Reportf(fn.Pos(), "%s should return nothing", fnName)
 	}
 	if tparams := typeparams.ForFuncType(fn.Type); tparams != nil && len(tparams.List) > 0 {
 		pass.Reportf(fn.Pos(), "%s should not have type params", fnName)
 	}

 	if fnName == "Example" {
 		// Nothing more to do.
 		return
 	}

 	var (
 		exName = strings.TrimPrefix(fnName, "Example")
 		elems  = strings.SplitN(exName, "_", 3)
 		ident  = elems[0]
 		objs   = lookup(pass.Pkg, ident)
 	)
 	if ident != "" && len(objs) == 0 {
 		// Check ExampleFoo and ExampleBadFoo.
 		pass.Reportf(fn.Pos(), "%s refers to unknown identifier: %s", fnName, ident)
 		// Abort since obj is absent and no subsequent checks can be performed.
 		return
 	}
 	if len(elems) < 2 {
 		// Nothing more to do.
 		return
 	}

 	if ident == "" {
 		// Check Example_suffix and Example_BadSuffix.
 		if residual := strings.TrimPrefix(exName, "_"); !isExampleSuffix(residual) {
 			pass.Reportf(fn.Pos(), "%s has malformed example suffix: %s", fnName, residual)
 		}
 		return
 	}

 	mmbr := elems[1]
 	if !isExampleSuffix(mmbr) {
 		// Check ExampleFoo_Method and ExampleFoo_BadMethod.
 		found := false
 		// Check if Foo.Method exists in this package or its imports.
 		for _, obj := range objs {
 			if obj, _, _ := types.LookupFieldOrMethod(obj.Type(), true, obj.Pkg(), mmbr); obj != nil {
 				found = true
 				break
 			}
 		}
 		if !found {
 			pass.Reportf(fn.Pos(), "%s refers to unknown field or method: %s.%s", fnName, ident, mmbr)
 		}
 	}
 	if len(elems) == 3 && !isExampleSuffix(elems[2]) {
 		// Check ExampleFoo_Method_suffix and ExampleFoo_Method_Badsuffix.
 		pass.Reportf(fn.Pos(), "%s has malformed example suffix: %s", fnName, elems[2])
 	}
 }

 func checkTest(pass *analysis.Pass, fn *ast.FuncDecl, prefix string) {
 	// Want functions with 0 results and 1 parameter.
 	if fn.Type.Results != nil && len(fn.Type.Results.List) > 0 ||
 		fn.Type.Params == nil ||
 		len(fn.Type.Params.List) != 1 ||
 		len(fn.Type.Params.List[0].Names) > 1 {
 		return
 	}

 	// The param must look like a *testing.T or *testing.B.
 	if !isTestParam(fn.Type.Params.List[0].Type, prefix[:1]) {
 		return
 	}

 	if tparams := typeparams.ForFuncType(fn.Type); tparams != nil && len(tparams.List) > 0 {
 		// Note: cmd/go/internal/load also errors about TestXXX and BenchmarkXXX functions with type parameters.
 		// We have currently decided to also warn before compilation/package loading. This can help users in IDEs.
 		// TODO(adonovan): use ReportRangef(tparams).
 		pass.Reportf(fn.Pos(), "%s has type parameters: it will not be run by go test as a %sXXX function", fn.Name.Name, prefix)
 	}

 	if !isTestSuffix(fn.Name.Name[len(prefix):]) {
 		// TODO(adonovan): use ReportRangef(fn.Name).
 		pass.Reportf(fn.Pos(), "%s has malformed name: first letter after '%s' must not be lowercase", fn.Name.Name, prefix)
 	}
 }
	// Copyright 2015 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package tests

	import (
	_ "embed"
	"fmt"
	"go/ast"
	"go/token"
	"go/types"
	"regexp"
	"strings"
	"unicode"
	"unicode/utf8"

	"golang.org/x/tools/go/analysis"
	"golang.org/x/tools/go/analysis/passes/internal/analysisutil"
	"golang.org/x/tools/internal/typeparams"
	)

	//go:embed doc.go
	var doc string

	var Analyzer = &analysis.Analyzer{
	Name: "tests",
	Doc: analysisutil.MustExtractDoc(doc, "tests"),
	URL: "https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/tests",
	Run: run,
	}

	var acceptedFuzzTypes = []types.Type{
	types.Typ[types.String],
	types.Typ[types.Bool],
	types.Typ[types.Float32],
	types.Typ[types.Float64],
	types.Typ[types.Int],
	types.Typ[types.Int8],
	types.Typ[types.Int16],
	types.Typ[types.Int32],
	types.Typ[types.Int64],
	types.Typ[types.Uint],
	types.Typ[types.Uint8],
	types.Typ[types.Uint16],
	types.Typ[types.Uint32],
	types.Typ[types.Uint64],
	types.NewSlice(types.Universe.Lookup("byte").Type()),
	}

	func run(pass *analysis.Pass) (interface{}, error) {
	for _, f := range pass.Files {
	if !strings.HasSuffix(pass.Fset.File(f.Pos()).Name(), "_test.go") {
	continue
	}
	for _, decl := range f.Decls {
	fn, ok := decl.(*ast.FuncDecl)
	if !ok \|\| fn.Recv != nil {
	// Ignore non-functions or functions with receivers.
	continue
	}
	switch {
	case strings.HasPrefix(fn.Name.Name, "Example"):
	checkExampleName(pass, fn)
	checkExampleOutput(pass, fn, f.Comments)
	case strings.HasPrefix(fn.Name.Name, "Test"):
	checkTest(pass, fn, "Test")
	case strings.HasPrefix(fn.Name.Name, "Benchmark"):
	checkTest(pass, fn, "Benchmark")
	case strings.HasPrefix(fn.Name.Name, "Fuzz"):
	checkTest(pass, fn, "Fuzz")
	checkFuzz(pass, fn)
	}
	}
	}
	return nil, nil
	}

	// checkFuzz checks the contents of a fuzz function.
	func checkFuzz(pass analysis.Pass, fn ast.FuncDecl) {
	params := checkFuzzCall(pass, fn)
	if params != nil {
	checkAddCalls(pass, fn, params)
	}
	}

	// checkFuzzCall checks the arguments of f.Fuzz() calls:
	//
	// 1. f.Fuzz() should call a function and it should be of type (*testing.F).Fuzz().
	// 2. The called function in f.Fuzz(func(){}) should not return result.
	// 3. First argument of func() should be of type *testing.T
	// 4. Second argument onwards should be of type []byte, string, bool, byte,
	// rune, float32, float64, int, int8, int16, int32, int64, uint, uint8, uint16,
	// uint32, uint64
	// 5. func() must not call any F methods, e.g. (F).Log, (F).Error, (F).Skip
	// The only F methods that are allowed in the (F).Fuzz function are (F).Failed and (F).Name.
	//
	// Returns the list of parameters to the fuzz function, if they are valid fuzz parameters.
	func checkFuzzCall(pass analysis.Pass, fn ast.FuncDecl) (params *types.Tuple) {
	ast.Inspect(fn, func(n ast.Node) bool {
	call, ok := n.(*ast.CallExpr)
	if ok {
	if !isFuzzTargetDotFuzz(pass, call) {
	return true
	}

	// Only one argument (func) must be passed to (*testing.F).Fuzz.
	if len(call.Args) != 1 {
	return true
	}
	expr := call.Args[0]
	if pass.TypesInfo.Types[expr].Type == nil {
	return true
	}
	t := pass.TypesInfo.Types[expr].Type.Underlying()
	tSign, argOk := t.(*types.Signature)
	// Argument should be a function
	if !argOk {
	pass.ReportRangef(expr, "argument to Fuzz must be a function")
	return false
	}
	// ff Argument function should not return
	if tSign.Results().Len() != 0 {
	pass.ReportRangef(expr, "fuzz target must not return any value")
	}
	// ff Argument function should have 1 or more argument
	if tSign.Params().Len() == 0 {
	pass.ReportRangef(expr, "fuzz target must have 1 or more argument")
	return false
	}
	ok := validateFuzzArgs(pass, tSign.Params(), expr)
	if ok && params == nil {
	params = tSign.Params()
	}
	// Inspect the function that was passed as an argument to make sure that
	// there are no calls to *F methods, except for Name and Failed.
	ast.Inspect(expr, func(n ast.Node) bool {
	if call, ok := n.(*ast.CallExpr); ok {
	if !isFuzzTargetDot(pass, call, "") {
	return true
	}
	if !isFuzzTargetDot(pass, call, "Name") && !isFuzzTargetDot(pass, call, "Failed") {
	pass.ReportRangef(call, "fuzz target must not call any *F methods")
	}
	}
	return true
	})
	// We do not need to look at any calls to f.Fuzz inside of a Fuzz call,
	// since they are not allowed.
	return false
	}
	return true
	})
	return params
	}

	// checkAddCalls checks that the arguments of f.Add calls have the same number and type of arguments as
	// the signature of the function passed to (*testing.F).Fuzz
	func checkAddCalls(pass analysis.Pass, fn ast.FuncDecl, params *types.Tuple) {
	ast.Inspect(fn, func(n ast.Node) bool {
	call, ok := n.(*ast.CallExpr)
	if ok {
	if !isFuzzTargetDotAdd(pass, call) {
	return true
	}

	// The first argument to function passed to (testing.F).Fuzz is (testing.T).
	if len(call.Args) != params.Len()-1 {
	pass.ReportRangef(call, "wrong number of values in call to (*testing.F).Add: %d, fuzz target expects %d", len(call.Args), params.Len()-1)
	return true
	}
	var mismatched []int
	for i, expr := range call.Args {
	if pass.TypesInfo.Types[expr].Type == nil {
	return true
	}
	t := pass.TypesInfo.Types[expr].Type
	if !types.Identical(t, params.At(i+1).Type()) {
	mismatched = append(mismatched, i)
	}
	}
	// If just one of the types is mismatched report for that
	// type only. Otherwise report for the whole call to (*testing.F).Add
	if len(mismatched) == 1 {
	i := mismatched[0]
	expr := call.Args[i]
	t := pass.TypesInfo.Types[expr].Type
	pass.ReportRangef(expr, fmt.Sprintf("mismatched type in call to (*testing.F).Add: %v, fuzz target expects %v", t, params.At(i+1).Type()))
	} else if len(mismatched) > 1 {
	var gotArgs, wantArgs []types.Type
	for i := 0; i < len(call.Args); i++ {
	gotArgs, wantArgs = append(gotArgs, pass.TypesInfo.Types[call.Args[i]].Type), append(wantArgs, params.At(i+1).Type())
	}
	pass.ReportRangef(call, fmt.Sprintf("mismatched types in call to (*testing.F).Add: %v, fuzz target expects %v", gotArgs, wantArgs))
	}
	}
	return true
	})
	}

	// isFuzzTargetDotFuzz reports whether call is (*testing.F).Fuzz().
	func isFuzzTargetDotFuzz(pass analysis.Pass, call ast.CallExpr) bool {
	return isFuzzTargetDot(pass, call, "Fuzz")
	}

	// isFuzzTargetDotAdd reports whether call is (*testing.F).Add().
	func isFuzzTargetDotAdd(pass analysis.Pass, call ast.CallExpr) bool {
	return isFuzzTargetDot(pass, call, "Add")
	}

	// isFuzzTargetDot reports whether call is (*testing.F).<name>().
	func isFuzzTargetDot(pass analysis.Pass, call ast.CallExpr, name string) bool {
	if selExpr, ok := call.Fun.(*ast.SelectorExpr); ok {
	if !isTestingType(pass.TypesInfo.Types[selExpr.X].Type, "F") {
	return false
	}
	if name == "" \|\| selExpr.Sel.Name == name {
	return true
	}
	}
	return false
	}

	// Validate the arguments of fuzz target.
	func validateFuzzArgs(pass analysis.Pass, params types.Tuple, expr ast.Expr) bool {
	fLit, isFuncLit := expr.(*ast.FuncLit)
	exprRange := expr
	ok := true
	if !isTestingType(params.At(0).Type(), "T") {
	if isFuncLit {
	exprRange = fLit.Type.Params.List[0].Type
	}
	pass.ReportRangef(exprRange, "the first parameter of a fuzz target must be *testing.T")
	ok = false
	}
	for i := 1; i < params.Len(); i++ {
	if !isAcceptedFuzzType(params.At(i).Type()) {
	if isFuncLit {
	curr := 0
	for _, field := range fLit.Type.Params.List {
	curr += len(field.Names)
	if i < curr {
	exprRange = field.Type
	break
	}
	}
	}
	pass.ReportRangef(exprRange, "fuzzing arguments can only have the following types: "+formatAcceptedFuzzType())
	ok = false
	}
	}
	return ok
	}

	func isTestingType(typ types.Type, testingType string) bool {
	ptr, ok := typ.(*types.Pointer)
	if !ok {
	return false
	}
	return analysisutil.IsNamedType(ptr.Elem(), "testing", testingType)
	}

	// Validate that fuzz target function's arguments are of accepted types.
	func isAcceptedFuzzType(paramType types.Type) bool {
	for _, typ := range acceptedFuzzTypes {
	if types.Identical(typ, paramType) {
	return true
	}
	}
	return false
	}

	func formatAcceptedFuzzType() string {
	var acceptedFuzzTypesStrings []string
	for _, typ := range acceptedFuzzTypes {
	acceptedFuzzTypesStrings = append(acceptedFuzzTypesStrings, typ.String())
	}
	acceptedFuzzTypesMsg := strings.Join(acceptedFuzzTypesStrings, ", ")
	return acceptedFuzzTypesMsg
	}

	func isExampleSuffix(s string) bool {
	r, size := utf8.DecodeRuneInString(s)
	return size > 0 && unicode.IsLower(r)
	}

	func isTestSuffix(name string) bool {
	if len(name) == 0 {
	// "Test" is ok.
	return true
	}
	r, _ := utf8.DecodeRuneInString(name)
	return !unicode.IsLower(r)
	}

	func isTestParam(typ ast.Expr, wantType string) bool {
	ptr, ok := typ.(*ast.StarExpr)
	if !ok {
	// Not a pointer.
	return false
	}
	// No easy way of making sure it's a testing.T or testing.B:
	// ensure the name of the type matches.
	if name, ok := ptr.X.(*ast.Ident); ok {
	return name.Name == wantType
	}
	if sel, ok := ptr.X.(*ast.SelectorExpr); ok {
	return sel.Sel.Name == wantType
	}
	return false
	}

	func lookup(pkg *types.Package, name string) []types.Object {
	if o := pkg.Scope().Lookup(name); o != nil {
	return []types.Object{o}
	}

	var ret []types.Object
	// Search through the imports to see if any of them define name.
	// It's hard to tell in general which package is being tested, so
	// for the purposes of the analysis, allow the object to appear
	// in any of the imports. This guarantees there are no false positives
	// because the example needs to use the object so it must be defined
	// in the package or one if its imports. On the other hand, false
	// negatives are possible, but should be rare.
	for _, imp := range pkg.Imports() {
	if obj := imp.Scope().Lookup(name); obj != nil {
	ret = append(ret, obj)
	}
	}
	return ret
	}

	// This pattern is taken from /go/src/go/doc/example.go
	var outputRe = regexp.MustCompile(`(?i)^[[:space:]]*(unordered )?output:`)

	type commentMetadata struct {
	isOutput bool
	pos token.Pos
	}

	func checkExampleOutput(pass analysis.Pass, fn ast.FuncDecl, fileComments []*ast.CommentGroup) {
	commentsInExample := []commentMetadata{}
	numOutputs := 0

	// Find the comment blocks that are in the example. These comments are
	// guaranteed to be in order of appearance.
	for _, cg := range fileComments {
	if cg.Pos() < fn.Pos() {
	continue
	} else if cg.End() > fn.End() {
	break
	}

	isOutput := outputRe.MatchString(cg.Text())
	if isOutput {
	numOutputs++
	}

	commentsInExample = append(commentsInExample, commentMetadata{
	isOutput: isOutput,
	pos: cg.Pos(),
	})
	}

	// Change message based on whether there are multiple output comment blocks.
	msg := "output comment block must be the last comment block"
	if numOutputs > 1 {
	msg = "there can only be one output comment block per example"
	}

	for i, cg := range commentsInExample {
	// Check for output comments that are not the last comment in the example.
	isLast := (i == len(commentsInExample)-1)
	if cg.isOutput && !isLast {
	pass.Report(
	analysis.Diagnostic{
	Pos: cg.pos,
	Message: msg,
	},
	)
	}
	}
	}

	func checkExampleName(pass analysis.Pass, fn ast.FuncDecl) {
	fnName := fn.Name.Name
	if params := fn.Type.Params; len(params.List) != 0 {
	pass.Reportf(fn.Pos(), "%s should be niladic", fnName)
	}
	if results := fn.Type.Results; results != nil && len(results.List) != 0 {
	pass.Reportf(fn.Pos(), "%s should return nothing", fnName)
	}
	if tparams := typeparams.ForFuncType(fn.Type); tparams != nil && len(tparams.List) > 0 {
	pass.Reportf(fn.Pos(), "%s should not have type params", fnName)
	}

	if fnName == "Example" {
	// Nothing more to do.
	return
	}

	var (
	exName = strings.TrimPrefix(fnName, "Example")
	elems = strings.SplitN(exName, "_", 3)
	ident = elems[0]
	objs = lookup(pass.Pkg, ident)
	)
	if ident != "" && len(objs) == 0 {
	// Check ExampleFoo and ExampleBadFoo.
	pass.Reportf(fn.Pos(), "%s refers to unknown identifier: %s", fnName, ident)
	// Abort since obj is absent and no subsequent checks can be performed.
	return
	}
	if len(elems) < 2 {
	// Nothing more to do.
	return
	}

	if ident == "" {
	// Check Example_suffix and Example_BadSuffix.
	if residual := strings.TrimPrefix(exName, "_"); !isExampleSuffix(residual) {
	pass.Reportf(fn.Pos(), "%s has malformed example suffix: %s", fnName, residual)
	}
	return
	}

	mmbr := elems[1]
	if !isExampleSuffix(mmbr) {
	// Check ExampleFoo_Method and ExampleFoo_BadMethod.
	found := false
	// Check if Foo.Method exists in this package or its imports.
	for _, obj := range objs {
	if obj, _, _ := types.LookupFieldOrMethod(obj.Type(), true, obj.Pkg(), mmbr); obj != nil {
	found = true
	break
	}
	}
	if !found {
	pass.Reportf(fn.Pos(), "%s refers to unknown field or method: %s.%s", fnName, ident, mmbr)
	}
	}
	if len(elems) == 3 && !isExampleSuffix(elems[2]) {
	// Check ExampleFoo_Method_suffix and ExampleFoo_Method_Badsuffix.
	pass.Reportf(fn.Pos(), "%s has malformed example suffix: %s", fnName, elems[2])
	}
	}

	func checkTest(pass analysis.Pass, fn ast.FuncDecl, prefix string) {
	// Want functions with 0 results and 1 parameter.
	if fn.Type.Results != nil && len(fn.Type.Results.List) > 0 \|\|
	fn.Type.Params == nil \|\|
	len(fn.Type.Params.List) != 1 \|\|
	len(fn.Type.Params.List[0].Names) > 1 {
	return
	}

	// The param must look like a testing.T or testing.B.
	if !isTestParam(fn.Type.Params.List[0].Type, prefix[:1]) {
	return
	}

	if tparams := typeparams.ForFuncType(fn.Type); tparams != nil && len(tparams.List) > 0 {
	// Note: cmd/go/internal/load also errors about TestXXX and BenchmarkXXX functions with type parameters.
	// We have currently decided to also warn before compilation/package loading. This can help users in IDEs.
	// TODO(adonovan): use ReportRangef(tparams).
	pass.Reportf(fn.Pos(), "%s has type parameters: it will not be run by go test as a %sXXX function", fn.Name.Name, prefix)
	}

	if !isTestSuffix(fn.Name.Name[len(prefix):]) {
	// TODO(adonovan): use ReportRangef(fn.Name).
	pass.Reportf(fn.Pos(), "%s has malformed name: first letter after '%s' must not be lowercase", fn.Name.Name, prefix)
	}
	}