src

code.go (19557B)

---

 // Package code answers structural and type questions about Go code.
 package code
 
 import (
 	"fmt"
 	"go/ast"
 	"go/build/constraint"
 	"go/constant"
 	"go/token"
 	"go/types"
 	"go/version"
 	"path/filepath"
 	"slices"
 	"strings"
 
 	"honnef.co/go/tools/analysis/facts/generated"
 	"honnef.co/go/tools/analysis/facts/purity"
 	"honnef.co/go/tools/analysis/facts/tokenfile"
 	"honnef.co/go/tools/go/types/typeutil"
 	"honnef.co/go/tools/knowledge"
 	"honnef.co/go/tools/pattern"
 
 	"golang.org/x/tools/go/analysis"
 )
 
 type Positioner interface {
 	Pos() token.Pos
 }
 
 func IsOfStringConvertibleByteSlice(pass *analysis.Pass, expr ast.Expr) bool {
 	typ, ok := pass.TypesInfo.TypeOf(expr).Underlying().(*types.Slice)
 	if !ok {
 		return false
 	}
 	elem := types.Unalias(typ.Elem())
 	if version.Compare(LanguageVersion(pass, expr), "go1.18") >= 0 {
 		// Before Go 1.18, one could not directly convert from []T (where 'type T byte')
 		// to string. See also https://github.com/golang/go/issues/23536.
 		elem = elem.Underlying()
 	}
 	return types.Identical(elem, types.Typ[types.Byte])
 }
 
 func IsOfPointerToTypeWithName(pass *analysis.Pass, expr ast.Expr, name string) bool {
 	ptr, ok := types.Unalias(pass.TypesInfo.TypeOf(expr)).(*types.Pointer)
 	if !ok {
 		return false
 	}
 	return typeutil.IsTypeWithName(ptr.Elem(), name)
 }
 
 func IsOfTypeWithName(pass *analysis.Pass, expr ast.Expr, name string) bool {
 	return typeutil.IsTypeWithName(pass.TypesInfo.TypeOf(expr), name)
 }
 
 func IsInTest(pass *analysis.Pass, node Positioner) bool {
 	// FIXME(dh): this doesn't work for global variables with
 	// initializers
 	f := pass.Fset.File(node.Pos())
 	return f != nil && strings.HasSuffix(f.Name(), "_test.go")
 }
 
 // IsMain reports whether the package being processed is a package
 // main.
 func IsMain(pass *analysis.Pass) bool {
 	return pass.Pkg.Name() == "main"
 }
 
 // IsMainLike reports whether the package being processed is a
 // main-like package. A main-like package is a package that is
 // package main, or that is intended to be used by a tool framework
 // such as cobra to implement a command.
 //
 // Note that this function errs on the side of false positives; it may
 // return true for packages that aren't main-like. IsMainLike is
 // intended for analyses that wish to suppress diagnostics for
 // main-like packages to avoid false positives.
 func IsMainLike(pass *analysis.Pass) bool {
 	if pass.Pkg.Name() == "main" {
 		return true
 	}
 	for _, imp := range pass.Pkg.Imports() {
 		if imp.Path() == "github.com/spf13/cobra" {
 			return true
 		}
 	}
 	return false
 }
 
 func SelectorName(pass *analysis.Pass, expr *ast.SelectorExpr) string {
 	info := pass.TypesInfo
 	sel := info.Selections[expr]
 	if sel == nil {
 		switch x := expr.X.(type) {
 		case *ast.Ident:
 			pkg, ok := info.ObjectOf(x).(*types.PkgName)
 			if !ok {
 				return fmt.Sprintf("(%s).%s", info.TypeOf(x), expr.Sel.Name)
 			}
 			return fmt.Sprintf("%s.%s", pkg.Imported().Path(), expr.Sel.Name)
 		case *ast.SelectorExpr:
 			return fmt.Sprintf("(%s).%s", SelectorName(pass, x), expr.Sel.Name)
 		default:
 			panic(fmt.Sprintf("unsupported selector: %v", expr))
 		}
 	}
 	if v, ok := sel.Obj().(*types.Var); ok && v.IsField() {
 		return fmt.Sprintf("(%s).%s", typeutil.DereferenceR(sel.Recv()), sel.Obj().Name())
 	} else {
 		return fmt.Sprintf("(%s).%s", sel.Recv(), sel.Obj().Name())
 	}
 }
 
 func IsNil(pass *analysis.Pass, expr ast.Expr) bool {
 	return pass.TypesInfo.Types[expr].IsNil()
 }
 
 func BoolConst(pass *analysis.Pass, expr ast.Expr) bool {
 	val := pass.TypesInfo.ObjectOf(expr.(*ast.Ident)).(*types.Const).Val()
 	return constant.BoolVal(val)
 }
 
 func IsBoolConst(pass *analysis.Pass, expr ast.Expr) bool {
 	// We explicitly don't support typed bools because more often than
 	// not, custom bool types are used as binary enums and the explicit
 	// comparison is desired. We err on the side of false negatives and
 	// treat aliases like other custom types.
 
 	ident, ok := expr.(*ast.Ident)
 	if !ok {
 		return false
 	}
 	obj := pass.TypesInfo.ObjectOf(ident)
 	c, ok := obj.(*types.Const)
 	if !ok {
 		return false
 	}
 	basic, ok := c.Type().(*types.Basic)
 	if !ok {
 		return false
 	}
 	if basic.Kind() != types.UntypedBool && basic.Kind() != types.Bool {
 		return false
 	}
 	return true
 }
 
 func ExprToInt(pass *analysis.Pass, expr ast.Expr) (int64, bool) {
 	tv := pass.TypesInfo.Types[expr]
 	if tv.Value == nil {
 		return 0, false
 	}
 	if tv.Value.Kind() != constant.Int {
 		return 0, false
 	}
 	return constant.Int64Val(tv.Value)
 }
 
 func ExprToString(pass *analysis.Pass, expr ast.Expr) (string, bool) {
 	val := pass.TypesInfo.Types[expr].Value
 	if val == nil {
 		return "", false
 	}
 	if val.Kind() != constant.String {
 		return "", false
 	}
 	return constant.StringVal(val), true
 }
 
 func CallName(pass *analysis.Pass, call *ast.CallExpr) string {
 	// See the comment in typeutil.FuncName for why this doesn't require special handling
 	// of aliases.
 
 	fun := ast.Unparen(call.Fun)
 
 	// Instantiating a function cannot return another generic function, so doing this once is enough
 	switch idx := fun.(type) {
 	case *ast.IndexExpr:
 		fun = idx.X
 	case *ast.IndexListExpr:
 		fun = idx.X
 	}
 
 	// (foo)[T] is not a valid instantiation, so no need to unparen again.
 
 	switch fun := fun.(type) {
 	case *ast.SelectorExpr:
 		fn, ok := pass.TypesInfo.ObjectOf(fun.Sel).(*types.Func)
 		if !ok {
 			return ""
 		}
 		return typeutil.FuncName(fn)
 	case *ast.Ident:
 		obj := pass.TypesInfo.ObjectOf(fun)
 		switch obj := obj.(type) {
 		case *types.Func:
 			return typeutil.FuncName(obj)
 		case *types.Builtin:
 			return obj.Name()
 		default:
 			return ""
 		}
 	default:
 		return ""
 	}
 }
 
 func IsCallTo(pass *analysis.Pass, node ast.Node, name string) bool {
 	// See the comment in typeutil.FuncName for why this doesn't require special handling
 	// of aliases.
 
 	call, ok := node.(*ast.CallExpr)
 	if !ok {
 		return false
 	}
 	return CallName(pass, call) == name
 }
 
 func IsCallToAny(pass *analysis.Pass, node ast.Node, names ...string) bool {
 	// See the comment in typeutil.FuncName for why this doesn't require special handling
 	// of aliases.
 
 	call, ok := node.(*ast.CallExpr)
 	if !ok {
 		return false
 	}
 	q := CallName(pass, call)
 	return slices.Contains(names, q)
 }
 
 func File(pass *analysis.Pass, node Positioner) *ast.File {
 	m := pass.ResultOf[tokenfile.Analyzer].(map[*token.File]*ast.File)
 	return m[pass.Fset.File(node.Pos())]
 }
 
 // BuildConstraints returns the build constraints for file f. It considers both //go:build lines as well as
 // GOOS and GOARCH in file names.
 func BuildConstraints(pass *analysis.Pass, f *ast.File) (constraint.Expr, bool) {
 	var expr constraint.Expr
 	for _, cmt := range f.Comments {
 		if len(cmt.List) == 0 {
 			continue
 		}
 		for _, el := range cmt.List {
 			if el.Pos() > f.Package {
 				break
 			}
 			if line := el.Text; strings.HasPrefix(line, "//go:build") {
 				var err error
 				expr, err = constraint.Parse(line)
 				if err != nil {
 					expr = nil
 				}
 				break
 			}
 		}
 	}
 
 	name := pass.Fset.PositionFor(f.Pos(), false).Filename
 	oexpr := constraintsFromName(name)
 	if oexpr != nil {
 		if expr == nil {
 			expr = oexpr
 		} else {
 			expr = &constraint.AndExpr{X: expr, Y: oexpr}
 		}
 	}
 
 	return expr, expr != nil
 }
 
 func constraintsFromName(name string) constraint.Expr {
 	name = filepath.Base(name)
 	name = strings.TrimSuffix(name, ".go")
 	name = strings.TrimSuffix(name, "_test")
 	var goos, goarch string
 	switch strings.Count(name, "_") {
 	case 0:
 		// No GOOS or GOARCH in the file name.
 	case 1:
 		_, c, _ := strings.Cut(name, "_")
 		if _, ok := knowledge.KnownGOOS[c]; ok {
 			goos = c
 		} else if _, ok := knowledge.KnownGOARCH[c]; ok {
 			goarch = c
 		}
 	default:
 		n := strings.LastIndex(name, "_")
 		if _, ok := knowledge.KnownGOOS[name[n+1:]]; ok {
 			// The file name is *_stuff_GOOS.go
 			goos = name[n+1:]
 		} else if _, ok := knowledge.KnownGOARCH[name[n+1:]]; ok {
 			// The file name is *_GOOS_GOARCH.go or *_stuff_GOARCH.go
 			goarch = name[n+1:]
 			_, c, _ := strings.Cut(name[:n], "_")
 			if _, ok := knowledge.KnownGOOS[c]; ok {
 				// The file name is *_GOOS_GOARCH.go
 				goos = c
 			}
 		} else {
 			// The file name could also be something like foo_windows_nonsense.go — and because nonsense
 			// isn't a known GOARCH, "windows" won't be interpreted as a GOOS, either.
 		}
 	}
 
 	var expr constraint.Expr
 	if goos != "" {
 		expr = &constraint.TagExpr{Tag: goos}
 	}
 	if goarch != "" {
 		if expr == nil {
 			expr = &constraint.TagExpr{Tag: goarch}
 		} else {
 			expr = &constraint.AndExpr{X: expr, Y: &constraint.TagExpr{Tag: goarch}}
 		}
 	}
 	return expr
 }
 
 // IsGenerated reports whether pos is in a generated file. It ignores
 // //line directives.
 func IsGenerated(pass *analysis.Pass, pos token.Pos) bool {
 	_, ok := Generator(pass, pos)
 	return ok
 }
 
 // Generator returns the generator that generated the file containing
 // pos. It ignores //line directives.
 func Generator(pass *analysis.Pass, pos token.Pos) (generated.Generator, bool) {
 	file := pass.Fset.PositionFor(pos, false).Filename
 	m := pass.ResultOf[generated.Analyzer].(map[string]generated.Generator)
 	g, ok := m[file]
 	return g, ok
 }
 
 // MayHaveSideEffects reports whether expr may have side effects. If
 // the purity argument is nil, this function implements a purely
 // syntactic check, meaning that any function call may have side
 // effects, regardless of the called function's body. Otherwise,
 // purity will be consulted to determine the purity of function calls.
 func MayHaveSideEffects(pass *analysis.Pass, expr ast.Expr, purity purity.Result) bool {
 	switch expr := expr.(type) {
 	case *ast.BadExpr:
 		return true
 	case *ast.Ellipsis:
 		return MayHaveSideEffects(pass, expr.Elt, purity)
 	case *ast.FuncLit:
 		// the literal itself cannot have side effects, only calling it
 		// might, which is handled by CallExpr.
 		return false
 	case *ast.ArrayType, *ast.StructType, *ast.FuncType, *ast.InterfaceType, *ast.MapType, *ast.ChanType:
 		// types cannot have side effects
 		return false
 	case *ast.BasicLit:
 		return false
 	case *ast.BinaryExpr:
 		return MayHaveSideEffects(pass, expr.X, purity) || MayHaveSideEffects(pass, expr.Y, purity)
 	case *ast.CallExpr:
 		if purity == nil {
 			return true
 		}
 		switch obj := typeutil.Callee(pass.TypesInfo, expr).(type) {
 		case *types.Func:
 			if _, ok := purity[obj]; !ok {
 				return true
 			}
 		case *types.Builtin:
 			switch obj.Name() {
 			case "len", "cap":
 			default:
 				return true
 			}
 		default:
 			return true
 		}
 		for _, arg := range expr.Args {
 			if MayHaveSideEffects(pass, arg, purity) {
 				return true
 			}
 		}
 		return false
 	case *ast.CompositeLit:
 		if MayHaveSideEffects(pass, expr.Type, purity) {
 			return true
 		}
 		for _, elt := range expr.Elts {
 			if MayHaveSideEffects(pass, elt, purity) {
 				return true
 			}
 		}
 		return false
 	case *ast.Ident:
 		return false
 	case *ast.IndexExpr:
 		return MayHaveSideEffects(pass, expr.X, purity) || MayHaveSideEffects(pass, expr.Index, purity)
 	case *ast.IndexListExpr:
 		// In theory, none of the checks are necessary, as IndexListExpr only involves types. But there is no harm in
 		// being safe.
 		if MayHaveSideEffects(pass, expr.X, purity) {
 			return true
 		}
 		for _, idx := range expr.Indices {
 			if MayHaveSideEffects(pass, idx, purity) {
 				return true
 			}
 		}
 		return false
 	case *ast.KeyValueExpr:
 		return MayHaveSideEffects(pass, expr.Key, purity) || MayHaveSideEffects(pass, expr.Value, purity)
 	case *ast.SelectorExpr:
 		return MayHaveSideEffects(pass, expr.X, purity)
 	case *ast.SliceExpr:
 		return MayHaveSideEffects(pass, expr.X, purity) ||
 			MayHaveSideEffects(pass, expr.Low, purity) ||
 			MayHaveSideEffects(pass, expr.High, purity) ||
 			MayHaveSideEffects(pass, expr.Max, purity)
 	case *ast.StarExpr:
 		return MayHaveSideEffects(pass, expr.X, purity)
 	case *ast.TypeAssertExpr:
 		return MayHaveSideEffects(pass, expr.X, purity)
 	case *ast.UnaryExpr:
 		if MayHaveSideEffects(pass, expr.X, purity) {
 			return true
 		}
 		return expr.Op == token.ARROW || expr.Op == token.AND
 	case *ast.ParenExpr:
 		return MayHaveSideEffects(pass, expr.X, purity)
 	case nil:
 		return false
 	default:
 		panic(fmt.Sprintf("internal error: unhandled type %T", expr))
 	}
 }
 
 // LanguageVersion returns the version of the Go language that node has access to. This
 // might differ from the version of the Go standard library.
 func LanguageVersion(pass *analysis.Pass, node Positioner) string {
 	// As of Go 1.21, two places can specify the minimum Go version:
 	// - 'go' directives in go.mod and go.work files
 	// - individual files by using '//go:build'
 	//
 	// Individual files can upgrade to a higher version than the module version. Individual files
 	// can also downgrade to a lower version, but only if the module version is at least Go 1.21.
 	//
 	// The restriction on downgrading doesn't matter to us. All language changes before Go 1.22 will
 	// not type-check on versions that are too old, and thus never reach our analyzes. In practice,
 	// such ineffective downgrading will always be useless, as the compiler will not restrict the
 	// language features used, and doesn't ever rely on minimum versions to restrict the use of the
 	// standard library. However, for us, both choices (respecting or ignoring ineffective
 	// downgrading) have equal complexity, but only respecting it has a non-zero chance of reducing
 	// noisy positives.
 	//
 	// The minimum Go versions are exposed via go/ast.File.GoVersion and go/types.Package.GoVersion.
 	// ast.File's version is populated by the parser, whereas types.Package's version is populated
 	// from the Go version specified in the types.Config, which is set by our package loader, based
 	// on the module information provided by go/packages, via 'go list -json'.
 	//
 	// As of Go 1.21, standard library packages do not present themselves as modules, and thus do
 	// not have a version set on their types.Package. In this case, we fall back to the version
 	// provided by our '-go' flag. In most cases, '-go' defaults to 'module', which falls back to
 	// the Go version that Staticcheck was built with when no module information exists. In the
 	// future, the standard library will hopefully be a proper module (see
 	// https://github.com/golang/go/issues/61174#issuecomment-1622471317). In that case, the version
 	// of standard library packages will match that of the used Go version. At that point,
 	// Staticcheck will refuse to work with Go versions that are too new, to avoid misinterpreting
 	// code due to language changes.
 	//
 	// We also lack module information when building in GOPATH mode. In this case, the implied
 	// language version is at most Go 1.21, as per https://github.com/golang/go/issues/60915. We
 	// don't handle this yet, and it will not matter until Go 1.22.
 	//
 	// It is not clear how per-file downgrading behaves in GOPATH mode. On the one hand, no module
 	// version at all is provided, which should preclude per-file downgrading. On the other hand,
 	// https://github.com/golang/go/issues/60915 suggests that the language version is at most 1.21
 	// in GOPATH mode, which would allow per-file downgrading. Again it doesn't affect us, as all
 	// relevant language changes before Go 1.22 will lead to type-checking failures and never reach
 	// us.
 	//
 	// Per-file upgrading is permitted in GOPATH mode.
 
 	// If the file has its own Go version, we will return that. Otherwise, we default to
 	// the type checker's GoVersion, which is populated from either the Go module, or from
 	// our '-go' flag.
 	return pass.TypesInfo.FileVersions[File(pass, node)]
 }
 
 // StdlibVersion returns the version of the Go standard library that node can expect to
 // have access to. This might differ from the language version for versions of Go older
 // than 1.21.
 func StdlibVersion(pass *analysis.Pass, node Positioner) string {
 	// The Go version as specified in go.mod or via the '-go' flag
 	n := pass.Pkg.GoVersion()
 
 	f := File(pass, node)
 	if f == nil {
 		panic(fmt.Sprintf("no file found for node with position %s", pass.Fset.PositionFor(node.Pos(), false)))
 	}
 
 	if nf := f.GoVersion; nf != "" {
 		if version.Compare(n, "go1.21") == -1 {
 			// Before Go 1.21, the Go version set in go.mod specified the maximum language
 			// version available to the module. It wasn't uncommon to set the version to
 			// Go 1.20 but restrict usage of 1.20 functionality (both language and stdlib)
 			// to files tagged for 1.20, and supporting a lower version overall. As such,
 			// a file tagged lower than the module version couldn't expect to have access
 			// to the standard library of the version set in go.mod.
 			//
 			// At the same time, a file tagged higher than the module version, while not
 			// able to use newer language features, would still have been able to use a
 			// newer standard library.
 			//
 			// While Go 1.21's behavior has been backported to 1.19.11 and 1.20.6, users'
 			// expectations have not.
 			return nf
 		} else {
 			// Go 1.21 and newer refuse to build modules that depend on versions newer
 			// than the used version of the Go toolchain. This means that in a 1.22 module
 			// with a file tagged as 1.17, the file can expect to have access to 1.22's
 			// standard library (but not to 1.22 language features). A file tagged with a
 			// version higher than the minimum version has access to the newer standard
 			// library (and language features.)
 			//
 			// Do note that strictly speaking we're conflating the Go version and the
 			// module version in our check. Nothing is stopping a user from using Go 1.17
 			// (which didn't implement the new rules for versions in go.mod) to build a Go
 			// 1.22 module, in which case a file tagged with go1.17 will not have access to the 1.22
 			// standard library. However, we believe that if a module requires 1.21 or
 			// newer, then the author clearly expects the new behavior, and doesn't care
 			// for the old one. Otherwise they would've specified an older version.
 			//
 			// In other words, the module version also specifies what it itself actually means, with
 			// >=1.21 being a minimum version for the toolchain, and <1.21 being a maximum version for
 			// the language.
 
 			if version.Compare(nf, n) == 1 {
 				return nf
 			}
 		}
 	}
 
 	return n
 }
 
 var integerLiteralQ = pattern.MustParse(`(IntegerLiteral tv)`)
 
 func IntegerLiteral(pass *analysis.Pass, node ast.Node) (types.TypeAndValue, bool) {
 	m, ok := Match(pass, integerLiteralQ, node)
 	if !ok {
 		return types.TypeAndValue{}, false
 	}
 	return m.State["tv"].(types.TypeAndValue), true
 }
 
 func IsIntegerLiteral(pass *analysis.Pass, node ast.Node, value constant.Value) bool {
 	tv, ok := IntegerLiteral(pass, node)
 	if !ok {
 		return false
 	}
 	return constant.Compare(tv.Value, token.EQL, value)
 }
 
 // IsMethod reports whether expr is a method call of a named method with signature meth.
 // If name is empty, it is not checked.
 // For now, method expressions (Type.Method(recv, ..)) are not considered method calls.
 func IsMethod(pass *analysis.Pass, expr *ast.SelectorExpr, name string, meth *types.Signature) bool {
 	if name != "" && expr.Sel.Name != name {
 		return false
 	}
 	sel, ok := pass.TypesInfo.Selections[expr]
 	if !ok || sel.Kind() != types.MethodVal {
 		return false
 	}
 	return types.Identical(sel.Type(), meth)
 }
 
 func RefersTo(pass *analysis.Pass, expr ast.Expr, ident types.Object) bool {
 	found := false
 	fn := func(node ast.Node) bool {
 		ident2, ok := node.(*ast.Ident)
 		if !ok {
 			return true
 		}
 		if ident == pass.TypesInfo.ObjectOf(ident2) {
 			found = true
 			return false
 		}
 		return true
 	}
 	ast.Inspect(expr, fn)
 	return found
 }