cmd/vet/types.go - tools - Git at Google

 // Copyright 2010 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.

 // This file contains the pieces of the tool that use typechecking from the go/types package.

 package main

 import (
 	"go/ast"
 	"go/token"

 	"golang.org/x/tools/go/types"
 )

 // imports is the canonical map of imported packages we need for typechecking.
 // It is created during initialization.
 var imports = make(map[string]*types.Package)

 var (
 	errorType     *types.Interface
 	stringerType  *types.Interface // possibly nil
 	formatterType *types.Interface // possibly nil
 )

 func init() {
 	errorType = types.Universe.Lookup("error").Type().Underlying().(*types.Interface)

 	if typ := importType("fmt", "Stringer"); typ != nil {
 		stringerType = typ.Underlying().(*types.Interface)
 	}

 	if typ := importType("fmt", "Formatter"); typ != nil {
 		formatterType = typ.Underlying().(*types.Interface)
 	}
 }

 // importType returns the type denoted by the qualified identifier
 // path.name, and adds the respective package to the imports map
 // as a side effect. In case of an error, importType returns nil.
 func importType(path, name string) types.Type {
 	pkg, err := types.DefaultImport(imports, path)
 	if err != nil {
 		// This can happen if the package at path hasn't been compiled yet.
 		warnf("import failed: %v", err)
 		return nil
 	}
 	if obj, ok := pkg.Scope().Lookup(name).(*types.TypeName); ok {
 		return obj.Type()
 	}
 	warnf("invalid type name %q", name)
 	return nil
 }

 func (pkg *Package) check(fs *token.FileSet, astFiles []*ast.File) error {
 	pkg.defs = make(map[*ast.Ident]types.Object)
 	pkg.uses = make(map[*ast.Ident]types.Object)
 	pkg.selectors = make(map[*ast.SelectorExpr]*types.Selection)
 	pkg.spans = make(map[types.Object]Span)
 	pkg.types = make(map[ast.Expr]types.TypeAndValue)
 	config := types.Config{
 		// We provide the same packages map for all imports to ensure
 		// that everybody sees identical packages for the given paths.
 		Packages: imports,
 		// By providing a Config with our own error function, it will continue
 		// past the first error. There is no need for that function to do anything.
 		Error: func(error) {},
 	}
 	info := &types.Info{
 		Selections: pkg.selectors,
 		Types:      pkg.types,
 		Defs:       pkg.defs,
 		Uses:       pkg.uses,
 	}
 	typesPkg, err := config.Check(pkg.path, fs, astFiles, info)
 	pkg.typesPkg = typesPkg
 	// update spans
 	for id, obj := range pkg.defs {
 		pkg.growSpan(id, obj)
 	}
 	for id, obj := range pkg.uses {
 		pkg.growSpan(id, obj)
 	}
 	return err
 }

 // isStruct reports whether the composite literal c is a struct.
 // If it is not (probably a struct), it returns a printable form of the type.
 func (pkg *Package) isStruct(c *ast.CompositeLit) (bool, string) {
 	// Check that the CompositeLit's type is a slice or array (which needs no field keys), if possible.
 	typ := pkg.types[c].Type
 	// If it's a named type, pull out the underlying type. If it's not, the Underlying
 	// method returns the type itself.
 	actual := typ
 	if actual != nil {
 		actual = actual.Underlying()
 	}
 	if actual == nil {
 		// No type information available. Assume true, so we do the check.
 		return true, ""
 	}
 	switch actual.(type) {
 	case *types.Struct:
 		return true, typ.String()
 	default:
 		return false, ""
 	}
 }

 // matchArgType reports an error if printf verb t is not appropriate
 // for operand arg.
 //
 // typ is used only for recursive calls; external callers must supply nil.
 //
 // (Recursion arises from the compound types {map,chan,slice} which
 // may be printed with %d etc. if that is appropriate for their element
 // types.)
 func (f *File) matchArgType(t printfArgType, typ types.Type, arg ast.Expr) bool {
 	return f.matchArgTypeInternal(t, typ, arg, make(map[types.Type]bool))
 }

 // matchArgTypeInternal is the internal version of matchArgType. It carries a map
 // remembering what types are in progress so we don't recur when faced with recursive
 // types or mutually recursive types.
 func (f *File) matchArgTypeInternal(t printfArgType, typ types.Type, arg ast.Expr, inProgress map[types.Type]bool) bool {
 	// %v, %T accept any argument type.
 	if t == anyType {
 		return true
 	}
 	if typ == nil {
 		// external call
 		typ = f.pkg.types[arg].Type
 		if typ == nil {
 			return true // probably a type check problem
 		}
 	}
 	// If the type implements fmt.Formatter, we have nothing to check.
 	// formatterTyp may be nil - be conservative and check for Format method in that case.
 	if formatterType != nil && types.Implements(typ, formatterType) || f.hasMethod(typ, "Format") {
 		return true
 	}
 	// If we can use a string, might arg (dynamically) implement the Stringer or Error interface?
 	if t&argString != 0 {
 		if types.AssertableTo(errorType, typ) || stringerType != nil && types.AssertableTo(stringerType, typ) {
 			return true
 		}
 	}

 	typ = typ.Underlying()
 	if inProgress[typ] {
 		// We're already looking at this type. The call that started it will take care of it.
 		return true
 	}
 	inProgress[typ] = true

 	switch typ := typ.(type) {
 	case *types.Signature:
 		return t&argPointer != 0

 	case *types.Map:
 		// Recur: map[int]int matches %d.
 		return t&argPointer != 0 ||
 			(f.matchArgTypeInternal(t, typ.Key(), arg, inProgress) && f.matchArgTypeInternal(t, typ.Elem(), arg, inProgress))

 	case *types.Chan:
 		return t&argPointer != 0

 	case *types.Array:
 		// Same as slice.
 		if types.Identical(typ.Elem().Underlying(), types.Typ[types.Byte]) && t&argString != 0 {
 			return true // %s matches []byte
 		}
 		// Recur: []int matches %d.
 		return t&argPointer != 0 || f.matchArgTypeInternal(t, typ.Elem().Underlying(), arg, inProgress)

 	case *types.Slice:
 		// Same as array.
 		if types.Identical(typ.Elem().Underlying(), types.Typ[types.Byte]) && t&argString != 0 {
 			return true // %s matches []byte
 		}
 		// Recur: []int matches %d. But watch out for
 		//	type T []T
 		// If the element is a pointer type (type T[]*T), it's handled fine by the Pointer case below.
 		return t&argPointer != 0 || f.matchArgTypeInternal(t, typ.Elem(), arg, inProgress)

 	case *types.Pointer:
 		// Ugly, but dealing with an edge case: a known pointer to an invalid type,
 		// probably something from a failed import.
 		if typ.Elem().String() == "invalid type" {
 			if *verbose {
 				f.Warnf(arg.Pos(), "printf argument %v is pointer to invalid or unknown type", f.gofmt(arg))
 			}
 			return true // special case
 		}
 		// If it's actually a pointer with %p, it prints as one.
 		if t == argPointer {
 			return true
 		}
 		// If it's pointer to struct, that's equivalent in our analysis to whether we can print the struct.
 		if str, ok := typ.Elem().Underlying().(*types.Struct); ok {
 			return f.matchStructArgType(t, str, arg, inProgress)
 		}
 		// The rest can print with %p as pointers, or as integers with %x etc.
 		return t&(argInt|argPointer) != 0

 	case *types.Struct:
 		return f.matchStructArgType(t, typ, arg, inProgress)

 	case *types.Interface:
 		// If the static type of the argument is empty interface, there's little we can do.
 		// Example:
 		//	func f(x interface{}) { fmt.Printf("%s", x) }
 		// Whether x is valid for %s depends on the type of the argument to f. One day
 		// we will be able to do better. For now, we assume that empty interface is OK
 		// but non-empty interfaces, with Stringer and Error handled above, are errors.
 		return typ.NumMethods() == 0

 	case *types.Basic:
 		switch typ.Kind() {
 		case types.UntypedBool,
 			types.Bool:
 			return t&argBool != 0

 		case types.UntypedInt,
 			types.Int,
 			types.Int8,
 			types.Int16,
 			types.Int32,
 			types.Int64,
 			types.Uint,
 			types.Uint8,
 			types.Uint16,
 			types.Uint32,
 			types.Uint64,
 			types.Uintptr:
 			return t&argInt != 0

 		case types.UntypedFloat,
 			types.Float32,
 			types.Float64:
 			return t&argFloat != 0

 		case types.UntypedComplex,
 			types.Complex64,
 			types.Complex128:
 			return t&argComplex != 0

 		case types.UntypedString,
 			types.String:
 			return t&argString != 0

 		case types.UnsafePointer:
 			return t&(argPointer|argInt) != 0

 		case types.UntypedRune:
 			return t&(argInt|argRune) != 0

 		case types.UntypedNil:
 			return t&argPointer != 0 // TODO?

 		case types.Invalid:
 			if *verbose {
 				f.Warnf(arg.Pos(), "printf argument %v has invalid or unknown type", f.gofmt(arg))
 			}
 			return true // Probably a type check problem.
 		}
 		panic("unreachable")
 	}

 	return false
 }

 // hasBasicType reports whether x's type is a types.Basic with the given kind.
 func (f *File) hasBasicType(x ast.Expr, kind types.BasicKind) bool {
 	t := f.pkg.types[x].Type
 	if t != nil {
 		t = t.Underlying()
 	}
 	b, ok := t.(*types.Basic)
 	return ok && b.Kind() == kind
 }

 // matchStructArgType reports whether all the elements of the struct match the expected
 // type. For instance, with "%d" all the elements must be printable with the "%d" format.
 func (f *File) matchStructArgType(t printfArgType, typ *types.Struct, arg ast.Expr, inProgress map[types.Type]bool) bool {
 	for i := 0; i < typ.NumFields(); i++ {
 		if !f.matchArgTypeInternal(t, typ.Field(i).Type(), arg, inProgress) {
 			return false
 		}
 	}
 	return true
 }

 // numArgsInSignature tells how many formal arguments the function type
 // being called has.
 func (f *File) numArgsInSignature(call *ast.CallExpr) int {
 	// Check the type of the function or method declaration
 	typ := f.pkg.types[call.Fun].Type
 	if typ == nil {
 		return 0
 	}
 	// The type must be a signature, but be sure for safety.
 	sig, ok := typ.(*types.Signature)
 	if !ok {
 		return 0
 	}
 	return sig.Params().Len()
 }

 // isErrorMethodCall reports whether the call is of a method with signature
 //	func Error() string
 // where "string" is the universe's string type. We know the method is called "Error".
 func (f *File) isErrorMethodCall(call *ast.CallExpr) bool {
 	typ := f.pkg.types[call].Type
 	if typ != nil {
 		// We know it's called "Error", so just check the function signature
 		// (stringerType has exactly one method, String).
 		if stringerType != nil && stringerType.NumMethods() == 1 {
 			return types.Identical(f.pkg.types[call.Fun].Type, stringerType.Method(0).Type())
 		}
 	}
 	// Without types, we can still check by hand.
 	// Is it a selector expression? Otherwise it's a function call, not a method call.
 	sel, ok := call.Fun.(*ast.SelectorExpr)
 	if !ok {
 		return false
 	}
 	// The package is type-checked, so if there are no arguments, we're done.
 	if len(call.Args) > 0 {
 		return false
 	}
 	// Check the type of the method declaration
 	typ = f.pkg.types[sel].Type
 	if typ == nil {
 		return false
 	}
 	// The type must be a signature, but be sure for safety.
 	sig, ok := typ.(*types.Signature)
 	if !ok {
 		return false
 	}
 	// There must be a receiver for it to be a method call. Otherwise it is
 	// a function, not something that satisfies the error interface.
 	if sig.Recv() == nil {
 		return false
 	}
 	// There must be no arguments. Already verified by type checking, but be thorough.
 	if sig.Params().Len() > 0 {
 		return false
 	}
 	// Finally the real questions.
 	// There must be one result.
 	if sig.Results().Len() != 1 {
 		return false
 	}
 	// It must have return type "string" from the universe.
 	return sig.Results().At(0).Type() == types.Typ[types.String]
 }

 // hasMethod reports whether the type contains a method with the given name.
 // It is part of the workaround for Formatters and should be deleted when
 // that workaround is no longer necessary.
 // TODO: This could be better once issue 6259 is fixed.
 func (f *File) hasMethod(typ types.Type, name string) bool {
 	// assume we have an addressable variable of type typ
 	obj, _, _ := types.LookupFieldOrMethod(typ, true, f.pkg.typesPkg, name)
 	_, ok := obj.(*types.Func)
 	return ok
 }
	// Copyright 2010 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.

	// This file contains the pieces of the tool that use typechecking from the go/types package.

	package main

	import (
	"go/ast"
	"go/token"

	"golang.org/x/tools/go/types"
	)

	// imports is the canonical map of imported packages we need for typechecking.
	// It is created during initialization.
	var imports = make(map[string]*types.Package)

	var (
	errorType *types.Interface
	stringerType *types.Interface // possibly nil
	formatterType *types.Interface // possibly nil
	)

	func init() {
	errorType = types.Universe.Lookup("error").Type().Underlying().(*types.Interface)

	if typ := importType("fmt", "Stringer"); typ != nil {
	stringerType = typ.Underlying().(*types.Interface)
	}

	if typ := importType("fmt", "Formatter"); typ != nil {
	formatterType = typ.Underlying().(*types.Interface)
	}
	}

	// importType returns the type denoted by the qualified identifier
	// path.name, and adds the respective package to the imports map
	// as a side effect. In case of an error, importType returns nil.
	func importType(path, name string) types.Type {
	pkg, err := types.DefaultImport(imports, path)
	if err != nil {
	// This can happen if the package at path hasn't been compiled yet.
	warnf("import failed: %v", err)
	return nil
	}
	if obj, ok := pkg.Scope().Lookup(name).(*types.TypeName); ok {
	return obj.Type()
	}
	warnf("invalid type name %q", name)
	return nil
	}

	func (pkg Package) check(fs token.FileSet, astFiles []*ast.File) error {
	pkg.defs = make(map[*ast.Ident]types.Object)
	pkg.uses = make(map[*ast.Ident]types.Object)
	pkg.selectors = make(map[ast.SelectorExpr]types.Selection)
	pkg.spans = make(map[types.Object]Span)
	pkg.types = make(map[ast.Expr]types.TypeAndValue)
	config := types.Config{
	// We provide the same packages map for all imports to ensure
	// that everybody sees identical packages for the given paths.
	Packages: imports,
	// By providing a Config with our own error function, it will continue
	// past the first error. There is no need for that function to do anything.
	Error: func(error) {},
	}
	info := &types.Info{
	Selections: pkg.selectors,
	Types: pkg.types,
	Defs: pkg.defs,
	Uses: pkg.uses,
	}
	typesPkg, err := config.Check(pkg.path, fs, astFiles, info)
	pkg.typesPkg = typesPkg
	// update spans
	for id, obj := range pkg.defs {
	pkg.growSpan(id, obj)
	}
	for id, obj := range pkg.uses {
	pkg.growSpan(id, obj)
	}
	return err
	}

	// isStruct reports whether the composite literal c is a struct.
	// If it is not (probably a struct), it returns a printable form of the type.
	func (pkg Package) isStruct(c ast.CompositeLit) (bool, string) {
	// Check that the CompositeLit's type is a slice or array (which needs no field keys), if possible.
	typ := pkg.types[c].Type
	// If it's a named type, pull out the underlying type. If it's not, the Underlying
	// method returns the type itself.
	actual := typ
	if actual != nil {
	actual = actual.Underlying()
	}
	if actual == nil {
	// No type information available. Assume true, so we do the check.
	return true, ""
	}
	switch actual.(type) {
	case *types.Struct:
	return true, typ.String()
	default:
	return false, ""
	}
	}

	// matchArgType reports an error if printf verb t is not appropriate
	// for operand arg.
	//
	// typ is used only for recursive calls; external callers must supply nil.
	//
	// (Recursion arises from the compound types {map,chan,slice} which
	// may be printed with %d etc. if that is appropriate for their element
	// types.)
	func (f *File) matchArgType(t printfArgType, typ types.Type, arg ast.Expr) bool {
	return f.matchArgTypeInternal(t, typ, arg, make(map[types.Type]bool))
	}

	// matchArgTypeInternal is the internal version of matchArgType. It carries a map
	// remembering what types are in progress so we don't recur when faced with recursive
	// types or mutually recursive types.
	func (f *File) matchArgTypeInternal(t printfArgType, typ types.Type, arg ast.Expr, inProgress map[types.Type]bool) bool {
	// %v, %T accept any argument type.
	if t == anyType {
	return true
	}
	if typ == nil {
	// external call
	typ = f.pkg.types[arg].Type
	if typ == nil {
	return true // probably a type check problem
	}
	}
	// If the type implements fmt.Formatter, we have nothing to check.
	// formatterTyp may be nil - be conservative and check for Format method in that case.
	if formatterType != nil && types.Implements(typ, formatterType) \|\| f.hasMethod(typ, "Format") {
	return true
	}
	// If we can use a string, might arg (dynamically) implement the Stringer or Error interface?
	if t&argString != 0 {
	if types.AssertableTo(errorType, typ) \|\| stringerType != nil && types.AssertableTo(stringerType, typ) {
	return true
	}
	}

	typ = typ.Underlying()
	if inProgress[typ] {
	// We're already looking at this type. The call that started it will take care of it.
	return true
	}
	inProgress[typ] = true

	switch typ := typ.(type) {
	case *types.Signature:
	return t&argPointer != 0

	case *types.Map:
	// Recur: map[int]int matches %d.
	return t&argPointer != 0 \|\|
	(f.matchArgTypeInternal(t, typ.Key(), arg, inProgress) && f.matchArgTypeInternal(t, typ.Elem(), arg, inProgress))

	case *types.Chan:
	return t&argPointer != 0

	case *types.Array:
	// Same as slice.
	if types.Identical(typ.Elem().Underlying(), types.Typ[types.Byte]) && t&argString != 0 {
	return true // %s matches []byte
	}
	// Recur: []int matches %d.
	return t&argPointer != 0 \|\| f.matchArgTypeInternal(t, typ.Elem().Underlying(), arg, inProgress)

	case *types.Slice:
	// Same as array.
	if types.Identical(typ.Elem().Underlying(), types.Typ[types.Byte]) && t&argString != 0 {
	return true // %s matches []byte
	}
	// Recur: []int matches %d. But watch out for
	// type T []T
	// If the element is a pointer type (type T[]*T), it's handled fine by the Pointer case below.
	return t&argPointer != 0 \|\| f.matchArgTypeInternal(t, typ.Elem(), arg, inProgress)

	case *types.Pointer:
	// Ugly, but dealing with an edge case: a known pointer to an invalid type,
	// probably something from a failed import.
	if typ.Elem().String() == "invalid type" {
	if *verbose {
	f.Warnf(arg.Pos(), "printf argument %v is pointer to invalid or unknown type", f.gofmt(arg))
	}
	return true // special case
	}
	// If it's actually a pointer with %p, it prints as one.
	if t == argPointer {
	return true
	}
	// If it's pointer to struct, that's equivalent in our analysis to whether we can print the struct.
	if str, ok := typ.Elem().Underlying().(*types.Struct); ok {
	return f.matchStructArgType(t, str, arg, inProgress)
	}
	// The rest can print with %p as pointers, or as integers with %x etc.
	return t&(argInt\|argPointer) != 0

	case *types.Struct:
	return f.matchStructArgType(t, typ, arg, inProgress)

	case *types.Interface:
	// If the static type of the argument is empty interface, there's little we can do.
	// Example:
	// func f(x interface{}) { fmt.Printf("%s", x) }
	// Whether x is valid for %s depends on the type of the argument to f. One day
	// we will be able to do better. For now, we assume that empty interface is OK
	// but non-empty interfaces, with Stringer and Error handled above, are errors.
	return typ.NumMethods() == 0

	case *types.Basic:
	switch typ.Kind() {
	case types.UntypedBool,
	types.Bool:
	return t&argBool != 0

	case types.UntypedInt,
	types.Int,
	types.Int8,
	types.Int16,
	types.Int32,
	types.Int64,
	types.Uint,
	types.Uint8,
	types.Uint16,
	types.Uint32,
	types.Uint64,
	types.Uintptr:
	return t&argInt != 0

	case types.UntypedFloat,
	types.Float32,
	types.Float64:
	return t&argFloat != 0

	case types.UntypedComplex,
	types.Complex64,
	types.Complex128:
	return t&argComplex != 0

	case types.UntypedString,
	types.String:
	return t&argString != 0

	case types.UnsafePointer:
	return t&(argPointer\|argInt) != 0

	case types.UntypedRune:
	return t&(argInt\|argRune) != 0

	case types.UntypedNil:
	return t&argPointer != 0 // TODO?

	case types.Invalid:
	if *verbose {
	f.Warnf(arg.Pos(), "printf argument %v has invalid or unknown type", f.gofmt(arg))
	}
	return true // Probably a type check problem.
	}
	panic("unreachable")
	}

	return false
	}

	// hasBasicType reports whether x's type is a types.Basic with the given kind.
	func (f *File) hasBasicType(x ast.Expr, kind types.BasicKind) bool {
	t := f.pkg.types[x].Type
	if t != nil {
	t = t.Underlying()
	}
	b, ok := t.(*types.Basic)
	return ok && b.Kind() == kind
	}

	// matchStructArgType reports whether all the elements of the struct match the expected
	// type. For instance, with "%d" all the elements must be printable with the "%d" format.
	func (f File) matchStructArgType(t printfArgType, typ types.Struct, arg ast.Expr, inProgress map[types.Type]bool) bool {
	for i := 0; i < typ.NumFields(); i++ {
	if !f.matchArgTypeInternal(t, typ.Field(i).Type(), arg, inProgress) {
	return false
	}
	}
	return true
	}

	// numArgsInSignature tells how many formal arguments the function type
	// being called has.
	func (f File) numArgsInSignature(call ast.CallExpr) int {
	// Check the type of the function or method declaration
	typ := f.pkg.types[call.Fun].Type
	if typ == nil {
	return 0
	}
	// The type must be a signature, but be sure for safety.
	sig, ok := typ.(*types.Signature)
	if !ok {
	return 0
	}
	return sig.Params().Len()
	}

	// isErrorMethodCall reports whether the call is of a method with signature
	// func Error() string
	// where "string" is the universe's string type. We know the method is called "Error".
	func (f File) isErrorMethodCall(call ast.CallExpr) bool {
	typ := f.pkg.types[call].Type
	if typ != nil {
	// We know it's called "Error", so just check the function signature
	// (stringerType has exactly one method, String).
	if stringerType != nil && stringerType.NumMethods() == 1 {
	return types.Identical(f.pkg.types[call.Fun].Type, stringerType.Method(0).Type())
	}
	}
	// Without types, we can still check by hand.
	// Is it a selector expression? Otherwise it's a function call, not a method call.
	sel, ok := call.Fun.(*ast.SelectorExpr)
	if !ok {
	return false
	}
	// The package is type-checked, so if there are no arguments, we're done.
	if len(call.Args) > 0 {
	return false
	}
	// Check the type of the method declaration
	typ = f.pkg.types[sel].Type
	if typ == nil {
	return false
	}
	// The type must be a signature, but be sure for safety.
	sig, ok := typ.(*types.Signature)
	if !ok {
	return false
	}
	// There must be a receiver for it to be a method call. Otherwise it is
	// a function, not something that satisfies the error interface.
	if sig.Recv() == nil {
	return false
	}
	// There must be no arguments. Already verified by type checking, but be thorough.
	if sig.Params().Len() > 0 {
	return false
	}
	// Finally the real questions.
	// There must be one result.
	if sig.Results().Len() != 1 {
	return false
	}
	// It must have return type "string" from the universe.
	return sig.Results().At(0).Type() == types.Typ[types.String]
	}

	// hasMethod reports whether the type contains a method with the given name.
	// It is part of the workaround for Formatters and should be deleted when
	// that workaround is no longer necessary.
	// TODO: This could be better once issue 6259 is fixed.
	func (f *File) hasMethod(typ types.Type, name string) bool {
	// assume we have an addressable variable of type typ
	obj, _, _ := types.LookupFieldOrMethod(typ, true, f.pkg.typesPkg, name)
	_, ok := obj.(*types.Func)
	return ok
	}