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// 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 (
// stdImporter is the importer we use to import packages.
// It is shared so that all packages are imported by the same importer.
var stdImporter types.Importer
var (
errorType *types.Interface
stringerType *types.Interface // possibly nil
formatterType *types.Interface // possibly nil
httpResponseType types.Type // possibly nil
httpClientType types.Type // possibly nil
func inittypes() {
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)
if typ := importType("net/http", "Response"); typ != nil {
httpResponseType = typ
if typ := importType("net/http", "Client"); typ != nil {
httpClientType = typ
// importType returns the type denoted by the qualified identifier
//, 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 := stdImporter.Import(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 {
if stdImporter == nil {
if *source {
stdImporter = importer.For("source", nil)
} else {
stdImporter = importer.Default()
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 use the same importer for all imports to ensure that
// everybody sees identical packages for the given paths.
Importer: stdImporter,
// 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) {},
Sizes: archSizes,
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
// 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.
if f.isFormatter(typ) {
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:
// There's little we can do.
// Whether any particular verb is valid depends on the argument.
// The user may have reasonable prior knowledge of the contents of the interface.
return true
case *types.Basic:
switch typ.Kind() {
case types.UntypedBool,
return t&argBool != 0
case types.UntypedInt,
return t&argInt != 0
case types.UntypedFloat,
return t&argFloat != 0
case types.UntypedComplex,
return t&argComplex != 0
case types.UntypedString,
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.
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
// 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
var archSizes = types.SizesFor("gc", build.Default.GOARCH)