io/fs: move FileInfo, FileMode, PathError, ErrInvalid, ... from os to io/fs

First step of creating the new io/fs package.

For #41190.

Change-Id: I1339b1abdd533b0f1deab283628088b2f706fb5b
Reviewed-on: https://go-review.googlesource.com/c/go/+/243906
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

6 files changed, 406 insertions, 193 deletions

diff --git a/api/except.txt b/api/except.txt
index 962bb14271..6f6f839ba6 100644
--- a/api/except.txt
+++ b/api/except.txt
@@ -2,12 +2,56 @@ pkg encoding/json, method (*RawMessage) MarshalJSON() ([]uint8, error)
 pkg math/big, const MaxBase = 36
 pkg math/big, type Word uintptr
 pkg net, func ListenUnixgram(string, *UnixAddr) (*UDPConn, error)
-pkg os, const ModeType = 2399141888
-pkg os, const ModeType = 2399666176
-pkg os (linux-arm), const O_SYNC = 4096
-pkg os (linux-arm-cgo), const O_SYNC = 4096
 pkg os (linux-arm), const O_SYNC = 1052672
+pkg os (linux-arm), const O_SYNC = 4096
 pkg os (linux-arm-cgo), const O_SYNC = 1052672
+pkg os (linux-arm-cgo), const O_SYNC = 4096
+pkg os, const ModeAppend FileMode
+pkg os, const ModeCharDevice FileMode
+pkg os, const ModeDevice FileMode
+pkg os, const ModeDir FileMode
+pkg os, const ModeExclusive FileMode
+pkg os, const ModeIrregular FileMode
+pkg os, const ModeNamedPipe FileMode
+pkg os, const ModePerm FileMode
+pkg os, const ModeSetgid FileMode
+pkg os, const ModeSetuid FileMode
+pkg os, const ModeSocket FileMode
+pkg os, const ModeSticky FileMode
+pkg os, const ModeSymlink FileMode
+pkg os, const ModeTemporary FileMode
+pkg os, const ModeType = 2399141888
+pkg os, const ModeType = 2399666176
+pkg os, const ModeType FileMode
+pkg os, func Chmod(string, FileMode) error
+pkg os, func Lstat(string) (FileInfo, error)
+pkg os, func Mkdir(string, FileMode) error
+pkg os, func MkdirAll(string, FileMode) error
+pkg os, func OpenFile(string, int, FileMode) (*File, error)
+pkg os, func SameFile(FileInfo, FileInfo) bool
+pkg os, func Stat(string) (FileInfo, error)
+pkg os, method (*File) Chmod(FileMode) error
+pkg os, method (*File) Readdir(int) ([]FileInfo, error)
+pkg os, method (*File) Stat() (FileInfo, error)
+pkg os, method (*PathError) Error() string
+pkg os, method (*PathError) Timeout() bool
+pkg os, method (*PathError) Unwrap() error
+pkg os, method (FileMode) IsDir() bool
+pkg os, method (FileMode) IsRegular() bool
+pkg os, method (FileMode) Perm() FileMode
+pkg os, method (FileMode) String() string
+pkg os, type FileInfo interface { IsDir, ModTime, Mode, Name, Size, Sys }
+pkg os, type FileInfo interface, IsDir() bool
+pkg os, type FileInfo interface, ModTime() time.Time
+pkg os, type FileInfo interface, Mode() FileMode
+pkg os, type FileInfo interface, Name() string
+pkg os, type FileInfo interface, Size() int64
+pkg os, type FileInfo interface, Sys() interface{}
+pkg os, type FileMode uint32
+pkg os, type PathError struct
+pkg os, type PathError struct, Err error
+pkg os, type PathError struct, Op string
+pkg os, type PathError struct, Path string
 pkg syscall (darwin-amd64), const ImplementsGetwd = false
 pkg syscall (darwin-amd64), func Fchflags(string, int) error
 pkg syscall (darwin-amd64-cgo), const ImplementsGetwd = false
@@ -18,22 +62,72 @@ pkg syscall (freebsd-386), const ELAST = 94
 pkg syscall (freebsd-386), const ImplementsGetwd = false
 pkg syscall (freebsd-386), const O_CLOEXEC = 0
 pkg syscall (freebsd-386), func Fchflags(string, int) error
+pkg syscall (freebsd-386), func Mknod(string, uint32, int) error
+pkg syscall (freebsd-386), type Dirent struct, Fileno uint32
+pkg syscall (freebsd-386), type Dirent struct, Namlen uint8
+pkg syscall (freebsd-386), type Stat_t struct, Blksize uint32
+pkg syscall (freebsd-386), type Stat_t struct, Dev uint32
+pkg syscall (freebsd-386), type Stat_t struct, Gen uint32
+pkg syscall (freebsd-386), type Stat_t struct, Ino uint32
+pkg syscall (freebsd-386), type Stat_t struct, Lspare int32
+pkg syscall (freebsd-386), type Stat_t struct, Nlink uint16
+pkg syscall (freebsd-386), type Stat_t struct, Pad_cgo_0 [8]uint8
+pkg syscall (freebsd-386), type Stat_t struct, Rdev uint32
+pkg syscall (freebsd-386), type Statfs_t struct, Mntfromname [88]int8
+pkg syscall (freebsd-386), type Statfs_t struct, Mntonname [88]int8
 pkg syscall (freebsd-386-cgo), const AF_MAX = 38
 pkg syscall (freebsd-386-cgo), const DLT_MATCHING_MAX = 242
 pkg syscall (freebsd-386-cgo), const ELAST = 94
 pkg syscall (freebsd-386-cgo), const ImplementsGetwd = false
 pkg syscall (freebsd-386-cgo), const O_CLOEXEC = 0
+pkg syscall (freebsd-386-cgo), func Mknod(string, uint32, int) error
+pkg syscall (freebsd-386-cgo), type Dirent struct, Fileno uint32
+pkg syscall (freebsd-386-cgo), type Dirent struct, Namlen uint8
+pkg syscall (freebsd-386-cgo), type Stat_t struct, Blksize uint32
+pkg syscall (freebsd-386-cgo), type Stat_t struct, Dev uint32
+pkg syscall (freebsd-386-cgo), type Stat_t struct, Gen uint32
+pkg syscall (freebsd-386-cgo), type Stat_t struct, Ino uint32
+pkg syscall (freebsd-386-cgo), type Stat_t struct, Lspare int32
+pkg syscall (freebsd-386-cgo), type Stat_t struct, Nlink uint16
+pkg syscall (freebsd-386-cgo), type Stat_t struct, Pad_cgo_0 [8]uint8
+pkg syscall (freebsd-386-cgo), type Stat_t struct, Rdev uint32
+pkg syscall (freebsd-386-cgo), type Statfs_t struct, Mntfromname [88]int8
+pkg syscall (freebsd-386-cgo), type Statfs_t struct, Mntonname [88]int8
 pkg syscall (freebsd-amd64), const AF_MAX = 38
 pkg syscall (freebsd-amd64), const DLT_MATCHING_MAX = 242
 pkg syscall (freebsd-amd64), const ELAST = 94
 pkg syscall (freebsd-amd64), const ImplementsGetwd = false
 pkg syscall (freebsd-amd64), const O_CLOEXEC = 0
 pkg syscall (freebsd-amd64), func Fchflags(string, int) error
+pkg syscall (freebsd-amd64), func Mknod(string, uint32, int) error
+pkg syscall (freebsd-amd64), type Dirent struct, Fileno uint32
+pkg syscall (freebsd-amd64), type Dirent struct, Namlen uint8
+pkg syscall (freebsd-amd64), type Stat_t struct, Blksize uint32
+pkg syscall (freebsd-amd64), type Stat_t struct, Dev uint32
+pkg syscall (freebsd-amd64), type Stat_t struct, Gen uint32
+pkg syscall (freebsd-amd64), type Stat_t struct, Ino uint32
+pkg syscall (freebsd-amd64), type Stat_t struct, Lspare int32
+pkg syscall (freebsd-amd64), type Stat_t struct, Nlink uint16
+pkg syscall (freebsd-amd64), type Stat_t struct, Rdev uint32
+pkg syscall (freebsd-amd64), type Statfs_t struct, Mntfromname [88]int8
+pkg syscall (freebsd-amd64), type Statfs_t struct, Mntonname [88]int8
 pkg syscall (freebsd-amd64-cgo), const AF_MAX = 38
 pkg syscall (freebsd-amd64-cgo), const DLT_MATCHING_MAX = 242
 pkg syscall (freebsd-amd64-cgo), const ELAST = 94
 pkg syscall (freebsd-amd64-cgo), const ImplementsGetwd = false
 pkg syscall (freebsd-amd64-cgo), const O_CLOEXEC = 0
+pkg syscall (freebsd-amd64-cgo), func Mknod(string, uint32, int) error
+pkg syscall (freebsd-amd64-cgo), type Dirent struct, Fileno uint32
+pkg syscall (freebsd-amd64-cgo), type Dirent struct, Namlen uint8
+pkg syscall (freebsd-amd64-cgo), type Stat_t struct, Blksize uint32
+pkg syscall (freebsd-amd64-cgo), type Stat_t struct, Dev uint32
+pkg syscall (freebsd-amd64-cgo), type Stat_t struct, Gen uint32
+pkg syscall (freebsd-amd64-cgo), type Stat_t struct, Ino uint32
+pkg syscall (freebsd-amd64-cgo), type Stat_t struct, Lspare int32
+pkg syscall (freebsd-amd64-cgo), type Stat_t struct, Nlink uint16
+pkg syscall (freebsd-amd64-cgo), type Stat_t struct, Rdev uint32
+pkg syscall (freebsd-amd64-cgo), type Statfs_t struct, Mntfromname [88]int8
+pkg syscall (freebsd-amd64-cgo), type Statfs_t struct, Mntonname [88]int8
 pkg syscall (freebsd-arm), const AF_MAX = 38
 pkg syscall (freebsd-arm), const BIOCGRTIMEOUT = 1074545262
 pkg syscall (freebsd-arm), const BIOCSRTIMEOUT = 2148287085
@@ -62,10 +156,22 @@ pkg syscall (freebsd-arm), const SizeofSockaddrDatalink = 56
 pkg syscall (freebsd-arm), const SizeofSockaddrUnix = 108
 pkg syscall (freebsd-arm), const TIOCTIMESTAMP = 1074558041
 pkg syscall (freebsd-arm), func Fchflags(string, int) error
+pkg syscall (freebsd-arm), func Mknod(string, uint32, int) error
 pkg syscall (freebsd-arm), type BpfHdr struct, Pad_cgo_0 [2]uint8
+pkg syscall (freebsd-arm), type Dirent struct, Fileno uint32
+pkg syscall (freebsd-arm), type Dirent struct, Namlen uint8
 pkg syscall (freebsd-arm), type RawSockaddrDatalink struct, Pad_cgo_0 [2]uint8
 pkg syscall (freebsd-arm), type RawSockaddrUnix struct, Pad_cgo_0 [2]uint8
+pkg syscall (freebsd-arm), type Stat_t struct, Blksize uint32
+pkg syscall (freebsd-arm), type Stat_t struct, Dev uint32
+pkg syscall (freebsd-arm), type Stat_t struct, Gen uint32
+pkg syscall (freebsd-arm), type Stat_t struct, Ino uint32
+pkg syscall (freebsd-arm), type Stat_t struct, Lspare int32
+pkg syscall (freebsd-arm), type Stat_t struct, Nlink uint16
 pkg syscall (freebsd-arm), type Stat_t struct, Pad_cgo_0 [4]uint8
+pkg syscall (freebsd-arm), type Stat_t struct, Rdev uint32
+pkg syscall (freebsd-arm), type Statfs_t struct, Mntfromname [88]int8
+pkg syscall (freebsd-arm), type Statfs_t struct, Mntonname [88]int8
 pkg syscall (freebsd-arm-cgo), const AF_MAX = 38
 pkg syscall (freebsd-arm-cgo), const BIOCGRTIMEOUT = 1074545262
 pkg syscall (freebsd-arm-cgo), const BIOCSRTIMEOUT = 2148287085
@@ -94,10 +200,22 @@ pkg syscall (freebsd-arm-cgo), const SizeofSockaddrDatalink = 56
 pkg syscall (freebsd-arm-cgo), const SizeofSockaddrUnix = 108
 pkg syscall (freebsd-arm-cgo), const TIOCTIMESTAMP = 1074558041
 pkg syscall (freebsd-arm-cgo), func Fchflags(string, int) error
+pkg syscall (freebsd-arm-cgo), func Mknod(string, uint32, int) error
 pkg syscall (freebsd-arm-cgo), type BpfHdr struct, Pad_cgo_0 [2]uint8
+pkg syscall (freebsd-arm-cgo), type Dirent struct, Fileno uint32
+pkg syscall (freebsd-arm-cgo), type Dirent struct, Namlen uint8
 pkg syscall (freebsd-arm-cgo), type RawSockaddrDatalink struct, Pad_cgo_0 [2]uint8
 pkg syscall (freebsd-arm-cgo), type RawSockaddrUnix struct, Pad_cgo_0 [2]uint8
+pkg syscall (freebsd-arm-cgo), type Stat_t struct, Blksize uint32
+pkg syscall (freebsd-arm-cgo), type Stat_t struct, Dev uint32
+pkg syscall (freebsd-arm-cgo), type Stat_t struct, Gen uint32
+pkg syscall (freebsd-arm-cgo), type Stat_t struct, Ino uint32
+pkg syscall (freebsd-arm-cgo), type Stat_t struct, Lspare int32
+pkg syscall (freebsd-arm-cgo), type Stat_t struct, Nlink uint16
 pkg syscall (freebsd-arm-cgo), type Stat_t struct, Pad_cgo_0 [4]uint8
+pkg syscall (freebsd-arm-cgo), type Stat_t struct, Rdev uint32
+pkg syscall (freebsd-arm-cgo), type Statfs_t struct, Mntfromname [88]int8
+pkg syscall (freebsd-arm-cgo), type Statfs_t struct, Mntonname [88]int8
 pkg syscall (linux-386), type Cmsghdr struct, X__cmsg_data [0]uint8
 pkg syscall (linux-386-cgo), type Cmsghdr struct, X__cmsg_data [0]uint8
 pkg syscall (linux-amd64), type Cmsghdr struct, X__cmsg_data [0]uint8
@@ -109,10 +227,10 @@ pkg syscall (netbsd-386-cgo), const ImplementsGetwd = false
 pkg syscall (netbsd-amd64), const ImplementsGetwd = false
 pkg syscall (netbsd-amd64-cgo), const ImplementsGetwd = false
 pkg syscall (netbsd-arm), const ImplementsGetwd = false
-pkg syscall (netbsd-arm-cgo), const ImplementsGetwd = false
 pkg syscall (netbsd-arm), const SizeofIfData = 132
 pkg syscall (netbsd-arm), func Fchflags(string, int) error
 pkg syscall (netbsd-arm), type IfMsghdr struct, Pad_cgo_1 [4]uint8
+pkg syscall (netbsd-arm-cgo), const ImplementsGetwd = false
 pkg syscall (netbsd-arm-cgo), const SizeofIfData = 132
 pkg syscall (netbsd-arm-cgo), func Fchflags(string, int) error
 pkg syscall (netbsd-arm-cgo), type IfMsghdr struct, Pad_cgo_1 [4]uint8
@@ -140,6 +258,7 @@ pkg syscall (openbsd-386), const SYS_GETITIMER = 86
 pkg syscall (openbsd-386), const SYS_GETRUSAGE = 117
 pkg syscall (openbsd-386), const SYS_GETTIMEOFDAY = 116
 pkg syscall (openbsd-386), const SYS_KEVENT = 270
+pkg syscall (openbsd-386), const SYS_KILL = 37
 pkg syscall (openbsd-386), const SYS_LSTAT = 293
 pkg syscall (openbsd-386), const SYS_NANOSLEEP = 240
 pkg syscall (openbsd-386), const SYS_SELECT = 93
@@ -193,6 +312,7 @@ pkg syscall (openbsd-386-cgo), const SYS_GETITIMER = 86
 pkg syscall (openbsd-386-cgo), const SYS_GETRUSAGE = 117
 pkg syscall (openbsd-386-cgo), const SYS_GETTIMEOFDAY = 116
 pkg syscall (openbsd-386-cgo), const SYS_KEVENT = 270
+pkg syscall (openbsd-386-cgo), const SYS_KILL = 37
 pkg syscall (openbsd-386-cgo), const SYS_LSTAT = 293
 pkg syscall (openbsd-386-cgo), const SYS_NANOSLEEP = 240
 pkg syscall (openbsd-386-cgo), const SYS_SELECT = 93
@@ -257,6 +377,7 @@ pkg syscall (openbsd-amd64), const SYS_GETITIMER = 86
 pkg syscall (openbsd-amd64), const SYS_GETRUSAGE = 117
 pkg syscall (openbsd-amd64), const SYS_GETTIMEOFDAY = 116
 pkg syscall (openbsd-amd64), const SYS_KEVENT = 270
+pkg syscall (openbsd-amd64), const SYS_KILL = 37
 pkg syscall (openbsd-amd64), const SYS_LSTAT = 293
 pkg syscall (openbsd-amd64), const SYS_NANOSLEEP = 240
 pkg syscall (openbsd-amd64), const SYS_SELECT = 93
@@ -320,6 +441,7 @@ pkg syscall (openbsd-amd64-cgo), const SYS_GETITIMER = 86
 pkg syscall (openbsd-amd64-cgo), const SYS_GETRUSAGE = 117
 pkg syscall (openbsd-amd64-cgo), const SYS_GETTIMEOFDAY = 116
 pkg syscall (openbsd-amd64-cgo), const SYS_KEVENT = 270
+pkg syscall (openbsd-amd64-cgo), const SYS_KILL = 37
 pkg syscall (openbsd-amd64-cgo), const SYS_LSTAT = 293
 pkg syscall (openbsd-amd64-cgo), const SYS_NANOSLEEP = 240
 pkg syscall (openbsd-amd64-cgo), const SYS_SELECT = 93
@@ -348,19 +470,6 @@ pkg syscall (openbsd-amd64-cgo), type Statfs_t struct, F_spare [3]uint32
 pkg syscall (openbsd-amd64-cgo), type Statfs_t struct, Pad_cgo_1 [4]uint8
 pkg syscall (openbsd-amd64-cgo), type Timespec struct, Pad_cgo_0 [4]uint8
 pkg syscall (openbsd-amd64-cgo), type Timespec struct, Sec int32
-pkg testing, func RegisterCover(Cover)
-pkg testing, func MainStart(func(string, string) (bool, error), []InternalTest, []InternalBenchmark, []InternalExample) *M
-pkg text/template/parse, type DotNode bool
-pkg text/template/parse, type Node interface { Copy, String, Type }
-pkg unicode, const Version = "6.2.0"
-pkg unicode, const Version = "6.3.0"
-pkg unicode, const Version = "7.0.0"
-pkg unicode, const Version = "8.0.0"
-pkg syscall (openbsd-386), const SYS_KILL = 37
-pkg syscall (openbsd-386-cgo), const SYS_KILL = 37
-pkg syscall (openbsd-amd64), const SYS_KILL = 37
-pkg syscall (openbsd-amd64-cgo), const SYS_KILL = 37
-pkg unicode, const Version = "9.0.0"
 pkg syscall (windows-386), const TOKEN_ALL_ACCESS = 983295
 pkg syscall (windows-386), type AddrinfoW struct, Addr uintptr
 pkg syscall (windows-386), type CertChainPolicyPara struct, ExtraPolicyPara uintptr
@@ -379,81 +488,16 @@ pkg syscall (windows-amd64), type CertRevocationInfo struct, CrlInfo uintptr
 pkg syscall (windows-amd64), type CertRevocationInfo struct, OidSpecificInfo uintptr
 pkg syscall (windows-amd64), type CertSimpleChain struct, TrustListInfo uintptr
 pkg syscall (windows-amd64), type RawSockaddrAny struct, Pad [96]int8
-pkg syscall (freebsd-386), func Mknod(string, uint32, int) error
-pkg syscall (freebsd-386), type Dirent struct, Fileno uint32
-pkg syscall (freebsd-386), type Dirent struct, Namlen uint8
-pkg syscall (freebsd-386), type Stat_t struct, Blksize uint32
-pkg syscall (freebsd-386), type Stat_t struct, Dev uint32
-pkg syscall (freebsd-386), type Stat_t struct, Gen uint32
-pkg syscall (freebsd-386), type Stat_t struct, Ino uint32
-pkg syscall (freebsd-386), type Stat_t struct, Lspare int32
-pkg syscall (freebsd-386), type Stat_t struct, Nlink uint16
-pkg syscall (freebsd-386), type Stat_t struct, Pad_cgo_0 [8]uint8
-pkg syscall (freebsd-386), type Stat_t struct, Rdev uint32
-pkg syscall (freebsd-386), type Statfs_t struct, Mntfromname [88]int8
-pkg syscall (freebsd-386), type Statfs_t struct, Mntonname [88]int8
-pkg syscall (freebsd-386-cgo), func Mknod(string, uint32, int) error
-pkg syscall (freebsd-386-cgo), type Dirent struct, Fileno uint32
-pkg syscall (freebsd-386-cgo), type Dirent struct, Namlen uint8
-pkg syscall (freebsd-386-cgo), type Stat_t struct, Blksize uint32
-pkg syscall (freebsd-386-cgo), type Stat_t struct, Dev uint32
-pkg syscall (freebsd-386-cgo), type Stat_t struct, Gen uint32
-pkg syscall (freebsd-386-cgo), type Stat_t struct, Ino uint32
-pkg syscall (freebsd-386-cgo), type Stat_t struct, Lspare int32
-pkg syscall (freebsd-386-cgo), type Stat_t struct, Nlink uint16
-pkg syscall (freebsd-386-cgo), type Stat_t struct, Pad_cgo_0 [8]uint8
-pkg syscall (freebsd-386-cgo), type Stat_t struct, Rdev uint32
-pkg syscall (freebsd-386-cgo), type Statfs_t struct, Mntfromname [88]int8
-pkg syscall (freebsd-386-cgo), type Statfs_t struct, Mntonname [88]int8
-pkg syscall (freebsd-amd64), func Mknod(string, uint32, int) error
-pkg syscall (freebsd-amd64), type Dirent struct, Fileno uint32
-pkg syscall (freebsd-amd64), type Dirent struct, Namlen uint8
-pkg syscall (freebsd-amd64), type Stat_t struct, Blksize uint32
-pkg syscall (freebsd-amd64), type Stat_t struct, Dev uint32
-pkg syscall (freebsd-amd64), type Stat_t struct, Gen uint32
-pkg syscall (freebsd-amd64), type Stat_t struct, Ino uint32
-pkg syscall (freebsd-amd64), type Stat_t struct, Lspare int32
-pkg syscall (freebsd-amd64), type Stat_t struct, Nlink uint16
-pkg syscall (freebsd-amd64), type Stat_t struct, Rdev uint32
-pkg syscall (freebsd-amd64), type Statfs_t struct, Mntfromname [88]int8
-pkg syscall (freebsd-amd64), type Statfs_t struct, Mntonname [88]int8
-pkg syscall (freebsd-amd64-cgo), func Mknod(string, uint32, int) error
-pkg syscall (freebsd-amd64-cgo), type Dirent struct, Fileno uint32
-pkg syscall (freebsd-amd64-cgo), type Dirent struct, Namlen uint8
-pkg syscall (freebsd-amd64-cgo), type Stat_t struct, Blksize uint32
-pkg syscall (freebsd-amd64-cgo), type Stat_t struct, Dev uint32
-pkg syscall (freebsd-amd64-cgo), type Stat_t struct, Gen uint32
-pkg syscall (freebsd-amd64-cgo), type Stat_t struct, Ino uint32
-pkg syscall (freebsd-amd64-cgo), type Stat_t struct, Lspare int32
-pkg syscall (freebsd-amd64-cgo), type Stat_t struct, Nlink uint16
-pkg syscall (freebsd-amd64-cgo), type Stat_t struct, Rdev uint32
-pkg syscall (freebsd-amd64-cgo), type Statfs_t struct, Mntfromname [88]int8
-pkg syscall (freebsd-amd64-cgo), type Statfs_t struct, Mntonname [88]int8
-pkg syscall (freebsd-arm), func Mknod(string, uint32, int) error
-pkg syscall (freebsd-arm), type Dirent struct, Fileno uint32
-pkg syscall (freebsd-arm), type Dirent struct, Namlen uint8
-pkg syscall (freebsd-arm), type Stat_t struct, Blksize uint32
-pkg syscall (freebsd-arm), type Stat_t struct, Dev uint32
-pkg syscall (freebsd-arm), type Stat_t struct, Gen uint32
-pkg syscall (freebsd-arm), type Stat_t struct, Ino uint32
-pkg syscall (freebsd-arm), type Stat_t struct, Lspare int32
-pkg syscall (freebsd-arm), type Stat_t struct, Nlink uint16
-pkg syscall (freebsd-arm), type Stat_t struct, Rdev uint32
-pkg syscall (freebsd-arm), type Statfs_t struct, Mntfromname [88]int8
-pkg syscall (freebsd-arm), type Statfs_t struct, Mntonname [88]int8
-pkg syscall (freebsd-arm-cgo), func Mknod(string, uint32, int) error
-pkg syscall (freebsd-arm-cgo), type Dirent struct, Fileno uint32
-pkg syscall (freebsd-arm-cgo), type Dirent struct, Namlen uint8
-pkg syscall (freebsd-arm-cgo), type Stat_t struct, Blksize uint32
-pkg syscall (freebsd-arm-cgo), type Stat_t struct, Dev uint32
-pkg syscall (freebsd-arm-cgo), type Stat_t struct, Gen uint32
-pkg syscall (freebsd-arm-cgo), type Stat_t struct, Ino uint32
-pkg syscall (freebsd-arm-cgo), type Stat_t struct, Lspare int32
-pkg syscall (freebsd-arm-cgo), type Stat_t struct, Nlink uint16
-pkg syscall (freebsd-arm-cgo), type Stat_t struct, Rdev uint32
-pkg syscall (freebsd-arm-cgo), type Statfs_t struct, Mntfromname [88]int8
-pkg syscall (freebsd-arm-cgo), type Statfs_t struct, Mntonname [88]int8
+pkg testing, func MainStart(func(string, string) (bool, error), []InternalTest, []InternalBenchmark, []InternalExample) *M
+pkg testing, func RegisterCover(Cover)
 pkg text/scanner, const GoTokens = 1012
+pkg text/template/parse, type DotNode bool
+pkg text/template/parse, type Node interface { Copy, String, Type }
 pkg unicode, const Version = "10.0.0"
 pkg unicode, const Version = "11.0.0"
 pkg unicode, const Version = "12.0.0"
+pkg unicode, const Version = "6.2.0"
+pkg unicode, const Version = "6.3.0"
+pkg unicode, const Version = "7.0.0"
+pkg unicode, const Version = "8.0.0"
+pkg unicode, const Version = "9.0.0"
diff --git a/api/next.txt b/api/next.txt
index 59422cca4d..3184a8ceae 100644
--- a/api/next.txt
+++ b/api/next.txt
@@ -223,15 +223,97 @@ pkg io, type ReadSeekCloser interface { Close, Read, Seek }
 pkg io, type ReadSeekCloser interface, Close() error
 pkg io, type ReadSeekCloser interface, Read([]uint8) (int, error)
 pkg io, type ReadSeekCloser interface, Seek(int64, int) (int64, error)
+pkg io/fs, const ModeAppend = 1073741824
+pkg io/fs, const ModeAppend FileMode
+pkg io/fs, const ModeCharDevice = 2097152
+pkg io/fs, const ModeCharDevice FileMode
+pkg io/fs, const ModeDevice = 67108864
+pkg io/fs, const ModeDevice FileMode
+pkg io/fs, const ModeDir = 2147483648
+pkg io/fs, const ModeDir FileMode
+pkg io/fs, const ModeExclusive = 536870912
+pkg io/fs, const ModeExclusive FileMode
+pkg io/fs, const ModeIrregular = 524288
+pkg io/fs, const ModeIrregular FileMode
+pkg io/fs, const ModeNamedPipe = 33554432
+pkg io/fs, const ModeNamedPipe FileMode
+pkg io/fs, const ModePerm = 511
+pkg io/fs, const ModePerm FileMode
+pkg io/fs, const ModeSetgid = 4194304
+pkg io/fs, const ModeSetgid FileMode
+pkg io/fs, const ModeSetuid = 8388608
+pkg io/fs, const ModeSetuid FileMode
+pkg io/fs, const ModeSocket = 16777216
+pkg io/fs, const ModeSocket FileMode
+pkg io/fs, const ModeSticky = 1048576
+pkg io/fs, const ModeSticky FileMode
+pkg io/fs, const ModeSymlink = 134217728
+pkg io/fs, const ModeSymlink FileMode
+pkg io/fs, const ModeTemporary = 268435456
+pkg io/fs, const ModeTemporary FileMode
+pkg io/fs, const ModeType = 2401763328
+pkg io/fs, const ModeType FileMode
+pkg io/fs, method (*PathError) Error() string
+pkg io/fs, method (*PathError) Timeout() bool
+pkg io/fs, method (*PathError) Unwrap() error
+pkg io/fs, method (FileMode) IsDir() bool
+pkg io/fs, method (FileMode) IsRegular() bool
+pkg io/fs, method (FileMode) Perm() FileMode
+pkg io/fs, method (FileMode) String() string
+pkg io/fs, method (FileMode) Type() FileMode
+pkg io/fs, type FileInfo interface { IsDir, ModTime, Mode, Name, Size, Sys }
+pkg io/fs, type FileInfo interface, IsDir() bool
+pkg io/fs, type FileInfo interface, ModTime() time.Time
+pkg io/fs, type FileInfo interface, Mode() FileMode
+pkg io/fs, type FileInfo interface, Name() string
+pkg io/fs, type FileInfo interface, Size() int64
+pkg io/fs, type FileInfo interface, Sys() interface{}
+pkg io/fs, type FileMode uint32
+pkg io/fs, type PathError struct
+pkg io/fs, type PathError struct, Err error
+pkg io/fs, type PathError struct, Op string
+pkg io/fs, type PathError struct, Path string
+pkg io/fs, var ErrClosed error
+pkg io/fs, var ErrExist error
+pkg io/fs, var ErrInvalid error
+pkg io/fs, var ErrNotExist error
+pkg io/fs, var ErrPermission error
 pkg net, var ErrClosed error
 pkg net/http, type Transport struct, GetProxyConnectHeader func(context.Context, *url.URL, string) (Header, error)
+pkg os, const ModeAppend fs.FileMode
+pkg os, const ModeCharDevice fs.FileMode
+pkg os, const ModeDevice fs.FileMode
+pkg os, const ModeDir fs.FileMode
+pkg os, const ModeExclusive fs.FileMode
+pkg os, const ModeIrregular fs.FileMode
+pkg os, const ModeNamedPipe fs.FileMode
+pkg os, const ModePerm fs.FileMode
+pkg os, const ModeSetgid fs.FileMode
+pkg os, const ModeSetuid fs.FileMode
+pkg os, const ModeSocket fs.FileMode
+pkg os, const ModeSticky fs.FileMode
+pkg os, const ModeSymlink fs.FileMode
+pkg os, const ModeTemporary fs.FileMode
+pkg os, const ModeType fs.FileMode
+pkg os, func Chmod(string, fs.FileMode) error
+pkg os, func Lstat(string) (fs.FileInfo, error)
+pkg os, func Mkdir(string, fs.FileMode) error
+pkg os, func MkdirAll(string, fs.FileMode) error
+pkg os, func OpenFile(string, int, fs.FileMode) (*File, error)
+pkg os, func SameFile(fs.FileInfo, fs.FileInfo) bool
+pkg os, func Stat(string) (fs.FileInfo, error)
+pkg os, method (*File) Chmod(fs.FileMode) error
 pkg os, method (*File) ReadDir(int) ([]DirEntry, error)
-pkg os, method (FileMode) Type() FileMode
+pkg os, method (*File) Readdir(int) ([]fs.FileInfo, error)
+pkg os, method (*File) Stat() (fs.FileInfo, error)
 pkg os, type DirEntry interface { Info, IsDir, Name, Type }
-pkg os, type DirEntry interface, Info() (FileInfo, error)
+pkg os, type DirEntry interface, Info() (fs.FileInfo, error)
 pkg os, type DirEntry interface, IsDir() bool
 pkg os, type DirEntry interface, Name() string
-pkg os, type DirEntry interface, Type() FileMode
+pkg os, type DirEntry interface, Type() fs.FileMode
+pkg os, type FileInfo = fs.FileInfo
+pkg os, type FileMode = fs.FileMode
+pkg os, type PathError = fs.PathError
 pkg os/signal, func NotifyContext(context.Context, ...os.Signal) (context.Context, context.CancelFunc)
 pkg testing/iotest, func ErrReader(error) io.Reader
 pkg text/template/parse, const NodeComment = 20
diff --git a/src/cmd/api/goapi.go b/src/cmd/api/goapi.go
index 6a80ed269b..b14d57c236 100644
--- a/src/cmd/api/goapi.go
+++ b/src/cmd/api/goapi.go
@@ -326,6 +326,18 @@ func compareAPI(w io.Writer, features, required, optional, exception []string, a
 	return
 }
 
+// aliasReplacer applies type aliases to earlier API files,
+// to avoid misleading negative results.
+// This makes all the references to os.FileInfo in go1.txt
+// be read as if they said fs.FileInfo, since os.FileInfo is now an alias.
+// If there are many of these, we could do a more general solution,
+// but for now the replacer is fine.
+var aliasReplacer = strings.NewReplacer(
+	"os.FileInfo", "fs.FileInfo",
+	"os.FileMode", "fs.FileMode",
+	"os.PathError", "fs.PathError",
+)
+
 func fileFeatures(filename string) []string {
 	if filename == "" {
 		return nil
@@ -334,7 +346,9 @@ func fileFeatures(filename string) []string {
 	if err != nil {
 		log.Fatalf("Error reading file %s: %v", filename, err)
 	}
-	lines := strings.Split(string(bs), "\n")
+	s := string(bs)
+	s = aliasReplacer.Replace(s)
+	lines := strings.Split(s, "\n")
 	var nonblank []string
 	for _, line := range lines {
 		line = strings.TrimSpace(line)
@@ -856,6 +870,10 @@ func (w *Walker) emitObj(obj types.Object) {
 func (w *Walker) emitType(obj *types.TypeName) {
 	name := obj.Name()
 	typ := obj.Type()
+	if obj.IsAlias() {
+		w.emitf("type %s = %s", name, w.typeString(typ))
+		return
+	}
 	switch typ := typ.Underlying().(type) {
 	case *types.Struct:
 		w.emitStructType(name, typ)
diff --git a/src/io/fs/fs.go b/src/io/fs/fs.go
new file mode 100644
index 0000000000..de5c465d9d
--- /dev/null
+++ b/src/io/fs/fs.go
@@ -0,0 +1,140 @@
+// Copyright 2020 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 fs defines basic interfaces to a file system.
+// A file system can be provided by the host operating system
+// but also by other packages.
+package fs
+
+import (
+	"internal/oserror"
+	"time"
+)
+
+// Generic file system errors.
+// Errors returned by file systems can be tested against these errors
+// using errors.Is.
+var (
+	ErrInvalid    = errInvalid()    // "invalid argument"
+	ErrPermission = errPermission() // "permission denied"
+	ErrExist      = errExist()      // "file already exists"
+	ErrNotExist   = errNotExist()   // "file does not exist"
+	ErrClosed     = errClosed()     // "file already closed"
+)
+
+func errInvalid() error    { return oserror.ErrInvalid }
+func errPermission() error { return oserror.ErrPermission }
+func errExist() error      { return oserror.ErrExist }
+func errNotExist() error   { return oserror.ErrNotExist }
+func errClosed() error     { return oserror.ErrClosed }
+
+// A FileInfo describes a file and is returned by Stat.
+type FileInfo interface {
+	Name() string       // base name of the file
+	Size() int64        // length in bytes for regular files; system-dependent for others
+	Mode() FileMode     // file mode bits
+	ModTime() time.Time // modification time
+	IsDir() bool        // abbreviation for Mode().IsDir()
+	Sys() interface{}   // underlying data source (can return nil)
+}
+
+// A FileMode represents a file's mode and permission bits.
+// The bits have the same definition on all systems, so that
+// information about files can be moved from one system
+// to another portably. Not all bits apply to all systems.
+// The only required bit is ModeDir for directories.
+type FileMode uint32
+
+// The defined file mode bits are the most significant bits of the FileMode.
+// The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
+// The values of these bits should be considered part of the public API and
+// may be used in wire protocols or disk representations: they must not be
+// changed, although new bits might be added.
+const (
+	// The single letters are the abbreviations
+	// used by the String method's formatting.
+	ModeDir        FileMode = 1 << (32 - 1 - iota) // d: is a directory
+	ModeAppend                                     // a: append-only
+	ModeExclusive                                  // l: exclusive use
+	ModeTemporary                                  // T: temporary file; Plan 9 only
+	ModeSymlink                                    // L: symbolic link
+	ModeDevice                                     // D: device file
+	ModeNamedPipe                                  // p: named pipe (FIFO)
+	ModeSocket                                     // S: Unix domain socket
+	ModeSetuid                                     // u: setuid
+	ModeSetgid                                     // g: setgid
+	ModeCharDevice                                 // c: Unix character device, when ModeDevice is set
+	ModeSticky                                     // t: sticky
+	ModeIrregular                                  // ?: non-regular file; nothing else is known about this file
+
+	// Mask for the type bits. For regular files, none will be set.
+	ModeType = ModeDir | ModeSymlink | ModeNamedPipe | ModeSocket | ModeDevice | ModeCharDevice | ModeIrregular
+
+	ModePerm FileMode = 0777 // Unix permission bits
+)
+
+func (m FileMode) String() string {
+	const str = "dalTLDpSugct?"
+	var buf [32]byte // Mode is uint32.
+	w := 0
+	for i, c := range str {
+		if m&(1<<uint(32-1-i)) != 0 {
+			buf[w] = byte(c)
+			w++
+		}
+	}
+	if w == 0 {
+		buf[w] = '-'
+		w++
+	}
+	const rwx = "rwxrwxrwx"
+	for i, c := range rwx {
+		if m&(1<<uint(9-1-i)) != 0 {
+			buf[w] = byte(c)
+		} else {
+			buf[w] = '-'
+		}
+		w++
+	}
+	return string(buf[:w])
+}
+
+// IsDir reports whether m describes a directory.
+// That is, it tests for the ModeDir bit being set in m.
+func (m FileMode) IsDir() bool {
+	return m&ModeDir != 0
+}
+
+// IsRegular reports whether m describes a regular file.
+// That is, it tests that no mode type bits are set.
+func (m FileMode) IsRegular() bool {
+	return m&ModeType == 0
+}
+
+// Perm returns the Unix permission bits in m (m & ModePerm).
+func (m FileMode) Perm() FileMode {
+	return m & ModePerm
+}
+
+// Type returns type bits in m (m & ModeType).
+func (m FileMode) Type() FileMode {
+	return m & ModeType
+}
+
+// PathError records an error and the operation and file path that caused it.
+type PathError struct {
+	Op   string
+	Path string
+	Err  error
+}
+
+func (e *PathError) Error() string { return e.Op + " " + e.Path + ": " + e.Err.Error() }
+
+func (e *PathError) Unwrap() error { return e.Err }
+
+// Timeout reports whether this error represents a timeout.
+func (e *PathError) Timeout() bool {
+	t, ok := e.Err.(interface{ Timeout() bool })
+	return ok && t.Timeout()
+}
diff --git a/src/os/error.go b/src/os/error.go
index 875cc9711f..7cd9f22bfb 100644
--- a/src/os/error.go
+++ b/src/os/error.go
@@ -7,6 +7,7 @@ package os
 import (
 	"internal/oserror"
 	"internal/poll"
+	"io/fs"
 )
 
 // Portable analogs of some common system call errors.
@@ -16,20 +17,17 @@ import (
 var (
 	// ErrInvalid indicates an invalid argument.
 	// Methods on File will return this error when the receiver is nil.
-	ErrInvalid = errInvalid() // "invalid argument"
+	ErrInvalid = fs.ErrInvalid // "invalid argument"
+
+	ErrPermission = fs.ErrPermission // "permission denied"
+	ErrExist      = fs.ErrExist      // "file already exists"
+	ErrNotExist   = fs.ErrNotExist   // "file does not exist"
+	ErrClosed     = fs.ErrClosed     // "file already closed"
 
-	ErrPermission       = errPermission()       // "permission denied"
-	ErrExist            = errExist()            // "file already exists"
-	ErrNotExist         = errNotExist()         // "file does not exist"
-	ErrClosed           = errClosed()           // "file already closed"
 	ErrNoDeadline       = errNoDeadline()       // "file type does not support deadline"
 	ErrDeadlineExceeded = errDeadlineExceeded() // "i/o timeout"
 )
 
-func errInvalid() error    { return oserror.ErrInvalid }
-func errPermission() error { return oserror.ErrPermission }
-func errExist() error      { return oserror.ErrExist }
-func errNotExist() error   { return oserror.ErrNotExist }
 func errClosed() error     { return oserror.ErrClosed }
 func errNoDeadline() error { return poll.ErrNoDeadline }
 
@@ -47,21 +45,7 @@ type timeout interface {
 }
 
 // PathError records an error and the operation and file path that caused it.
-type PathError struct {
-	Op   string
-	Path string
-	Err  error
-}
-
-func (e *PathError) Error() string { return e.Op + " " + e.Path + ": " + e.Err.Error() }
-
-func (e *PathError) Unwrap() error { return e.Err }
-
-// Timeout reports whether this error represents a timeout.
-func (e *PathError) Timeout() bool {
-	t, ok := e.Err.(timeout)
-	return ok && t.Timeout()
-}
+type PathError = fs.PathError
 
 // SyscallError records an error from a specific system call.
 type SyscallError struct {
diff --git a/src/os/types.go b/src/os/types.go
index 0f51a48286..d8edd98b68 100644
--- a/src/os/types.go
+++ b/src/os/types.go
@@ -5,8 +5,8 @@
 package os
 
 import (
+	"io/fs"
 	"syscall"
-	"time"
 )
 
 // Getpagesize returns the underlying system's memory page size.
@@ -18,21 +18,14 @@ type File struct {
 }
 
 // A FileInfo describes a file and is returned by Stat and Lstat.
-type FileInfo interface {
-	Name() string       // base name of the file
-	Size() int64        // length in bytes for regular files; system-dependent for others
-	Mode() FileMode     // file mode bits
-	ModTime() time.Time // modification time
-	IsDir() bool        // abbreviation for Mode().IsDir()
-	Sys() interface{}   // underlying data source (can return nil)
-}
+type FileInfo = fs.FileInfo
 
 // A FileMode represents a file's mode and permission bits.
 // The bits have the same definition on all systems, so that
 // information about files can be moved from one system
 // to another portably. Not all bits apply to all systems.
 // The only required bit is ModeDir for directories.
-type FileMode uint32
+type FileMode = fs.FileMode
 
 // The defined file mode bits are the most significant bits of the FileMode.
 // The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
@@ -42,74 +35,26 @@ type FileMode uint32
 const (
 	// The single letters are the abbreviations
 	// used by the String method's formatting.
-	ModeDir        FileMode = 1 << (32 - 1 - iota) // d: is a directory
-	ModeAppend                                     // a: append-only
-	ModeExclusive                                  // l: exclusive use
-	ModeTemporary                                  // T: temporary file; Plan 9 only
-	ModeSymlink                                    // L: symbolic link
-	ModeDevice                                     // D: device file
-	ModeNamedPipe                                  // p: named pipe (FIFO)
-	ModeSocket                                     // S: Unix domain socket
-	ModeSetuid                                     // u: setuid
-	ModeSetgid                                     // g: setgid
-	ModeCharDevice                                 // c: Unix character device, when ModeDevice is set
-	ModeSticky                                     // t: sticky
-	ModeIrregular                                  // ?: non-regular file; nothing else is known about this file
+	ModeDir        = fs.ModeDir        // d: is a directory
+	ModeAppend     = fs.ModeAppend     // a: append-only
+	ModeExclusive  = fs.ModeExclusive  // l: exclusive use
+	ModeTemporary  = fs.ModeTemporary  // T: temporary file; Plan 9 only
+	ModeSymlink    = fs.ModeSymlink    // L: symbolic link
+	ModeDevice     = fs.ModeDevice     // D: device file
+	ModeNamedPipe  = fs.ModeNamedPipe  // p: named pipe (FIFO)
+	ModeSocket     = fs.ModeSocket     // S: Unix domain socket
+	ModeSetuid     = fs.ModeSetuid     // u: setuid
+	ModeSetgid     = fs.ModeSetgid     // g: setgid
+	ModeCharDevice = fs.ModeCharDevice // c: Unix character device, when ModeDevice is set
+	ModeSticky     = fs.ModeSticky     // t: sticky
+	ModeIrregular  = fs.ModeIrregular  // ?: non-regular file; nothing else is known about this file
 
 	// Mask for the type bits. For regular files, none will be set.
-	ModeType = ModeDir | ModeSymlink | ModeNamedPipe | ModeSocket | ModeDevice | ModeCharDevice | ModeIrregular
+	ModeType = fs.ModeType
 
-	ModePerm FileMode = 0777 // Unix permission bits
+	ModePerm = fs.ModePerm // Unix permission bits, 0o777
 )
 
-func (m FileMode) String() string {
-	const str = "dalTLDpSugct?"
-	var buf [32]byte // Mode is uint32.
-	w := 0
-	for i, c := range str {
-		if m&(1<<uint(32-1-i)) != 0 {
-			buf[w] = byte(c)
-			w++
-		}
-	}
-	if w == 0 {
-		buf[w] = '-'
-		w++
-	}
-	const rwx = "rwxrwxrwx"
-	for i, c := range rwx {
-		if m&(1<<uint(9-1-i)) != 0 {
-			buf[w] = byte(c)
-		} else {
-			buf[w] = '-'
-		}
-		w++
-	}
-	return string(buf[:w])
-}
-
-// IsDir reports whether m describes a directory.
-// That is, it tests for the ModeDir bit being set in m.
-func (m FileMode) IsDir() bool {
-	return m&ModeDir != 0
-}
-
-// IsRegular reports whether m describes a regular file.
-// That is, it tests that no mode type bits are set.
-func (m FileMode) IsRegular() bool {
-	return m&ModeType == 0
-}
-
-// Perm returns the Unix permission bits in m (m & ModePerm).
-func (m FileMode) Perm() FileMode {
-	return m & ModePerm
-}
-
-// Type returns type bits in m (m & ModeType).
-func (m FileMode) Type() FileMode {
-	return m & ModeType
-}
-
 func (fs *fileStat) Name() string { return fs.name }
 func (fs *fileStat) IsDir() bool  { return fs.Mode().IsDir() }