encoding/asn1: Marshal doesn't respect application tag

[hirochachacha]

Please answer these questions before submitting your issue. Thanks!

What did you do?

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

package main

import (
	"encoding/asn1"
	"fmt"
)

type Foo struct {
	Bar int `asn1:"application,tag:0"`
	Baz int `asn1:"application,tag:1,explicit"`
}

func main() {
	bs, err := asn1.Marshal(Foo{Bar: 1, Baz: 2})
	if err != nil {
		panic(err)
	}

	var foo Foo
	rest, err := asn1.Unmarshal(bs, &foo)
	if err != nil {
		panic(err)
	}
	if len(rest) != 0 {
		panic("rest is not empty")
	}
	fmt.Printf("%v\n", foo)
}

What did you expect to see?

{1 2}

What did you see instead?

panic: asn1: structure error: tags don't match (0 vs {class:2 tag:0 length:1 isCompound:false}) {optional:false explicit:false application:true defaultValue:<nil> tag:0xc420016160 stringType:0 timeType:0 set:false omitEmpty:false} int @2

goroutine 1 [running]:
main.main()
	/Users/hiro/o.go:22 +0x20d
exit status 2

Does this issue reproduce with the latest release (go1.8.3)?

I think so.

System details

go version devel +e0e4891827 Wed May 24 21:56:48 2017 +0000 darwin/amd64
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/hiro/.go"
GORACE=""
GOROOT="/Users/hiro/go"
GOTOOLDIR="/Users/hiro/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/wq/dwn8hs0x7njbzty9f68y61700000gn/T/go-build434465536=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOROOT/bin/go version: go version devel +e0e4891827 Wed May 24 21:56:48 2017 +0000 darwin/amd64
GOROOT/bin/go tool compile -V: compile version devel +e0e4891827 Wed May 24 21:56:48 2017 +0000 X:framepointer
uname -v: Darwin Kernel Version 16.6.0: Fri Apr 14 16:21:16 PDT 2017; root:xnu-3789.60.24~6/RELEASE_X86_64
ProductName:	Mac OS X
ProductVersion:	10.12.5
BuildVersion:	16F73
lldb --version: lldb-370.0.42
  Swift-3.1
gdb --version: GNU gdb (GDB) 7.12.1

[gopherbot]

CL https://golang.org/cl/44110 mentions this issue.