proposal: encoding/json: add Int() and Int32() methods on json.Number

[wgliang]

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go version go1.9.2 darwin/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/wangguoliang/Documents/mos"
GORACE=""
GOROOT="/usr/local/Cellar/go/1.9.2/libexec"
GOTOOLDIR="/usr/local/Cellar/go/1.9.2/libexec/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/zd/20dl0mb523v4tjk_pf_hdscr0000gn/T/go-build194310903=/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"

What did you do?

json.Number supports both the Int64 () and Float64 () interfaces, and I think I should support other types, such as Int () and Int32, though the user himself can use the Int64 interface through conversions.

Related PR

cc @bradfitz

What did you expect to see?

encoding/json package.
I want support Built-in interface:

func (n Number) Int() (int, error)
func (n Number) Int32() (int32, error)

What did you see instead?

[ianlancetaylor]

As you say, you can just write a conversion. It doesn't even take an extra line of code, just a few more characters. Why should we add more methods? And if we add more, why shouldn't we add methods for all the numeric types?

[wgliang]

I think we should add methods for all the numeric types. We have it as a number type, so the interface itself should support direct access to its corresponding type value instead of letting the user cast it to the type he needs.

[ianlancetaylor]

What about my other question: why should we add more methods?

[robpike]

We should not.

[rsc]

Use strconv.Atoi(string(n)) instead of the non-existent n.Int.