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"var" and ":=" declaration treated differently for slices in reflect.DeepEqual() #43857

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mqrc81 opened this issue Jan 22, 2021 · 1 comment
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"var" and ":=" declaration treated differently for slices in reflect.DeepEqual() #43857

mqrc81 opened this issue Jan 22, 2021 · 1 comment
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@mqrc81
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mqrc81 commented Jan 22, 2021

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

$ go version go1.15.5 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

go env Output
$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/ms/Library/Caches/go-build"
GOENV="/Users/ms/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/ms/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/ms/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/Users/ms/sdk/go1.15.5"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/Users/ms/sdk/go1.15.5/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/ms/Projects/Test-Go/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/8s/qkvh49xx19x8qnd4hv5wlrlw0000gn/T/go-build946297595=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Here's the code: https://play.golang.org/p/yfTT4rvR4cb

When testing my Go web application, I realized that var arr1 []someStruct and arr2 := []someStruct{} are treated differently with reflect.DeepEqual(arr1, arr2). This is very misleading, since they're treated the same for single struct (not slices).

What did you expect to see?

I expected both slices of an empty struct to be exactly the same, so reflect.DeepEqual() => true.

What did you see instead?

As seen in the code, the var arr1 []someStruct and arr2 := []someStruct{} declarations behave differently in the reflect.DeepEqual() function.
@seankhliao
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They are different things, a nil slice and empty slice

For questions please refer to https://github.com/golang/go/wiki/Questions

@golang golang locked and limited conversation to collaborators Jan 22, 2022
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