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Cannot use errors.As() with new #71331

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andig opened this issue Jan 19, 2025 · 2 comments
Closed

Cannot use errors.As() with new #71331

andig opened this issue Jan 19, 2025 · 2 comments
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BugReport Issues describing a possible bug in the Go implementation.

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@andig
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andig commented Jan 19, 2025

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

$ go version
go version go1.23.5 darwin/arm64

Does this issue reproduce with the latest release?

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

go env Output
$ go env
GO111MODULE=''
GOARCH='arm64'
GOBIN=''
GOCACHE='/Users/andig/Library/Caches/go-build'
GOENV='/Users/andig/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/andig/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/andig/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/opt/homebrew/Cellar/go/1.23.5/libexec'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/opt/homebrew/Cellar/go/1.23.5/libexec/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.23.5'
GODEBUG=''
GOTELEMETRY='on'
GOTELEMETRYDIR='/Users/andig/Library/Application Support/go/telemetry'
GCCGO='gccgo'
GOARM64='v8.0'
AR='ar'
CC='cc'
CXX='c++'
CGO_ENABLED='1'
GOMOD='/Users/andig/htdocs/evcc/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/sv/rs_453y57xj86xsbz3kw1mbc0000gn/T/go-build3430922146=/tmp/go-build -gno-record-gcc-switches -fno-common'
GOROOT/bin/go version: go version go1.23.5 darwin/arm64
GOROOT/bin/go tool compile -V: compile version go1.23.5
uname -v: Darwin Kernel Version 24.2.0: Fri Dec  6 18:40:14 PST 2024; root:xnu-11215.61.5~2/RELEASE_ARM64_T8103
ProductName:		macOS
ProductVersion:		15.2
BuildVersion:		24C101
lldb --version: lldb-1600.0.39.109
Apple Swift version 6.0.3 (swiftlang-6.0.3.1.10 clang-1600.0.30.1)

What did you do?

Check for error return type using errors.As(err, new(Err)): https://play.golang.com/p/nlxAmD6LtLm

What did you expect to see?

Successful compile

What did you see instead?

second argument to errors.As must be a non-nil pointer to either a type that implements error, or to any interface type

It seems that the second parameter is a non-nil pointer and hence should compile or the error message be improved. I understand that I can use and error variable of the specific type but since the actual typed error is not needed it would be nice if the anonymous new could be used here.
@gabyhelp
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(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)

@gabyhelp gabyhelp added the BugReport Issues describing a possible bug in the Go implementation. label Jan 19, 2025
@andig andig closed this as completed Jan 19, 2025
@andig
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andig commented Jan 19, 2025

The trick here is

pointer to either a type that implements error

hence it would need pointer to pointer receiver. Or rather implement error on the base receiver.

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