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cmd/compile: compile error while using generics #63981

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qqxhb opened this issue Nov 7, 2023 · 3 comments
Closed

cmd/compile: compile error while using generics #63981

qqxhb opened this issue Nov 7, 2023 · 3 comments
Labels
compiler/runtime Issues related to the Go compiler and/or runtime. NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided.
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@qqxhb
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qqxhb commented Nov 7, 2023

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

$ 1.20.10

Does this issue reproduce with the latest release?

no

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

go env Output
$ GO111MODULE="on"
GOARCH="amd64"
GOBIN=""

GOEXE=""

GOEXPERIMENT=""

GOFLAGS=""

GOHOSTARCH="amd64"

GOHOSTOS="darwin"

GOINSECURE=""


GOOS="darwin"


GOSUMDB="sum.golang.google.cn"

GOTMPDIR=""

GOVCS=""

GOVERSION="go1.20.10"

GCCGO="gccgo"

GOAMD64="v1"

AR="ar"

CC="clang"

CXX="clang++"

CGO_ENABLED="1"

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 x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/qg/7jl0rh4502v1w663txn71wnm0000gp/T/go-build2599608933=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Implement generic interfaces

type DO struct {
}

func (d *DO) Delete(models ...interface{}) (info interface, err error) {
	return nil, nil
}

type IGenericsDo[T IGenericsDo[T, E], E any] interface {
	Delete(...E) (info interface, err error)
}

func NewGenericsDo[T IGenericsDo[T, E], E any](realDo T) IGenericsDo[T, E] {
	return &genericsDo[T, E]{realDo: realDo}
}

type genericsDo[T IGenericsDo[T, E], E any] struct {
	realDo T
	DO
}

func (b *genericsDo[T, E]) Delete(models ...E) (result interface, err error) {
	return b.realDo.Delete(models...)
}

compile err: Cannot use '&genericsDo[T, E]{realDo: realDo}' (type *genericsDo[T, E]) as the type IGenericsDo[T, E] Type does not implement 'IGenericsDo[T, E]' need the method: Delete(...E) (info interface{}, err error) have the method: Delete(models ...interface{}) (info interface{}, err error)

What did you expect to see?

What did you see instead?

When I remove the inherited DO, it work.

type IGenericsDo[T IGenericsDo[T, E], E any] interface {
	Delete(...E) (info interface, err error)
}

func NewGenericsDo[T IGenericsDo[T, E], E any](realDo T) IGenericsDo[T, E] {
	return &genericsDo[T, E]{realDo: realDo}
}

type genericsDo[T IGenericsDo[T, E], E any] struct {
	realDo T
	//DO
}

func (b *genericsDo[T, E]) Delete(models ...E) (result interface, err error) {
	return b.realDo.Delete(models...)
}
@Jorropo
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Jorropo commented Nov 7, 2023

Are you using gccgo ?
With dc74a3d 1.21 and 1.20.10 I get:

./prog.go:12:6: invalid recursive type: IGenericsDo refers to itself
./prog.go:26:18: b.realDo.Delete undefined (type T has no field or method Delete)

Which looks correct to me.

@heschi
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heschi commented Nov 7, 2023

cc @golang/compiler

@heschi heschi added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Nov 7, 2023
@heschi heschi added this to the Backlog milestone Nov 7, 2023
@heschi heschi added the WaitingForInfo Issue is not actionable because of missing required information, which needs to be provided. label Nov 7, 2023
@heschi heschi changed the title affected/package: generic cmd/compile: compile error while using generics Nov 7, 2023
@gopherbot gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Nov 7, 2023
@griesemer
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  1. I assume you meant (info interface{}, err error) in the signature of Do.Delete? As written, (info interface, err error) is not valid syntax.

  2. After fixing the syntax, I agree with @Jorropo . This program is not correct.

I am going to close this. If you believe this is a mistake and there's a real issue here, please re-open with a small, syntactically correct reproducer. Thanks.

As an aside, gccgo's generics implementation is not sufficiently far along yet I believe to be useable in general (@ianlancetaylor , please correct me if I am mistaken).

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@griesemer @gopherbot @Jorropo @heschi @qqxhb