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Cannot pass variadic method expression with variadic of generic type #49516

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kylelemons opened this issue Nov 11, 2021 · 1 comment
Closed

Cannot pass variadic method expression with variadic of generic type #49516

kylelemons opened this issue Nov 11, 2021 · 1 comment
Labels
FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done. release-blocker
Milestone
Go1.18

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

$ go version
go version devel go1.18-4d0683965b Wed Nov 10 22:16:25 2021 +0000 windows/amd64

Does this issue reproduce with the latest release?

With the latest gotip

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

go env Output
$ go env
set GO111MODULE=
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\kyle\AppData\Local\go-build
set GOENV=C:\Users\kyle\AppData\Roaming\go\env
set GOEXE=.exe
set GOEXPERIMENT=
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\kyle\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\kyle\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=C:\Users\kyle\sdk\gotip
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=C:\Users\kyle\sdk\gotip\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=devel go1.18-4d0683965b Wed Nov 10 22:16:25 2021 +0000
set GCCGO=gccgo
set GOAMD64=v1
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=0
set GOMOD=C:\Users\kyle\dev\generics_exp\go.mod
set GOWORK=
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=C:\Users\kyle\AppData\Local\Temp\go-build3149543561=/tmp/go-build -gno-record-gcc-switches
GOROOT/bin/go version: go version devel go1.18-4d0683965b Wed Nov 10 22:16:25 2021 +0000 windows/amd64
GOROOT/bin/go tool compile -V: compile version devel go1.18-4d0683965b Wed Nov 10 22:16:25 2021 +0000

What did you do?

This code works, even with generics:

func pushN(push func(*Q[int], int), n int) 
package repro

import "testing"

type Q[T any] struct {
	s []T
}

func (q *Q[T]) Push(v T) {
	q.s = append(q.s, v)
}

func pushN(push func(*Q[int], int), n int) {
	var q Q[int]
	for i := 0; i < n; i++ {
		push(&q, i)
	}
}

func TestPushN(t *testing.T) {
	pushN((*Q[int]).Push, 100)
}

However, if I change the Push to be variadic on T:

package repro

import "testing"

type Q[T any] struct {
	s []T
}

func (q *Q[T]) Push(v ...T) {
	q.s = append(q.s, v...)
}

func pushN(push func(*Q[int], ...int), n int) {
	var q Q[int]
	for i := 0; i < n; i++ {
		push(&q, i)
	}
}

func TestPushN(t *testing.T) {
	pushN((*Q[int]).Push, 100)
}

I get

$ gotip test
# generics_exp/dequeue/repro [generics_exp/dequeue/repro.test]
.\repro_test.go:21:17: cannot use a1 (type []int) as type go.shape.int_0 in argument to (*Q[go.shape.int_0]).Push
FAIL    generics_exp/dequeue/repro [build failed]

This works with a non-generic type, of course:

func pushN(push func(*Q, ...int), n int) 
package repro

import "testing"

type Q struct {
	s []int
}

func (q *Q) Push(v ...int) {
	q.s = append(q.s, v...)
}

func pushN(push func(*Q, ...int), n int) {
	var q Q
	for i := 0; i < n; i++ {
		push(&q, i)
	}
}

func TestPushN(t *testing.T) {
	pushN((*Q).Push, 100)
}
@cuonglm cuonglm self-assigned this Nov 11, 2021
@cuonglm cuonglm added the NeedsFix The path to resolution is known, but the work has not been done. label Nov 11, 2021
@cuonglm cuonglm added this to the Go1.18 milestone Nov 11, 2021
@gopherbot
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Change https://golang.org/cl/363314 mentions this issue: cmd/compile: fix missing ddd when building call for function instantiation closure

@rsc rsc unassigned cuonglm Jun 23, 2022
@golang golang locked and limited conversation to collaborators Jun 23, 2023
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done. release-blocker
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@kylelemons @cuonglm @gopherbot