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cmd/vet: cannot convert s (variable of type parameter T constrained by ~string) to string #49186

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wojas opened this issue Oct 27, 2021 · 5 comments
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cmd/vet: cannot convert s (variable of type parameter T constrained by ~string) to string #49186

wojas opened this issue Oct 27, 2021 · 5 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
Milestone
Go1.18

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@wojas
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wojas commented Oct 27, 2021

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

Latest gotip:

$ go version
go version devel go1.18-cfb532158f Wed Oct 27 13:12:49 2021 +0000 darwin/amd64

Does this issue reproduce with the latest release?

Yes, tried with latest gotip.

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

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/wojas/Library/Caches/go-build"
GOENV="/Users/wojas/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/wojas/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/wojas/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/Users/wojas/sdk/gotip"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/Users/wojas/sdk/gotip/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="devel go1.18-cfb532158f Wed Oct 27 13:12:49 2021 +0000"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/wojas/go/experiments/go.mod"
GOWORK=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/cr/nj9c04_x215dl0wm3z3cdyp00000gs/T/go-build2473934211=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Contents of foo_test.go:

package foo

import "testing"

func foo[T ~string](s T) T {
	return T(string(s))
}

func Test_foo(t *testing.T) {
	foo("bar")
}

This fails on a go vet check:

$ gotip test .
vet: ./foo_test.go:6:18: cannot convert s (variable of type parameter T constrained by ~string) to string
FAIL	experiments.example [build failed]
FAIL

The compiler does accept it, as can be seen when running with -vet=off:

$ gotip test -vet=off .
ok  	experiments.example	0.256s

What did you expect to see?

No vet error.

What did you see instead?

cannot convert s (variable of type parameter T constrained by ~string) to string
@seankhliao seankhliao added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Oct 27, 2021
@seankhliao
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cc @matloob

@ianlancetaylor
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CC @findleyr @griesemer

@griesemer
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The necessary fix is pending review (CL 359137).

@griesemer griesemer added this to the Go1.18 milestone Oct 27, 2021
@griesemer griesemer added NeedsFix The path to resolution is known, but the work has not been done. and removed NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Oct 27, 2021
@findleyr
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This should now be resolved with CL 359137. Please re-open if not.

@wojas
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wojas commented Oct 29, 2021

It works as expected in today's go1.18-2c7cdec2a7, thanks!

@golang golang locked and limited conversation to collaborators Jun 23, 2023
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Go1.18
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@wojas @ianlancetaylor @griesemer @gopherbot @seankhliao @findleyr