`gochecksumtype`: works only inside one package

[maratori]

Welcome

• Yes, I'm using a binary release within 2 latest major releases. Only such installations are supported.
• Yes, I've searched similar issues on GitHub and didn't find any.
• Yes, I've read the typecheck section of the FAQ (https://golangci-lint.run/usage/faq/#why-do-you-have-typecheck-errors).
• Yes, I've tried with the standalone linter if available (e.g., gocritic, go vet, etc.). (https://golangci-lint.run/usage/linters/)

Description of the problem

gochecksumtype doesn't report missing cases if the sum type is declared in one package and the type switch is in a different package (see #3671 (comment)).

Version of golangci-lint

$ golangci-lint --version
golangci-lint has version v1.55.0 built with go1.21.3 from de1c3919 on 2023-10-20T11:56:32Z

Configuration

# paste configuration file or CLI flags here

Go environment

$ go version && go env
go version go1.21.3 linux/amd64
GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/root/.cache/go-build'
GOENV='/root/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='local'
GOTOOLDIR='/usr/local/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.21.3'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/app/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 -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build2772357518=/tmp/go-build -gno-record-gcc-switches'

Verbose output of running

$ golangci-lint cache clean
$ golangci-lint run -v
# paste output here

A minimal reproducible example or link to a public repository

/decl/decl.go

package decl

//sumtype:decl
type MySumType interface {
        sealed()
}

type VariantA struct{}

func (*VariantA) sealed() {}

type VariantB struct{}

func (*VariantB) sealed() {}

/usage/usage.go

package usage

import "decl"

func DoSomething(x decl.MySumType) {
        switch x.(type) { // <-- here is expected a report about missing VariantB
        case *decl.VariantA:
        }
}

Validation

• Yes, I've included all information above (version, config, etc.).

[ldez]

Hello,

there is something missing in your report: Does the standalone linter has the same behavior?

After it's not unexpected based on how golangci-lint analyzes things.

[maratori]

Does the standalone linter has the same behavior?

No, the standalone linter works well if you pass all packages to it (go-check-sumtype ./...).

[navijation]

Analysis drivers like golangci-lint may leverage the analysis framework's fact interface to avoid rerunning analysis on packages that are not either directly or indirectly modified since the last run. What this means is that an analyzer should:

1. not strongly (caching might be fine for some drivers) rely on any kind of statefulness across packages, except for state exported using the facts API
2. store all information that is required across packages and not available natively from Go's type system as facts

It looks like go-check-sumtype does not leverage facts at all. So it seems incompatible golangci-lint's caching mechanism unless rewritten appropriately such as in exhaustive.