panics with reverted switch + external package

[antonio-antuan]

package somepkg

type Enum int

const (
	EnumValue1 Enum = iota
	EnumValue2
	EnumValue3
)

package main

import "somepkg"

type nested struct {
	Value somepkg.Enum
}

type ext struct {
	Foo1 nested
	Foo2 nested
	Foo3 nested
	Foo4 nested
}

func check(){
	s := ext{}
	switch somepkg.EnumValue2 {
	case s.Foo1.Value, s.Foo2.Value, s.Foo3.Value:
	}
}

in this situation error appears:

golangci-lint has version v1.41.0 built from (unknown, mod sum: "h1:1kfytWKEn2EPjniwD5xCwWtHAHR57q+vmDX3+VBoJac=") on (unknown)
ERRO [runner] Panic: exhaustive: package "main" (isInitialPkg: true, needAnalyzeSource: true): interface conversion: ast.Expr is *ast.SelectorExpr, not *ast.Ident: goroutine 86804 [running]:
runtime/debug.Stack()
        /usr/lib/go/src/runtime/debug/stack.go:24 +0x65
github.com/golangci/golangci-lint/pkg/golinters/goanalysis.(*action).analyzeSafe.func1()
        /home/boris/go/pkg/mod/github.com/golangci/golangci-lint@v1.41.0/pkg/golinters/goanalysis/runner_action.go:101 +0x155
panic({0x124f940, 0xc01b19c0f0})
        /usr/lib/go/src/runtime/panic.go:1038 +0x215
github.com/nishanths/exhaustive.missingCasesTextEdit(0x0, 0x1565c10, 0x0, 0xc009ae12c0, 0xc00ad74100, 0xc01b19c000)
        /home/boris/go/pkg/mod/github.com/nishanths/exhaustive@v0.1.0/switch.go:395 +0x65c
github.com/nishanths/exhaustive.computeFix(0x2, 0xc00fd57c80, 0x203005, 0xc009ae12c0, 0xc016c7f5f0, 0x6, 0xc01b19c000)
        /home/boris/go/pkg/mod/github.com/nishanths/exhaustive@v0.1.0/switch.go:257 +0xc7
github.com/nishanths/exhaustive.reportSwitch(0xc01df17d40, 0xc009ae12c0, 0x0, 0xc00ad74100, 0x2, 0x131c080, 0x0, 0x0)
        /home/boris/go/pkg/mod/github.com/nishanths/exhaustive@v0.1.0/switch.go:229 +0xd1
github.com/nishanths/exhaustive.checkSwitchStatements.func1({0x1562668, 0xc009ae12c0}, 0xa, {0xc009e8e300, 0xc0221f1ca0, 0xc01484b810})
        /home/boris/go/pkg/mod/github.com/nishanths/exhaustive@v0.1.0/switch.go:148 +0x526
golang.org/x/tools/go/ast/inspector.(*Inspector).WithStack(0xc012674b10, {0xc003393b68, 0x1285160, 0xc015f7b390}, 0xc00a443b78)
        /home/boris/go/pkg/mod/golang.org/x/tools@v0.1.3/go/ast/inspector/inspector.go:126 +0x19a
github.com/nishanths/exhaustive.checkSwitchStatements(0xc01df17d40, 0xf1fdba, 0x1be59a0, 0x14)
        /home/boris/go/pkg/mod/github.com/nishanths/exhaustive@v0.1.0/switch.go:29 +0x99
github.com/nishanths/exhaustive.run(0xc01df17d40)
        /home/boris/go/pkg/mod/github.com/nishanths/exhaustive@v0.1.0/exhaustive.go:181 +0x1a5
github.com/golangci/golangci-lint/pkg/golinters/goanalysis.(*action).analyze(0xc006b309b0)
        /home/boris/go/pkg/mod/github.com/golangci/golangci-lint@v1.41.0/pkg/golinters/goanalysis/runner_action.go:187 +0x9c4
github.com/golangci/golangci-lint/pkg/golinters/goanalysis.(*action).analyzeSafe.func2()
        /home/boris/go/pkg/mod/github.com/golangci/golangci-lint@v1.41.0/pkg/golinters/goanalysis/runner_action.go:105 +0x1d
github.com/golangci/golangci-lint/pkg/timeutils.(*Stopwatch).TrackStage(0xc00187ef50, {0x1381a1e, 0xa}, 0xc00351ff60)
        /home/boris/go/pkg/mod/github.com/golangci/golangci-lint@v1.41.0/pkg/timeutils/stopwatch.go:111 +0x4a
github.com/golangci/golangci-lint/pkg/golinters/goanalysis.(*action).analyzeSafe(0xc006b309b0)
        /home/boris/go/pkg/mod/github.com/golangci/golangci-lint@v1.41.0/pkg/golinters/goanalysis/runner_action.go:104 +0x85
github.com/golangci/golangci-lint/pkg/golinters/goanalysis.(*loadingPackage).analyze.func2(0x0)
        /home/boris/go/pkg/mod/github.com/golangci/golangci-lint@v1.41.0/pkg/golinters/goanalysis/runner_loadingpackage.go:80 +0x67
created by github.com/golangci/golangci-lint/pkg/golinters/goanalysis.(*loadingPackage).analyze
        /home/boris/go/pkg/mod/github.com/golangci/golangci-lint@v1.41.0/pkg/golinters/goanalysis/runner_loadingpackage.go:75 +0x1fd 
WARN [runner] Can't run linter goanalysis_metalinter: goanalysis_metalinter: exhaustive: package "main" (isInitialPkg: true, needAnalyzeSource: true): interface conversion: ast.Expr is *ast.SelectorExpr, not *ast.Ident 

[Antonboom]

+1

[nishanths]

Thank you for the detailed report. I think I see what the issue in exhaustive is. I will fix and tag a new release, and comment here when it's done.

In the meantime, you may work around the issue by ignoring such switch statements in your code.

[nishanths]

This should be fixed in v0.3.1. The code that caused the panic is no longer present. A related test case has been added:

exhaustive/testdata/switchtest/otherpkg/otherpkg.go

Lines 32 to 38 in b3688ce

	func switchNotExpectedSelExpr(b switchtest.Biome, l local) {
	switch b {
	case l.inner.f:
	case switchtest.Desert:
	case l.f:
	}
	}

Thanks again for the detailed issue report!

[nishanths]

From the stack trace, it appears you were running exhaustive through golangci-lint.

The golangci-lint repo should automatically get the new exhaustive version when it upgrades its dependencies. But I also intend to expose some new exhaustive flags in golangci-lint (#20), so I plan to make a pull request to golangci-lint and manually upgrade the exhaustive version.

Either way golangci-lint will get the upgraded exhaustive version by whichever of these two happens first.

[nishanths]

This merged golangci-lint golangci/golangci-lint#2344 PR upgrades exhaustive in golangci-lint with these changes.