go: x/tools/go/ssa: panic with Go 1.17 slice-to-array conversions

I’m not sure if this is a bug or not, considering that Go 1.17 is not out yet, but then again, Go 1.17 Beta 1 is already out. The original issue is mvdan/unparam#55. Using golang.org/x/tools with the latest master version (v0.1.5-0.20210629191230-72e4d1bb8d47), ssa.(*Package).Build seems to panic with:

panic: in command-line-arguments.main: cannot convert *t0 ([]int) to *[4]int

Full panic message:

panic: in command-line-arguments.main: cannot convert *t0 ([]int) to *[4]int

goroutine 720 [running]:
golang.org/x/tools/go/ssa.emitConv(0xc0001de500, {0x705fd8, 0xc0007b02a0}, {0x700820, 0xc000205e90})
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/emit.go:242 +0x7b9
golang.org/x/tools/go/ssa.(*builder).expr0(0x665ac0, 0xc0001de500, {0x700d40, 0xc00009b4c0}, {0x7, {0x700820, 0xc000205e90}, {0x0, 0x0}})
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:573 +0x925
golang.org/x/tools/go/ssa.(*builder).expr(0x0, 0xc0001de500, {0x700d40, 0xc00009b4c0})
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:530 +0x19f
golang.org/x/tools/go/ssa.(*builder).addr(0x665ac0, 0xc0001de500, {0x701340, 0xc000450db0}, 0x0)
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:417 +0xc8c
golang.org/x/tools/go/ssa.(*builder).expr(0x540eff, 0xc0001de500, {0x701340, 0xc000450db0})
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:528 +0x145
golang.org/x/tools/go/ssa.(*builder).emitCallArgs(0xc00037b5c0, 0x7012b0, 0xc000495ce0, 0xc00009b500, {0x0, 0x0, 0x40cbe7})
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:906 +0x7ed
golang.org/x/tools/go/ssa.(*builder).setCall(0x665ac0, 0xc0001de500, 0xc00009b500, 0xc0007b4240)
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:969 +0x94
golang.org/x/tools/go/ssa.(*builder).expr0(0x665ac0, 0xc0001de500, {0x700d40, 0xc00009b500}, {0x7, {0x7008c0, 0xc0000b4468}, {0x0, 0x0}})
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:596 +0x1f8e
golang.org/x/tools/go/ssa.(*builder).expr(0x604d01744c010008, 0xc0001de500, {0x700d40, 0xc00009b500})
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:530 +0x19f
golang.org/x/tools/go/ssa.(*builder).stmt(0xcab743c011aa6, 0xc0001de500, {0x700ef0, 0xc000205dd0})
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:1988 +0x135b
golang.org/x/tools/go/ssa.(*builder).stmtList(0x9b0f931c01228310, 0x1a5400057420010c, {0xc00020aaa0, 0x2, 0x274002022ff228a})
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:790 +0x67
golang.org/x/tools/go/ssa.(*builder).stmt(0xc0001de500, 0xc0001de500, {0x700ce0, 0xc000183800})
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:2105 +0x1331
golang.org/x/tools/go/ssa.(*builder).buildFunction(0x665f40, 0xc0001de500)
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:2198 +0x465
golang.org/x/tools/go/ssa.(*builder).buildFuncDecl(0x6652e0, 0xc00037b5c0, 0xc000183830)
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:2228 +0x154
golang.org/x/tools/go/ssa.(*Package).build(0xc00037b5c0)
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:2344 +0xd05
sync.(*Once).doSlow(0xc0004d97b8, 0x5fc89e)
	/home/ainar/go/go1.17/src/sync/once.go:68 +0xd2
sync.(*Once).Do(...)
	/home/ainar/go/go1.17/src/sync/once.go:59
golang.org/x/tools/go/ssa.(*Package).Build(...)
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:2263
golang.org/x/tools/go/ssa.(*Program).Build.func1(0x0)
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:2247 +0x4c
created by golang.org/x/tools/go/ssa.(*Program).Build
	/home/ainar/go/pkg/mod/golang.org/x/tools@v0.1.5-0.20210629191230-72e4d1bb8d47/go/ssa/builder.go:2246 +0x1a5

I’ve tested it using two analysers that use SSA, unparam and nilness, and both are panicking.

About this issue

Original URL
State: closed
Created 3 years ago
Reactions: 1
Comments: 17 (14 by maintainers)

Commits related to this issue

go/ssa/interp: handle nil slice convert to array pointer Converting from nil slice to a zero length array pointer must be nil. Updates golang/go#46987 Change-Id: I8894b92bd85fae8ea77bf01b92ee56f1a2... — committed to golang/tools by cuonglm 3 years ago

Most upvoted comments

It has been a few days without more input. The conversation seems to be heading towards adding a SliceToArrayPointer instruction. Please speak up in the next couple of days if you would prefer a different solution.

timothy-king on Jul 19, 2021

@timothy-king @dominikh I’m leaning to add new instruction, as now I realize that mixing slice to array pointer in Convert seems make the current code more complicated.

For reference, the compiler SSA backend also add new op for this conversion.

cuonglm on Jul 15, 2021