cmd/compile: internal compiler error: weird package in name: p.a => a from "test/p", not ""

[zhuah]

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

$ go version
go version devel go1.19-6da16b6ad5 Tue Mar 1 23:49:01 2022 +0000 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

go env Output

$ go env

What did you do?

go compiler panicked with generics code, i made a reproduce demo at: https://go.dev/play/p/F8oOkWnPvfG?v=gotip

-- go.mod --
module test
-- p/p.go --
package p

type Comparator[T any] func(v1, v2 T) int

func CompareInt[T ~int](a, b T) int {
	if a < b {
		return -1
	}
	if a == b {
		return 0
	}
	return 1
}
-- main.go --
package main

import "test/p"

func Comparator() p.Comparator[int] {
	return p.CompareInt[int]
}

func main() {
	Comparator()(1, 2)
}

and the error logs:

# test
./main.go:6:11: internal compiler error: weird package in name: p.a => a from "test/p", not ""

goroutine 1 [running]:
runtime/debug.Stack()
	/usr/local/go/src/runtime/debug/stack.go:24 +0x65
cmd/compile/internal/base.FatalfAt({0x0?, 0x0?}, {0xd40041, 0x2f}, {0xc0000c3308, 0x4, 0x4})
	/usr/local/go/src/cmd/compile/internal/base/print.go:227 +0x1d7
cmd/compile/internal/base.Fatalf(...)
	/usr/local/go/src/cmd/compile/internal/base/print.go:196
cmd/compile/internal/typecheck.(*exportWriter).localIdent(0xc0003ed500?, 0xc0003c4870?)
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:2276 +0x287
cmd/compile/internal/typecheck.(*exportWriter).param(0x40a2f3?, 0xc0003c4a00)
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:1130 +0xac
cmd/compile/internal/typecheck.(*exportWriter).paramList(0xc0003ed500, {0xc00008ce70, 0x2, 0xb?})
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:1124 +0x50
cmd/compile/internal/typecheck.(*exportWriter).signature(0xc0003ed500, 0xc0003d8730?)
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:1097 +0x65
cmd/compile/internal/typecheck.(*exportWriter).expr(0xc0003ed500, {0xe945d0?, 0xc0003d8730?})
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:1841 +0x105
cmd/compile/internal/typecheck.(*exportWriter).expr(0xc0003ed500, {0xe948f0?, 0xc0003d86e0?})
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:2021 +0x110f
cmd/compile/internal/typecheck.(*exportWriter).exprList(0xc0003ed500, {0xc00008d210?, 0x1, 0xc000378770?})
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:1718 +0x76
cmd/compile/internal/typecheck.(*exportWriter).stmt(0xc0003ed500, {0xe95ed0, 0xc0003d8690})
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:1611 +0x91f
cmd/compile/internal/typecheck.(*exportWriter).node(0xc0004a3380?, {0xe95ed0, 0xc0003d8690})
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:1520 +0x65
cmd/compile/internal/typecheck.(*exportWriter).stmtList(0xc0003ed500, {0xc00008d1f0?, 0x1, 0xcefda0?})
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:1513 +0x76
cmd/compile/internal/typecheck.(*exportWriter).funcBody(0xc0003ed500?, 0xc0003b9080)
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:1508 +0x5b
cmd/compile/internal/typecheck.(*iexporter).doInline(0xc00031e6e0, 0xc0003c8680)
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:664 +0xc5
cmd/compile/internal/typecheck.(*exportWriter).funcExt(0xc0003ed3b0, 0xc0003c8680)
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:1445 +0x1cd
cmd/compile/internal/typecheck.(*iexporter).doDecl(0xc00031e6e0, 0xc0003c8680)
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:536 +0x215
cmd/compile/internal/typecheck.WriteExports({0xe8e7e0, 0xc0004a3170}, 0x1)
	/usr/local/go/src/cmd/compile/internal/typecheck/iexport.go:334 +0x2f0
cmd/compile/internal/noder.WriteExports(0xc0004a4430)
	/usr/local/go/src/cmd/compile/internal/noder/export.go:40 +0x7a
cmd/compile/internal/gc.dumpCompilerObj(0xc0004a4430?)
	/usr/local/go/src/cmd/compile/internal/gc/obj.go:107 +0x28
cmd/compile/internal/gc.dumpobj1({0x7ffd5299ac6b, 0x24}, 0x3)
	/usr/local/go/src/cmd/compile/internal/gc/obj.go:63 +0x17b
cmd/compile/internal/gc.dumpobj()
	/usr/local/go/src/cmd/compile/internal/gc/obj.go:44 +0x36
cmd/compile/internal/gc.Main(0xd4e0b0)
	/usr/local/go/src/cmd/compile/internal/gc/main.go:318 +0x1105
main.main()
	/usr/local/go/src/cmd/compile/main.go:55 +0xdd


Go build failed.

What did you expect to see?

What did you see instead?

[mengzhuo]

cc @griesemer @ianlancetaylor @randall77

[griesemer]

@mdempsky The error comes from iexport.go from some code changed in CL 281292. Any insights?

[cuonglm]

This seems to me a problem with noder pass. Somehow, the instantiated function was processed twice with inlining? Disable inlining make the code compiled.

FWIW, the non-generic version works well, and also unified IR code.

[randall77]

I'm not sure entirely what is going on here yet. Might have something to do with function values. if you replace the body of Comparator with:

return func(x, y int) int { return a.CompareInt[int](x,y) }

Then it works.

[aclements]

Ping. This is marked as a release-blocker and we're very close to the release. Do we understand the underlying issue yet? Given that this causes an ICE instead of mis-compilation, should it be a release-blocker at this point?

[cuonglm]

Ping. This is marked as a release-blocker and we're very close to the release. Do we understand the underlying issue yet? Given that this causes an ICE instead of mis-compilation, should it be a release-blocker at this point?

I think this is a release-blocker, since when it's an ICE on valid code.

[cuonglm]

Also cc @danscales

[gopherbot]

Change https://go.dev/cl/391574 mentions this issue: cmd/compile: fix re-export closure

[dr2chase]

I'm trying a different approach to this, but thus far lack success. The problem appears to be that "wrong" names are left on a closure signature on an Inl.Body, but those names are probably unimportant. Therefore, when constructing an Inl.Body, strip them out from an OCLOSURE node (which is what causes the problem here) to disappear the problem.

Unfortunately, that doesn't seem to work, not sure why, and it also causes a single inscrutable failure in typeparam/issue49246.go. So this is not a good approach, yet.

[randall77]

Reopening for backport to 1.18 release branch.