x/tools/go/packages: Unexpected package creation during export data loading (load generic package)

[tsh96]

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

$ go version
go version go1.18 linux/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
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/vscode/.cache/go-build"
GOENV="/home/vscode/.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=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.18"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/workspace/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 -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build2277327549=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Load type and type info from a generic package.

github repo: https://github.com/tsh96/reproducing-go-generic-load-packages-error

main.go

package main

import (
	_ "github.com/tsh96/reproducing-go-generic-load-packages-error/g"

	"golang.org/x/tools/go/packages"
)

func main() {
	mode := packages.NeedTypes | packages.NeedTypesInfo
	packages.Load(&packages.Config{Mode: mode}, ".")
}

g/util.go

package g

type A[T any] struct{}

func NewA[T any]() *A[T] { return new(A[T]) }

func NewIntA() *A[int] { return NewA[int]() } // <-- This line is triggering the issue

go.mod

module github.com/tsh96/reproducing-go-generic-load-packages-error

go 1.18

require golang.org/x/tools v0.1.11-0.20220325212234-e693fb417253

require (
	golang.org/x/mod v0.6.0-dev.0.20220106191415-9b9b3d81d5e3 // indirect
	golang.org/x/sys v0.0.0-20220325203850-36772127a21f // indirect
	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
)

What did you expect to see?

Nothing, success.

What did you see instead?

$ go run .
2022/03/26 02:31:45 golang.org/x/tools/go/packages: unexpected new packages during load of github.com/tsh96/reproducing-go-generic-load-packages-error/g
panic: golang.org/x/tools/go/packages: unexpected new packages during load of github.com/tsh96/reproducing-go-generic-load-packages-error/g

goroutine 21 [running]:
log.Panicf({0x63e7ca?, 0x3d?}, {0xc00005dbb0?, 0xc0000773b0?, 0xc0000b6200?})
        /usr/local/go/src/log/log.go:392 +0x67
golang.org/x/tools/go/packages.(*loader).loadFromExportData(0xc00013c000, 0xc0000b1f60)
        /workspace/vendor/golang.org/x/tools/go/packages/packages.go:1240 +0x4f7
golang.org/x/tools/go/packages.(*loader).loadPackage(0xc00013c000, 0xc0000b1f60)
        /workspace/vendor/golang.org/x/tools/go/packages/packages.go:864 +0x3aa
golang.org/x/tools/go/packages.(*loader).loadRecursive.func1()
        /workspace/vendor/golang.org/x/tools/go/packages/packages.go:829 +0x1a9
sync.(*Once).doSlow(0xc0001527a8?, 0x1?)
        /usr/local/go/src/sync/once.go:68 +0xc2
sync.(*Once).Do(...)
        /usr/local/go/src/sync/once.go:59
golang.org/x/tools/go/packages.(*loader).loadRecursive(0x43c085?, 0x0?)
        /workspace/vendor/golang.org/x/tools/go/packages/packages.go:817 +0x52
golang.org/x/tools/go/packages.(*loader).loadRecursive.func1.1(0x0?)
        /workspace/vendor/golang.org/x/tools/go/packages/packages.go:824 +0x2c
created by golang.org/x/tools/go/packages.(*loader).loadRecursive.func1
        /workspace/vendor/golang.org/x/tools/go/packages/packages.go:823 +0x8f
exit status 2

An unexpected package package named go.shape is added to the view after following line of code:
https://github.com/golang/tools/blob/198cae37294c48f180c54b9f66617d821e185fdc/go/packages/packages.go#L1209

[heschi]

cc @matloob

[AlekSi]

Might be related to #45218.