cmd/go: panic: LoadImport called with empty package path when listing GOROOT/test/*.go

[bcmills]

What did you do?

~$ gotip version
go version devel go1.21-5534f044 Tue May 16 16:01:08 2023 +0000 linux/amd64

~$ cd $(gotip env GOROOT)/test

~/sdk/gotip/test$ gotip list *.go
panic: LoadImport called with empty package path

goroutine 1 [running]:
cmd/go/internal/load.loadImport({0xb57718, 0xee60e0}, {0x0, 0x0, 0x0, 0x1, 0x0, 0x0}, 0x0, {0xc00051f5ee, ...}, ...)
        /usr/local/google/home/bcmills/sdk/gotip/src/cmd/go/internal/load/pkg.go:727 +0x124a
cmd/go/internal/load.LoadImport(...)
        /usr/local/google/home/bcmills/sdk/gotip/src/cmd/go/internal/load/pkg.go:710
cmd/go/internal/load.(*Package).load(0xc0001bcc00, {0xb57718, 0xee60e0}, {0x0, 0x0, 0x0, 0x1, 0x0, 0x0}, {0xa59638, ...}, ...)
        /usr/local/google/home/bcmills/sdk/gotip/src/cmd/go/internal/load/pkg.go:2004 +0x1a49
cmd/go/internal/load.GoFilesPackage({0xb57718, 0xee60e0}, {0x0, 0x0, 0x0, 0x1, 0x0, 0x0}, {0xc000134020, 0x145, ...})
        /usr/local/google/home/bcmills/sdk/gotip/src/cmd/go/internal/load/pkg.go:3181 +0x827
cmd/go/internal/load.PackagesAndErrors({0xb57718?, 0xee60e0?}, {0x0, 0x0, 0x0, 0x1, 0x0, 0x0}, {0xc000134020, 0x145, ...})
        /usr/local/google/home/bcmills/sdk/gotip/src/cmd/go/internal/load/pkg.go:2826 +0x253
cmd/go/internal/list.runList({0xb57718?, 0xee60e0}, 0xeaad60?, {0xc000134020?, 0x145, 0x14e})
        /usr/local/google/home/bcmills/sdk/gotip/src/cmd/go/internal/list/list.go:612 +0xcf0
main.invoke(0xeaad60, {0xc000134010, 0x146, 0x14f})
        /usr/local/google/home/bcmills/sdk/gotip/src/cmd/go/main.go:243 +0x4d6
main.main()
        /usr/local/google/home/bcmills/sdk/gotip/src/cmd/go/main.go:183 +0x7cf

What did you expect to see?

An error message explaining why I can't load all of the .go files in GOROOT/test as a single package.

What did you see instead?

Panic!

[bcmills]

(CC @matloob)