env GO111MODULE=off

# issue 29899: handling files with non-Go extension
go list -e -test -json -- c.c x.go
stdout '"Err": "named files must be .go files: c.c"'

! go list -test -json -- c.c x.go
stderr '^named files must be \.go files: c\.c$'

-- x.go --
package main
-- c.c --
package c