This test verifies that we don't drop type checking errors on the floor when we
fail to compute positions for their related errors.

-- go.mod --
module play.ground

-- p.go --
package p

import (
	. "play.ground/foo"
)

const C = 1 //@diag("C", re"C already declared through dot-import")
var _ = C

-- foo/foo.go --
package foo

const C = 2