Module example.com/ambiguous/a is a prefix of example.com/a/b.
It contains package example.com/a/b.
-- .mod --
module example.com/ambiguous/a

go 1.16

require example.com/ambiguous/a/b v0.0.0-empty
-- .info --
{"Version":"v1.0.0"}
-- go.mod --
module example.com/ambiguous/a

go 1.16

require example.com/ambiguous/a/b v0.0.0-empty
-- b/b.go --

Module example.com/ambiguous/a/b is a suffix of example.com/a.
This version contains no package.
-- .mod --
module example.com/ambiguous/a/b

go 1.16
-- .info --
{"Version":"v0.0.0-empty"}
-- go.mod --
module example.com/ambiguous/a/b

}

func (A) F() {}
func (A) G() {}

type B struct{
	G int
	H int
}

func (B) F() {}

type C struct {
	A
	B
}

var _ = C.F // ERROR "ambiguous"
var _ = C.G // ERROR "ambiguous"
var _ = C.H // ERROR "ambiguous"

with the same version.

-- .mod --
module example.net/ambiguous/nested

go 1.16
-- .info --
{"Version": "v0.1.0"}
-- go.mod --
module example.net/ambiguous/nested

go 1.16
-- pkg/pkg.go --
// Package pkg exists in both example.net/ambiguous v0.1.0
// and example.net/ambiguous/nested v0.1.0

-- .mod --
module example.com/retract/ambiguous/other

go 1.16

require example.com/retract/ambiguous v1.0.0
-- .info --
{"Version":"v1.0.0"}
-- other.go --
package other

	_ = S2{}.C
	_ = S2{}.D /* ERROR "no field or method" */
	_ = S3{}.S1 /* ERROR "ambiguous selector S3{}.S1" */
	_ = S3{}.A
	_ = S3{}.B /* ERROR "ambiguous selector S3{}.B" */
	_ = S3{}.D
	_ = S3{}.E
	_ = S4{}.A
	_ = S4{}.B /* ERROR "no field or method" */
	_ = S5{}.X /* ERROR "ambiguous selector S5{}.X" */
	_ = S5{}.Y
	_ = S10{}.X /* ERROR "ambiguous selector S10{}.X" */
	_ = S10{}.Y
}

with the same version.

-- .mod --
module example.net/ambiguous

go 1.16
-- .info --
{"Version": "v0.2.0"}
-- go.mod --
module example.net/ambiguous

go 1.16
-- nested/pkg/README.txt --
// Package pkg no longer exists in this module at v0.2.0.

cd a
! go build
stderr '^ambiguous import: found package image in multiple modules:\s+image\s+.+\s.+image.+\s$'


cd ../b
! go build -mod=vendor
stderr '^main.go:4:5: ambiguous import: found package image in multiple directories:\s+.+image\s+.+image\s+$'

cd ../c
! go build -mod=vendor
stderr 'main.go:4:5: package p is not in std'

-- a/go.mod --
module image

-- a/main.go --
package main

func main() {

Carlos Amedee <******@****.***> 1715265901 -0400

go mod init example.com/foo
go get example.com/split/subpkg@v1.0.0
go list -m all
stdout 'example.com/split v1.0.0'

# A 'go get' that simultaneously upgrades away conflicting package definitions is not ambiguous.
go get example.com/split/subpkg@v1.1.0

# A 'go get' without an upgrade should find the package.
rm go.mod
go mod init example.com/foo
go get example.com/split/subpkg
go list -m all