target: target,
		list:   downgraded,
		Reqs:   reqs,
	})
	if err != nil {
		return nil, err
	}
	actualVersion := make(map[string]string, len(actual))
	for _, m := range actual {
		actualVersion[m.Path] = m.Version
	}

	downgraded = downgraded[:0]
	for _, m := range list {
		if v, ok := actualVersion[m.Path]; ok {
			downgraded = append(downgraded, module.Version{Path: m.Path, Version: v})
		}

stderr '^go: added toolchain go1.22.1$'
! stderr '(added|removed|upgraded|downgraded) go'
grep 'toolchain go1.22.1' go.mod

go get toolchain@none
stderr '^go: removed toolchain go1.22.1$'
! stderr '(added|removed|upgraded|downgraded) go'
! grep toolchain go.mod

go get toolchain@go1.22.1
stderr '^go: added toolchain go1.22.1$'
! stderr '(added|removed|upgraded|downgraded) go'
grep 'toolchain go1.22.1' go.mod

go get go@1.22.3

go get rsc.io/sampler@none
stderr '^go: downgraded rsc.io/quote v1.5.2 => v1.3.0$'
stderr '^go: removed rsc.io/sampler v1.3.0$'
! stderr '^go get.*golang.org/x/text'
cmp go.mod go.mod.downgrade

# When removing or downgrading a requirement, 'go get' also prints a message
# for explicit dependencies removed as a consequence.
cp go.mod.usequote go.mod
go get rsc.io/quote@v1.5.1
stderr '^go: downgraded rsc.io/quote v1.5.2 => v1.5.1$'

go get example.com/a@v1.0.2 go@1.28rc1
go list -f '{{.Module.GoVersion}}'
stdout 1.28rc1
go get go@1.24.2
stderr '^go: downgraded go 1.28rc1 => 1.24.2$'
stderr '^go: downgraded example.com/a v1.0.2 => v1.0.1$'
stderr '^go: downgraded example.com/b v1.0.2 => v1.0.1$'
go list -f '{{.Module.GoVersion}}'
stdout 1.24.2

-- go.mod --
module m
go 1.21

require (
	example.com/a v1.0.0

   Constraint path ':test:unspecified' --> 'org:foo:{strictly 1.0}' because of the following reason: version resolved in configuration ':other' by consistent resolution"""
    }

    def "first level dependency can be downgraded only if it's a preferred version"() {
        repository {
            'org:foo:1.0'()
            'org:foo:1.1'()
        }

        buildFile << """
            configurations {
                other

stderr '^go: removed toolchain go1.999testmod$'
grep 'go 1.23.9' go.mod
! grep 'toolchain go1.23.9' go.mod  # implied

# go get toolchain@go1.22 should use the latest Go 1.22 and downgrade go.
go get toolchain@go1.22
stderr '^go: downgraded go 1.23.9 => 1.22.9$'
grep 'go 1.22.9' go.mod
! grep 'toolchain go1.22.9' go.mod # implied

# go get toolchain@patch should use the latest patch release
go get toolchain@go1.22.1

B3: D2
C1: B2.hidden
C2: D2
D1:
D2:
build A1: A1 B3 D2
downgrade A1 D1: A1 B1 D1 E1
build A: A B3 C2 D2
downgrade A D1: A B2.hidden C1 D1

# Both B3 and C3 require D2.
# If we downgrade D to D1, then in isolation B3 would downgrade to B1,
# and C3 would downgrade to C1.
# But C1 requires B2.hidden, and B1 requires C2.hidden, so we can't
# downgrade to either of those without pulling the other back up a little.
#

NOTE: Dependency constraints are only published when using <<publishing_gradle_module_metadata.adoc#sec:understanding-gradle-module-md,Gradle Module Metadata>>.

stdout '^example.com/a v0.1.0 '
stdout '^example.com/b v0.2.0 '
stdout '^example.com/c v0.1.0 '

# At this point, b.2 is still an explicit root, so its dependency on c
# is still tracked, and it will still be downgraded away if we remove c.
# ('go get' never makes a root into a non-root. Only 'go mod tidy' does that.)

go get example.com/c@none
go list -m all
! stdout '^example.com/a '
! stdout '^example.com/b '
! stdout '^example.com/c '

    /**
     * The required version of a module (which may be an exact version or a version range).
     *
     * The required version of a module can typically be upgraded during dependency resolution, but not downgraded.
     *
     * @return the required version, or empty string if no required version specified. Never null.
     */
    String getRequiredVersion();

    /**