buildflags: make work on go 1.22 by reverting rangefunc usage

go.mod

@@ -1,6 +1,6 @@
 module github.com/docker/buildx
 
-go 1.23.0
+go 1.22.0
 
 require (
 	github.com/Masterminds/semver/v3 v3.2.1

util/buildflags/attests_cty.go

@@ -22,16 +22,19 @@ func (e *Attests) FromCtyValue(in cty.Value, p cty.Path) error {
 	return p.NewErrorf("%s", convert.MismatchMessage(got, want))
 }
 
-func (e *Attests) fromCtyValue(in cty.Value, p cty.Path) error {
+func (e *Attests) fromCtyValue(in cty.Value, p cty.Path) (retErr error) {
 	*e = make([]*Attest, 0, in.LengthInt())
-	for value := range eachElement(in) {
+
+	yield := func(value cty.Value) bool {
 		entry := &Attest{}
-		if err := entry.FromCtyValue(value, p); err != nil {
-			return err
+		if retErr = entry.FromCtyValue(value, p); retErr != nil {
+			return false
 		}
 		*e = append(*e, entry)
+		return true
 	}
-	return nil
+	eachElement(in)(yield)
+	return retErr
 }
 
 func (e Attests) ToCtyValue() cty.Value {

util/buildflags/cache_cty.go

@@ -21,26 +21,30 @@ func (o *CacheOptions) FromCtyValue(in cty.Value, p cty.Path) error {
 	return p.NewErrorf("%s", convert.MismatchMessage(got, want))
 }
 
-func (o *CacheOptions) fromCtyValue(in cty.Value, p cty.Path) error {
+func (o *CacheOptions) fromCtyValue(in cty.Value, p cty.Path) (retErr error) {
 	*o = make([]*CacheOptionsEntry, 0, in.LengthInt())
-	for value := range eachElement(in) {
+
+	yield := func(value cty.Value) bool {
 		// Special handling for a string type to handle ref only format.
 		if value.Type() == cty.String {
-			entries, err := ParseCacheEntry([]string{value.AsString()})
-			if err != nil {
-				return err
+			var entries CacheOptions
+			entries, retErr = ParseCacheEntry([]string{value.AsString()})
+			if retErr != nil {
+				return false
 			}
 			*o = append(*o, entries...)
-			continue
+			return true
 		}
 
 		entry := &CacheOptionsEntry{}
-		if err := entry.FromCtyValue(value, p); err != nil {
-			return err
+		if retErr = entry.FromCtyValue(value, p); retErr != nil {
+			return false
 		}
 		*o = append(*o, entry)
+		return true
 	}
-	return nil
+	eachElement(in)(yield)
+	return retErr
 }
 
 func (o CacheOptions) ToCtyValue() cty.Value {

util/buildflags/export_cty.go

@@ -21,16 +21,19 @@ func (e *Exports) FromCtyValue(in cty.Value, p cty.Path) error {
 	return p.NewErrorf("%s", convert.MismatchMessage(got, want))
 }
 
-func (e *Exports) fromCtyValue(in cty.Value, p cty.Path) error {
+func (e *Exports) fromCtyValue(in cty.Value, p cty.Path) (retErr error) {
 	*e = make([]*ExportEntry, 0, in.LengthInt())
-	for value := range eachElement(in) {
+
+	yield := func(value cty.Value) bool {
 		entry := &ExportEntry{}
-		if err := entry.FromCtyValue(value, p); err != nil {
-			return err
+		if retErr = entry.FromCtyValue(value, p); retErr != nil {
+			return false
 		}
 		*e = append(*e, entry)
+		return true
 	}
-	return nil
+	eachElement(in)(yield)
+	return retErr
 }
 
 func (e Exports) ToCtyValue() cty.Value {

util/buildflags/secrets_cty.go

@@ -28,16 +28,19 @@ func (s *Secrets) FromCtyValue(in cty.Value, p cty.Path) error {
 	return p.NewErrorf("%s", convert.MismatchMessage(got, want))
 }
 
-func (s *Secrets) fromCtyValue(in cty.Value, p cty.Path) error {
+func (s *Secrets) fromCtyValue(in cty.Value, p cty.Path) (retErr error) {
 	*s = make([]*Secret, 0, in.LengthInt())
-	for value := range eachElement(in) {
+
+	yield := func(value cty.Value) bool {
 		entry := &Secret{}
-		if err := entry.FromCtyValue(value, p); err != nil {
-			return err
+		if retErr = entry.FromCtyValue(value, p); retErr != nil {
+			return false
 		}
 		*s = append(*s, entry)
+		return true
 	}
-	return nil
+	eachElement(in)(yield)
+	return retErr
 }
 
 func (s Secrets) ToCtyValue() cty.Value {

util/buildflags/ssh_cty.go

@@ -28,16 +28,19 @@ func (s *SSHKeys) FromCtyValue(in cty.Value, p cty.Path) error {
 	return p.NewErrorf("%s", convert.MismatchMessage(got, want))
 }
 
-func (s *SSHKeys) fromCtyValue(in cty.Value, p cty.Path) error {
+func (s *SSHKeys) fromCtyValue(in cty.Value, p cty.Path) (retErr error) {
 	*s = make([]*SSH, 0, in.LengthInt())
-	for value := range eachElement(in) {
+
+	yield := func(value cty.Value) bool {
 		entry := &SSH{}
-		if err := entry.FromCtyValue(value, p); err != nil {
-			return err
+		if retErr = entry.FromCtyValue(value, p); retErr != nil {
+			return false
 		}
 		*s = append(*s, entry)
+		return true
 	}
-	return nil
+	eachElement(in)(yield)
+	return retErr
 }
 
 func (s SSHKeys) ToCtyValue() cty.Value {

util/buildflags/utils.go

@@ -1,8 +1,6 @@
 package buildflags
 
 import (
-	"iter"
-
 	"github.com/zclconf/go-cty/cty"
 	"github.com/zclconf/go-cty/cty/gocty"
 )
@@ -57,7 +55,12 @@ func isEmptyOrUnknown(v cty.Value) bool {
 	return !v.IsKnown() || (v.Type() == cty.String && v.AsString() == "")
 }
 
-func eachElement(in cty.Value) iter.Seq[cty.Value] {
+// Seq is a temporary definition of iter.Seq until we are able to migrate
+// to using go1.23 as our minimum version. This can be removed when go1.24
+// is released and usages can be changed to use rangefunc.
+type Seq[V any] func(yield func(V) bool)
+
+func eachElement(in cty.Value) Seq[cty.Value] {
 	return func(yield func(v cty.Value) bool) {
 		for elem := in.ElementIterator(); elem.Next(); {
 			_, value := elem.Element()