resource/aws_eip: Default to default domain when vpc not set

.changelog/26716.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+resource/aws_eip: Defaults to default regional `domain` when `vpc` not set
+```

internal/service/acm/sweep.go

@@ -72,7 +72,7 @@ func sweepCertificates(region string) error {
 				for _, iub := range output.Certificate.InUseBy {
 					m[aws.StringValue(iub)[:77]] = ""
 				}
-				for k, _ := range m {
+				for k := range m {
 					log.Printf("[INFO]  %s...", k)
 				}
 				continue

internal/service/ec2/ec2_eip.go

@@ -131,12 +131,10 @@ func resourceEIPCreate(d *schema.ResourceData, meta interface{}) error {
 	defaultTagsConfig := meta.(*conns.AWSClient).DefaultTagsConfig
 	tags := defaultTagsConfig.MergeTags(tftags.New(d.Get("tags").(map[string]interface{})))
 
-	if _, ok := d.GetOk("vpc"); !ok {
-		return errors.New(`with the retirement of EC2-Classic no new non-VPC EC2 EIPs can be created`)
-	}
+	input := &ec2.AllocateAddressInput{}
 
-	input := &ec2.AllocateAddressInput{
-		Domain: aws.String(ec2.DomainTypeVpc),
+	if v := d.Get("vpc"); v != nil && v.(bool) {
+		input.Domain = aws.String(ec2.DomainTypeVpc)
 	}
 
 	if v, ok := d.GetOk("address"); ok {

internal/service/ec2/ec2_eip_test.go

@@ -68,6 +68,34 @@ func TestAccEC2EIP_disappears(t *testing.T) {
 	})
 }
 
+func TestAccEC2EIP_noVPC(t *testing.T) {
+	var conf ec2.Address
+	resourceName := "aws_eip.test"
+
+	resource.ParallelTest(t, resource.TestCase{
+		PreCheck:                 func() { acctest.PreCheck(t) },
+		ErrorCheck:               acctest.ErrorCheck(t, ec2.EndpointsID),
+		ProtoV5ProviderFactories: acctest.ProtoV5ProviderFactories,
+		CheckDestroy:             testAccCheckEIPDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: testAccEIPConfig_noVPC,
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckEIPExists(resourceName, &conf),
+					resource.TestCheckResourceAttr(resourceName, "domain", "vpc"),
+					resource.TestCheckResourceAttrSet(resourceName, "public_ip"),
+					testAccCheckEIPPublicDNS(resourceName),
+				),
+			},
+			{
+				ResourceName:      resourceName,
+				ImportState:       true,
+				ImportStateVerify: true,
+			},
+		},
+	})
+}
+
 func TestAccEC2EIP_tags(t *testing.T) {
 	var conf ec2.Address
 	resourceName := "aws_eip.test"
@@ -745,6 +773,11 @@ resource "aws_eip" "test" {
 }
 `
 
+const testAccEIPConfig_noVPC = `
+resource "aws_eip" "test" {
+}
+`
+
 func testAccEIPConfig_tags1(tagKey1, tagValue1 string) string {
 	return fmt.Sprintf(`
 resource "aws_eip" "test" {

website/docs/r/eip.html.markdown

@@ -103,9 +103,11 @@ The following arguments are supported:
 * `instance` - (Optional) EC2 instance ID.
 * `network_border_group` - (Optional) Location from which the IP address is advertised. Use this parameter to limit the address to this location.
 * `network_interface` - (Optional) Network interface ID to associate with.
-* `public_ipv4_pool` - (Optional) EC2 IPv4 address pool identifier or `amazon`. This option is only available for VPC EIPs.
+* `public_ipv4_pool` - (Optional) EC2 IPv4 address pool identifier or `amazon`.
+  This option is only available for VPC EIPs.
 * `tags` - (Optional) Map of tags to assign to the resource. Tags can only be applied to EIPs in a VPC. If configured with a provider [`default_tags` configuration block](https://registry.terraform.io/providers/hashicorp/aws/latest/docs#default_tags-configuration-block) present, tags with matching keys will overwrite those defined at the provider-level.
 * `vpc` - (Optional) Boolean if the EIP is in a VPC or not.
+  Defaults to `true` unless the region supports EC2-Classic.
 
 ~> **NOTE:** You can specify either the `instance` ID or the `network_interface` ID, but not both. Including both will **not** return an error from the AWS API, but will have undefined behavior. See the relevant [AssociateAddress API Call][1] for more information.
 
@@ -120,7 +122,7 @@ In addition to all arguments above, the following attributes are exported:
 * `association_id` - ID representing the association of the address with an instance in a VPC.
 * `carrier_ip` - Carrier IP address.
 * `customer_owned_ip` - Customer owned IP.
-* `domain` - Indicates if this EIP is for use in VPC (`vpc`) or EC2 Classic (`standard`).
+* `domain` - Indicates if this EIP is for use in VPC (`vpc`) or EC2-Classic (`standard`).
 * `id` - Contains the EIP allocation ID.
 * `private_dns` - The Private DNS associated with the Elastic IP address (if in VPC).
 * `private_ip` - Contains the private IP address (if in VPC).
@@ -146,7 +148,7 @@ EIPs in a VPC can be imported using their Allocation ID, e.g.,
 $ terraform import aws_eip.bar eipalloc-00a10e96
 ```
 
-EIPs in EC2 Classic can be imported using their Public IP, e.g.,
+EIPs in EC2-Classic can be imported using their Public IP, e.g.,
 
 ```
 $ terraform import aws_eip.bar 52.0.0.0