Incorrect indentation for arrays of custom types

Describe the bug Using the SetIndentTables(true) option does not correctly indent keys of arrays of custom types. It does work correctly if the custom type is not a slice. Example: If I have some data structure a.b.c I expect the generated TOML to look like the following:

# comment A
[A]
  # comment B
  [A.B]
    # comment C
    [A.B.C]

Assuming c is an array I would expect the following:

# comment A
[A]
  # comment B
  [A.B]
    # comment C
    [[A.B.C]]
      # Entry 1
    [[A.B.C]]
      # Entry 2

Instead, go-toml gives me something like the following:

# comment A
[A]
  # comment B
  [A.B]
    # comment C
[[A.B.C]]
      # Entry 1
[[A.B.C]]
      # Entry 2

To Reproduce

package main

import (
    "bytes"
    "fmt"

    toml "github.com/pelletier/go-toml/v2"
)

func main() {
    cfg := layer0{
        Value: "value",
        Layer1: []layer1{
            {
                Value: "value",
                Layer2: []layer2{
                    {
                        Value: "value",
                        Layer3: []layer3{
                            {
                                Value: "value",
                                CustomType: customType{
                                    Value: "value",
                                },
                            },
                        },
                    },
                },
            },
        },
    }

    buf := bytes.Buffer{}
    enc := toml.NewEncoder(&buf).
        SetIndentTables(true).
        SetIndentSymbol("+") // Using "+" as indent symbol for easier comparison
    if err := enc.Encode(cfg); err != nil {
        panic(err)
    }

    fmt.Println(buf.String())
}

type layer0 struct {
    Value  string   `toml:"value" comment:"value comment"`
    Layer1 []layer1 `toml:"layer1" comment:"layer1 comment"`
}

type layer1 struct {
    Value  string   `toml:"value" comment:"value comment"`
    Layer2 []layer2 `toml:"layer2" comment:"layer2 comment"`
}

type layer2 struct {
    Value  string   `toml:"value" comment:"value comment"`
    Layer3 []layer3 `toml:"layer3" comment:"layer3 comment"`
}

type layer3 struct {
    Value      string     `toml:"value" comment:"value comment"`
    CustomType customType `toml:"customType" comment:"customType comment"`
}

type customType struct {
    Value string `toml:"value" comment:"value comment"`
}

Expected behavior I'm expecting the generated TOML to look like the following, correctly indenting layer1.layer2 with + and layer1.layer2.layer3 with two ++:

$ go run ./
# value comment
value = 'value'

# layer1 comment
[[layer1]]
+# value comment
+value = 'value'

+# layer2 comment
+[[layer1.layer2]]
++# value comment
++value = 'value'

++# layer3 comment
++[[layer1.layer2.layer3]]
+++# value comment
+++value = 'value'

+++# customType comment
+++[layer1.layer2.layer3.customType]
++++# value comment
++++value = 'value'

In practice, only the comments for layer1.layer2 and layer1.layer2.layer3 are indented, the keys are not:

$ go run ./
# value comment
value = 'value'

# layer1 comment
[[layer1]]
+# value comment
+value = 'value'

+# layer2 comment
[[layer1.layer2]]
++# value comment
++value = 'value'

++# layer3 comment
[[layer1.layer2.layer3]]
+++# value comment
+++value = 'value'

+++# customType comment
+++[layer1.layer2.layer3.customType]
++++# value comment
++++value = 'value'

Versions

go-toml: v2.2.0
go: 1.22.1
operating system: Linux

Additional context Add any other context about the problem here that you think may help to diagnose.

pelletier / go-toml

Incorrect indentation for arrays of custom types #943