Unexpected marshalling result for deeply-embedded structs

[falau]

• Go version: 1.22.6
• BurntSushi/toml@v1.4.0

For structs layers below, the output doesn't seem to be correct:

Example code:

package main

import (
	"fmt"
	"os"

	"github.com/BurntSushi/toml"
)

type (
	StructA struct{ StructB }
	StructB struct{ StructC }
	StructC struct{ StructD }
	StructD struct {
		FieldD1 string
		FieldD2 string
		FieldD3 string
	}
)

func main() {
	err := toml.NewEncoder(os.Stdout).Encode(StructA{
		StructB: StructB{
			StructC: StructC{
				StructD: StructD{
					FieldD1: "V1",
					FieldD2: "V2",
					FieldD3: "V3",
				},
			},
		},
	})
	fmt.Println("err:", err)
}

Outputs:

FieldD3 = "V3"
FieldD3 = "V3"
FieldD3 = "V3"

vs json.Marshal:

{
    "FieldD1":"V1",
    "FieldD2":"V2",
    "FieldD3":"V3"
}

This behaviour seems like only happens in this specific case. If I embed StructD into StructC, then the result is correct. I didn't dig into .Encode, nor tried any other composition of structs, so perhaps there are more strange cases like this.

[arp242]

It works if I comment out this if is32Bit { line so it always runs: bafff94

I put that in because tests on 32bit systems were failing; never quite understood why though; someone sent a patch and that fixes it, so 🤷

Added a test and CI passes: bafff94

Need to sit down and understand what's going on here.