Problem with emphasized link text

[jmooring]

Tested with v1.7.3

Input:

[*[a]*](b)

Expected output:
https://spec.commonmark.org/dingus/?text=%5B*%5Ba%5D*%5D(b)

<p><a href="b"><em>[a]</em></a></p>

Actual output:

<p><a href="b">*[a]*</a></p>

test.go

package main

import (
	"bytes"
	"fmt"

	"github.com/yuin/goldmark"
)

func main() {
	md := goldmark.New()

	input := `[*[a]*](b)`

	var buf bytes.Buffer
	if err := md.Convert([]byte(input), &buf); err != nil {
		panic(err)
	}

	fmt.Println(buf.String())
}