From d0d001625c115f3e000fd782a3715ea3ae883ef6 Mon Sep 17 00:00:00 2001
From: Thomas Pelletier <pelletier.thomas@gmail.com>
Date: Mon, 25 Oct 2021 16:47:10 -0400
Subject: [PATCH] unmarshal: don't panic when storing table in slice (#641)

New error message:

```
toml: cannot store a table in a slice
1| [things]
 |  ~~~~~~ cannot store a table in a slice
2| foo = "bar"
```

Fixes #623
---
 unmarshaler.go      |  3 +++
 unmarshaler_test.go | 12 ++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/unmarshaler.go b/unmarshaler.go
index 6e3abc6..5d589fa 100644
--- a/unmarshaler.go
+++ b/unmarshaler.go
@@ -488,6 +488,9 @@ func (d *decoder) handleArrayTablePart(key ast.Iterator, v reflect.Value) (refle
 // cannot handle it.
 func (d *decoder) handleTable(key ast.Iterator, v reflect.Value) (reflect.Value, error) {
 	if v.Kind() == reflect.Slice {
+		if v.Len() == 0 {
+			return reflect.Value{}, newDecodeError(key.Node().Data, "cannot store a table in a slice")
+		}
 		elem := v.Index(v.Len() - 1)
 		x, err := d.handleTable(key, elem)
 		if err != nil {
diff --git a/unmarshaler_test.go b/unmarshaler_test.go
index 362e937..b0ae20e 100644
--- a/unmarshaler_test.go
+++ b/unmarshaler_test.go
@@ -1810,6 +1810,18 @@ func TestIssue602(t *testing.T) {
 	require.Equal(t, expected, v)
 }
 
+func TestIssue623(t *testing.T) {
+	definition := struct {
+		Things []string
+	}{}
+
+	values := `[things]
+foo = "bar"`
+
+	err := toml.Unmarshal([]byte(values), &definition)
+	require.Error(t, err)
+}
+
 //nolint:funlen
 func TestUnmarshalDecodeErrors(t *testing.T) {
 	examples := []struct {