<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/62549>62549</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            New Clang-Format style option: PackInheritanceList
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          Stadly
      </td>
    </tr>
</table>

<pre>
    `Clang-Format` seems to be missing a style option for packing inheritance lists. I think we should have a `PackInheritanceList` behaving exactly like `PackConstructorInitializers` but for inheritance lists.

Suggested new option:
**PackInheritanceList** (`PackInheritanceListStyle`)
The pack inheritance list style to use.

Possible values:

- `PILS_Never` (in configuration: `Never`) Always put each inherited class/struct on its own line.
```
class A
    : B,
      C
{}
```

- `PILS_BinPack` (in configuration: `BinPack`) Bin-pack inherited classes/structs.
```
class A
    : Aaaaaaaaaaaaaaaaaaaa, Bbbbbbbbbbbbbbbbbbbb,
      Cccccccccccccccccccc
{}
```

- `PILS_CurrentLine` (in configuration: `CurrentLine`) Put all inherited classes/structs on the current line if they fit. Otherwise, put each one on its own line.
```
class A : B, C
{}

class A
    : Aaaaaaaaaaaaaaaaaaaa,
      Bbbbbbbbbbbbbbbbbbbb,
 Ddddddddddddd
{}
```

- `PCIL_NextLine` (in configuration: `NextLine`) Same as `PCIS_CurrentLine` except that if all inherited classes/structs do not fit on the current line, try to fit them on the next line.
```
class A : B, C
{}

class A
    : Aaaaaaaaaaaaaaaaaaaa, Bbbbbbbbbbbbbbbbbbbb, Ddddddddddddd
{}

class A
    : Aaaaaaaaaaaaaaaaaaaa,
      Bbbbbbbbbbbbbbbbbbbb,
 Cccccccccccccccccccc
{}
```

- `PILS_NextLineOnly` (in configuration: `NextLineOnly`) Put all inherited classes/structs on the next line if they fit. Otherwise, put each one on its own line.
```
class A
    : B, C
{}

class A
    : Aaaaaaaaaaaaaaaaaaaa, Bbbbbbbbbbbbbbbbbbbb, Ddddddddddddd
{}

class A
    : Aaaaaaaaaaaaaaaaaaaa,
      Bbbbbbbbbbbbbbbbbbbb,
 Cccccccccccccccccccc
{}
```

Inheritance lists and constructor initializers go hand in hand. With the proposed new style option, we have symmetry with the following options:

`BreakConstructorInitializers` <=> `BreakInheritanceList`
`PackConstructorInitializers` <=> `PackInheritanceList`

And then we have `ConstructorInitializerIndentWidth` that affect both inheritance lists and constructor initializers.
</pre>
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