<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/130571>130571</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Add inlay hints for default arguments
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clangd
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          ilya-biryukov
      </td>
    </tr>
</table>

<pre>
    It would be great to show default arguments in various places through inlay hints.

Right now, only parameter names are shown in calls:

It would definitely be great if one could also see the default arguments from declarations on the definition and use sites (comments below mark inlay hints I'm proposing to add):
```cpp
void foo(int a = 10);
void foo(int a /* = 10*/) {
}

void test() {
  foo(/*10*/)
}
```

Going a bit further, we could also consider adding inlay hints for default arguments, although they look like a harder sell to me because I expect more noise (e.g. `unique_ptr` has a default deleter, `vector` has an allocator and `unordered_map` have hash defaults that are going to be popping up everywhere):

```cpp
template <class T = int>
struct Foo {
};

Foo</*int*/> x;
```
</pre>
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