[Issue 16312] "Error: Overlapping fields" caused by use of deprecated features in referred to fields

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=16312

Mathias Lang <mathias.lang at sociomantic.com> changed:

           What    |Removed                     |Added
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                 CC|                            |mathias.lang at sociomantic.co
                   |                            |m

--- Comment #1 from Mathias Lang <mathias.lang at sociomantic.com> ---
Note: Only when compiled with `-de`.

They are two things at play here:

- First, when the compiler encounter an error, it 'poison' the AST node.
That can lead to wrong error messages in places not adjusted to deal with the
poisoning.

- Second, the compiler treat a non-fatal error (e.g. a warning when `-w` is
provided or a deprecation when `-de` is provided) as a fatal one. This can have
extremely dangerous consequences, e.g. the following will still compiles, just
have different behaviour:

```
class Deprecated
{
    int j;
    this (T) (T i)
    {
        this.j = (i, T.init);
    }
}

template Foo (T) if (__traits(compiles, { T a = new T(42); }))
{
    enum Foo = "First instance";
}

template Foo (T) if (!__traits(compiles, { T a = new T(42); }))
{
    enum Foo = "Second instance";
}

pragma(msg, Foo!(Deprecated));
```

The second bug is well known, so I suppose this ER is about the first point ?

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