Auto merge of #94530 - tmiasko:alignment-impls, r=dtolnay

bors · bors · commit 9257f5aad02b · 2022-05-21T19:49:51.000Z
Implement Copy, Clone, PartialEq and Eq for core::fmt::Alignment

Alignment is a fieldless exhaustive enum, so it is already possible to
clone and compare it by matching, but it is inconvenient to do so. For
example, if one would like to create a struct describing a formatter
configuration and provide a clone implementation:

```rust
pub struct Format {
    fill: char,
    width: Option&lt;usize&gt;,
    align: fmt::Alignment,
}

impl Clone for Format {
    fn clone(&amp;self) -&gt; Self {
        Format {
            align: match self.align {
                fmt::Alignment::Left =&gt; fmt::Alignment::Left,
                fmt::Alignment::Right =&gt; fmt::Alignment::Right,
                fmt::Alignment::Center =&gt; fmt::Alignment::Center,
            },
            .. *self
        }
    }
}
```

Derive Copy, Clone, PartialEq, and Eq for Alignment for convenience.
diff --git a/library/core/src/fmt/mod.rs b/library/core/src/fmt/mod.rs
@@ -21,7 +21,7 @@ mod num;
 #[stable(feature = "fmt_flags_align", since = "1.28.0")]
 #[cfg_attr(not(test), rustc_diagnostic_item = "Alignment")]
 /// Possible alignments returned by `Formatter::align`
-#[derive(Debug)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum Alignment {
     #[stable(feature = "fmt_flags_align", since = "1.28.0")]
     /// Indication that contents should be left-aligned.
