Rollup merge of #92418 - dtolnay:emptystructpat, r=michaelwoerister

Fix spacing in pretty printed PatKind::Struct with no fields

Follow-up to #92238 fixing one of the FIXMEs.

```rust
macro_rules! repro {
    ($pat:pat) => {
        stringify!($pat)
    };
}

fn main() {
    println!("{}", repro!(Struct {}));
}
```

Before:&ensp;<code>Struct&nbsp;{&nbsp;&nbsp;}</code>
After:&ensp;<code>Struct&nbsp;{}</code>

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -2461,7 +2461,11 @@ impl<'a> State<'a> {
                     self.print_path(path, true, 0);
                 }
                 self.nbsp();
-                self.word_space("{");
+                self.word("{");
+                let empty = fields.is_empty() && !etc;
+                if !empty {
+                    self.space();
+                }
                 self.commasep_cmnt(
                     Consistent,
                     &fields,
@@ -2482,7 +2486,9 @@ impl<'a> State<'a> {
                     }
                     self.word("..");
                 }
-                self.space();
+                if !empty {
+                    self.space();
+                }
                 self.word("}");
             }
             PatKind::Tuple(ref elts) => {