Auto merge of #115782 - a1phyr:improve_pad_adapter, r=dtolnay

Improve `PadAdapter::write_char`

Split from #108043

1 files changed, 8 insertions, 0 deletions

diff --git a/library/core/src/fmt/builders.rs b/library/core/src/fmt/builders.rs
index d2c9f980042..9227248041e 100644
--- a/library/core/src/fmt/builders.rs
+++ b/library/core/src/fmt/builders.rs
@@ -40,6 +40,14 @@ impl fmt::Write for PadAdapter<'_, '_> {
 
         Ok(())
     }
+
+    fn write_char(&mut self, c: char) -> fmt::Result {
+        if self.state.on_newline {
+            self.buf.write_str("    ")?;
+        }
+        self.state.on_newline = c == '\n';
+        self.buf.write_char(c)
+    }
 }
 
 /// A struct to help with [`fmt::Debug`](Debug) implementations.