From d3d3049f3a37687981eb48559470f59337694bf6 Mon Sep 17 00:00:00 2001
From: Lukas Kalbertodt <lukas.kalbertodt@gmail.com>
Date: Mon, 1 Apr 2019 02:36:20 +0200
Subject: [PATCH] Forward formatter settings to bounds of `Range<T>` in
 `fmt::Debug` impl

Before this change, formatter settings were lost when printing a
`Range`. For example, printing a `Range<f32>` with `{:.2?}` would not
apply the precision modifier when printing the floats. Now the `Debug`
impls look a bit more verbose, but modifier are not lost.
---
 src/libcore/ops/range.rs | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/libcore/ops/range.rs b/src/libcore/ops/range.rs
index 4f71c8e794954..5b6023f2e2cbb 100644
--- a/src/libcore/ops/range.rs
+++ b/src/libcore/ops/range.rs
@@ -85,7 +85,10 @@ pub struct Range<Idx> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<Idx: fmt::Debug> fmt::Debug for Range<Idx> {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        write!(fmt, "{:?}..{:?}", self.start, self.end)
+        self.start.fmt(fmt)?;
+        write!(fmt, "..")?;
+        self.end.fmt(fmt)?;
+        Ok(())
     }
 }
 
@@ -184,7 +187,9 @@ pub struct RangeFrom<Idx> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<Idx: fmt::Debug> fmt::Debug for RangeFrom<Idx> {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        write!(fmt, "{:?}..", self.start)
+        self.start.fmt(fmt)?;
+        write!(fmt, "..")?;
+        Ok(())
     }
 }
 
@@ -266,7 +271,9 @@ pub struct RangeTo<Idx> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<Idx: fmt::Debug> fmt::Debug for RangeTo<Idx> {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        write!(fmt, "..{:?}", self.end)
+        write!(fmt, "..")?;
+        self.end.fmt(fmt)?;
+        Ok(())
     }
 }
 
@@ -467,7 +474,10 @@ impl<Idx> RangeInclusive<Idx> {
 #[stable(feature = "inclusive_range", since = "1.26.0")]
 impl<Idx: fmt::Debug> fmt::Debug for RangeInclusive<Idx> {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        write!(fmt, "{:?}..={:?}", self.start, self.end)
+        self.start.fmt(fmt)?;
+        write!(fmt, "..=")?;
+        self.end.fmt(fmt)?;
+        Ok(())
     }
 }
 
@@ -602,7 +612,9 @@ pub struct RangeToInclusive<Idx> {
 #[stable(feature = "inclusive_range", since = "1.26.0")]
 impl<Idx: fmt::Debug> fmt::Debug for RangeToInclusive<Idx> {
     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
-        write!(fmt, "..={:?}", self.end)
+        write!(fmt, "..=")?;
+        self.end.fmt(fmt)?;
+        Ok(())
     }
 }