From 619003d1d414167630331efffe83702f74413be6 Mon Sep 17 00:00:00 2001
From: Phlosioneer <mattmdrr2@gmail.com>
Date: Tue, 20 Mar 2018 05:33:59 -0400
Subject: Implement some trivial size_hints for various iterators

This also implements ExactSizeIterator where applicable.

Addresses most of the Iterator traits mentioned in #23708.
---
 src/libsyntax_ext/format_foreign.rs | 9 +++++++++
 1 file changed, 9 insertions(+)

(limited to 'src/libsyntax_ext')

diff --git a/src/libsyntax_ext/format_foreign.rs b/src/libsyntax_ext/format_foreign.rs
index 0476d7d4fcc..e95c6f2e124 100644
--- a/src/libsyntax_ext/format_foreign.rs
+++ b/src/libsyntax_ext/format_foreign.rs
@@ -272,6 +272,11 @@ pub mod printf {
             self.s = tail;
             Some(sub)
         }
+
+        fn size_hint(&self) -> (usize, Option<usize>) {
+            // Substitutions are at least 2 characters long.
+            (0, Some(self.s.len() / 2))
+        }
     }
 
     enum State {
@@ -782,6 +787,10 @@ pub mod shell {
                 None => None,
             }
         }
+
+        fn size_hint(&self) -> (usize, Option<usize>) {
+            (0, Some(self.s.len()))
+        }
     }
 
     /// Parse the next substitution from the input string.
-- 
cgit 1.4.1-3-g733a5