From 9698e41994fad31474a20e2dc5f8664364404e1b Mon Sep 17 00:00:00 2001
From: rail <12975677+rail-rain@users.noreply.github.com>
Date: Sat, 23 Mar 2019 15:36:48 +0900
Subject: [PATCH] Change explicit_counter_loop's message to add parentheses if
 necessary

---
 clippy_lints/src/loops.rs             |  6 +++++-
 tests/ui/explicit_counter_loop.rs     |  9 +++++++++
 tests/ui/explicit_counter_loop.stderr | 12 +++++++++---
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/clippy_lints/src/loops.rs b/clippy_lints/src/loops.rs
index d88f3e678..8f9323056 100644
--- a/clippy_lints/src/loops.rs
+++ b/clippy_lints/src/loops.rs
@@ -1499,7 +1499,11 @@ fn check_for_loop_explicit_counter<'a, 'tcx>(
                                  {1}) in {2}.enumerate()` or similar iterators",
                                 name,
                                 snippet(cx, pat.span, "_"),
-                                snippet(cx, arg.span, "_")
+                                if higher::range(cx, arg).is_some() {
+                                    format!("({})", snippet(cx, arg.span, "_"))
+                                } else {
+                                    format!("{}", sugg::Sugg::hir(cx, arg, "_").maybe_par())
+                                }
                             ),
                         );
                     }
diff --git a/tests/ui/explicit_counter_loop.rs b/tests/ui/explicit_counter_loop.rs
index 5efac85cf..71ef1e867 100644
--- a/tests/ui/explicit_counter_loop.rs
+++ b/tests/ui/explicit_counter_loop.rs
@@ -113,3 +113,12 @@ mod issue_3308 {
         }
     }
 }
+
+mod issue_1670 {
+    pub fn test() {
+        let mut count = 0;
+        for _i in 3..10 {
+            count += 1;
+        }
+    }
+}
diff --git a/tests/ui/explicit_counter_loop.stderr b/tests/ui/explicit_counter_loop.stderr
index 84ca0db83..8982c28eb 100644
--- a/tests/ui/explicit_counter_loop.stderr
+++ b/tests/ui/explicit_counter_loop.stderr
@@ -1,4 +1,4 @@
-error: the variable `_index` is used as a loop counter. Consider using `for (_index, _v) in &vec.enumerate()` or similar iterators
+error: the variable `_index` is used as a loop counter. Consider using `for (_index, _v) in (&vec).enumerate()` or similar iterators
   --> $DIR/explicit_counter_loop.rs:6:15
    |
 LL |     for _v in &vec {
@@ -6,7 +6,7 @@ LL |     for _v in &vec {
    |
    = note: `-D clippy::explicit-counter-loop` implied by `-D warnings`
 
-error: the variable `_index` is used as a loop counter. Consider using `for (_index, _v) in &vec.enumerate()` or similar iterators
+error: the variable `_index` is used as a loop counter. Consider using `for (_index, _v) in (&vec).enumerate()` or similar iterators
   --> $DIR/explicit_counter_loop.rs:12:15
    |
 LL |     for _v in &vec {
@@ -24,5 +24,11 @@ error: the variable `count` is used as a loop counter. Consider using `for (coun
 LL |         for ch in text.chars() {
    |                   ^^^^^^^^^^^^
 
-error: aborting due to 4 previous errors
+error: the variable `count` is used as a loop counter. Consider using `for (count, _i) in (3..10).enumerate()` or similar iterators
+  --> $DIR/explicit_counter_loop.rs:120:19
+   |
+LL |         for _i in 3..10 {
+   |                   ^^^^^
+
+error: aborting due to 5 previous errors