From 0250f0244b320b1cecabc05c108178171c733f6c Mon Sep 17 00:00:00 2001
From: Maybe Waffle <waffle.lapkin@gmail.com>
Date: Tue, 26 Jul 2022 14:17:15 +0400
Subject: [PATCH] allow or avoid for loops over option in compiler and tests

---
 compiler/rustc_ast/src/visit.rs         | 14 ++++++--------
 src/test/ui/drop/dropck_legal_cycles.rs | 14 +++++++-------
 src/test/ui/issues/issue-30371.rs       |  1 +
 3 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
index a71e055a4b3..c6c80e613e3 100644
--- a/compiler/rustc_ast/src/visit.rs
+++ b/compiler/rustc_ast/src/visit.rs
@@ -244,14 +244,12 @@ pub trait Visitor<'ast>: Sized {
 
 #[macro_export]
 macro_rules! walk_list {
-    ($visitor: expr, $method: ident, $list: expr) => {
-        for elem in $list {
-            $visitor.$method(elem)
-        }
-    };
-    ($visitor: expr, $method: ident, $list: expr, $($extra_args: expr),*) => {
-        for elem in $list {
-            $visitor.$method(elem, $($extra_args,)*)
+    ($visitor: expr, $method: ident, $list: expr $(, $($extra_args: expr),* )?) => {
+        {
+            #[cfg_attr(not(bootstrap), allow(for_loop_over_fallibles))]
+            for elem in $list {
+                $visitor.$method(elem $(, $($extra_args,)* )?)
+            }
         }
     }
 }
diff --git a/src/test/ui/drop/dropck_legal_cycles.rs b/src/test/ui/drop/dropck_legal_cycles.rs
index 27a599315dc..6a0fe7784fb 100644
--- a/src/test/ui/drop/dropck_legal_cycles.rs
+++ b/src/test/ui/drop/dropck_legal_cycles.rs
@@ -1017,7 +1017,7 @@ impl<'a> Children<'a> for HM<'a> {
         where C: Context + PrePost<Self>, Self: Sized
     {
         if let Some(ref hm) = self.contents.get() {
-            for (k, v) in hm.iter().nth(index / 2) {
+            if let Some((k, v)) = hm.iter().nth(index / 2) {
                 [k, v][index % 2].descend_into_self(context);
             }
         }
@@ -1032,7 +1032,7 @@ impl<'a> Children<'a> for VD<'a> {
         where C: Context + PrePost<Self>, Self: Sized
     {
         if let Some(ref vd) = self.contents.get() {
-            for r in vd.iter().nth(index) {
+            if let Some(r) = vd.iter().nth(index) {
                 r.descend_into_self(context);
             }
         }
@@ -1047,7 +1047,7 @@ impl<'a> Children<'a> for VM<'a> {
         where C: Context + PrePost<VM<'a>>
     {
         if let Some(ref vd) = self.contents.get() {
-            for (_idx, r) in vd.iter().nth(index) {
+            if let Some((_idx, r)) = vd.iter().nth(index) {
                 r.descend_into_self(context);
             }
         }
@@ -1062,7 +1062,7 @@ impl<'a> Children<'a> for LL<'a> {
         where C: Context + PrePost<LL<'a>>
     {
         if let Some(ref ll) = self.contents.get() {
-            for r in ll.iter().nth(index) {
+            if let Some(r) = ll.iter().nth(index) {
                 r.descend_into_self(context);
             }
         }
@@ -1077,7 +1077,7 @@ impl<'a> Children<'a> for BH<'a> {
         where C: Context + PrePost<BH<'a>>
     {
         if let Some(ref bh) = self.contents.get() {
-            for r in bh.iter().nth(index) {
+            if let Some(r) = bh.iter().nth(index) {
                 r.descend_into_self(context);
             }
         }
@@ -1092,7 +1092,7 @@ impl<'a> Children<'a> for BTM<'a> {
         where C: Context + PrePost<BTM<'a>>
     {
         if let Some(ref bh) = self.contents.get() {
-            for (k, v) in bh.iter().nth(index / 2) {
+            if let Some((k, v)) = bh.iter().nth(index / 2) {
                 [k, v][index % 2].descend_into_self(context);
             }
         }
@@ -1107,7 +1107,7 @@ impl<'a> Children<'a> for BTS<'a> {
         where C: Context + PrePost<BTS<'a>>
     {
         if let Some(ref bh) = self.contents.get() {
-            for r in bh.iter().nth(index) {
+            if let Some(r) = bh.iter().nth(index) {
                 r.descend_into_self(context);
             }
         }
diff --git a/src/test/ui/issues/issue-30371.rs b/src/test/ui/issues/issue-30371.rs
index a1ae9a36bc1..880558eb5b6 100644
--- a/src/test/ui/issues/issue-30371.rs
+++ b/src/test/ui/issues/issue-30371.rs
@@ -1,5 +1,6 @@
 // run-pass
 #![allow(unreachable_code)]
+#![allow(for_loop_over_fallibles)]
 #![deny(unused_variables)]
 
 fn main() {