From 09f60272243ea1ed4389cb45145222641200add1 Mon Sep 17 00:00:00 2001
From: liudingming <liudingming@bytedance.com>
Date: Mon, 9 Aug 2021 20:25:57 +0800
Subject: [PATCH] Workaround of early exiting when `ExprUseVisitor` meets
 unresolved type var.

Add regression test for issue-87814

Set needs_to_read to true when typeck errors.
---
 compiler/rustc_typeck/src/expr_use_visitor.rs | 10 ++++++++--
 src/test/ui/closures/issue-87814-1.rs         |  8 ++++++++
 src/test/ui/closures/issue-87814-2.rs         | 11 +++++++++++
 3 files changed, 27 insertions(+), 2 deletions(-)
 create mode 100644 src/test/ui/closures/issue-87814-1.rs
 create mode 100644 src/test/ui/closures/issue-87814-2.rs

diff --git a/compiler/rustc_typeck/src/expr_use_visitor.rs b/compiler/rustc_typeck/src/expr_use_visitor.rs
index b0c95939bb77d..8d401b7f44442 100644
--- a/compiler/rustc_typeck/src/expr_use_visitor.rs
+++ b/compiler/rustc_typeck/src/expr_use_visitor.rs
@@ -243,7 +243,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                 let ExprUseVisitor { ref mc, body_owner: _, delegate: _ } = *self;
                 let mut needs_to_be_read = false;
                 for arm in arms.iter() {
-                    return_if_err!(mc.cat_pattern(discr_place.clone(), &arm.pat, |place, pat| {
+                    match mc.cat_pattern(discr_place.clone(), &arm.pat, |place, pat| {
                         match &pat.kind {
                             PatKind::Binding(.., opt_sub_pat) => {
                                 // If the opt_sub_pat is None, than the binding does not count as
@@ -290,7 +290,13 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                                 // examined
                             }
                         }
-                    }));
+                    }) {
+                        Ok(_) => (),
+                        Err(_) => {
+                            // If typeck failed, assume borrow is needed.
+                            needs_to_be_read = true;
+                        }
+                    }
                 }
 
                 if needs_to_be_read {
diff --git a/src/test/ui/closures/issue-87814-1.rs b/src/test/ui/closures/issue-87814-1.rs
new file mode 100644
index 0000000000000..5cf01ddf5d71b
--- /dev/null
+++ b/src/test/ui/closures/issue-87814-1.rs
@@ -0,0 +1,8 @@
+// check-pass
+fn main() {
+    let mut schema_all = vec![];
+    (0..42).for_each(|_x| match Err(()) as Result<(), _> {
+        Ok(()) => schema_all.push(()),
+        Err(_) => (),
+    });
+}
diff --git a/src/test/ui/closures/issue-87814-2.rs b/src/test/ui/closures/issue-87814-2.rs
new file mode 100644
index 0000000000000..7a5facdac58c3
--- /dev/null
+++ b/src/test/ui/closures/issue-87814-2.rs
@@ -0,0 +1,11 @@
+// check-pass
+#![feature(try_reserve)]
+
+fn main() {
+    let mut schema_all: (Vec<String>, Vec<String>) = (vec![], vec![]);
+
+    let _c = || match schema_all.0.try_reserve(1) as Result<(), _> {
+        Ok(()) => (),
+        Err(_) => (),
+    };
+}