From 47cc221e9827ab1b92f20353f423916a3f14d182 Mon Sep 17 00:00:00 2001
From: csmoe <csmoe@msn.com>
Date: Fri, 22 May 2020 10:11:17 +0800
Subject: [PATCH 1/3] add mcve for issue 72442

---
 src/test/ui/async-await/issue-72442.rs | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 src/test/ui/async-await/issue-72442.rs

diff --git a/src/test/ui/async-await/issue-72442.rs b/src/test/ui/async-await/issue-72442.rs
new file mode 100644
index 0000000000000..cced1da48f693
--- /dev/null
+++ b/src/test/ui/async-await/issue-72442.rs
@@ -0,0 +1,25 @@
+// edition:2018
+
+use std::fs::File;
+use std::future::Future;
+use std::io::prelude::*;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    block_on(async {
+        {
+            let path = std::path::Path::new(".");
+            let mut f = File::open(path.to_str())?;
+            //~^ ERROR the trait bound `std::option::Option<&str>: std::convert::AsRef<std::path::Path>` is not satisfied
+            let mut src = String::new();
+            f.read_to_string(&mut src)?;
+            Ok(())
+        }
+    })
+}
+
+fn block_on<F>(f: F) -> F::Output
+where
+    F: Future<Output = Result<(), Box<dyn std::error::Error>>>,
+{
+    Ok(())
+}

From 7cdc8972342e8f4946b518ac4886079f604cf2c1 Mon Sep 17 00:00:00 2001
From: csmoe <csmoe@msn.com>
Date: Fri, 22 May 2020 10:11:52 +0800
Subject: [PATCH 2/3] only try to suggest for try trait_ref

---
 src/libcore/ops/try.rs                                     | 1 +
 src/librustc_hir/lang_items.rs                             | 2 ++
 src/librustc_trait_selection/traits/error_reporting/mod.rs | 6 +++++-
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/libcore/ops/try.rs b/src/libcore/ops/try.rs
index 996a01d413cbc..e15ea11569f34 100644
--- a/src/libcore/ops/try.rs
+++ b/src/libcore/ops/try.rs
@@ -25,6 +25,7 @@
     )
 )]
 #[doc(alias = "?")]
+#[cfg_attr(not(bootstrap), lang = "try")]
 pub trait Try {
     /// The type of this value when viewed as successful.
     #[unstable(feature = "try_trait", issue = "42327")]
diff --git a/src/librustc_hir/lang_items.rs b/src/librustc_hir/lang_items.rs
index 53f72804a848d..8921cc0c99dca 100644
--- a/src/librustc_hir/lang_items.rs
+++ b/src/librustc_hir/lang_items.rs
@@ -256,4 +256,6 @@ language_item_table! {
     AlignOffsetLangItem,         "align_offset",       align_offset_fn,         Target::Fn;
 
     TerminationTraitLangItem,    "termination",        termination,             Target::Trait;
+
+    TryTraitLangItem,            "try",                try_trait,               Target::Trait;
 }
diff --git a/src/librustc_trait_selection/traits/error_reporting/mod.rs b/src/librustc_trait_selection/traits/error_reporting/mod.rs
index 139b860072224..f18a417cccd05 100644
--- a/src/librustc_trait_selection/traits/error_reporting/mod.rs
+++ b/src/librustc_trait_selection/traits/error_reporting/mod.rs
@@ -402,7 +402,11 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                         self.suggest_remove_reference(&obligation, &mut err, &trait_ref);
                         self.suggest_semicolon_removal(&obligation, &mut err, span, &trait_ref);
                         self.note_version_mismatch(&mut err, &trait_ref);
-                        self.suggest_await_before_try(&mut err, &obligation, &trait_ref, span);
+
+                        if Some(trait_ref.def_id()) == tcx.lang_items().try_trait() {
+                            self.suggest_await_before_try(&mut err, &obligation, &trait_ref, span);
+                        }
+
                         if self.suggest_impl_trait(&mut err, span, &obligation, &trait_ref) {
                             err.emit();
                             return;

From 16ba3e129d5d37c63b7000fcd4b52261e7f1c4f1 Mon Sep 17 00:00:00 2001
From: csmoe <csmoe@msn.com>
Date: Fri, 22 May 2020 10:12:03 +0800
Subject: [PATCH 3/3] bless issue-72442

---
 src/test/ui/async-await/issue-72442.rs     |  3 ++-
 src/test/ui/async-await/issue-72442.stderr | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 src/test/ui/async-await/issue-72442.stderr

diff --git a/src/test/ui/async-await/issue-72442.rs b/src/test/ui/async-await/issue-72442.rs
index cced1da48f693..61c8c8c1594d3 100644
--- a/src/test/ui/async-await/issue-72442.rs
+++ b/src/test/ui/async-await/issue-72442.rs
@@ -1,4 +1,5 @@
 // edition:2018
+// compile-flags:-Cincremental=tmp/issue-72442
 
 use std::fs::File;
 use std::future::Future;
@@ -9,7 +10,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         {
             let path = std::path::Path::new(".");
             let mut f = File::open(path.to_str())?;
-            //~^ ERROR the trait bound `std::option::Option<&str>: std::convert::AsRef<std::path::Path>` is not satisfied
+            //~^ ERROR the trait bound
             let mut src = String::new();
             f.read_to_string(&mut src)?;
             Ok(())
diff --git a/src/test/ui/async-await/issue-72442.stderr b/src/test/ui/async-await/issue-72442.stderr
new file mode 100644
index 0000000000000..5685433357871
--- /dev/null
+++ b/src/test/ui/async-await/issue-72442.stderr
@@ -0,0 +1,14 @@
+error[E0277]: the trait bound `std::option::Option<&str>: std::convert::AsRef<std::path::Path>` is not satisfied
+  --> $DIR/issue-72442.rs:12:36
+   |
+LL |             let mut f = File::open(path.to_str())?;
+   |                                    ^^^^^^^^^^^^^ the trait `std::convert::AsRef<std::path::Path>` is not implemented for `std::option::Option<&str>`
+   | 
+  ::: $SRC_DIR/libstd/fs.rs:LL:COL
+   |
+LL |     pub fn open<P: AsRef<Path>>(path: P) -> io::Result<File> {
+   |                    ----------- required by this bound in `std::fs::File::open`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.