From 2983d9c154576dc5332d8870c39a2478d6b9f24d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Mon, 4 Mar 2019 21:30:07 -0800
Subject: [PATCH] Elide invalid method receiver error when it contains TyErr

Fix #58712.
---
 src/librustc_typeck/check/wfcheck.rs  |  4 +++-
 src/test/ui/issues/issue-58712.rs     | 15 +++++++++++++++
 src/test/ui/issues/issue-58712.stderr | 15 +++++++++++++++
 3 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 src/test/ui/issues/issue-58712.rs
 create mode 100644 src/test/ui/issues/issue-58712.stderr

diff --git a/src/librustc_typeck/check/wfcheck.rs b/src/librustc_typeck/check/wfcheck.rs
index b7c862a89a1b4..1c764b7248986 100644
--- a/src/librustc_typeck/check/wfcheck.rs
+++ b/src/librustc_typeck/check/wfcheck.rs
@@ -842,7 +842,9 @@ fn receiver_is_valid<'fcx, 'tcx, 'gcx>(
         } else {
             debug!("receiver_is_valid: type `{:?}` does not deref to `{:?}`",
                 receiver_ty, self_ty);
-            return false
+            // If he receiver already has errors reported due to it, consider it valid to avoid
+            // unecessary errors (#58712).
+            return receiver_ty.references_error();
         }
 
         // without the `arbitrary_self_types` feature, `receiver_ty` must directly deref to
diff --git a/src/test/ui/issues/issue-58712.rs b/src/test/ui/issues/issue-58712.rs
new file mode 100644
index 0000000000000..577709cf2919d
--- /dev/null
+++ b/src/test/ui/issues/issue-58712.rs
@@ -0,0 +1,15 @@
+struct AddrVec<H, A> {
+    h: H,
+    a: A,
+}
+
+impl<H> AddrVec<H, DeviceId> {
+    //~^ ERROR cannot find type `DeviceId` in this scope
+    pub fn device(&self) -> DeviceId {
+    //~^ ERROR cannot find type `DeviceId` in this scope
+        self.tail()
+    }
+}
+
+fn main() {}
+
diff --git a/src/test/ui/issues/issue-58712.stderr b/src/test/ui/issues/issue-58712.stderr
new file mode 100644
index 0000000000000..6164ad7ee19b2
--- /dev/null
+++ b/src/test/ui/issues/issue-58712.stderr
@@ -0,0 +1,15 @@
+error[E0412]: cannot find type `DeviceId` in this scope
+  --> $DIR/issue-58712.rs:6:20
+   |
+LL | impl<H> AddrVec<H, DeviceId> {
+   |                    ^^^^^^^^ not found in this scope
+
+error[E0412]: cannot find type `DeviceId` in this scope
+  --> $DIR/issue-58712.rs:8:29
+   |
+LL |     pub fn device(&self) -> DeviceId {
+   |                             ^^^^^^^^ not found in this scope
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0412`.