From 53187c5753e09006f0e03799ab01d7cb7ec676c7 Mon Sep 17 00:00:00 2001
From: phosphorus <steepout@qq.com>
Date: Fri, 11 Oct 2019 20:16:09 +0800
Subject: [PATCH] Slides path lifetime to the lifetime resolver

add test to for the fix

add descriptive text for the fix

simplified code logics

update descriptive comments

update to cope with the tidyness requirement

merged commit suggestions

Co-Authored-By: varkor <github@varkor.com>

truncated redundant comments

update to cope with tidy-check
---
 src/librustc/hir/lowering.rs                  | 12 +++++++----
 ...incorrect-explicit-lifetime-name-needed.rs | 14 +++++++++++++
 ...rrect-explicit-lifetime-name-needed.stderr | 21 +++++++++++++++++++
 3 files changed, 43 insertions(+), 4 deletions(-)
 create mode 100644 src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.rs
 create mode 100644 src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.stderr

diff --git a/src/librustc/hir/lowering.rs b/src/librustc/hir/lowering.rs
index 72fd054ee8a..ecf16d94430 100644
--- a/src/librustc/hir/lowering.rs
+++ b/src/librustc/hir/lowering.rs
@@ -3281,10 +3281,14 @@ impl<'a> LoweringContext<'a> {
                 let id = self.sess.next_node_id();
                 self.new_named_lifetime(id, span, hir::LifetimeName::Error)
             }
-            // This is the normal case.
-            AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span),
-
-            AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span),
+            // `PassThrough` is the normal case.
+            // `new_error_lifetime`, which would usually be used in the case of `ReportError`,
+            // is unsuitable here, as these can occur from missing lifetime parameters in a
+            // `PathSegment`, for which there is no associated `'_` or `&T` with no explicit
+            // lifetime. Instead, we simply create an implicit lifetime, which will be checked
+            // later, at which point a suitable error will be emitted.
+          | AnonymousLifetimeMode::PassThrough
+          | AnonymousLifetimeMode::ReportError => self.new_implicit_lifetime(span),
         }
     }
 
diff --git a/src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.rs b/src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.rs
new file mode 100644
index 00000000000..54b483f53d4
--- /dev/null
+++ b/src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.rs
@@ -0,0 +1,14 @@
+#![crate_type="lib"]
+
+struct Nested<K>(K);
+
+fn should_error<T>() where T : Into<&u32> {}
+//~^ ERROR `&` without an explicit lifetime name cannot be used here [E0637]
+
+trait X<'a, K: 'a> {
+    fn foo<'b, L: X<&'b Nested<K>>>();
+    //~^ ERROR missing lifetime specifier [E0106]
+}
+
+fn bar<'b, L: X<&'b Nested<i32>>>(){}
+//~^ ERROR missing lifetime specifier [E0106]
diff --git a/src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.stderr b/src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.stderr
new file mode 100644
index 00000000000..8720288b53e
--- /dev/null
+++ b/src/test/ui/generics/issue-65285-incorrect-explicit-lifetime-name-needed.stderr
@@ -0,0 +1,21 @@
+error[E0637]: `&` without an explicit lifetime name cannot be used here
+  --> $DIR/issue-65285-incorrect-explicit-lifetime-name-needed.rs:5:37
+   |
+LL | fn should_error<T>() where T : Into<&u32> {}
+   |                                     ^ explicit lifetime name needed here
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/issue-65285-incorrect-explicit-lifetime-name-needed.rs:9:19
+   |
+LL |     fn foo<'b, L: X<&'b Nested<K>>>();
+   |                   ^^^^^^^^^^^^^^^^ expected lifetime parameter
+
+error[E0106]: missing lifetime specifier
+  --> $DIR/issue-65285-incorrect-explicit-lifetime-name-needed.rs:13:15
+   |
+LL | fn bar<'b, L: X<&'b Nested<i32>>>(){}
+   |               ^^^^^^^^^^^^^^^^^^ expected lifetime parameter
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0106`.