From a12ebd3027e9c2b63f3d94c122c9d95d2d3ac739 Mon Sep 17 00:00:00 2001
From: Matthew Jasper <mjjasper1@gmail.com>
Date: Thu, 2 Apr 2020 20:31:51 +0100
Subject: [PATCH] unerase regions in `infer_placeholder_type`

---
 src/librustc_typeck/collect/type_of.rs       |  6 +++++-
 src/test/ui/suggestions/const-no-type.rs     |  5 +++++
 src/test/ui/suggestions/const-no-type.stderr | 12 +++++++++---
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/src/librustc_typeck/collect/type_of.rs b/src/librustc_typeck/collect/type_of.rs
index 1d34a58fabb31..e6099b98dc82b 100644
--- a/src/librustc_typeck/collect/type_of.rs
+++ b/src/librustc_typeck/collect/type_of.rs
@@ -655,7 +655,11 @@ fn infer_placeholder_type(
         }
     }
 
-    ty
+    // Typeck doesn't expect erased regions to be returned from `type_of`.
+    tcx.fold_regions(&ty, &mut false, |r, _| match r {
+        ty::ReErased => tcx.lifetimes.re_static,
+        _ => r,
+    })
 }
 
 fn report_assoc_ty_on_inherent_impl(tcx: TyCtxt<'_>, span: Span) {
diff --git a/src/test/ui/suggestions/const-no-type.rs b/src/test/ui/suggestions/const-no-type.rs
index 6b79697e9839e..b931a04c2860c 100644
--- a/src/test/ui/suggestions/const-no-type.rs
+++ b/src/test/ui/suggestions/const-no-type.rs
@@ -35,6 +35,11 @@ const C = 42;
 //~| HELP provide a type for the item
 //~| SUGGESTION C: i32
 
+const D = &&42;
+//~^ ERROR missing type for `const` item
+//~| HELP provide a type for the item
+//~| SUGGESTION D: &&i32
+
 static S = Vec::<String>::new();
 //~^ ERROR missing type for `static` item
 //~| HELP provide a type for the item
diff --git a/src/test/ui/suggestions/const-no-type.stderr b/src/test/ui/suggestions/const-no-type.stderr
index a7b5aa5e5b124..874c1bac10bd5 100644
--- a/src/test/ui/suggestions/const-no-type.stderr
+++ b/src/test/ui/suggestions/const-no-type.stderr
@@ -4,14 +4,20 @@ error: missing type for `const` item
 LL | const C = 42;
    |       ^ help: provide a type for the item: `C: i32`
 
+error: missing type for `const` item
+  --> $DIR/const-no-type.rs:38:7
+   |
+LL | const D = &&42;
+   |       ^ help: provide a type for the item: `D: &&i32`
+
 error: missing type for `static` item
-  --> $DIR/const-no-type.rs:38:8
+  --> $DIR/const-no-type.rs:43:8
    |
 LL | static S = Vec::<String>::new();
    |        ^ help: provide a type for the item: `S: std::vec::Vec<std::string::String>`
 
 error: missing type for `static mut` item
-  --> $DIR/const-no-type.rs:43:12
+  --> $DIR/const-no-type.rs:48:12
    |
 LL | static mut SM = "abc";
    |            ^^ help: provide a type for the item: `SM: &str`
@@ -34,5 +40,5 @@ error: missing type for `static mut` item
 LL | static mut SM2 = "abc";
    |            ^^^ help: provide a type for the item: `SM2: <type>`
 
-error: aborting due to 6 previous errors
+error: aborting due to 7 previous errors