From 020be74f6bc5131b79a46d94a1111c35b187469a Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Thu, 19 Dec 2019 13:45:28 +0100
Subject: [PATCH 1/4] Clean up E0120 long explanation

---
 src/librustc_error_codes/error_codes/E0120.md | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/librustc_error_codes/error_codes/E0120.md b/src/librustc_error_codes/error_codes/E0120.md
index 99c2a493a46b9..4861ed8e89718 100644
--- a/src/librustc_error_codes/error_codes/E0120.md
+++ b/src/librustc_error_codes/error_codes/E0120.md
@@ -1,5 +1,7 @@
-An attempt was made to implement Drop on a trait, which is not allowed: only
-structs and enums can implement Drop. An example causing this error:
+The Drop was implemented on a trait, which is not allowed: only structs and
+enums can implement Drop.
+
+Erroneous code example:
 
 ```compile_fail,E0120
 trait MyTrait {}
@@ -10,7 +12,7 @@ impl Drop for MyTrait {
 ```
 
 A workaround for this problem is to wrap the trait up in a struct, and implement
-Drop on that. An example is shown below:
+Drop on that:
 
 ```
 trait MyTrait {}
@@ -22,7 +24,7 @@ impl <T: MyTrait> Drop for MyWrapper<T> {
 
 ```
 
-Alternatively, wrapping trait objects requires something like the following:
+Alternatively, wrapping trait objects requires something:
 
 ```
 trait MyTrait {}

From 94d207f4b27ba45b8d33e7e73d0829074a02117d Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume1.gomez@gmail.com>
Date: Thu, 19 Dec 2019 13:45:36 +0100
Subject: [PATCH 2/4] Clean up E0121 long explanation

---
 src/librustc_error_codes/error_codes/E0121.md | 24 +++++++++++++++----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/src/librustc_error_codes/error_codes/E0121.md b/src/librustc_error_codes/error_codes/E0121.md
index 069d0fc48fb0f..6c20b2803cbe3 100644
--- a/src/librustc_error_codes/error_codes/E0121.md
+++ b/src/librustc_error_codes/error_codes/E0121.md
@@ -1,10 +1,24 @@
-In order to be consistent with Rust's lack of global type inference,
-type and const placeholders are disallowed by design in item signatures.
+The type placeholder `_` was used withing a type on an item's signature.
 
-Examples of this error include:
+Erroneous code example:
 
 ```compile_fail,E0121
-fn foo() -> _ { 5 } // error, explicitly write out the return type instead
+fn foo() -> _ { 5 } // error
 
-static BAR: _ = "test"; // error, explicitly write out the type instead
+static BAR: _ = "test"; // error
+```
+
+In those cases, you need to provide the type explicitly:
+
+```
+fn foo() -> i32 { 5 } // ok!
+
+static BAR: &str = "test"; // ok!
+```
+
+The type placeholder `_` can be used outside item's signature as follows:
+
+```
+let x = "a4a".split('4')
+    .collect::<Vec<_>>(); // No need to precise the Vec's generic type.
 ```

From 7f0741db9e521355ab732601f4ab53d586748ad1 Mon Sep 17 00:00:00 2001
From: Dylan DPC <dylan.dpc@gmail.com>
Date: Fri, 20 Dec 2019 16:50:20 +0530
Subject: [PATCH 3/4] Update E0120.md

---
 src/librustc_error_codes/error_codes/E0120.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/librustc_error_codes/error_codes/E0120.md b/src/librustc_error_codes/error_codes/E0120.md
index 4861ed8e89718..dc7258d87317f 100644
--- a/src/librustc_error_codes/error_codes/E0120.md
+++ b/src/librustc_error_codes/error_codes/E0120.md
@@ -1,4 +1,4 @@
-The Drop was implemented on a trait, which is not allowed: only structs and
+Drop was implemented on a trait, which is not allowed: only structs and
 enums can implement Drop.
 
 Erroneous code example:

From dce0f06f953d4f0f46cc7ca108c55f326febc790 Mon Sep 17 00:00:00 2001
From: Dylan DPC <dylan.dpc@gmail.com>
Date: Fri, 20 Dec 2019 17:02:39 +0530
Subject: [PATCH 4/4] Update E0121.md

---
 src/librustc_error_codes/error_codes/E0121.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/librustc_error_codes/error_codes/E0121.md b/src/librustc_error_codes/error_codes/E0121.md
index 6c20b2803cbe3..06fe396d50d3b 100644
--- a/src/librustc_error_codes/error_codes/E0121.md
+++ b/src/librustc_error_codes/error_codes/E0121.md
@@ -1,4 +1,4 @@
-The type placeholder `_` was used withing a type on an item's signature.
+The type placeholder `_` was used within a type on an item's signature.
 
 Erroneous code example: