Add E0619 error explanation

Author: GuillaumeGomez

src/librustc_typeck/diagnostics.rs

@@ -4666,6 +4666,7 @@ i_am_a_function();
 "##,
 
 E0619: r##"
+<<<<<<< HEAD
 The type-checker needed to know the type of an expression, but that type had not
 yet been inferred.
 
@@ -4726,6 +4727,26 @@ let x = &[1_usize, 2] as &[usize]; // ok!
 ```
 "##,
 
+E0621: r##"
+An intrinsic was declared without being a function.
+
+Erroneous code example:
+
+```compile_fail,E0621
+#![feature(intrinsics)]
+extern "rust-intrinsic" {
+    pub static breakpoint : unsafe extern "rust-intrinsic" fn();
+    // error: intrinsic must be a function
+}
+
+fn main() { unsafe { breakpoint(); } }
+```
+
+An intrinsic is a function available for use in a given programming language
+whose implementation is handled specially by the compiler. In order to fix this
+error, just declare a function.
+"##,
+
 }
 
 register_diagnostics! {

src/test/compile-fail/E0619.rs

@@ -1,4 +1,4 @@
-// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -8,11 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-fn main() {
-    let x;
-
-    match x {
-        (..) => {} //~ ERROR E0619
-        _ => {}
-    }
+#![feature(intrinsics)]
+extern "rust-intrinsic" {
+    pub static breakpoint : unsafe extern "rust-intrinsic" fn();
+    //~^ ERROR intrinsic must be a function [E0619]
 }
+fn main() { unsafe { breakpoint(); } }