inform user where to give a type annotation

src/librustc_typeck/check/method/probe.rs

@@ -337,7 +337,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                                 lint::builtin::TYVAR_BEHIND_RAW_POINTER,
                                 scope_expr_id,
                                 span,
-                                &format!("the type of this value must be known in this context"));
+                                &format!("type annotations needed"));
                         }
                     } else {
                         let t = self.structurally_resolved_type(span, final_ty);

src/librustc_typeck/check/mod.rs

@@ -5052,9 +5052,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             ty
         } else {
             if !self.is_tainted_by_errors() {
-                type_error_struct!(self.tcx.sess, sp, ty, E0619,
-                                    "the type of this value must be known in this context")
-                .emit();
+                self.need_type_info((**self).body_id, sp, ty);
             }
             self.demand_suptype(sp, self.tcx.types.err, ty);
             self.tcx.types.err

src/librustc_typeck/diagnostics.rs

@@ -4368,12 +4368,13 @@ i_am_a_function();
 "##,
 
 E0619: r##"
+#### Note: this error code is no longer emitted by the compiler.
 The type-checker needed to know the type of an expression, but that type had not
 yet been inferred.
 
 Erroneous code example:
 
-```compile_fail,E0619
+```compile_fail
 let mut x = vec![];
 match x.pop() {
     Some(v) => {

src/test/compile-fail/epoch-raw-pointer-method-2015.rs

@@ -18,6 +18,6 @@ fn main() {
     let x = 0;
     let y = &x as *const _;
     let _ = y.is_null();
-    //~^ error: the type of this value must be known in this context [tyvar_behind_raw_pointer]
+    //~^ error: type annotations needed [tyvar_behind_raw_pointer]
     //~^^ warning: this was previously accepted
 }

src/test/compile-fail/issue-15965.rs

@@ -11,7 +11,7 @@
 fn main() {
     return
         { return () }
-//~^ ERROR the type of this value must be known in this context
+//~^ ERROR type annotations needed [E0282]
     ()
     ;
 }

src/test/compile-fail/issue-2151.rs

@@ -10,5 +10,5 @@
 
 fn main() {
     let x = panic!();
-    x.clone(); //~ ERROR the type of this value must be known in this context
+    x.clone(); //~ ERROR type annotations needed
 }

src/test/compile-fail/match-vec-mismatch.rs

@@ -43,6 +43,6 @@ fn main() {
 fn another_fn_to_avoid_suppression() {
     match Default::default()
     {
-        [] => {}  //~ ERROR the type of this value
+        [] => {}  //~ ERROR type annotations needed
     };
 }

src/test/compile-fail/pat-tuple-bad-type.rs

@@ -12,7 +12,7 @@ fn main() {
     let x;
 
     match x {
-        (..) => {} //~ ERROR the type of this value must be known in this context
+        (..) => {} //~ ERROR type annotations needed
         _ => {}
     }
 

src/test/compile-fail/unboxed-closures-failed-recursive-fn-2.rs

@@ -24,7 +24,7 @@ fn a() {
                 match closure0.take() {
                     Some(c) => {
                         return c();
-                        //~^ ERROR the type of this value must be known in this context
+                        //~^ ERROR type annotations needed
                     }
                     None => { }
                 }

src/test/ui/inference-variable-behind-raw-pointer.stderr

@@ -1,4 +1,4 @@
-warning: the type of this value must be known in this context
+warning: type annotations needed
   --> $DIR/inference-variable-behind-raw-pointer.rs:18:13
    |
 18 |     if data.is_null() {}

src/test/ui/span/issue-42234-unknown-receiver-type.rs

@@ -15,11 +15,11 @@
 fn shines_a_beacon_through_the_darkness() {
     let x: Option<_> = None;
     x.unwrap().method_that_could_exist_on_some_type();
-    //~^ ERROR 17:5: 17:15: the type of this value must be known in this context
+    //~^ ERROR 17:5: 17:15: type annotations needed
 }
 
 fn courier_to_des_moines_and_points_west(data: &[u32]) -> String {
-    data.iter() //~ ERROR 22:5: 23:20: the type of this value must be known in this context
+    data.iter() //~ ERROR 22:5: 23:20: type annotations needed
         .sum::<_>()
         .to_string()
 }

src/test/ui/span/issue-42234-unknown-receiver-type.stderr

@@ -1,15 +1,17 @@
-error[E0619]: the type of this value must be known in this context
+error[E0282]: type annotations needed
   --> $DIR/issue-42234-unknown-receiver-type.rs:17:5
    |
+16 |     let x: Option<_> = None;
+   |         - consider giving `x` a type
 17 |     x.unwrap().method_that_could_exist_on_some_type();
-   |     ^^^^^^^^^^
+   |     ^^^^^^^^^^ cannot infer type for `T`
 
-error[E0619]: the type of this value must be known in this context
+error[E0282]: type annotations needed
   --> $DIR/issue-42234-unknown-receiver-type.rs:22:5
    |
-22 | /     data.iter() //~ ERROR 22:5: 23:20: the type of this value must be known in this context
+22 | /     data.iter() //~ ERROR 22:5: 23:20: type annotations needed
 23 | |         .sum::<_>()
-   | |___________________^
+   | |___________________^ cannot infer type for `_`
 
 error: aborting due to 2 previous errors