Updated error message E0282

Author: Adam Medziński

src/librustc/traits/error_reporting.rs

@@ -870,10 +870,12 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
 
     fn need_type_info(&self, span: Span, ty: Ty<'tcx>) {
-        span_err!(self.tcx.sess, span, E0282,
-                  "unable to infer enough type information about `{}`; \
-                   type annotations or generic parameter binding required",
-                  ty);
+        let mut err = struct_span_err!(self.tcx.sess, span, E0282,
+                                       "unable to infer enough type information about `{}`",
+                                       ty);
+        err.note("type annotations or generic parameter binding required");
+        err.span_label(span, &format!("cannot infer type for `{}`", ty));
+        err.emit()
     }
 
     fn note_obligation_cause<T>(&self,

src/test/compile-fail/issue-12187-1.rs

@@ -14,5 +14,7 @@ fn new<T>() -> &'static T {
 
 fn main() {
     let &v = new();
-    //~^ ERROR type annotations or generic parameter binding required
+    //~^ ERROR unable to infer enough type information about `_` [E0282]
+    //~| NOTE cannot infer type for `_`
+    //~| NOTE type annotations or generic parameter binding
 }

src/test/compile-fail/issue-12187-2.rs

@@ -14,5 +14,7 @@ fn new<'r, T>() -> &'r T {
 
 fn main() {
     let &v = new();
-    //~^ ERROR type annotations or generic parameter binding required
+    //~^ ERROR unable to infer enough type information about `_` [E0282]
+    //~| NOTE cannot infer type for `_`
+    //~| NOTE type annotations or generic parameter binding
 }

src/test/compile-fail/issue-23041.rs

@@ -14,4 +14,6 @@ fn main()
     fn bar(x:i32) ->i32 { 3*x };
     let b:Box<Any> = Box::new(bar as fn(_)->_);
     b.downcast_ref::<fn(_)->_>(); //~ ERROR E0282
+                                  //~| NOTE cannot infer type for `_`
+                                  //~| NOTE type annotations or generic parameter binding required
 }

src/test/compile-fail/issue-5062.rs

@@ -9,4 +9,4 @@
 // except according to those terms.
 
 fn main() { format!("{:?}", None); }
-    //~^ ERROR type annotations or generic parameter binding required
+    //~^ ERROR unable to infer enough type information about `_` [E0282]

src/test/compile-fail/issue-6458-2.rs

@@ -11,5 +11,5 @@
 fn main() {
     // Unconstrained type:
     format!("{:?}", None);
-    //~^ ERROR type annotations or generic parameter binding required
+    //~^ ERROR unable to infer enough type information about `_` [E0282]
 }

src/test/compile-fail/issue-6458-3.rs

@@ -12,5 +12,7 @@ use std::mem;
 
 fn main() {
     mem::transmute(0);
-    //~^ ERROR type annotations or generic parameter binding required
+    //~^ ERROR unable to infer enough type information about `_` [E0282]
+    //~| NOTE cannot infer type for `_`
+    //~| NOTE type annotations or generic parameter binding
 }

src/test/compile-fail/issue-6458-4.rs

@@ -10,7 +10,9 @@
 
 fn foo(b: bool) -> Result<bool,String> {
     Err("bar".to_string());
-    //~^ ERROR type annotations or generic parameter binding required
+    //~^ ERROR unable to infer enough type information about `_` [E0282]
+    //~| NOTE cannot infer type for `_`
+    //~| NOTE type annotations or generic parameter binding
 }
 
 fn main() {

src/test/compile-fail/issue-6458.rs

@@ -17,7 +17,9 @@ pub fn foo<State>(_: TypeWithState<State>) {}
 
 pub fn bar() {
    foo(TypeWithState(marker::PhantomData));
-   //~^ ERROR type annotations or generic parameter binding required
+   //~^ ERROR unable to infer enough type information about `_` [E0282]
+   //~| NOTE cannot infer type for `_`
+   //~| NOTE type annotations or generic parameter binding
 }
 
 fn main() {

src/test/compile-fail/issue-7813.rs

@@ -10,5 +10,7 @@
 
 fn main() {
     let v = &[];
-    let it = v.iter(); //~ ERROR type annotations or generic parameter binding required
+    let it = v.iter(); //~ ERROR unable to infer enough type information about `_` [E0282]
+                       //~| NOTE cannot infer type for `_`
+                       //~| NOTE type annotations or generic parameter binding
 }