Update E0207 to use struct_span_err, add span_label

src/librustc_typeck/collect.rs

@@ -2314,8 +2314,12 @@ fn report_unused_parameter(ccx: &CrateCtxt,
                            kind: &str,
                            name: &str)
 {
-    span_err!(ccx.tcx.sess, span, E0207,
-              "the {} parameter `{}` is not constrained by the \
-               impl trait, self type, or predicates",
-              kind, name);
+    struct_span_err!(
+        ccx.tcx.sess, span, E0207,
+        "the {} parameter `{}` is not constrained by the \
+        impl trait, self type, or predicates",
+        kind, name)
+        .span_label(span, &format!("unconstrained lifetime parameter"))
+        .emit();
+
 }

src/test/compile-fail/E0207.rs

@@ -11,6 +11,7 @@
 struct Foo;
 
 impl<T: Default> Foo { //~ ERROR E0207
+                       //~| NOTE unconstrained lifetime parameter
     fn get(&self) -> T {
         <T as Default>::default()
     }

src/test/compile-fail/impl-unused-rps-in-assoc-type.rs

@@ -19,6 +19,7 @@ trait Fun {
 struct Holder { x: String }
 
 impl<'a> Fun for Holder { //~ ERROR E0207
+                          //~| NOTE unconstrained lifetime parameter
     type Output = &'a str;
     fn call<'b>(&'b self) -> &'b str {
         &self.x[..]

src/test/compile-fail/issue-22886.rs

@@ -21,6 +21,7 @@ fn crash_please() {
 struct Newtype(Option<Box<usize>>);
 
 impl<'a> Iterator for Newtype { //~ ERROR E0207
+                                //~| NOTE unconstrained lifetime parameter
     type Item = &'a Box<usize>;
 
     fn next(&mut self) -> Option<&Box<usize>> {

src/test/compile-fail/issue-35139.rs

@@ -17,6 +17,7 @@ pub trait MethodType {
 pub struct MTFn;
 
 impl<'a> MethodType for MTFn { //~ ERROR E0207
+                               //~| NOTE unconstrained lifetime parameter
     type GetProp = fmt::Debug + 'a;
 }