improve "Doesn't live long enough" error

src/librustc_borrowck/borrowck/mod.rs

@@ -1024,13 +1024,14 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
             }
 
             err_out_of_scope(super_scope, sub_scope, cause) => {
-                let (value_kind, value_msg) = match err.cmt.cat {
+                let (value_kind, value_msg, is_temporary) = match err.cmt.cat {
                     mc::Categorization::Rvalue(_) =>
-                        ("temporary value", "temporary value created here"),
+                        ("temporary value", "temporary value created here", true),
                     _ =>
-                        ("borrowed value", "does not live long enough")
+                        ("borrowed value", "does not live long enough", false)
                 };
-                match cause {
+
+                let is_closure = match cause {
                     euv::ClosureCapture(s) => {
                         // The primary span starts out as the closure creation point.
                         // Change the primary span here to highlight the use of the variable
@@ -1041,21 +1042,36 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                                 db.span = MultiSpan::from_span(s);
                                 db.span_label(primary, &format!("capture occurs here"));
                                 db.span_label(s, &value_msg);
+                                true
                             }
-                            None => ()
+                            None => false
                         }
                     }
                     _ => {
                         db.span_label(error_span, &value_msg);
+                        false
                     }
-                }
+                };
 
                 let sub_span = self.region_end_span(sub_scope);
                 let super_span = self.region_end_span(super_scope);
 
                 match (sub_span, super_span) {
                     (Some(s1), Some(s2)) if s1 == s2 => {
-                        db.span_label(s1, &format!("{} dropped before borrower", value_kind));
+                        if !is_temporary && !is_closure {
+                            db.span = MultiSpan::from_span(s1);
+                            db.span_label(error_span, &format!("borrow occurs here"));
+                            let msg = match opt_loan_path(&err.cmt) {
+                                None => "borrowed value".to_string(),
+                                Some(lp) => {
+                                    format!("`{}`", self.loan_path_to_string(&lp))
+                                }
+                            };
+                            db.span_label(s1,
+                                          &format!("{} dropped here while still borrowed", msg));
+                        } else {
+                            db.span_label(s1, &format!("{} dropped before borrower", value_kind));
+                        }
                         db.note("values in a scope are dropped in the opposite order \
                                 they are created");
                     }

src/test/compile-fail-fulldeps/dropck_tarena_cycle_checked.rs

@@ -123,5 +123,5 @@ fn f<'a>(arena: &'a TypedArena<C<'a>>) {
 
 fn main() {
     let arena = TypedArena::new();
-    f(&arena); //~ ERROR `arena` does not live long enough
-}
+    f(&arena);
+} //~ ERROR `arena` does not live long enough

src/test/compile-fail-fulldeps/dropck_tarena_unsound_drop.rs

@@ -46,5 +46,6 @@ fn f<'a>(_arena: &'a TypedArena<C<'a>>) {}
 
 fn main() {
     let arena: TypedArena<C> = TypedArena::new();
-    f(&arena); //~ ERROR `arena` does not live long enough
-}
+    f(&arena);
+} //~ ERROR `arena` does not live long enough
+

src/test/ui/dropck/dropck-eyepatch-extern-crate.stderr

@@ -1,44 +1,44 @@
 error: `c` does not live long enough
-  --> $DIR/dropck-eyepatch-extern-crate.rs:39:20
+  --> $DIR/dropck-eyepatch-extern-crate.rs:55:1
    |
 39 |     dt = Dt("dt", &c); //~ ERROR `c` does not live long enough
-   |                    ^ does not live long enough
+   |                    - borrow occurs here
 ...
 55 | }
-   | - borrowed value dropped before borrower
+   | ^ `c` dropped here while still borrowed
    |
    = note: values in a scope are dropped in the opposite order they are created
 
 error: `c` does not live long enough
-  --> $DIR/dropck-eyepatch-extern-crate.rs:40:20
+  --> $DIR/dropck-eyepatch-extern-crate.rs:55:1
    |
 40 |     dr = Dr("dr", &c); //~ ERROR `c` does not live long enough
-   |                    ^ does not live long enough
+   |                    - borrow occurs here
 ...
 55 | }
-   | - borrowed value dropped before borrower
+   | ^ `c` dropped here while still borrowed
    |
    = note: values in a scope are dropped in the opposite order they are created
 
 error: `c` does not live long enough
-  --> $DIR/dropck-eyepatch-extern-crate.rs:47:29
+  --> $DIR/dropck-eyepatch-extern-crate.rs:55:1
    |
 47 |     pt = Pt("pt", &c_long, &c); //~ ERROR `c` does not live long enough
-   |                             ^ does not live long enough
+   |                             - borrow occurs here
 ...
 55 | }
-   | - borrowed value dropped before borrower
+   | ^ `c` dropped here while still borrowed
    |
    = note: values in a scope are dropped in the opposite order they are created
 
 error: `c` does not live long enough
-  --> $DIR/dropck-eyepatch-extern-crate.rs:48:29
+  --> $DIR/dropck-eyepatch-extern-crate.rs:55:1
    |
 48 |     pr = Pr("pr", &c_long, &c); //~ ERROR `c` does not live long enough
-   |                             ^ does not live long enough
+   |                             - borrow occurs here
 ...
 55 | }
-   | - borrowed value dropped before borrower
+   | ^ `c` dropped here while still borrowed
    |
    = note: values in a scope are dropped in the opposite order they are created
 

src/test/ui/dropck/dropck-eyepatch-reorder.stderr

@@ -1,44 +1,44 @@
 error: `c` does not live long enough
-  --> $DIR/dropck-eyepatch-reorder.rs:57:20
+  --> $DIR/dropck-eyepatch-reorder.rs:73:1
    |
 57 |     dt = Dt("dt", &c); //~ ERROR `c` does not live long enough
-   |                    ^ does not live long enough
+   |                    - borrow occurs here
 ...
 73 | }
-   | - borrowed value dropped before borrower
+   | ^ `c` dropped here while still borrowed
    |
    = note: values in a scope are dropped in the opposite order they are created
 
 error: `c` does not live long enough
-  --> $DIR/dropck-eyepatch-reorder.rs:58:20
+  --> $DIR/dropck-eyepatch-reorder.rs:73:1
    |
 58 |     dr = Dr("dr", &c); //~ ERROR `c` does not live long enough
-   |                    ^ does not live long enough
+   |                    - borrow occurs here
 ...
 73 | }
-   | - borrowed value dropped before borrower
+   | ^ `c` dropped here while still borrowed
    |
    = note: values in a scope are dropped in the opposite order they are created
 
 error: `c` does not live long enough
-  --> $DIR/dropck-eyepatch-reorder.rs:65:29
+  --> $DIR/dropck-eyepatch-reorder.rs:73:1
    |
 65 |     pt = Pt("pt", &c_long, &c); //~ ERROR `c` does not live long enough
-   |                             ^ does not live long enough
+   |                             - borrow occurs here
 ...
 73 | }
-   | - borrowed value dropped before borrower
+   | ^ `c` dropped here while still borrowed
    |
    = note: values in a scope are dropped in the opposite order they are created
 
 error: `c` does not live long enough
-  --> $DIR/dropck-eyepatch-reorder.rs:66:29
+  --> $DIR/dropck-eyepatch-reorder.rs:73:1
    |
 66 |     pr = Pr("pr", &c_long, &c); //~ ERROR `c` does not live long enough
-   |                             ^ does not live long enough
+   |                             - borrow occurs here
 ...
 73 | }
-   | - borrowed value dropped before borrower
+   | ^ `c` dropped here while still borrowed
    |
    = note: values in a scope are dropped in the opposite order they are created
 

src/test/ui/dropck/dropck-eyepatch.stderr

@@ -1,44 +1,44 @@
 error: `c` does not live long enough
-  --> $DIR/dropck-eyepatch.rs:80:20
+  --> $DIR/dropck-eyepatch.rs:96:1
    |
 80 |     dt = Dt("dt", &c); //~ ERROR `c` does not live long enough
-   |                    ^ does not live long enough
+   |                    - borrow occurs here
 ...
 96 | }
-   | - borrowed value dropped before borrower
+   | ^ `c` dropped here while still borrowed
    |
    = note: values in a scope are dropped in the opposite order they are created
 
 error: `c` does not live long enough
-  --> $DIR/dropck-eyepatch.rs:81:20
+  --> $DIR/dropck-eyepatch.rs:96:1
    |
 81 |     dr = Dr("dr", &c); //~ ERROR `c` does not live long enough
-   |                    ^ does not live long enough
+   |                    - borrow occurs here
 ...
 96 | }
-   | - borrowed value dropped before borrower
+   | ^ `c` dropped here while still borrowed
    |
    = note: values in a scope are dropped in the opposite order they are created
 
 error: `c` does not live long enough
-  --> $DIR/dropck-eyepatch.rs:88:29
+  --> $DIR/dropck-eyepatch.rs:96:1
    |
 88 |     pt = Pt("pt", &c_long, &c); //~ ERROR `c` does not live long enough
-   |                             ^ does not live long enough
+   |                             - borrow occurs here
 ...
 96 | }
-   | - borrowed value dropped before borrower
+   | ^ `c` dropped here while still borrowed
    |
    = note: values in a scope are dropped in the opposite order they are created
 
 error: `c` does not live long enough
-  --> $DIR/dropck-eyepatch.rs:89:29
+  --> $DIR/dropck-eyepatch.rs:96:1
    |
 89 |     pr = Pr("pr", &c_long, &c); //~ ERROR `c` does not live long enough
-   |                             ^ does not live long enough
+   |                             - borrow occurs here
 ...
 96 | }
-   | - borrowed value dropped before borrower
+   | ^ `c` dropped here while still borrowed
    |
    = note: values in a scope are dropped in the opposite order they are created
 

src/test/compile-fail/borrowck/borrowck-let-suggestion-suffixes.rs → src/test/ui/span/borrowck-let-suggestion-suffixes.rs

@@ -17,9 +17,7 @@ fn f() {
     let young = ['y'];       // statement 3
 
     v2.push(&young[0]);      // statement 4
-    //~^ ERROR `young[..]` does not live long enough
-    //~| NOTE does not live long enough
-    //~| NOTE values in a scope are dropped in the opposite order they are created
+    //~^ NOTE borrow occurs here
 
     let mut v3 = Vec::new(); // statement 5
 
@@ -52,7 +50,9 @@ fn f() {
 
     v1.push(&old[0]);
 }
-//~^ NOTE borrowed value dropped before borrower
+//~^ ERROR `young[..]` does not live long enough
+//~| NOTE `young[..]` dropped here while still borrowed
+//~| NOTE values in a scope are dropped in the opposite order they are created
 //~| NOTE temporary value needs to live until here
 //~| NOTE temporary value needs to live until here
 

src/test/ui/span/borrowck-let-suggestion-suffixes.stderr

@@ -0,0 +1,52 @@
+error: `young[..]` does not live long enough
+  --> $DIR/borrowck-let-suggestion-suffixes.rs:52:1
+   |
+19 |     v2.push(&young[0]);      // statement 4
+   |              -------- borrow occurs here
+...
+52 | }
+   | ^ `young[..]` dropped here while still borrowed
+   |
+   = note: values in a scope are dropped in the opposite order they are created
+
+error: borrowed value does not live long enough
+  --> $DIR/borrowck-let-suggestion-suffixes.rs:24:14
+   |
+24 |     v3.push(&'x');           // statement 6
+   |              ^^^ - temporary value only lives until here
+   |              |
+   |              temporary value created here
+...
+52 | }
+   | - temporary value needs to live until here
+   |
+   = note: consider using a `let` binding to increase its lifetime
+
+error: borrowed value does not live long enough
+  --> $DIR/borrowck-let-suggestion-suffixes.rs:34:18
+   |
+34 |         v4.push(&'y');
+   |                  ^^^ - temporary value only lives until here
+   |                  |
+   |                  temporary value created here
+...
+40 |     }                       // (statement 7)
+   |     - temporary value needs to live until here
+   |
+   = note: consider using a `let` binding to increase its lifetime
+
+error: borrowed value does not live long enough
+  --> $DIR/borrowck-let-suggestion-suffixes.rs:45:14
+   |
+45 |     v5.push(&'z');
+   |              ^^^ - temporary value only lives until here
+   |              |
+   |              temporary value created here
+...
+52 | }
+   | - temporary value needs to live until here
+   |
+   = note: consider using a `let` binding to increase its lifetime
+
+error: aborting due to 4 previous errors
+

src/test/compile-fail/dropck-object-cycle.rs → src/test/ui/span/dropck-object-cycle.rs

@@ -35,7 +35,7 @@ impl<'t> MakerTrait for Box<Trait<'t>+'static> {
 pub fn main() {
     let m : Box<Trait+'static> = make_val();
     assert_eq!(object_invoke1(&*m), (4,5));
-    //~^ ERROR `*m` does not live long enough
+    //~^ NOTE borrow occurs here
 
     // the problem here is that the full type of `m` is
     //
@@ -55,3 +55,7 @@ pub fn main() {
     // the type of `m` *strictly outlives* `'m`. Hence we get an
     // error.
 }
+//~^ ERROR `*m` does not live long enough
+//~| NOTE `*m` dropped here while still borrowed
+//~| NOTE values in a scope are dropped in the opposite order they are created
+

src/test/ui/span/dropck-object-cycle.stderr

@@ -0,0 +1,13 @@
+error: `*m` does not live long enough
+  --> $DIR/dropck-object-cycle.rs:57:1
+   |
+37 |     assert_eq!(object_invoke1(&*m), (4,5));
+   |                                -- borrow occurs here
+...
+57 | }
+   | ^ `*m` dropped here while still borrowed
+   |
+   = note: values in a scope are dropped in the opposite order they are created
+
+error: aborting due to previous error
+

src/test/compile-fail/dropck_arr_cycle_checked.rs → src/test/ui/span/dropck_arr_cycle_checked.rs

@@ -100,13 +100,19 @@ fn f() {
     b1 = B::new();
     b2 = B::new();
     b3 = B::new();
-    b1.a[0].v.set(Some(&b2)); //~ ERROR `b2` does not live long enough
-    b1.a[1].v.set(Some(&b3)); //~ ERROR `b3` does not live long enough
-    b2.a[0].v.set(Some(&b2)); //~ ERROR `b2` does not live long enough
-    b2.a[1].v.set(Some(&b3)); //~ ERROR `b3` does not live long enough
-    b3.a[0].v.set(Some(&b1)); //~ ERROR `b1` does not live long enough
-    b3.a[1].v.set(Some(&b2)); //~ ERROR `b2` does not live long enough
+    b1.a[0].v.set(Some(&b2));
+    b1.a[1].v.set(Some(&b3));
+    b2.a[0].v.set(Some(&b2));
+    b2.a[1].v.set(Some(&b3));
+    b3.a[0].v.set(Some(&b1));
+    b3.a[1].v.set(Some(&b2));
 }
+//~^ ERROR `b2` does not live long enough
+//~| ERROR `b3` does not live long enough
+//~| ERROR `b2` does not live long enough
+//~| ERROR `b3` does not live long enough
+//~| ERROR `b1` does not live long enough
+//~| ERROR `b2` does not live long enough
 
 fn main() {
     f();