stop reporting "unsatisfied lifetime bounds" errors after the first

In particular, after the first for a given region variable. This
suppresses a lot of duplicate errors.

Author: nikomatsakis

src/librustc_mir/borrow_check/nll/region_infer/mod.rs

@@ -1208,6 +1208,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             // to report the error. This gives better error messages
             // in some cases.
             self.report_error(mir, infcx, mir_def_id, longer_fr, shorter_fr, errors_buffer);
+            return; // continuing to iterate just reports more errors than necessary
         }
     }
 

src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.rs

@@ -47,7 +47,6 @@ fn supply<'a, 'b>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) {
 
         // Only works if 'x: 'y:
         demand_y(x, y, x.get())
-        //~^ ERROR unsatisfied lifetime constraints
     });
 }
 

src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.stderr

@@ -7,7 +7,6 @@ LL | |         //~^ ERROR borrowed data escapes outside of function
 LL | |
 LL | |         // Only works if 'x: 'y:
 LL | |         demand_y(x, y, x.get())
-LL | |         //~^ ERROR unsatisfied lifetime constraints
 LL | |     });
    | |_____^
    |
@@ -44,21 +43,9 @@ LL | |         //~^ ERROR borrowed data escapes outside of function
 LL | |
 LL | |         // Only works if 'x: 'y:
 LL | |         demand_y(x, y, x.get())
-LL | |         //~^ ERROR unsatisfied lifetime constraints
 LL | |     });
    | |______^ `cell_a` escapes the function body here
 
-error: unsatisfied lifetime constraints
-  --> $DIR/propagate-approximated-shorter-to-static-no-bound.rs:49:9
-   |
-LL | fn supply<'a, 'b>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) {
-   |           --  -- lifetime `'b` defined here
-   |           |
-   |           lifetime `'a` defined here
-...
-LL |         demand_y(x, y, x.get())
-   |         ^^^^^^^^^^^^^^^^^^^^^^^ argument requires that `'a` must outlive `'b`
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0521`.

src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-wrong-bound.rs

@@ -47,9 +47,9 @@ fn demand_y<'x, 'y>(_cell_x: &Cell<&'x u32>, _cell_y: &Cell<&'y u32>, _y: &'y u3
 fn supply<'a, 'b>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) {
     establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y| {
         //~^ ERROR borrowed data escapes outside of function
+
         // Only works if 'x: 'y:
         demand_y(x, y, x.get())
-        //~^ ERROR unsatisfied lifetime constraints
     });
 }
 

src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-wrong-bound.stderr

@@ -4,9 +4,9 @@ note: External requirements
 LL |       establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y| {
    |  _______________________________________________^
 LL | |         //~^ ERROR borrowed data escapes outside of function
+LL | |
 LL | |         // Only works if 'x: 'y:
 LL | |         demand_y(x, y, x.get())
-LL | |         //~^ ERROR unsatisfied lifetime constraints
 LL | |     });
    | |_____^
    |
@@ -25,7 +25,7 @@ note: No external requirements
 LL | / fn supply<'a, 'b>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) {
 LL | |     establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y| {
 LL | |         //~^ ERROR borrowed data escapes outside of function
-LL | |         // Only works if 'x: 'y:
+LL | |
 ...  |
 LL | |     });
 LL | | }
@@ -40,23 +40,12 @@ LL |   fn supply<'a, 'b>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) {
    |                     ------ `cell_a` is a reference that is only valid in the function body
 LL | /     establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y| {
 LL | |         //~^ ERROR borrowed data escapes outside of function
+LL | |
 LL | |         // Only works if 'x: 'y:
 LL | |         demand_y(x, y, x.get())
-LL | |         //~^ ERROR unsatisfied lifetime constraints
 LL | |     });
    | |______^ `cell_a` escapes the function body here
 
-error: unsatisfied lifetime constraints
-  --> $DIR/propagate-approximated-shorter-to-static-wrong-bound.rs:51:9
-   |
-LL | fn supply<'a, 'b>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) {
-   |           --  -- lifetime `'b` defined here
-   |           |
-   |           lifetime `'a` defined here
-...
-LL |         demand_y(x, y, x.get())
-   |         ^^^^^^^^^^^^^^^^^^^^^^^ argument requires that `'a` must outlive `'b`
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0521`.

src/test/ui/nll/user-annotations/closure-substs.rs

@@ -23,8 +23,6 @@ fn foo1() {
     // Here `x` is bound in the closure sig:
     |x: &i32| -> &'static i32 {
         return x; //~ ERROR unsatisfied lifetime constraints
-        //~^ ERROR unsatisfied lifetime constraints
-        //~| ERROR unsatisfied lifetime constraints
     };
 }
 
@@ -38,9 +36,7 @@ fn bar<'a>() {
 fn bar1() {
     // Here `x` is bound in the closure sig:
     |x: &i32, b: fn(&'static i32)| {
-        b(x); //~ ERROR
-        //~^ ERROR borrowed data escapes outside of closure
-        //~| ERROR unsatisfied lifetime constraints
+        b(x); //~ ERROR borrowed data escapes outside of closure
     };
 }
 

src/test/ui/nll/user-annotations/closure-substs.stderr

@@ -16,67 +16,22 @@ LL |         return x; //~ ERROR unsatisfied lifetime constraints
    |                ^ returning this value requires that `'1` must outlive `'static`
 
 error: unsatisfied lifetime constraints
-  --> $DIR/closure-substs.rs:25:16
-   |
-LL |     |x: &i32| -> &'static i32 {
-   |         -                   - return type of closure is &'2 i32
-   |         |
-   |         let's call the lifetime of this reference `'1`
-LL |         return x; //~ ERROR unsatisfied lifetime constraints
-   |                ^ returning this value requires that `'1` must outlive `'2`
-
-error: unsatisfied lifetime constraints
-  --> $DIR/closure-substs.rs:25:16
-   |
-LL |     |x: &i32| -> &'static i32 {
-   |     -------------------------
-   |     |   |
-   |     |   let's call the lifetime of this reference `'1`
-   |     lifetime `'2` represents this closure's body
-LL |         return x; //~ ERROR unsatisfied lifetime constraints
-   |                ^ closure was supposed to return data with lifetime `'2` but it is returning data with lifetime `'1`
-   |
-   = note: closure implements `Fn`, so references to captured variables can't escape the closure
-
-error: unsatisfied lifetime constraints
-  --> $DIR/closure-substs.rs:34:9
+  --> $DIR/closure-substs.rs:32:9
    |
 LL | fn bar<'a>() {
    |        -- lifetime `'a` defined here
 ...
 LL |         b(x); //~ ERROR unsatisfied lifetime constraints
    |         ^^^^ argument requires that `'a` must outlive `'static`
 
-error: borrowed data escapes outside of closure
-  --> $DIR/closure-substs.rs:41:9
+error[E0521]: borrowed data escapes outside of closure
+  --> $DIR/closure-substs.rs:39:9
    |
 LL |     |x: &i32, b: fn(&'static i32)| {
    |      - `x` is a reference that is only valid in the closure body
-LL |         b(x); //~ ERROR
-   |         ^^^^ `x` escapes the closure body here
-
-error: borrowed data escapes outside of closure
-  --> $DIR/closure-substs.rs:41:9
-   |
-LL |     |x: &i32, b: fn(&'static i32)| {
-   |      -        - `b` is declared here, outside of the closure body
-   |      |
-   |      `x` is a reference that is only valid in the closure body
-LL |         b(x); //~ ERROR
+LL |         b(x); //~ ERROR borrowed data escapes outside of closure
    |         ^^^^ `x` escapes the closure body here
 
-error: unsatisfied lifetime constraints
-  --> $DIR/closure-substs.rs:41:9
-   |
-LL |     |x: &i32, b: fn(&'static i32)| {
-   |     ------------------------------
-   |     |   |
-   |     |   let's call the lifetime of this reference `'1`
-   |     lifetime `'2` represents this closure's body
-LL |         b(x); //~ ERROR
-   |         ^^^^ argument requires that `'1` must outlive `'2`
-   |
-   = note: closure implements `Fn`, so references to captured variables can't escape the closure
-
-error: aborting due to 8 previous errors
+error: aborting due to 4 previous errors
 
+For more information about this error, try `rustc --explain E0521`.

src/test/ui/regions/regions-static-bound.ll.stderr

@@ -20,7 +20,7 @@ LL |     static_id(&u); //[ll]~ ERROR explicit lifetime required in the type of
    |     ^^^^^^^^^ lifetime `'static` required
 
 error[E0621]: explicit lifetime required in the type of `v`
-  --> $DIR/regions-static-bound.rs:27:5
+  --> $DIR/regions-static-bound.rs:26:5
    |
 LL | fn error(u: &(), v: &()) {
    |                     --- help: add explicit lifetime `'static` to the type of `v`: `&'static ()`

src/test/ui/regions/regions-static-bound.nll.stderr

@@ -15,35 +15,14 @@ LL |     static_id(&u); //[ll]~ ERROR explicit lifetime required in the type of
    |     ^^^^^^^^^^^^^ lifetime `'static` required
 
 error[E0621]: explicit lifetime required in the type of `v`
-  --> $DIR/regions-static-bound.rs:27:5
+  --> $DIR/regions-static-bound.rs:26:5
    |
 LL | fn error(u: &(), v: &()) {
    |                     --- help: add explicit lifetime `'static` to the type of `v`: `&'static ()`
 ...
 LL |     static_id_indirect(&v); //[ll]~ ERROR explicit lifetime required in the type of `v` [E0621]
    |     ^^^^^^^^^^^^^^^^^^^^^^ lifetime `'static` required
 
-error: unsatisfied lifetime constraints
-  --> $DIR/regions-static-bound.rs:24:5
-   |
-LL | fn error(u: &(), v: &()) {
-   |             -       - let's call the lifetime of this reference `'2`
-   |             |
-   |             let's call the lifetime of this reference `'1`
-LL |     static_id(&u); //[ll]~ ERROR explicit lifetime required in the type of `u` [E0621]
-   |     ^^^^^^^^^^^^^ argument requires that `'1` must outlive `'2`
-
-error: unsatisfied lifetime constraints
-  --> $DIR/regions-static-bound.rs:27:5
-   |
-LL | fn error(u: &(), v: &()) {
-   |             -       - let's call the lifetime of this reference `'1`
-   |             |
-   |             let's call the lifetime of this reference `'2`
-...
-LL |     static_id_indirect(&v); //[ll]~ ERROR explicit lifetime required in the type of `v` [E0621]
-   |     ^^^^^^^^^^^^^^^^^^^^^^ argument requires that `'1` must outlive `'2`
-
-error: aborting due to 5 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0621`.

src/test/ui/regions/regions-static-bound.rs

@@ -23,10 +23,8 @@ fn static_id_wrong_way<'a>(t: &'a ()) -> &'static () where 'static: 'a {
 fn error(u: &(), v: &()) {
     static_id(&u); //[ll]~ ERROR explicit lifetime required in the type of `u` [E0621]
     //[nll]~^ ERROR explicit lifetime required in the type of `u` [E0621]
-    //[nll]~| ERROR unsatisfied lifetime constraints
     static_id_indirect(&v); //[ll]~ ERROR explicit lifetime required in the type of `v` [E0621]
     //[nll]~^ ERROR explicit lifetime required in the type of `v` [E0621]
-    //[nll]~| ERROR unsatisfied lifetime constraints
 }
 
 fn main() {}