On long E0277 primary span label, move it to a help

Long span labels don't read well.

Author: estebank

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -328,6 +328,11 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             }
                         } else if let Some(custom_explanation) = safe_transmute_explanation {
                             err.span_label(span, custom_explanation);
+                        } else if explanation.len() > self.tcx.sess.diagnostic_width() {
+                            // Really long types don't look good as span labels, instead move it
+                            // to a `help`.
+                            err.span_label(span, "unsatisfied trait bound");
+                            err.help(explanation);
                         } else {
                             err.span_label(span, explanation);
                         }

tests/ui/async-await/async-closures/not-clone-closure.stderr

@@ -2,8 +2,9 @@ error[E0277]: the trait bound `NotClonableUpvar: Clone` is not satisfied in `{as
   --> $DIR/not-clone-closure.rs:32:15
    |
 LL |     not_clone.clone();
-   |               ^^^^^ within `{async closure@$DIR/not-clone-closure.rs:29:21: 29:34}`, the trait `Clone` is not implemented for `NotClonableUpvar`
+   |               ^^^^^ unsatisfied trait bound
    |
+   = help: within `{async closure@$DIR/not-clone-closure.rs:29:21: 29:34}`, the trait `Clone` is not implemented for `NotClonableUpvar`
 note: required because it's used within this closure
   --> $DIR/not-clone-closure.rs:29:21
    |

tests/ui/async-await/coroutine-not-future.stderr

@@ -30,10 +30,11 @@ error[E0277]: the trait bound `{async block@$DIR/coroutine-not-future.rs:39:21:
   --> $DIR/coroutine-not-future.rs:39:21
    |
 LL |     takes_coroutine(async {});
-   |     --------------- ^^^^^^^^ the trait `Coroutine<_>` is not implemented for `{async block@$DIR/coroutine-not-future.rs:39:21: 39:26}`
+   |     --------------- ^^^^^^^^ unsatisfied trait bound
    |     |
    |     required by a bound introduced by this call
    |
+   = help: the trait `Coroutine<_>` is not implemented for `{async block@$DIR/coroutine-not-future.rs:39:21: 39:26}`
 note: required by a bound in `takes_coroutine`
   --> $DIR/coroutine-not-future.rs:19:39
    |

tests/ui/const-generics/adt_const_params/const_param_ty_bad.stderr

@@ -20,10 +20,11 @@ error[E0277]: `{closure@$DIR/const_param_ty_bad.rs:8:11: 8:13}` can't be used as
   --> $DIR/const_param_ty_bad.rs:8:11
    |
 LL |     check(|| {});
-   |     ----- ^^^^^ the trait `UnsizedConstParamTy` is not implemented for closure `{closure@$DIR/const_param_ty_bad.rs:8:11: 8:13}`
+   |     ----- ^^^^^ unsatisfied trait bound
    |     |
    |     required by a bound introduced by this call
    |
+   = help: the trait `UnsizedConstParamTy` is not implemented for closure `{closure@$DIR/const_param_ty_bad.rs:8:11: 8:13}`
 note: required by a bound in `check`
   --> $DIR/const_param_ty_bad.rs:4:18
    |

tests/ui/coroutine/clone-impl.stderr

@@ -25,8 +25,9 @@ LL |     move || {
    |     ------- within this `{coroutine@$DIR/clone-impl.rs:43:5: 43:12}`
 ...
 LL |     check_copy(&gen_clone_0);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^ within `{coroutine@$DIR/clone-impl.rs:43:5: 43:12}`, the trait `Copy` is not implemented for `Vec<char>`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
    |
+   = help: within `{coroutine@$DIR/clone-impl.rs:43:5: 43:12}`, the trait `Copy` is not implemented for `Vec<char>`
 note: coroutine does not implement `Copy` as this value is used across a yield
   --> $DIR/clone-impl.rs:45:9
    |
@@ -67,8 +68,9 @@ LL |     move || {
    |     ------- within this `{coroutine@$DIR/clone-impl.rs:58:5: 58:12}`
 ...
 LL |     check_copy(&gen_clone_1);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^ within `{coroutine@$DIR/clone-impl.rs:58:5: 58:12}`, the trait `Copy` is not implemented for `Vec<char>`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
    |
+   = help: within `{coroutine@$DIR/clone-impl.rs:58:5: 58:12}`, the trait `Copy` is not implemented for `Vec<char>`
 note: coroutine does not implement `Copy` as this value is used across a yield
   --> $DIR/clone-impl.rs:64:9
    |
@@ -115,8 +117,9 @@ LL |     move || {
    |     ------- within this `{coroutine@$DIR/clone-impl.rs:79:5: 79:12}`
 ...
 LL |     check_clone(&gen_non_clone);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ within `{coroutine@$DIR/clone-impl.rs:79:5: 79:12}`, the trait `Clone` is not implemented for `NonClone`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
    |
+   = help: within `{coroutine@$DIR/clone-impl.rs:79:5: 79:12}`, the trait `Clone` is not implemented for `NonClone`
 note: captured value does not implement `Clone`
   --> $DIR/clone-impl.rs:81:14
    |

tests/ui/coroutine/issue-105084.stderr

@@ -29,8 +29,9 @@ LL |     || {
    |     -- within this `{coroutine@$DIR/issue-105084.rs:15:5: 15:7}`
 ...
 LL |     let mut h = copy(g);
-   |                 ^^^^^^^ within `{coroutine@$DIR/issue-105084.rs:15:5: 15:7}`, the trait `Copy` is not implemented for `Box<(i32, ())>`
+   |                 ^^^^^^^ unsatisfied trait bound
    |
+   = help: within `{coroutine@$DIR/issue-105084.rs:15:5: 15:7}`, the trait `Copy` is not implemented for `Box<(i32, ())>`
 note: coroutine does not implement `Copy` as this value is used across a yield
   --> $DIR/issue-105084.rs:22:22
    |

tests/ui/suggestions/fn-ctor-passed-as-arg-where-it-should-have-been-called.stderr

@@ -20,10 +20,11 @@ error[E0277]: the trait bound `{closure@$DIR/fn-ctor-passed-as-arg-where-it-shou
   --> $DIR/fn-ctor-passed-as-arg-where-it-should-have-been-called.rs:19:9
    |
 LL |     bar(closure);
-   |     --- ^^^^^^^ the trait `T` is not implemented for closure `{closure@$DIR/fn-ctor-passed-as-arg-where-it-should-have-been-called.rs:18:19: 18:21}`
+   |     --- ^^^^^^^ unsatisfied trait bound
    |     |
    |     required by a bound introduced by this call
    |
+   = help: the trait `T` is not implemented for closure `{closure@$DIR/fn-ctor-passed-as-arg-where-it-should-have-been-called.rs:18:19: 18:21}`
 note: required by a bound in `bar`
   --> $DIR/fn-ctor-passed-as-arg-where-it-should-have-been-called.rs:14:16
    |

tests/ui/suggestions/issue-84973-blacklist.stderr

@@ -40,10 +40,11 @@ error[E0277]: `{static coroutine@$DIR/issue-84973-blacklist.rs:17:26: 17:35}` ca
   --> $DIR/issue-84973-blacklist.rs:17:26
    |
 LL |     f_unpin(#[coroutine] static || { yield; });
-   |     -------              ^^^^^^^^^^^^^^^^^^^^ the trait `Unpin` is not implemented for `{static coroutine@$DIR/issue-84973-blacklist.rs:17:26: 17:35}`
+   |     -------              ^^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
    |     |
    |     required by a bound introduced by this call
    |
+   = help: the trait `Unpin` is not implemented for `{static coroutine@$DIR/issue-84973-blacklist.rs:17:26: 17:35}`
    = note: consider using the `pin!` macro
            consider using `Box::pin` if you need to access the pinned value outside of the current scope
 note: required by a bound in `f_unpin`

tests/ui/traits/fn-pointer/bare-fn-no-impl-fn-ptr-99875.stderr

@@ -20,10 +20,11 @@ error[E0277]: the trait bound `{closure@$DIR/bare-fn-no-impl-fn-ptr-99875.rs:14:
   --> $DIR/bare-fn-no-impl-fn-ptr-99875.rs:14:11
    |
 LL |     takes(|_: Argument| -> Return { todo!() });
-   |     ----- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for closure `{closure@$DIR/bare-fn-no-impl-fn-ptr-99875.rs:14:11: 14:34}`
+   |     ----- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unsatisfied trait bound
    |     |
    |     required by a bound introduced by this call
    |
+   = help: the trait `Trait` is not implemented for closure `{closure@$DIR/bare-fn-no-impl-fn-ptr-99875.rs:14:11: 14:34}`
    = help: the trait `Trait` is implemented for fn pointer `fn(Argument) -> Return`
 note: required by a bound in `takes`
   --> $DIR/bare-fn-no-impl-fn-ptr-99875.rs:9:18

tests/ui/transmutability/assoc-bound.stderr

@@ -2,8 +2,9 @@ error[E0277]: the trait bound `<T as A>::AssocA: TransmuteFrom<(), Assume { alig
   --> $DIR/assoc-bound.rs:16:19
    |
 LL |     type AssocB = T::AssocA;
-   |                   ^^^^^^^^^ the trait `TransmuteFrom<(), Assume { alignment: false, lifetimes: false, safety: false, validity: false }>` is not implemented for `<T as A>::AssocA`
+   |                   ^^^^^^^^^ unsatisfied trait bound
    |
+   = help: the trait `TransmuteFrom<(), Assume { alignment: false, lifetimes: false, safety: false, validity: false }>` is not implemented for `<T as A>::AssocA`
 note: required by a bound in `B::AssocB`
   --> $DIR/assoc-bound.rs:9:18
    |

tests/ui/where-clauses/higher-ranked-fn-type.verbose.stderr

@@ -2,8 +2,9 @@ error[E0277]: the trait bound `for<Region(BrNamed(DefId(0:6 ~ higher_ranked_fn_t
   --> $DIR/higher-ranked-fn-type.rs:20:5
    |
 LL |     called()
-   |     ^^^^^^^^ the trait `for<Region(BrNamed(DefId(0:6 ~ higher_ranked_fn_type[9e51]::called::'b), 'b))> Foo` is not implemented for `fn(&'^1_0.Named(DefId(0:6 ~ higher_ranked_fn_type[9e51]::called::'b), "'b") ())`
+   |     ^^^^^^^^ unsatisfied trait bound
    |
+   = help: the trait `for<Region(BrNamed(DefId(0:6 ~ higher_ranked_fn_type[9e51]::called::'b), 'b))> Foo` is not implemented for `fn(&'^1_0.Named(DefId(0:6 ~ higher_ranked_fn_type[9e51]::called::'b), "'b") ())`
 help: this trait has no implementations, consider adding one
   --> $DIR/higher-ranked-fn-type.rs:6:1
    |