Rollup merge of #81634 - jesusprubio:jesusprubio/add-long-explanation-e0521, r=GuillaumeGomez

Add long explanation e0521

Helps with #61137

25 files changed, 55 insertions, 4 deletions

diff --git a/compiler/rustc_error_codes/src/error_codes.rs b/compiler/rustc_error_codes/src/error_codes.rs
index c669f7fed27..9ce74dd9b5a 100644
--- a/compiler/rustc_error_codes/src/error_codes.rs
+++ b/compiler/rustc_error_codes/src/error_codes.rs
@@ -267,6 +267,7 @@ E0516: include_str!("./error_codes/E0516.md"),
 E0517: include_str!("./error_codes/E0517.md"),
 E0518: include_str!("./error_codes/E0518.md"),
 E0520: include_str!("./error_codes/E0520.md"),
+E0521: include_str!("./error_codes/E0521.md"),
 E0522: include_str!("./error_codes/E0522.md"),
 E0524: include_str!("./error_codes/E0524.md"),
 E0525: include_str!("./error_codes/E0525.md"),
@@ -597,7 +598,6 @@ E0780: include_str!("./error_codes/E0780.md"),
     E0514, // metadata version mismatch
     E0519, // local crate and dependency have same (crate-name, disambiguator)
     // two dependencies have same (crate-name, disambiguator) but different SVH
-    E0521, // borrowed data escapes outside of closure
     E0523,
 //  E0526, // shuffle indices are not constant
 //  E0540, // multiple rustc_deprecated attributes
diff --git a/compiler/rustc_error_codes/src/error_codes/E0521.md b/compiler/rustc_error_codes/src/error_codes/E0521.md
new file mode 100644
index 00000000000..65dcac983ac
--- /dev/null
+++ b/compiler/rustc_error_codes/src/error_codes/E0521.md
@@ -0,0 +1,28 @@
+Borrowed data escapes outside of closure.
+
+Erroneous code example:
+
+```compile_fail,E0521
+let mut list: Vec<&str> = Vec::new();
+
+let _add = |el: &str| {
+    list.push(el); // error: `el` escapes the closure body here
+};
+```
+
+A type anotation of a closure parameter implies a new lifetime declaration.
+Consider to drop it, the compiler is reliably able to infer them.
+
+```
+let mut list: Vec<&str> = Vec::new();
+
+let _add = |el| {
+    list.push(el);
+};
+```
+
+See the [Closure type inference and annotation][closure-infere-annotation] and
+[Lifetime elision][lifetime-elision] sections of the Book for more details.
+
+[closure-infere-annotation]: https://doc.rust-lang.org/book/ch13-01-closures.html#closure-type-inference-and-annotation
+[lifetime-elision]: https://doc.rust-lang.org/reference/lifetime-elision.html
diff --git a/src/test/ui/async-await/issues/issue-62097.nll.stderr b/src/test/ui/async-await/issues/issue-62097.nll.stderr
index 2a399540e52..ab10e5f1810 100644
--- a/src/test/ui/async-await/issues/issue-62097.nll.stderr
+++ b/src/test/ui/async-await/issues/issue-62097.nll.stderr
@@ -26,4 +26,5 @@ LL |         foo(|| self.bar()).await;
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0373`.
+Some errors have detailed explanations: E0373, E0521.
+For more information about an error, try `rustc --explain E0373`.
diff --git a/src/test/ui/borrowck/issue-45983.stderr b/src/test/ui/borrowck/issue-45983.stderr
index efd414a2d44..feb098c5985 100644
--- a/src/test/ui/borrowck/issue-45983.stderr
+++ b/src/test/ui/borrowck/issue-45983.stderr
@@ -10,3 +10,4 @@ LL |     give_any(|y| x = Some(y));
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/borrowck/issue-7573.stderr b/src/test/ui/borrowck/issue-7573.stderr
index 815419db833..9d86286b867 100644
--- a/src/test/ui/borrowck/issue-7573.stderr
+++ b/src/test/ui/borrowck/issue-7573.stderr
@@ -12,3 +12,4 @@ LL |         lines_to_use.push(installed_id);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/borrowck/regions-escape-bound-fn-2.stderr b/src/test/ui/borrowck/regions-escape-bound-fn-2.stderr
index 1dc60bb1554..14393bc8eee 100644
--- a/src/test/ui/borrowck/regions-escape-bound-fn-2.stderr
+++ b/src/test/ui/borrowck/regions-escape-bound-fn-2.stderr
@@ -10,3 +10,4 @@ LL |     with_int(|y| x = Some(y));
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/borrowck/regions-escape-bound-fn.stderr b/src/test/ui/borrowck/regions-escape-bound-fn.stderr
index 5c548ec2876..a23fdacdee6 100644
--- a/src/test/ui/borrowck/regions-escape-bound-fn.stderr
+++ b/src/test/ui/borrowck/regions-escape-bound-fn.stderr
@@ -10,3 +10,4 @@ LL |     with_int(|y| x = Some(y));
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/borrowck/regions-escape-unboxed-closure.stderr b/src/test/ui/borrowck/regions-escape-unboxed-closure.stderr
index f2a49e70d27..153f77c8913 100644
--- a/src/test/ui/borrowck/regions-escape-unboxed-closure.stderr
+++ b/src/test/ui/borrowck/regions-escape-unboxed-closure.stderr
@@ -10,3 +10,4 @@ LL |     with_int(&mut |y| x = Some(y));
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/closures/closure-expected-type/expect-region-supply-region.stderr b/src/test/ui/closures/closure-expected-type/expect-region-supply-region.stderr
index 213071abfff..0d97fa7e230 100644
--- a/src/test/ui/closures/closure-expected-type/expect-region-supply-region.stderr
+++ b/src/test/ui/closures/closure-expected-type/expect-region-supply-region.stderr
@@ -20,3 +20,4 @@ LL |         f = Some(x);
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/generator/ref-escapes-but-not-over-yield.stderr b/src/test/ui/generator/ref-escapes-but-not-over-yield.stderr
index 9986220218e..5fc81004098 100644
--- a/src/test/ui/generator/ref-escapes-but-not-over-yield.stderr
+++ b/src/test/ui/generator/ref-escapes-but-not-over-yield.stderr
@@ -12,3 +12,4 @@ LL |         a = &b;
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/impl-header-lifetime-elision/dyn-trait.nll.stderr b/src/test/ui/impl-header-lifetime-elision/dyn-trait.nll.stderr
index 8e660d6814c..d72435bc631 100644
--- a/src/test/ui/impl-header-lifetime-elision/dyn-trait.nll.stderr
+++ b/src/test/ui/impl-header-lifetime-elision/dyn-trait.nll.stderr
@@ -10,3 +10,4 @@ LL |     static_val(x);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/issues/issue-16683.nll.stderr b/src/test/ui/issues/issue-16683.nll.stderr
index b82b0b552e2..51d86eaf9e6 100644
--- a/src/test/ui/issues/issue-16683.nll.stderr
+++ b/src/test/ui/issues/issue-16683.nll.stderr
@@ -8,3 +8,4 @@ LL |         self.a();
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/issues/issue-17758.nll.stderr b/src/test/ui/issues/issue-17758.nll.stderr
index 23557b4d956..075c141ed7a 100644
--- a/src/test/ui/issues/issue-17758.nll.stderr
+++ b/src/test/ui/issues/issue-17758.nll.stderr
@@ -8,3 +8,4 @@ LL |         self.foo();
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/lifetimes/lifetime-bound-will-change-warning.nll.stderr b/src/test/ui/lifetimes/lifetime-bound-will-change-warning.nll.stderr
index 60420973e1e..57dab46df6b 100644
--- a/src/test/ui/lifetimes/lifetime-bound-will-change-warning.nll.stderr
+++ b/src/test/ui/lifetimes/lifetime-bound-will-change-warning.nll.stderr
@@ -22,3 +22,4 @@ LL |     lib::ref_obj(x)
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr b/src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr
index 0115f5412f2..0932f941548 100644
--- a/src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr
+++ b/src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr
@@ -83,4 +83,5 @@ LL | }
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0597`.
+Some errors have detailed explanations: E0521, E0597.
+For more information about an error, try `rustc --explain E0521`.
diff --git a/src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.stderr b/src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.stderr
index e55d033d2c7..bf6e2a922ed 100644
--- a/src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.stderr
+++ b/src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.stderr
@@ -51,3 +51,4 @@ LL | |     });
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-wrong-bound.stderr b/src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-wrong-bound.stderr
index ac4a4579c9c..a3d993848cb 100644
--- a/src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-wrong-bound.stderr
+++ b/src/test/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-wrong-bound.stderr
@@ -51,3 +51,4 @@ LL | |     });
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/nll/outlives-suggestion-simple.stderr b/src/test/ui/nll/outlives-suggestion-simple.stderr
index 6300ea66511..bfe98a71a99 100644
--- a/src/test/ui/nll/outlives-suggestion-simple.stderr
+++ b/src/test/ui/nll/outlives-suggestion-simple.stderr
@@ -106,3 +106,4 @@ LL |         Bar2::new(&self)
 
 error: aborting due to 9 previous errors
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/nll/user-annotations/closure-substs.stderr b/src/test/ui/nll/user-annotations/closure-substs.stderr
index e3e294106d1..37e751aeb67 100644
--- a/src/test/ui/nll/user-annotations/closure-substs.stderr
+++ b/src/test/ui/nll/user-annotations/closure-substs.stderr
@@ -38,3 +38,4 @@ LL |         b(x);
 
 error: aborting due to 4 previous errors
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/object-lifetime/object-lifetime-default-mybox.nll.stderr b/src/test/ui/object-lifetime/object-lifetime-default-mybox.nll.stderr
index d871eb5327d..42dae7e40db 100644
--- a/src/test/ui/object-lifetime/object-lifetime-default-mybox.nll.stderr
+++ b/src/test/ui/object-lifetime/object-lifetime-default-mybox.nll.stderr
@@ -23,3 +23,4 @@ LL |     load0(ss)
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/regions/issue-78262.nll.stderr b/src/test/ui/regions/issue-78262.nll.stderr
index 4607dbad422..fafff35e415 100644
--- a/src/test/ui/regions/issue-78262.nll.stderr
+++ b/src/test/ui/regions/issue-78262.nll.stderr
@@ -8,3 +8,4 @@ LL |     let f = |x: &dyn TT| x.func();
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/regions/region-invariant-static-error-reporting.nll.stderr b/src/test/ui/regions/region-invariant-static-error-reporting.nll.stderr
index d941030d824..89a22adc8f0 100644
--- a/src/test/ui/regions/region-invariant-static-error-reporting.nll.stderr
+++ b/src/test/ui/regions/region-invariant-static-error-reporting.nll.stderr
@@ -11,3 +11,4 @@ LL |         x.unwrap()
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/regions/regions-bounded-method-type-parameters-trait-bound.nll.stderr b/src/test/ui/regions/regions-bounded-method-type-parameters-trait-bound.nll.stderr
index 92a3942c916..ed7b17c207c 100644
--- a/src/test/ui/regions/regions-bounded-method-type-parameters-trait-bound.nll.stderr
+++ b/src/test/ui/regions/regions-bounded-method-type-parameters-trait-bound.nll.stderr
@@ -13,3 +13,4 @@ LL |     f.method(b);
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/regions/regions-nested-fns.nll.stderr b/src/test/ui/regions/regions-nested-fns.nll.stderr
index 9d966486f98..60754f4c228 100644
--- a/src/test/ui/regions/regions-nested-fns.nll.stderr
+++ b/src/test/ui/regions/regions-nested-fns.nll.stderr
@@ -50,4 +50,5 @@ LL |         if false { return x; }
 
 error: aborting due to 4 previous errors
 
-For more information about this error, try `rustc --explain E0597`.
+Some errors have detailed explanations: E0521, E0597.
+For more information about an error, try `rustc --explain E0521`.
diff --git a/src/test/ui/suggestions/impl-on-dyn-trait-with-implicit-static-bound.nll.stderr b/src/test/ui/suggestions/impl-on-dyn-trait-with-implicit-static-bound.nll.stderr
index 697467dc3a6..6c235ae8f02 100644
--- a/src/test/ui/suggestions/impl-on-dyn-trait-with-implicit-static-bound.nll.stderr
+++ b/src/test/ui/suggestions/impl-on-dyn-trait-with-implicit-static-bound.nll.stderr
@@ -40,3 +40,4 @@ LL |         MyTrait::use_self(val)
 
 error: aborting due to 4 previous errors
 
+For more information about this error, try `rustc --explain E0521`.