Use a label instead of a note for member constraint errors

Author: oli-obk

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -116,7 +116,7 @@ pub(super) fn note_and_explain_region(
     emit_msg_span(err, prefix, description, span, suffix);
 }
 
-pub(super) fn note_and_explain_free_region(
+fn explain_free_region(
     tcx: TyCtxt<'tcx>,
     err: &mut DiagnosticBuilder<'_>,
     prefix: &str,
@@ -125,7 +125,7 @@ pub(super) fn note_and_explain_free_region(
 ) {
     let (description, span) = msg_span_from_free_region(tcx, region, None);
 
-    emit_msg_span(err, prefix, description, span, suffix);
+    label_msg_span(err, prefix, description, span, suffix);
 }
 
 fn msg_span_from_free_region(
@@ -210,6 +210,22 @@ fn emit_msg_span(
     }
 }
 
+fn label_msg_span(
+    err: &mut DiagnosticBuilder<'_>,
+    prefix: &str,
+    description: String,
+    span: Option<Span>,
+    suffix: &str,
+) {
+    let message = format!("{}{}{}", prefix, description, suffix);
+
+    if let Some(span) = span {
+        err.span_label(span, &message);
+    } else {
+        err.note(&message);
+    }
+}
+
 pub fn unexpected_hidden_region_diagnostic(
     tcx: TyCtxt<'tcx>,
     span: Span,
@@ -244,7 +260,7 @@ pub fn unexpected_hidden_region_diagnostic(
             //
             // (*) if not, the `tainted_by_errors` field would be set to
             // `Some(ErrorReported)` in any case, so we wouldn't be here at all.
-            note_and_explain_free_region(
+            explain_free_region(
                 tcx,
                 &mut err,
                 &format!("hidden type `{}` captures ", hidden_ty),

src/test/ui/impl-trait/hidden-lifetimes.stderr

@@ -2,25 +2,17 @@ error[E0700]: hidden type for `impl Trait` captures lifetime that does not appea
   --> $DIR/hidden-lifetimes.rs:28:54
    |
 LL | fn hide_ref<'a, 'b, T: 'static>(x: &'a mut &'b T) -> impl Swap + 'a {
-   |                                                      ^^^^^^^^^^^^^^
-   |
-note: hidden type `&'a mut &'b T` captures the lifetime `'b` as defined here
-  --> $DIR/hidden-lifetimes.rs:28:17
-   |
-LL | fn hide_ref<'a, 'b, T: 'static>(x: &'a mut &'b T) -> impl Swap + 'a {
-   |                 ^^
+   |                 --                                   ^^^^^^^^^^^^^^
+   |                 |
+   |                 hidden type `&'a mut &'b T` captures the lifetime `'b` as defined here
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/hidden-lifetimes.rs:45:70
    |
 LL | fn hide_rc_refcell<'a, 'b: 'a, T: 'static>(x: Rc<RefCell<&'b T>>) -> impl Swap + 'a {
-   |                                                                      ^^^^^^^^^^^^^^
-   |
-note: hidden type `Rc<RefCell<&'b T>>` captures the lifetime `'b` as defined here
-  --> $DIR/hidden-lifetimes.rs:45:24
-   |
-LL | fn hide_rc_refcell<'a, 'b: 'a, T: 'static>(x: Rc<RefCell<&'b T>>) -> impl Swap + 'a {
-   |                        ^^
+   |                        --                                            ^^^^^^^^^^^^^^
+   |                        |
+   |                        hidden type `Rc<RefCell<&'b T>>` captures the lifetime `'b` as defined here
 
 error: aborting due to 2 previous errors
 

src/test/ui/impl-trait/multiple-lifetimes/error-handling-2.stderr

@@ -2,13 +2,9 @@ error[E0700]: hidden type for `impl Trait` captures lifetime that does not appea
   --> $DIR/error-handling-2.rs:13:60
    |
 LL | fn foo<'a: 'b, 'b, 'c>(x: &'static i32, mut y: &'a i32) -> E<'b, 'c> {
-   |                                                            ^^^^^^^^^
-   |
-note: hidden type `*mut &'a i32` captures the lifetime `'a` as defined here
-  --> $DIR/error-handling-2.rs:13:8
-   |
-LL | fn foo<'a: 'b, 'b, 'c>(x: &'static i32, mut y: &'a i32) -> E<'b, 'c> {
-   |        ^^
+   |        --                                                  ^^^^^^^^^
+   |        |
+   |        hidden type `*mut &'a i32` captures the lifetime `'a` as defined here
 
 error: aborting due to previous error
 

src/test/ui/impl-trait/region-escape-via-bound.stderr

@@ -3,12 +3,9 @@ error[E0700]: hidden type for `impl Trait` captures lifetime that does not appea
    |
 LL | fn foo(x: Cell<&'x u32>) -> impl Trait<'y>
    |                             ^^^^^^^^^^^^^^
-   |
-note: hidden type `Cell<&'x u32>` captures the lifetime `'x` as defined here
-  --> $DIR/region-escape-via-bound.rs:17:7
-   |
+LL |
 LL | where 'x: 'y
-   |       ^^
+   |       -- hidden type `Cell<&'x u32>` captures the lifetime `'x` as defined here
 
 error: aborting due to previous error