Improve error message

Author: Nadrieril

compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs

@@ -309,18 +309,18 @@ impl IntRange {
                 pcx.span,
                 |lint| {
                     let mut err = lint.build("multiple patterns overlap on their endpoints");
-                    err.span_label(pcx.span, "overlapping range endpoints");
+                    err.span_label(pcx.span, "... with this range");
                     for (int_range, span) in overlaps {
                         // Use the real type for user display of the ranges:
                         err.span_label(
                             span,
                             &format!(
-                                "this range overlaps on `{}`",
+                                "this range overlaps on `{}`...",
                                 int_range.to_pat(pcx.cx.tcx, pcx.ty)
                             ),
                         );
                     }
-                    // FIXME: add note
+                    err.note("this is likely to be a mistake");
                     err.emit();
                 },
             );

src/test/ui/pattern/usefulness/integer-ranges/overlapping_range_endpoints.stderr

@@ -2,73 +2,88 @@ error: multiple patterns overlap on their endpoints
   --> $DIR/overlapping_range_endpoints.rs:15:22
    |
 LL |     m!(0u8, 20..=30, 30..=40);
-   |             -------  ^^^^^^^ overlapping range endpoints
+   |             -------  ^^^^^^^ ... with this range
    |             |
-   |             this range overlaps on `30_u8`
+   |             this range overlaps on `30_u8`...
    |
 note: the lint level is defined here
   --> $DIR/overlapping_range_endpoints.rs:2:9
    |
 LL | #![deny(overlapping_range_endpoints)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: this is likely to be a mistake
 
 error: multiple patterns overlap on their endpoints
   --> $DIR/overlapping_range_endpoints.rs:16:22
    |
 LL |     m!(0u8, 30..=40, 20..=30);
-   |             -------  ^^^^^^^ overlapping range endpoints
+   |             -------  ^^^^^^^ ... with this range
    |             |
-   |             this range overlaps on `30_u8`
+   |             this range overlaps on `30_u8`...
+   |
+   = note: this is likely to be a mistake
 
 error: multiple patterns overlap on their endpoints
   --> $DIR/overlapping_range_endpoints.rs:19:22
    |
 LL |     m!(0u8, 20.. 30, 29..=40);
-   |             -------  ^^^^^^^ overlapping range endpoints
+   |             -------  ^^^^^^^ ... with this range
    |             |
-   |             this range overlaps on `29_u8`
+   |             this range overlaps on `29_u8`...
+   |
+   = note: this is likely to be a mistake
 
 error: multiple patterns overlap on their endpoints
   --> $DIR/overlapping_range_endpoints.rs:23:22
    |
 LL |     m!(0u8, 20..=30, 30..=31);
-   |             -------  ^^^^^^^ overlapping range endpoints
+   |             -------  ^^^^^^^ ... with this range
    |             |
-   |             this range overlaps on `30_u8`
+   |             this range overlaps on `30_u8`...
+   |
+   = note: this is likely to be a mistake
 
 error: multiple patterns overlap on their endpoints
   --> $DIR/overlapping_range_endpoints.rs:27:22
    |
 LL |     m!(0u8, 20..=30, 19..=20);
-   |             -------  ^^^^^^^ overlapping range endpoints
+   |             -------  ^^^^^^^ ... with this range
    |             |
-   |             this range overlaps on `20_u8`
+   |             this range overlaps on `20_u8`...
+   |
+   = note: this is likely to be a mistake
 
 error: multiple patterns overlap on their endpoints
   --> $DIR/overlapping_range_endpoints.rs:39:9
    |
 LL |         0..=10 => {}
-   |         ------ this range overlaps on `10_u8`
+   |         ------ this range overlaps on `10_u8`...
 LL |         20..=30 => {}
-   |         ------- this range overlaps on `20_u8`
+   |         ------- this range overlaps on `20_u8`...
 LL |         10..=20 => {}
-   |         ^^^^^^^ overlapping range endpoints
+   |         ^^^^^^^ ... with this range
+   |
+   = note: this is likely to be a mistake
 
 error: multiple patterns overlap on their endpoints
   --> $DIR/overlapping_range_endpoints.rs:50:16
    |
 LL |         (true, 0..=10) => {}
-   |                ------ this range overlaps on `10_u8`
+   |                ------ this range overlaps on `10_u8`...
 LL |         (true, 10..20) => {}
-   |                ^^^^^^ overlapping range endpoints
+   |                ^^^^^^ ... with this range
+   |
+   = note: this is likely to be a mistake
 
 error: multiple patterns overlap on their endpoints
   --> $DIR/overlapping_range_endpoints.rs:56:14
    |
 LL |         Some(0..=10) => {}
-   |              ------ this range overlaps on `10_u8`
+   |              ------ this range overlaps on `10_u8`...
 LL |         Some(10..20) => {}
-   |              ^^^^^^ overlapping range endpoints
+   |              ^^^^^^ ... with this range
+   |
+   = note: this is likely to be a mistake
 
 error: aborting due to 8 previous errors