Fix range splitting

src/librustc_mir/hair/pattern/_match.rs

@@ -725,8 +725,8 @@ fn ranges_subtract_pattern<'a, 'tcx>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
             } else {
                 // The pattern intersects the middle of the subrange,
                 // so we create two ranges either side of the intersection.)
-                remaining_ranges.push((subrange_lo, pat_interval.lo));
-                remaining_ranges.push((pat_interval.hi, subrange_hi));
+                remaining_ranges.push((subrange_lo, pat_interval.lo - 1));
+                remaining_ranges.push((pat_interval.hi + 1, subrange_hi));
             }
         }
         // Convert the remaining ranges from pairs to inclusive `ConstantRange`s.

src/test/ui/exhaustive_integer_patterns.stderr

@@ -16,11 +16,11 @@ error[E0004]: non-exhaustive patterns: `128u8...255u8` not covered
 LL |     match x { //~ ERROR non-exhaustive patterns: `128u8...255u8` not covered
    |           ^ pattern `128u8...255u8` not covered
 
-error[E0004]: non-exhaustive patterns: `11u8...20u8`, `30u8...35u8`, `35u8...70u8` and 1 more not covered
+error[E0004]: non-exhaustive patterns: `11u8...19u8`, `31u8...34u8`, `36u8...69u8` and 1 more not covered
   --> $DIR/exhaustive_integer_patterns.rs:42:11
    |
 LL |     match x { //~ ERROR non-exhaustive patterns
-   |           ^ patterns `11u8...20u8`, `30u8...35u8`, `35u8...70u8` and 1 more not covered
+   |           ^ patterns `11u8...19u8`, `31u8...34u8`, `36u8...69u8` and 1 more not covered
 
 error: unreachable pattern
   --> $DIR/exhaustive_integer_patterns.rs:53:9
@@ -28,11 +28,11 @@ error: unreachable pattern
 LL |         -2..=20 => {} //~ ERROR unreachable pattern
    |         ^^^^^^^
 
-error[E0004]: non-exhaustive patterns: `-128i8...-5i8`, `120i8...121i8` and `121i8...127i8` not covered
+error[E0004]: non-exhaustive patterns: `-128i8...-6i8` and `122i8...127i8` not covered
   --> $DIR/exhaustive_integer_patterns.rs:50:11
    |
 LL |     match x { //~ ERROR non-exhaustive patterns
-   |           ^ patterns `-128i8...-5i8`, `120i8...121i8` and `121i8...127i8` not covered
+   |           ^ patterns `-128i8...-6i8` and `122i8...127i8` not covered
 
 error: aborting due to 5 previous errors