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+A lower range wasn't less than the upper range.
+
+Erroneous code example:
+
+```compile_fail,E0579
+#![feature(exclusive_range_pattern)]
+
+fn main() {
+    match 5u32 {
+        // This range is ok, albeit pointless.
+        1 .. 2 => {}
+        // This range is empty, and the compiler can tell.
+        5 .. 5 => {} // error!
+    }
+}
+```
+
+When matching against an exclusive range, the compiler verifies that the range
+is non-empty. Exclusive range patterns include the start point but not the end
+point, so this is equivalent to requiring the start of the range to be less
+than the end of the range.