refactor: Move assert for disjoint substitution spans

Author: Muscraft

compiler/rustc_errors/src/emitter.rs

@@ -2354,7 +2354,6 @@ impl HumanEmitter {
                         .sum();
                     let underline_start = (span_start_pos + start) as isize + offset;
                     let underline_end = (span_start_pos + start + sub_len) as isize + offset;
-                    assert!(underline_start >= 0 && underline_end >= 0);
                     let padding: usize = max_line_num_len + 3;
                     for p in underline_start..underline_end {
                         if let DisplaySuggestion::Underline = show_code_change

compiler/rustc_errors/src/lib.rs

@@ -381,6 +381,12 @@ impl CodeSuggestion {
                 // Assumption: all spans are in the same file, and all spans
                 // are disjoint. Sort in ascending order.
                 substitution.parts.sort_by_key(|part| part.span.lo());
+                // Verify the assumption that all spans are disjoint
+                assert_eq!(
+                    substitution.parts.array_windows().find(|[a, b]| a.span.overlaps(b.span)),
+                    None,
+                    "all spans must be disjoint",
+                );
 
                 // Find the bounding span.
                 let lo = substitution.parts.iter().map(|part| part.span.lo()).min()?;