fix: Avoid pattern exprs in range patterns during mutation generation

Author: zalanlevai

mutest-emit/src/codegen/mutation.rs

@@ -539,6 +539,9 @@ impl<'tcx, 'ast, 'op, 'trg, 'm> ast::visit::Visitor<'ast> for MutationCollector<
             // NOTE: We do not want to visit pattern expressions (i.e. literal, const block, path), since
             //       we cannot introduce dynamic mutations in them.
             ast::PatKind::Expr(_) => {}
+            // NOTE: We do not want to visit range patterns, since
+            //       we cannot introduce dynamic mutations in them.
+            ast::PatKind::Range(_, _, _) => {}
             _ => ast::visit::walk_pat(self, pat),
         }
     }

tests/ui/mutation/codegen/avoid_visiting_pat_exprs.rs

@@ -1,7 +1,7 @@
 //@ build
 //@ stderr: empty
 
-fn mutable_fn(c @ ('Z' | _): char) {
+fn mutable_fn_with_pat_exprs(c @ ('Z' | _): char) {
     if let 'Z' | 'z' = c {}
 
     match c {
@@ -11,7 +11,15 @@ fn mutable_fn(c @ ('Z' | _): char) {
     }
 }
 
+fn mutable_fn_with_range_pats(name: &str) -> bool {
+    if let b'a'..=b'i' | b'k'..=b'y' | b'A'..=b'I' | b'K'..=b'Y' = name.as_bytes()[0] {
+        return true;
+    }
+    false
+}
+
 #[test]
 fn test() {
-    mutable_fn('Z');
+    mutable_fn_with_pat_exprs('Z');
+    mutable_fn_with_range_pats("abc");
 }