Add regression test for nested replacement ranges in cfg_eval

tests/ui/conditional-compilation/nested-replacement-ranges-regression.rs

@@ -0,0 +1,65 @@
+// Regression test for #132727
+//
+// This ensures we correctly handle nested replacement ranges in cfg_eval.
+// PR #129346 included a code simplification in collect_tokens that
+// caused a regression with nested cfg attributes, which was reverted in #132587.
+
+//@ check-pass
+
+#![feature(cfg_eval)]
+#![feature(stmt_expr_attributes)]
+
+fn nested_cfg_attributes() -> u32 {
+    // This test reproduces the core issue: nested cfg replacement ranges
+    // The outer #[cfg_eval] processes the inner #[cfg] attribute,
+    // creating a nested replacement range situation
+    #[cfg_eval] #[cfg(not(FALSE))] 0
+}
+
+// Another test case with more complex nesting
+fn multi_level_nesting() -> u32 {
+    let result = {
+        #[cfg_eval]
+        {
+            #[cfg(not(FALSE))]
+            {
+                #[cfg(not(FALSE))]
+                42
+            }
+        }
+    };
+    result
+}
+
+// Test for overlapping nested cfg attributes with different conditions
+fn overlapping_cfg_attributes() -> u32 {
+    // This tests a more complex case where the cfg attributes have different conditions
+    // and are deeply nested, which could potentially trigger issues with replacement ranges
+    #[cfg_eval]
+    {
+        #[cfg(any(not(FALSE), FALSE))]
+        {
+            #[cfg(all(not(FALSE), not(FALSE)))]
+            {
+                #[cfg(not(FALSE))]
+                100
+            }
+        }
+    }
+}
+
+// Test for the interaction between cfg_eval and cfg_attr
+fn cfg_eval_with_cfg_attr() -> u32 {
+    // This tests the interaction between cfg_eval and cfg_attr, which was
+    // one of the main issues addressed in the regression fix
+    #[cfg_eval]
+    #[cfg_attr(not(FALSE), cfg_attr(not(FALSE), cfg(not(FALSE))))]
+    200
+}
+
+fn main() {
+    assert_eq!(nested_cfg_attributes(), 0);
+    assert_eq!(multi_level_nesting(), 42);
+    assert_eq!(overlapping_cfg_attributes(), 100);
+    assert_eq!(cfg_eval_with_cfg_attr(), 200);
+}