Add explanation for ExpectChange unsafe autocorrection

Author: lovro-bikic

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Master (Unreleased)
 
+- Add explanation why `RSpec/ExpectChange` autocorrection is unsafe. ([@lovro-bikic])
 - Fix false positive in `RSpec/Pending`, where it would mark the default block `it` as an offense. ([@bquorning])
 
 ## 3.5.0 (2025-02-16)

docs/modules/ROOT/pages/cops_rspec.adoc

@@ -2130,6 +2130,17 @@ or passing a block that reads the attribute value.
 
 This cop can be configured using the `EnforcedStyle` option.
 
+[#safety-rspecexpectchange]
+=== Safety
+
+Autocorrection is unsafe because `block` style evaluates the object
+twice (before and after evaluating `expect` block), whereas
+`method_call` style evaluates the object only once.
+
+If you currently pass a block to `change` and expect the object to
+be evaluated before and after `expect` block, changing to
+`method_call` style may break your test.
+
 [#examples-rspecexpectchange]
 === Examples
 

lib/rubocop/cop/rspec/expect_change.rb

@@ -10,6 +10,15 @@ module RSpec
       #
       # This cop can be configured using the `EnforcedStyle` option.
       #
+      # @safety
+      #   Autocorrection is unsafe because `block` style evaluates the object
+      #   twice (before and after evaluating `expect` block), whereas
+      #   `method_call` style evaluates the object only once.
+      #
+      #   If you currently pass a block to `change` and expect the object to
+      #   be evaluated before and after `expect` block, changing to
+      #   `method_call` style may break your test.
+      #
       # @example `EnforcedStyle: method_call` (default)
       #   # bad
       #   expect { run }.to change { Foo.bar }