Fix: set-state-in-use-effect false negative when there are multiple instances

Fixes issue #35291 where the ESLint rule was not catching setState calls in effect callbacks when a component had multiple useState and useEffect hooks.

The issue was an overly strict optimization check that skipped analyzing some function expressions. Now all function expressions are properly analyzed for setState calls.

Changes:
- Removed the faulty optimization check in validateNoSetStateInEffects
- Added test fixture to prevent regressions

Author: YASHRDX0001

compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateNoSetStateInEffects.ts

@@ -74,22 +74,13 @@ export function validateNoSetStateInEffects(
           break;
         }
         case 'FunctionExpression': {
-          if (
-            // faster-path to check if the function expression references a setState
-            [...eachInstructionValueOperand(instr.value)].some(
-              operand =>
-                isSetStateType(operand.identifier) ||
-                setStateFunctions.has(operand.identifier.id),
-            )
-          ) {
-            const callee = getSetStateCall(
-              instr.value.loweredFunc.func,
-              setStateFunctions,
-              env,
-            );
-            if (callee !== null) {
-              setStateFunctions.set(instr.lvalue.identifier.id, callee);
-            }
+          const callee = getSetStateCall(
+            instr.value.loweredFunc.func,
+            setStateFunctions,
+            env,
+          );
+          if (callee !== null) {
+            setStateFunctions.set(instr.lvalue.identifier.id, callee);
           }
           break;
         }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/invalid-setState-in-useEffect-multiple-instances.js

@@ -0,0 +1,16 @@
+// @loggerTestOnly @validateNoSetStateInEffects
+import {useEffect, useState} from 'react';
+
+function Component() {
+  const [loading, setLoading] = useState(false);
+  useEffect(() => {
+    setLoading(true);
+  }, []);
+  const [firstName, setFirstName] = useState('');
+  const [lastName, setLastName] = useState('');
+  const [fullName, setFullName] = useState('');
+  useEffect(() => {
+    setFullName(`${firstName} ${lastName}`);
+  }, [firstName, lastName]);
+  return null;
+}