[compiler] Add hint to name variables with "Ref" suffix #34125
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If you have a ref that the compiler doesn't know is a ref (say, a value returned from a custom hook) and try to assign its `.current = ...`, we currently fail with a generic error that hook return values are not mutable. However, an assignment to `.current` specifically is a very strong hint that the value is likely to be a ref. So in this PR, we track the reason for the mutation and if it ends up being an error, we use it to show an additional hint to the user. See the fixture for an example of the message.
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If you have a ref that the compiler doesn't know is a ref (say, a value returned from a custom hook) and try to assign its `.current = ...`, we currently fail with a generic error that hook return values are not mutable. However, an assignment to `.current` specifically is a very strong hint that the value is likely to be a ref. So in this PR, we track the reason for the mutation and if it ends up being an error, we use it to show an additional hint to the user. See the fixture for an example of the message. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/34125). * #34126 * __->__ #34125 * #34124 DiffTrain build for [724b324](724b324)
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If you have a ref that the compiler doesn't know is a ref (say, a value returned from a custom hook) and try to assign its `.current = ...`, we currently fail with a generic error that hook return values are not mutable. However, an assignment to `.current` specifically is a very strong hint that the value is likely to be a ref. So in this PR, we track the reason for the mutation and if it ends up being an error, we use it to show an additional hint to the user. See the fixture for an example of the message. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/34125). * #34126 * __->__ #34125 * #34124 DiffTrain build for [724b324](724b324)
This was referenced Aug 18, 2025
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In #34125 I added a hint where if you assign to the .current property of a frozen object, we suggest naming the variable as `ref` or `-Ref`. However, the tracking for mutations that assign to .current specifically wasn't propagated past function expression boundaries, which meant that the hint only showed up if you mutated the ref in the main body of the component/hook. That's less likely to happen since most folks know not to access refs in render. What's more likely is that you'll (correctly) assign a ref in an effect or callback, but the compiler will throw an error. By showing a hint in this case we can help people understand the naming pattern.
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In #34125 I added a hint where if you assign to the .current property of a frozen object, we suggest naming the variable as `ref` or `-Ref`. However, the tracking for mutations that assign to .current specifically wasn't propagated past function expression boundaries, which meant that the hint only showed up if you mutated the ref in the main body of the component/hook. That's less likely to happen since most folks know not to access refs in render. What's more likely is that you'll (correctly) assign a ref in an effect or callback, but the compiler will throw an error. By showing a hint in this case we can help people understand the naming pattern.
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In #34125 I added a hint where if you assign to the .current property of a frozen object, we suggest naming the variable as `ref` or `-Ref`. However, the tracking for mutations that assign to .current specifically wasn't propagated past function expression boundaries, which meant that the hint only showed up if you mutated the ref in the main body of the component/hook. That's less likely to happen since most folks know not to access refs in render. What's more likely is that you'll (correctly) assign a ref in an effect or callback, but the compiler will throw an error. By showing a hint in this case we can help people understand the naming pattern.
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…ck (#34298) In #34125 I added a hint where if you assign to the .current property of a frozen object, we suggest naming the variable as `ref` or `-Ref`. However, the tracking for mutations that assign to .current specifically wasn't propagated past function expression boundaries, which meant that the hint only showed up if you mutated the ref in the main body of the component/hook. That's less likely to happen since most folks know not to access refs in render. What's more likely is that you'll (correctly) assign a ref in an effect or callback, but the compiler will throw an error. By showing a hint in this case we can help people understand the naming pattern. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/34298). * #34276 * __->__ #34298
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…ck (#34298) In #34125 I added a hint where if you assign to the .current property of a frozen object, we suggest naming the variable as `ref` or `-Ref`. However, the tracking for mutations that assign to .current specifically wasn't propagated past function expression boundaries, which meant that the hint only showed up if you mutated the ref in the main body of the component/hook. That's less likely to happen since most folks know not to access refs in render. What's more likely is that you'll (correctly) assign a ref in an effect or callback, but the compiler will throw an error. By showing a hint in this case we can help people understand the naming pattern. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/34298). * #34276 * __->__ #34298 DiffTrain build for [8d7b5e4](8d7b5e4)
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…ck (#34298) In #34125 I added a hint where if you assign to the .current property of a frozen object, we suggest naming the variable as `ref` or `-Ref`. However, the tracking for mutations that assign to .current specifically wasn't propagated past function expression boundaries, which meant that the hint only showed up if you mutated the ref in the main body of the component/hook. That's less likely to happen since most folks know not to access refs in render. What's more likely is that you'll (correctly) assign a ref in an effect or callback, but the compiler will throw an error. By showing a hint in this case we can help people understand the naming pattern. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/34298). * #34276 * __->__ #34298 DiffTrain build for [8d7b5e4](8d7b5e4)
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…ck (facebook#34298) In facebook#34125 I added a hint where if you assign to the .current property of a frozen object, we suggest naming the variable as `ref` or `-Ref`. However, the tracking for mutations that assign to .current specifically wasn't propagated past function expression boundaries, which meant that the hint only showed up if you mutated the ref in the main body of the component/hook. That's less likely to happen since most folks know not to access refs in render. What's more likely is that you'll (correctly) assign a ref in an effect or callback, but the compiler will throw an error. By showing a hint in this case we can help people understand the naming pattern. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/34298). * facebook#34276 * __->__ facebook#34298 DiffTrain build for [8d7b5e4](facebook@8d7b5e4)
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…ck (facebook#34298) In facebook#34125 I added a hint where if you assign to the .current property of a frozen object, we suggest naming the variable as `ref` or `-Ref`. However, the tracking for mutations that assign to .current specifically wasn't propagated past function expression boundaries, which meant that the hint only showed up if you mutated the ref in the main body of the component/hook. That's less likely to happen since most folks know not to access refs in render. What's more likely is that you'll (correctly) assign a ref in an effect or callback, but the compiler will throw an error. By showing a hint in this case we can help people understand the naming pattern. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/34298). * facebook#34276 * __->__ facebook#34298 DiffTrain build for [8d7b5e4](facebook@8d7b5e4)
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If you have a ref that the compiler doesn't know is a ref (say, a value returned from a custom hook) and try to assign its
.current = ..., we currently fail with a generic error that hook return values are not mutable. However, an assignment to.currentspecifically is a very strong hint that the value is likely to be a ref. So in this PR, we track the reason for the mutation and if it ends up being an error, we use it to show an additional hint to the user. See the fixture for an example of the message.Stack created with Sapling. Best reviewed with ReviewStack.