[compiler] Avoid empty switch cases #33625
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This was referenced Jun 23, 2025
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Substantially improves the last major known issue with the new inference model's implementation: inferring effects of function expressions. I knowingly used a really simple (dumb) approach in InferFunctionExpressionAliasingEffects but it worked surprisingly well on a ton of code. However, investigating during the sync I saw that we the algorithm was literally running out of memory, or crashing from arrays that exceeded the maximum capacity. We were accumluating data flow in a way that could lead to lists of data flow captures compounding on themselves and growing very large very quickly. Plus, we were incorrectly recording some data flow, leading to cases where we reported false positive "can't mutate frozen value" for example. So I went back to the drawing board. InferMutationAliasingRanges already builds up a data flow graph which it uses to figure out what values would be affected by mutations of other values, and update mutable ranges. Well, the key question that we really want to answer for inferring a function expression's aliasing effects is which values alias/capture where. Per the docs I wrote up, we only have to record such aliasing _if they are observable via mutations_. So, lightbulb: simulate mutations of the params, free variables, and return of the function expression and see which params/free-vars would be affected! That's what we do now, giving us precise information about which such values alias/capture where. When the "into" is a param/context-var we use Capture, iwhen the destination is the return we use Alias to be conservative. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33584). * #33626 * #33625 * #33624 * __->__ #33584
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Substantially improves the last major known issue with the new inference model's implementation: inferring effects of function expressions. I knowingly used a really simple (dumb) approach in InferFunctionExpressionAliasingEffects but it worked surprisingly well on a ton of code. However, investigating during the sync I saw that we the algorithm was literally running out of memory, or crashing from arrays that exceeded the maximum capacity. We were accumluating data flow in a way that could lead to lists of data flow captures compounding on themselves and growing very large very quickly. Plus, we were incorrectly recording some data flow, leading to cases where we reported false positive "can't mutate frozen value" for example. So I went back to the drawing board. InferMutationAliasingRanges already builds up a data flow graph which it uses to figure out what values would be affected by mutations of other values, and update mutable ranges. Well, the key question that we really want to answer for inferring a function expression's aliasing effects is which values alias/capture where. Per the docs I wrote up, we only have to record such aliasing _if they are observable via mutations_. So, lightbulb: simulate mutations of the params, free variables, and return of the function expression and see which params/free-vars would be affected! That's what we do now, giving us precise information about which such values alias/capture where. When the "into" is a param/context-var we use Capture, iwhen the destination is the return we use Alias to be conservative. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33584). * #33626 * #33625 * #33624 * __->__ #33584 DiffTrain build for [94cf60b](94cf60b)
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Substantially improves the last major known issue with the new inference model's implementation: inferring effects of function expressions. I knowingly used a really simple (dumb) approach in InferFunctionExpressionAliasingEffects but it worked surprisingly well on a ton of code. However, investigating during the sync I saw that we the algorithm was literally running out of memory, or crashing from arrays that exceeded the maximum capacity. We were accumluating data flow in a way that could lead to lists of data flow captures compounding on themselves and growing very large very quickly. Plus, we were incorrectly recording some data flow, leading to cases where we reported false positive "can't mutate frozen value" for example. So I went back to the drawing board. InferMutationAliasingRanges already builds up a data flow graph which it uses to figure out what values would be affected by mutations of other values, and update mutable ranges. Well, the key question that we really want to answer for inferring a function expression's aliasing effects is which values alias/capture where. Per the docs I wrote up, we only have to record such aliasing _if they are observable via mutations_. So, lightbulb: simulate mutations of the params, free variables, and return of the function expression and see which params/free-vars would be affected! That's what we do now, giving us precise information about which such values alias/capture where. When the "into" is a param/context-var we use Capture, iwhen the destination is the return we use Alias to be conservative. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33584). * #33626 * #33625 * #33624 * __->__ #33584 DiffTrain build for [94cf60b](94cf60b)
Closes #33577, a bug with ExtractScopeDeclarationsFromDestructuring and codegen when a function param is reassigned.
Small cosmetic win, found this when i was looking at some code internally with lots of cases that all share the same logic. Previously, all the but last one would have an empty block.
This was referenced Jun 25, 2025
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…33624) Closes #33577, a bug with ExtractScopeDeclarationsFromDestructuring and codegen when a function param is reassigned. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33624). * #33643 * #33642 * #33640 * #33625 * __->__ #33624
josephsavona
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Jun 25, 2025
We now have `HIRFunction.returns: Place` as well as `returnType: Type`.
I want to add additional return information, so as a first step i'm
consolidating everything under an object at `HIRFunction.returns:
{place: Place}`. We use the type of this place as the return type. Next
step is to add more properties to this object to represent things like
the return kind.
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33640).
* #33643
* #33642
* __->__ #33640
* #33625
* #33624
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Small cosmetic win, found this when i was looking at some code internally with lots of cases that all share the same logic. Previously, all the but last one would have an empty block. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33625). * #33643 * #33642 * #33640 * __->__ #33625 * #33624 DiffTrain build for [e130c08](e130c08)
github-actions bot
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Small cosmetic win, found this when i was looking at some code internally with lots of cases that all share the same logic. Previously, all the but last one would have an empty block. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33625). * #33643 * #33642 * #33640 * __->__ #33625 * #33624 DiffTrain build for [e130c08](e130c08)
github-actions bot
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Jun 25, 2025
We now have `HIRFunction.returns: Place` as well as `returnType: Type`.
I want to add additional return information, so as a first step i'm
consolidating everything under an object at `HIRFunction.returns:
{place: Place}`. We use the type of this place as the return type. Next
step is to add more properties to this object to represent things like
the return kind.
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33640).
* #33643
* #33642
* __->__ #33640
* #33625
* #33624
DiffTrain build for [123ff13](123ff13)
github-actions bot
pushed a commit
that referenced
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Jun 25, 2025
We now have `HIRFunction.returns: Place` as well as `returnType: Type`.
I want to add additional return information, so as a first step i'm
consolidating everything under an object at `HIRFunction.returns:
{place: Place}`. We use the type of this place as the return type. Next
step is to add more properties to this object to represent things like
the return kind.
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33640).
* #33643
* #33642
* __->__ #33640
* #33625
* #33624
DiffTrain build for [123ff13](123ff13)
github-actions bot
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that referenced
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Jun 25, 2025
…33624) Closes #33577, a bug with ExtractScopeDeclarationsFromDestructuring and codegen when a function param is reassigned. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33624). * #33643 * #33642 * #33640 * #33625 * __->__ #33624 DiffTrain build for [9894c48](9894c48)
github-actions bot
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Jun 25, 2025
…33624) Closes #33577, a bug with ExtractScopeDeclarationsFromDestructuring and codegen when a function param is reassigned. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33624). * #33643 * #33642 * #33640 * #33625 * __->__ #33624 DiffTrain build for [9894c48](9894c48)
This was referenced Jun 25, 2025
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Small cosmetic win, found this when i was looking at some code internally with lots of cases that all share the same logic. Previously, all the but last one would have an empty block.
Stack created with Sapling. Best reviewed with ReviewStack.