[compiler] Preserve Create effects, guarantee effects initialize once #33558

josephsavona · 2025-06-17T23:26:18Z

Ensures that effects are well-formed with respect to the rules:

For a given instruction, each place is only initialized once (w one of Create, CreateFrom, Assign)
Ensures that Alias targets are already initialized within the same instruction (should have a Create before them)
Preserves Create and similar instructions
Avoids duplicate instructions when inferring effects of function expressions

Stack created with Sapling. Best reviewed with ReviewStack.

mofeiZ · 2025-06-18T17:37:13Z

compiler/packages/babel-plugin-react-compiler/src/Inference/InferMutationAliasingEffects.ts

@@ -524,6 +529,13 @@ function applyEffect(
      break;
    }
    case 'Create': {
+      CompilerError.invariant(!initialized.has(effect.into.identifier.id), {
+        reason: `Cannot re-initialize variable within an instruction`,


Makes sense! Does something else also ensure that we don't have duplicate Create / CreateFroms for the same Identifier / IdentifierId across multiple instructions (i.e. StoreLocals to the same lvalue), or is that case not an issue?

There is a todo for this in InferMutationAliasingRanges. Only two fixtures fail if i enable that invariant though, for understandable reasons, so in general we are preserving this guarantee.

This is covered by iife-inline-ternary --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33572). * #33571 * #33558 * #33547 * #33543 * #33533 * #33532 * #33530 * #33526 * #33522 * #33518 * #33514 * #33513 * #33512 * #33504 * #33500 * #33497 * #33496 * #33495 * #33494 * __->__ #33572

Squashed, review-friendly version of the stack from #33488. This is new version of our mutability and inference model, designed to replace the core algorithm for determining the sets of instructions involved in constructing a given value or set of values. The new model replaces InferReferenceEffects, InferMutableRanges (and all of its subcomponents), and parts of AnalyzeFunctions. The new model does not use per-Place effect values, but in order to make this drop-in the end _result_ of the inference adds these per-Place effects. I'll write up a larger document on the model, first i'm doing some housekeeping to rebase the PR. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33494). * #33571 * #33558 * #33547 * #33543 * #33533 * #33532 * #33530 * #33526 * #33522 * #33518 * #33514 * #33513 * #33512 * #33504 * #33500 * #33497 * #33496 * #33495 * __->__ #33494 * #33572

--- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33495). * #33571 * #33558 * #33547 * #33543 * #33533 * #33532 * #33530 * #33526 * #33522 * #33518 * #33514 * #33513 * #33512 * #33504 * #33500 * #33497 * #33496 * __->__ #33495 * #33494 * #33572

--- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33496). * #33571 * #33558 * #33547 * #33543 * #33533 * #33532 * #33530 * #33526 * #33522 * #33518 * #33514 * #33513 * #33512 * #33504 * #33500 * #33497 * __->__ #33496

--- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33497). * #33571 * #33558 * #33547 * #33543 * #33533 * #33532 * #33530 * #33526 * #33522 * #33518 * #33514 * #33513 * #33512 * #33504 * #33500 * __->__ #33497 * #33496

We're already tracking which variables are hoisted context variables, so if we see a mutation of a frozen value we can emit a custom error message to help users identify the problem. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33504). * #33571 * #33558 * #33547 * #33543 * #33533 * #33532 * #33530 * #33526 * #33522 * #33518 * #33514 * #33513 * #33512 * __->__ #33504 * #33500 * #33497 * #33496

…nce (#33512) This has always been awkward: `FunctionExpression.context` places have locations set to the declaration of the identifier, whereas other references have locations pointing to the reference itself. Here, we update context operands to have their location point to the first reference of that variable within the function. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33512). * #33571 * #33558 * #33547 * #33543 * #33533 * #33532 * #33530 * #33526 * #33522 * #33518 * #33514 * #33513 * __->__ #33512 * #33504 * #33500 * #33497 * #33496

The previous error message was generic, because the old style function signature didn't support a way to specify a reason alongside a freeze effect. This meant we could only say why a value was frozen for instructions, but not hooks which use function signatures. By defining a new aliasing signature for custom hooks we can specify a reason and provide a better error message. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33513). * #33571 * #33558 * #33547 * #33543 * #33533 * #33532 * #33530 * #33526 * #33522 * #33518 * #33514 * __->__ #33513

--- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33573). * #33571 * #33558 * #33547 * #33543 * #33533 * #33532 * #33530 * #33526 * #33522 * #33518 * #33514 * __->__ #33573

The previous error for hoisting violations pointed only to the variable declaration, but didn't show where the value was accessed before that declaration. We now track where each hoisted variable is first accessed and report two errors, one for the reference and one for the declaration. When we improve our diagnostic infra to support reporting errors at multiple locations we can merge these into a single conceptual error. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33514). * #33571 * #33558 * #33547 * #33543 * #33533 * #33532 * #33530 * #33526 * #33522 * #33518 * __->__ #33514 * #33573

When we apply new aliasing signatures we can generate new temporaries, which causes the abstract memory model to not converge. The fix is to make sure we cache the applications of these signatures. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33518). * #33571 * #33558 * #33547 * #33543 * #33533 * #33532 * #33530 * #33526 * #33522 * __->__ #33518

In comparing compilation output of the old/new inference models I found this case (heavily distilled into a fixture). Roughly speaking the scenario is: * Create a mutable object `x` * Extract part of that object and pass it to a hook/jsx so that _part_ becomes frozen * Mutate `x`, even indirectly. In the old model we can still independently memoize the value from the middle step, since we assume that part of the larger value is not changing. In the new model, the mutation from the later step effectively overrides the freeze effect in step 2, and considers the value to have changed later anyway. We've already rolled out and vetted the previous behavior, confirming that the heuristic of "that part of the mutable object is fozen now" is generally safe. I'll fix in a follow-up. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33522). * #33571 * #33558 * #33547 * #33543 * #33533 * #33532 * #33530 * #33526 * __->__ #33522 * #33518

This allows us to type things like `nullthrows()` or `identity()` functions where the return type is polymorphic on the input. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33526). * #33571 * #33558 * #33547 * #33543 * #33533 * #33532 * #33530 * __->__ #33526 * #33522 * #33518

Now that we have support for defining aliasing signatures in moduleTypeProvider, which uses string names for receiver/args/returns/etc, we can reuse that same form for builtin declarations. The declarations are written in the unparsed form and than parsed/validated when registered (in the addFunction/addHook call). This also required flushing out configs/schemas for more effect types. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33530). * #33571 * #33558 * #33547 * #33543 * #33533 * #33532 * __->__ #33530

--- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33532). * #33571 * #33558 * #33547 * #33543 * #33533 * __->__ #33532 * #33530

Start of docs describing the effects and the inference rules. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33533). * #33571 * #33558 * #33547 * #33543 * __->__ #33533 * #33532 * #33530

…tion expressions (#33543) Adds some typed helpers to represent aliasing, assign, capture, createfrom, and mutate effects along with representative runtime behavior, and then adds tests to demonstrate that we model capture->createfrom and createfrom->capture correctly. There is one case (createfrom->capture in a lambda) where we infer a less precise effect, but in the more conservative direction (we include more code/deps than necesssary rather than fewer). --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33543). * #33571 * #33558 * #33547 * __->__ #33543

By accident we were only ever checking the compiled output, but the intention was in general to be able to compare memoization with/without forget.

Ensures that effects are well-formed with respect to the rules: * For a given instruction, each place is only initialized once (w one of Create, CreateFrom, Assign) * Ensures that Alias targets are already initialized within the same instruction (should have a Create before them) * Preserves Create and similar instructions * Avoids duplicate instructions when inferring effects of function expressions

By accident we were only ever checking the compiled output, but the intention was in general to be able to compare memoization with/without forget. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33547). * #33571 * #33558 * __->__ #33547

Removes unnecessary debugging code in the new inference passes now that they've stabilized more. --- [//]: # (BEGIN SAPLING FOOTER) Stack created with [Sapling](https://sapling-scm.com). Best reviewed with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33571). * __->__ #33571 * #33558 * #33547

facebook-github-bot added the CLA Signed label Jun 17, 2025

github-actions bot added the React Core Team Opened by a member of the React Core Team label Jun 17, 2025

josephsavona mentioned this pull request Jun 18, 2025

[compiler] Cleanup debugging code #33571

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josephsavona force-pushed the pr33558 branch from 9987335 to 2218542 Compare June 18, 2025 16:39

josephsavona mentioned this pull request Jun 18, 2025

[compiler] Remove unnecessary fixture #33572

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josephsavona force-pushed the pr33558 branch from 2218542 to 3c9cc32 Compare June 18, 2025 16:54

mofeiZ reviewed Jun 18, 2025

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josephsavona force-pushed the pr33558 branch from 3c9cc32 to 11fbdb2 Compare June 18, 2025 20:00

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josephsavona mentioned this pull request Jun 18, 2025

[compiler] update fixtures #33573

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josephsavona force-pushed the pr33558 branch from 85dce8e to 387a6bb Compare June 18, 2025 22:31

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josephsavona added 2 commits June 18, 2025 15:59

[compiler] Fix <ValidateMemoization>

963970b

By accident we were only ever checking the compiled output, but the intention was in general to be able to compare memoization with/without forget.

josephsavona force-pushed the pr33558 branch from 64a065a to fc2c4f2 Compare June 18, 2025 23:00

josephsavona merged commit d37faa0 into main Jun 18, 2025
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Upgrade React from b7e2de63-20250611 to 79d9aed7-20250620 vercel/next.js#80710

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Upgrade React from 197d6a04-20250424 to 79d9aed7-20250620 vercel/next.js#79477

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[compiler] Preserve Create effects, guarantee effects initialize once #33558

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josephsavona commented Jun 17, 2025 •

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[compiler] Preserve Create effects, guarantee effects initialize once #33558

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