[compiler] Add fault tolerance plan document

[everettbu]

Mirror of facebook/react#35828
Original author: josephsavona

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Add detailed plan for making the React Compiler fault-tolerant by
accumulating errors across all passes instead of stopping at the first
error. This enables reporting multiple compilation errors at once.

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Stack created with Sapling. Best reviewed with ReviewStack.

• #35838
• #35837
• #35836
• #35835
• #35834
• #35833
• #35832
• #35831
• #35830
• #35829
• -> #35828

[greptile-apps]

Greptile Summary

This PR adds a detailed plan document for making the React Compiler fault-tolerant by accumulating errors across all compilation passes instead of halting at the first error. The plan outlines 8 phases covering environment infrastructure, pipeline changes, HIR lowering, validation/inference pass updates, codegen, integration, and testing.

• The plan is well-structured and technically accurate based on the current codebase (e.g., lower() returning Result<HIRFunction, CompilerError>, validation passes using .unwrap(), runWithEnvironment returning CodegenFunction directly)
• Proposes an incremental migration path using env.tryRecord() as a transitional safety net, allowing phases to be landed independently
• Minor typo on line 20 ("construct record" should be "record" or "construct and record")
• Pattern labeling skips from "Pattern B" to "Pattern D" (no "Pattern C")

Confidence Score: 4/5

• This PR is safe to merge — it only adds a planning document with no code changes.
• Score of 4 reflects that this is a documentation-only PR with no runtime impact. The plan document is technically sound and aligns with the actual codebase structure. Minor issues (a typo and a skipped pattern label) are non-blocking.
• No files require special attention — this is a documentation-only change.

Important Files Changed

Filename	Overview
compiler/fault-tolerance-overview.md	New plan document detailing an 8-phase approach for making the React Compiler fault-tolerant. Technically sound and well-structured; minor typo on line 20.

_{Last reviewed commit: d30d189}

[greptile-apps]

_{1 file reviewed, 2 comments}

_{Edit Code Review Agent Settings | Greptile}

[greptile-apps]

Typo: duplicate word
"we should instead construct record the todo error" appears to have an extra word. Should this be "we should instead record the todo error" or "we should instead construct and record the todo error"?

Suggested change

	* BuildHIR should always produce an HIR without error. For syntax forms that are unsupported (currently throwing a Todo error), we should instead construct record the todo error on the environment, and construct a partial HIR. The exact form of the partial HIR can be situation specific:
	* BuildHIR should always produce an HIR without error. For syntax forms that are unsupported (currently throwing a Todo error), we should instead record the todo error on the environment, and construct a partial HIR. The exact form of the partial HIR can be situation specific:

Prompt To Fix With AI

This is a comment left during a code review.
Path: compiler/fault-tolerance-overview.md
Line: 20

Comment:
**Typo: duplicate word**
"we should instead construct record the todo error" appears to have an extra word. Should this be "we should instead **record** the todo error" or "we should instead **construct and record** the todo error"?

```suggestion
* BuildHIR should always produce an HIR without error. For syntax forms that are unsupported (currently throwing a Todo error), we should instead record the todo error on the environment, and construct a partial HIR. The exact form of the partial HIR can be situation specific:
```

How can I resolve this? If you propose a fix, please make it concise.

[greptile-apps]

Missing "Pattern C" label
The document labels error handling patterns as "Pattern A", "Pattern B", and "Pattern D", skipping "Pattern C". Was there an intended Pattern C that was removed, or should "Pattern D" be relabeled to "Pattern C" for consistency?

Prompt To Fix With AI

This is a comment left during a code review.
Path: compiler/fault-tolerance-overview.md
Line: 201

Comment:
**Missing "Pattern C" label**
The document labels error handling patterns as "Pattern A", "Pattern B", and "Pattern D", skipping "Pattern C". Was there an intended Pattern C that was removed, or should "Pattern D" be relabeled to "Pattern C" for consistency?

How can I resolve this? If you propose a fix, please make it concise.

[everettbu]

Upstream PR was closed or merged. Code is synced via branch mirror.