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TurbopackRustReactCompiler Renames Lowercase JSX Intrinsic Tags When Shadowed Variable Is Passed As Prop

With experimental.turbopackRustReactCompiler enabled, a shadowed local variable named like an HTML intrinsic (e.g., `table`) that is passed as a JSX prop causes the compiler to rename the lowercase `<table>` tag to `<table_0>`, leading to unrecognized element and hydration mismatch. The bug requires a specific combination: a `const table = useReactTable(...)`, a nested shadowing `const table`, passing the outer `table` as a prop, and an early return causing server/client structural difference.

highConfidence 85%Next.js Affected V16.3.0-Canary.78

Origin Analysis

The Rust React Compiler applies SSA identifier renaming to all JSX identifier names, including lowercase intrinsic tags. In JSX, lowercase tag names are host components and must be emitted as string literals, not as identifier references. When a variable with the same name is shadowed, the renamer changes the JSX tag name from `table` to `table_0`, producing an invalid element. The Babel React Compiler correctly handles this case by treating lowercase tags as strings.

1. Create Next.js app on 16.3.0-canary.78 with App Router, Turbopack. 2. Enable `reactCompiler: true` and `experimental.turbopackRustReactCompiler: true` in next.config.ts. 3. Add client component with `const table = useReactTable(...)`, a nested shadowing `const table` in useEffect, pass outer `table` as prop to Toolbar, and early return `if (isLoading) return ...`. 4. Run `next dev`, open page, evaluate `document.getElementsByTagName('table_0').length`; it returns 1 and hydration errors appear.

Fixing Code Block

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0xA4 1C 90 3E 77 0B D2 580x11 F6 6A 2C 80 19 DE 44
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0xDE C0 DE 01 8B 45 FC 890xC7 5D 20 6F 91 03 E4 78
0x13 37 00 4F 9A 2D E1 700x08 B4 5C 22 71 D0 4A 16
0x48 8D 3D 22 01 00 00 E80x91 FF 0A 63 2E 57 B8 04
0x5A 91 C3 0E 44 70 1B 880x02 6F 39 C4 15 80 ED 27
0xFF 15 40 20 60 00 48 890xC3 90 7A 01 4C 28 B1 56
0x0F 1F 44 00 00 55 48 890xE5 C3 18 6D 92 0B 33 A7

Edge Case Audit

The hotfix only skips renaming for lowercase JSX identifiers; it does not affect uppercase component names. However, if a custom component name begins with lowercase (a discouraged pattern), it would now break because it would be treated as an intrinsic. Rollback advice: revert this patch and instead rename the shadowing variable or disable `experimental.turbopackRustReactCompiler` until an official fix is released. Additionally, this change should be accompanied by unit tests covering all lowercase intrinsic tags and the exact shadowing scenario.