Fix union type error reporting in getIterationTypesOfIterable

[Copilot]

When checking iterability of union types, errors were reported on individual non-iterable constituents (e.g., Type 'undefined') instead of the full union type (e.g., Type '[number, number] | undefined'), diverging from TypeScript's behavior.

declare let indices: RegExpIndicesArray; // extends Array<[number, number] | undefined>
let [[x, y]] = indices;
// Before: error TS2488: Type 'undefined' must have a '[Symbol.iterator]()' method...
// After:  error TS2488: Type '[number, number] | undefined' must have a '[Symbol.iterator]()' method...

Changes

• Move union handling from getIterationTypesOfIterableWorker to getIterationTypesOfIterable — TypeScript handles union iteration types in the outer function, iterating over constituents and failing the entire resolution if any constituent is non-iterable. The Go port was handling unions in the worker, which reported errors per-constituent and combined partial results instead of failing.
• Add compiler test regExpIndicesArrayDestructuring.ts covering the reported case.
• Delete 7 submodule diff files — existing baselines for ES5For-ofTypeCheck7, ES5For-ofTypeCheck9, ES5For-of30, noImplicitAnyLoopCrash, and destructuringArrayBindingPatternAndAssignment4 now match TypeScript exactly.

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Original prompt

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This section details on the original issue you should resolve

<issue_title>Spreading variable of RegExpIndicesArray type will cause error</issue_title>
<issue_description>## Steps to reproduce

1. Start a plain new project, with @typescript/native-preview@npm:7.0.0-dev.20260211.1 as dependency.
2. Run npx tsgo --init to get the default tsconfig.
3. Add a src/main.ts & run npx tsgo --noEmit.

// src/main.ts

declare let indices: RegExpIndicesArray;
let [[x, y]] = indices;

Behavior with typescript@6.0

No error, as it should be. See https://tsplay.dev/mqb9ZW.

Behavior with tsgo

src/main.ts:4:6 - error TS2488: Type 'undefined' must have a '[Symbol.iterator]()' method that returns an iterator.

4 let [[x, y]] = indices;
       ~~


Found 1 error in src/main.ts:4

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Note: The error is the same as if indices is of type indices | undefined. It seems only happen to RegExpIndicesArray, so I wonder if it is the case that tsgo cannot infer extended array element type correctly during spreading.</issue_description>

<agent_instructions>Make a compiler test for this issue first and commit it and its baselines, then look into the problem </agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Spreading variable of RegExpIndicesArray type will cause error #2767

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