fix: ignore typescript abstract methods during code transformation

[caiquetorres]

Problem

When transforming TypeScript code, abstract methods were incorrectly included in the generated JavaScript output. Given the following TypeScript code:

abstract class MyClass {
    abstract myMethod(): void;
}

The transformation produced invalid JavaScript:

class MyClass {
    myMethod()
}

This resulted in a syntax error in the browser.

Solution

This PR ensures that abstract methods are removed during transformation, so the output JavaScript becomes:

class MyClass {}

Resolves #15260

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Tests and linting

• Run the tests with pnpm test and lint the project with pnpm lint

[changeset-bot]

🦋 Changeset detected

Latest commit: 4723578

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
svelte	Patch

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[github-actions]

Playground

pnpm add https://pkg.pr.new/svelte@15267

[dummdidumm]

Thank you, but we should instead strip that AST node completely within https://github.com/sveltejs/svelte/blob/main/packages/svelte/src/compiler/phases/1-parse/remove_typescript_nodes.js - that way we don't need to deal with TS-specifics later on in the compiler.

[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-svelte-15267-svelte.vercel.app/

[dummdidumm]

thank you!