[swift2objc] fear: support operator overloading

[Hassnaa9]

Summary

This PR addresses the issue of the generator crashing when encountering Swift operator declarations (e.g., +, ***, +=). It introduces a robust mechanism to sanitize illegal Objective-C identifiers and correctly parse operator symbols from the Swift SymbolGraph.

Changes

Parser

• Added support for swift.func.op in parse_declarations.dart.
  I verified through SymbolGraph JSON analysis (see attached evidence) that swift.func.op symbols share the same structure as regular swift.func.
• Reused parseMethodDeclaration with isStatic: true for these symbols, which is safe and consistent with Swift's static operator implementation.

UniqueNamer

• Implemented a _sanitize method to transform non-alphanumeric characters into valid Objective-C identifiers.
• Added a mapping dictionary for common operators (e.g., + → plus, - → minus).
• Implemented a fallback mechanism to ASCII codes (opXX) for custom or unknown symbols to prevent naming collisions and illegal syntax.
• Ensured that identifiers do not start with numbers (prefixed with n).
  fixes: [swift2objc] Support operator overloading #2947

[Hassnaa9]

@liamappelbe Can you check this PR please?
thanks in advance!

[github-actions]

PR Health

License Headers ✔️

// Copyright (c) 2026, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

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pkgs/hooks_runner/test_data/download_assets/hook/build.dart
pkgs/jni/test/debug_release_test.dart
pkgs/objective_c/example/command_line/lib/main.dart
pkgs/objective_c/lib/src/ns_input_stream.dart

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[coveralls]

coverage: 81.707%. remained the same
when pulling 9d84eff on Hassnaa9:feature/operator-overload-conversion
into 4fe954c on dart-lang:main.

[liamappelbe]

@Hassnaa9 You'll need to fix the analysis errors reported by the bot before the tests will run. Make sure to do dart analyze and dart format before you upload so that the tests will run.