Add deprecation warning for computed property names in enums

[magic-akari]

Summary

Add a deprecation warning for computed property names in enum members (e.g., ["key"] or [`key`]), along with a quick fix to convert them to simple string literals.

• Fix: Enum declarations should consistently disallow computed keys #42468

Background

As discussed in #42468 and #62649, TypeScript currently allows computed property names with literal expressions in enums:

enum CHAR {
    ['\t'] = 0x09,  // allowed, but semantically equivalent to '\t' = 0x09
    [`\r`] = 0x0D,
}

This syntax is:

• Rarely used in practice
• Not supported by Babel or typescript-eslint
• Semantically redundant — only literal expressions are allowed, so ['key'] is always equivalent to 'key'

Approach

To avoid breaking existing code, this PR takes a gradual deprecation approach:

1. Phase 1 (this PR): Add a suggestion diagnostic marking this syntax as deprecated, with an auto-fix
2. Phase 2 (future): Disallow this syntax entirely

This aligns with Anders' comment in #42468:
I wouldn't be opposed to disallowing computed property names in enums altogether... That said, I hate to break stuff.

Changes

• Add suggestion diagnostic (code 1550) for literal computed property names in enums
• Add quick fix: "Remove unnecessary computed property name syntax"
• Add "Fix All" support for batch conversion

[typescript-bot]

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

[typescript-bot]

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

[Copilot]

Pull request overview

This PR implements a gradual deprecation strategy for computed property names with literal expressions in enum members (e.g., ['\t'], [`\r`]). The approach adds a suggestion diagnostic (code 1550) with an automatic fix, preparing for eventual removal of this syntax while avoiding breaking existing code immediately.

Key changes:

• Added deprecation suggestion diagnostic for literal computed property names in enums
• Implemented quick fix to convert computed property syntax to simple string literals
• Added comprehensive fourslash tests for errors, suggestions, and code fixes

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/compiler/diagnosticMessages.json	Adds diagnostic message 1550 for deprecation warning and messages 95198/95199 for codefix descriptions
src/compiler/checker.ts	Adds suggestion diagnostic in computeEnumMemberValue when computed property names are detected
src/services/codefixes/convertComputedEnumMemberName.ts	Implements the codefix to convert ['\t'] → "\t" style transformations with fix-all support
src/services/_namespaces/ts.codefix.ts	Registers the new codefix module
tests/cases/fourslash/enumComputedPropertyNameError.ts	Tests that non-literal computed properties get error 1164
tests/cases/fourslash/enumComputedPropertyNameDeprecated.ts	Tests that literal computed properties get suggestion 1550
tests/cases/fourslash/codeFixEnumComputedPropertyName.ts	Tests single instance code fix application
tests/cases/fourslash/codeFixEnumComputedPropertyNameAll.ts	Tests fix-all functionality across multiple instances