Allow element access on enum as computed property name in type literal

[driphtyio]

Fixes #25083

Problem

Enum keys with non-identifier names (e.g., '3x14') cannot be used as computed property keys in type literals because bracket access (Type['3x14']) produces an ElementAccessExpression node that isLateBindableAST() does not recognize.

Reproduction

enum Type {
  Foo = 'foo',
  '3x14' = '3x14'
}

type TypeMap = {
  [Type.Foo]: any
  [Type['3x14']]: any  // Error 1170
}

Fix

3-line addition to isLateBindableAST() in src/compiler/checker.ts: when the expression is an ElementAccessExpression with a string literal argument on an entity name, treat it as late-bindable.

Properties

• Minimal: 3 lines added
• Only expands acceptance (never rejects previously accepted code)
• Fixes a Good First Issue labeled Bug in the Backlog milestone

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Updates documentation wording and broadens the TypeScript checker’s definition of “late-bindable” AST nodes to include a specific element-access pattern.

Changes:

• Clarify Set.size JSDoc wording in es2015.collection.d.ts.
• Extend isLateBindableAST to treat Entity["prop"] (string-literal element access off an entity name) as late-bindable.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
src/lib/es2015.collection.d.ts	Small JSDoc wording tweak for Set.size.
src/compiler/checker.ts	Expands late-bindable detection logic for additional AST form.

Comments suppressed due to low confidence (1)

src/compiler/checker.ts:1

• The mixed || / && expression relies on operator precedence, which is easy to misread and error-prone during future edits (especially with the line break). Add explicit parentheses (or assign the element-access sub-check to a well-named boolean) to make the intended grouping unambiguous.

[RyanCavanaugh]

This doesn't meet the 6.0 patch bar #62963 (comment)