Support braced Unicode escapes #67279

Which @angular/* package(s) are relevant/related to the feature request?

compiler

Description

Angular template expressions currently do not support ES6 braced Unicode escapes (e.g. \u{1F600}) in string literals. This limits the ability to represent modern Unicode code points (such as emoji and historic scripts) directly in templates.

Minimal reproduction

<div>{{ '\u{1F600}' }}</div>

Expected: Renders 😀
Actual: Renders the literal string \u{1F600} or an error.

Proposed solution

Extend the Angular compiler's template expression parser to support ES6 braced Unicode escapes (\u{...}) in string literals, matching JavaScript semantics. Legacy \uXXXX escapes should remain supported for backward compatibility.

Alternatives considered

• Using legacy \uXXXX escapes with surrogate pairs for non-BMP characters (e.g., emoji). This is error-prone and less readable, requiring manual calculation and two code units per character.
• Avoiding Unicode escapes and directly pasting Unicode characters. This is not always practical for code points outside BMP or for code generation scenarios.