Which @angular/* package(s) are the source of the bug?

compiler

Is this a regression?

No

Description

Since the introduction of the control flow syntax, the { and } characters must be replaced in templates by HTML character entities, i.e. { and }, or &#lbrace; and &#rbrace.

But when you use these character entities with the goal of showing the syntax Angular uses for interpolation, then the compiler interprets these entities as actual braces and considers it's a real interpolation.

So, for example, having {{ }} in a template makes the compiler fail with the error

NG5002: Parser Error: Blank expressions are not allowed in interpolated strings at column 0 in [{{ }}
]

Please provide a link to a minimal reproduction of the bug

https://stackblitz.com/edit/stackblitz-starters-yvltw3bh?file=src%2Fmain.ts

Please provide the exception or error you saw

NG5002: Parser Error: Blank expressions are not allowed in interpolated strings at column 0 in [{{ }}
]

Please provide the environment you discovered this bug in (run ng version)

Angular CLI: 20.0.3
Node: 22.16.0
Package Manager: npm 10.9.2
OS: darwin x64

Angular: 20.0.4
... common, compiler, compiler-cli, core, forms
... platform-browser, platform-server, router

Package                      Version
------------------------------------------------------
@angular-devkit/architect    0.2000.3
@angular-devkit/core         20.0.3
@angular-devkit/schematics   20.0.3
@angular/build               20.0.3
@angular/cli                 20.0.3
@angular/ssr                 20.0.3
@schematics/angular          20.0.3
rxjs                         7.8.2
typescript                   5.8.3
zone.js                      0.15.1

Anything else?

I would expect the compiler to treat ignore character entities regarding interpolation, just as it ignores them regarding the control flow.