The compiler does not flag the code as an error when missing parentheses for extension methods that embed string interpolation

[Nora-Zhou01]

.NET version

.NET SDK 10.0.100-alpha.1.24573.1

Did it work in .NET Framework?

Yes

Did it work in any of the earlier releases of .NET Core or .NET 5+?

Yes, it's a regression issue, it works in .NET 5.0, but does not work in .NET 6.0 and latest 10.0.

Issue description

When miss the parentheses for an extension method that embeds string interpolation, the compiler does not flag the code as an error and the code compiles without errors

.NET 10.0 (.NET 8.0 and .NET 9.0 with the same results)

.NET 7.0 （.NET 6.0 results are the same)

.NET 5.0

Steps to reproduce

1. Launch the StringInterpolationFeature.zip project
2. View Test.cs code

More info:
The initial feedback ticket is: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/2307287

[merriemcgaw]

This looks like a potential language issue, so we're moving this over to Roslyn to see if it looks familiar to them.