Guard parser expression compilation behind IsDynamicCodeSupported check

[ZingBallyhoo]

Removes ~1.5mb of dead code from the resulting binary when compiling with NativeAOT.

[sebastienros]

Is the intent that the whole compilation chain becomes removed from the final bit and only the standard behavior used? Which I am fine with, just want to understand how this behaves then. I assume this automatically makes the library safer for nativeaot support.

[ZingBallyhoo]

Is the intent that the whole compilation chain becomes removed from the final bit and only the standard behavior used?

Yes. While System.Linq.Expressions can work when trimming and under NativeAOT(via an interpreter), the implementation in Parlot+FastExpressionCompiler can't. The interpreter is quite big and just ends up being dead code as the AOT compiler can't reason that CompilationThreshold is never set to anything that isn't 0.

Apart from that, the library is fully trim compatible. Just annotating it is awkward because it requires adding

[RequiresUnreferencedCode("...incompatible with trimming")]
[RequiresDynamicCode("...incompatible with aot")]
public CompilationResult Compile(CompilationContext context)

on every single implementation of ICompilable.