Configuration option to treat checked context as the default instead of unchecked

[ds5678]

Is your feature request related to a problem?

In most of my projects, I enable <CheckForOverflowUnderflow>true</CheckForOverflowUnderflow> for the extra safety, which makes operators use their checked variants. This configuration option would make decompiled output closer to what I would write.

Describe the solution you'd like

I haven't looked into the implementation details, but I know ILSpy has some context tracking for whether operations are currently happening in checked or unchecked context. I assume it should be fairly simple to switch which one is used "globally."

Additional context

I'm unsure how to make the compiler use a build property like CheckForOverflowUnderflow for the pretty test.

As with all my issues, I'm willing to contribute an implementation.

[siegfriedpammer]

For the test cases: the CompilerOptions enum should get a new member CheckForOverflowUnderflow or similar, just as we already have Force32Bit and NullableEnable. The implementation of Tester.CompileCSharp then needs to check for this flag and adjust all compiler invocations accordingly (add -checked- or -checked+ depending on flag).

For the implementation: I believe everything you need should be in AddCheckedBlocks (a C# AST transform).

[dgrunwald]

The actual AddCheckedBlocks implementation change is trivial.
The transform uses dynamic programming to minimize the "cost" described in the comment there; so it already solves for both cases (surrounding context is checked/unchecked).
You'd only need to change AddCheckedBlocks.Run to use the NodesToInsertInCheckedContext instead of the NodesToInsertInUncheckedContext, if the overall project-level context is checked.