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A dumber but related habit I've gotten into is that if I want to use AI to do some sort of refactoring on a C# codebase, instead of asking it to edit the code d

A dumber but related habit I've gotten into is that if I want to use AI to do some sort of refactoring on a C# codebase, instead of asking it to edit the code directly I ask it to write a code transformation using the Roslyn compiler API, then run that on the code. The result is less likely to have subtle bugs if it appears to work and gets through a light code review on the transformation (i.e., attempts to cheat with weird special-casing are more likely to stand out amongst the Roslyn API code, and if there isn't such weird special-casing but the code is wrong, the result is more likely to be completely broken rather than subtly broken)

twosdai 2mo ago
This sounds interesting, I am really naive. I don't code in C#, is there an analogy for other programming languages, like GO, or Python or Typescript? Like are you prompting like: --- I need code that does X,Y, and Z. Write it so that the Roslyn compiler on this machine can compile and the code passes the repo's styling and formatting requirements. --- Or something else.
- bob1029 2mo ago
  Here's the official docs if it helps https://learn.microsoft.com/en-us/dotnet/csharp/roslyn-sdk/tutorials/how-to-write-csharp-analyzer-code-fix https://learn.microsoft.com/en-us/dotnet/csharp/roslyn-sdk/t...
- kaashif 2mo ago
  No, they are talking about refactoring, not adding new functionality to code. So it would be something like: Rewrite this Python code to use match/case instead of if/elif/else chains, write a script using the ast module to rewrite the code, do not edit it yourself, also write some tests with clear inputs and outputs I can inspect. Or something.
  - xenophonf 2mo ago
    > Rewrite this Python code to use match/case instead of if/elif/else chains Is this a real example of something people use AI to do? If so, I don't understand why that's difficult, because prompting the AI to do stuff with ASTs etc. seems a bit over the top.
    - kaashif 2mo ago
      Why? Are people actually using AI to do programmatic refactors over million line codebases directly? That is far more insane. Using AI to write ruff rules or clang-tidy rules with fixes is literally the same thing and obviously best practice over running AI in a pre-commit hook to do those checks and refactors...
- contextfree 2mo ago
  Roslyn API basically lets you plug in to the C# compiler or use parts of it so that you can get the same view of the abstract syntax tree, typechecking, flow analysis, etc. that the compiler does. So it's a way to work with C# code at that level rather than just via textual manipulation. I'm less familiar with other languages but I think many have compilers with analogous capabilities, I know Haskell has the GHC API and I think the LLVM-based Clang (C++) and Rust compilers let you do similar things
rubenvanwyk 2mo ago
Is it open source, can you share? Have been pondering using source generators to achieve a similar effect and have the LLM build the source generator ‘framework’ that code would derive from rather than just generating the code itself, you create the code generation framework.

twosdai 2mo ago

This sounds interesting, I am really naive. I don't code in C#, is there an analogy for other programming languages, like GO, or Python or Typescript? Like are you prompting like: --- I need code that does X,Y, and Z. Write it so that the Roslyn compiler on this machine can compile and the code passes the repo's styling and formatting requirements. --- Or something else.

bob1029 2mo ago
Here's the official docs if it helps https://learn.microsoft.com/en-us/dotnet/csharp/roslyn-sdk/tutorials/how-to-write-csharp-analyzer-code-fix https://learn.microsoft.com/en-us/dotnet/csharp/roslyn-sdk/t...
kaashif 2mo ago
No, they are talking about refactoring, not adding new functionality to code. So it would be something like: Rewrite this Python code to use match/case instead of if/elif/else chains, write a script using the ast module to rewrite the code, do not edit it yourself, also write some tests with clear inputs and outputs I can inspect. Or something.
- xenophonf 2mo ago
  > Rewrite this Python code to use match/case instead of if/elif/else chains Is this a real example of something people use AI to do? If so, I don't understand why that's difficult, because prompting the AI to do stuff with ASTs etc. seems a bit over the top.
  - kaashif 2mo ago
    Why? Are people actually using AI to do programmatic refactors over million line codebases directly? That is far more insane. Using AI to write ruff rules or clang-tidy rules with fixes is literally the same thing and obviously best practice over running AI in a pre-commit hook to do those checks and refactors...
contextfree 2mo ago
Roslyn API basically lets you plug in to the C# compiler or use parts of it so that you can get the same view of the abstract syntax tree, typechecking, flow analysis, etc. that the compiler does. So it's a way to work with C# code at that level rather than just via textual manipulation. I'm less familiar with other languages but I think many have compilers with analogous capabilities, I know Haskell has the GHC API and I think the LLVM-based Clang (C++) and Rust compilers let you do similar things

rubenvanwyk 2mo ago

Is it open source, can you share? Have been pondering using source generators to achieve a similar effect and have the LLM build the source generator ‘framework’ that code would derive from rather than just generating the code itself, you create the code generation framework.