aaron.ballman added inline comments.
================
Comment at: clang/test/Preprocessor/suggest-typoed-directive.c:3
+
+// id: not suggested to '#if'
+// ifd: expected-warning@+11 {{invalid preprocessing directive, did you
mean '#if'?}}
----------------
This still suggests that something's wrong as I would imagine this would have
an edit distance of 1. Oh, interesting... setting the replacement option to
`false` may have made things better for the `elfindef` case but worse for the
`id` case?
This is tricky because we want to identify things that are most likely simple
typos but exclude things that may reasonably not be a typo but a custom
preprocessor directive. Based on that, I *think* setting the replacement option
to `true` gives the more conservative answer (it treats a replacement as 1 edit
rather than 2). @erichkeane -- do you have thoughts?
================
Comment at: clang/test/Preprocessor/suggest-typoed-directive.c:10
+// expected-warning@+11 {{'#elfidef' directive not found, did you mean
'#elifdef'?}}
+// expected-warning@+11 {{'#elfindef' directive not found, did you mean
'#elifdef'?}}
+// expected-warning@+11 {{'#elsi' directive not found, did you mean '#else'?}}
----------------
ken-matsui wrote:
> aaron.ballman wrote:
> > ken-matsui wrote:
> > > aaron.ballman wrote:
> > > > ken-matsui wrote:
> > > > > aaron.ballman wrote:
> > > > > > It's interesting that this one suggested `#elifdef` instead of
> > > > > > `#elifndef` -- is there anything that can be done for that?
> > > > > >
> > > > > > Also, one somewhat interesting question is whether we want to
> > > > > > recommend `#elifdef` and `#elifndef` outside of C2x/C++2b mode.
> > > > > > Those directives only exist in the latest language standard, but
> > > > > > Clang supports them as a conforming extension in all language
> > > > > > modes. Given that this diagnostic is about typos, I think I'm okay
> > > > > > suggesting the directives even in older language modes. That's as
> > > > > > likely to be a correct suggestion as not, IMO.
> > > > > > It's interesting that this one suggested `#elifdef` instead of
> > > > > > `#elifndef` -- is there anything that can be done for that?
> > > > >
> > > > > I found I have to use `std::min_element` instead of
> > > > > `std::max_element` because we are finding the nearest (most minimum
> > > > > distance) string. Meanwhile, `#elfindef` has 2 distance with both
> > > > > `#elifdef` and `#elifndef`. After replacing `std::max_element` with
> > > > > `std::min_element`, I could suggest `#elifndef` from `#elfinndef`.
> > > > >
> > > > > > Also, one somewhat interesting question is whether we want to
> > > > > > recommend `#elifdef` and `#elifndef` outside of C2x/C++2b mode.
> > > > > > Those directives only exist in the latest language standard, but
> > > > > > Clang supports them as a conforming extension in all language
> > > > > > modes. Given that this diagnostic is about typos, I think I'm okay
> > > > > > suggesting the directives even in older language modes. That's as
> > > > > > likely to be a correct suggestion as not, IMO.
> > > > >
> > > > > I agree with you because Clang implements those directives, and the
> > > > > suggested code will also be compilable. I personally think only not
> > > > > compilable suggestions should be avoided. (Or, we might place
> > > > > additional info for outside of C2x/C++2b mode like `this is a
> > > > > C2x/C++2b feature but compilable on Clang`?)
> > > > >
> > > > > ---
> > > > >
> > > > > According to the algorithm of `std::min_element`, we only get an
> > > > > iterator of the first element even if there is another element that
> > > > > has the same distance. So, `#elfindef` only suggests `#elifdef` in
> > > > > accordance with the order of `Candidates`, and I don't think it is
> > > > > beautiful to depend on the order of candidates. I would say that we
> > > > > can suggest all the same distance like the following, but I'm not
> > > > > sure this is preferable:
> > > > >
> > > > > ```
> > > > > #elfindef // diag: unknown directive, did you mean #elifdef or
> > > > > #elifndef?
> > > > > ```
> > > > >
> > > > > I agree with you because Clang implements those directives, and the
> > > > > suggested code will also be compilable. I personally think only not
> > > > > compilable suggestions should be avoided. (Or, we might place
> > > > > additional info for outside of C2x/C++2b mode like this is a
> > > > > C2x/C++2b feature but compilable on Clang?)
> > > >
> > > > I may be changing my mind on this a bit. I now see we don't issue an
> > > > extension warning when using `#elifdef` or `#elifndef` in older
> > > > language modes. That means suggesting those will be correct but only
> > > > for Clang, and the user won't have any other diagnostics to tell them
> > > > about the portability issue. And those particular macros are reasonably
> > > > likely to be used in a header where the user is trying to aim for
> > > > portability. So I'm starting to think we should only suggest those two
> > > > in C2x mode (and we should probably add a portability warning for
> > > > #elifdef and #elifndef, so I filed:
> > > > https://github.com/llvm/llvm-project/issues/55306)
> > > >
> > > > > I would say that we can suggest all the same distance like the
> > > > > following, but I'm not sure this is preferable:
> > > >
> > > > The way we typically handle this is to attach FixIt hints to a note
> > > > instead of to the diagnostic. This way, automatic fixes aren't applied
> > > > (because there are multiple choices to pick from) but the user is still
> > > > able to apply whichever fix they want in an IDE or other tool. It might
> > > > be worth trying that approach (e.g., if there's only one candidate,
> > > > attach it to the warning, and if there are two or more, emit a warning
> > > > without a "did you mean" in it and use a new note for the fixit. e.g.,
> > > > ```
> > > > #elfindef // expected-warning {{invalid preprocessing directive}} \
> > > > expected-note {{did you mean '#elifdef'?}} \
> > > > expected-note {{did you mean '#elifndef'?}}
> > > > ```
> > > > WDYT?
> > > > I may be changing my mind on this a bit. I now see we don't issue an
> > > > extension warning when using `#elifdef` or `#elifndef` in older
> > > > language modes. That means suggesting those will be correct but only
> > > > for Clang, and the user won't have any other diagnostics to tell them
> > > > about the portability issue. And those particular macros are reasonably
> > > > likely to be used in a header where the user is trying to aim for
> > > > portability. So I'm starting to think we should only suggest those two
> > > > in C2x mode (and we should probably add a portability warning for
> > > > #elifdef and #elifndef, so I filed:
> > > > https://github.com/llvm/llvm-project/issues/55306)
> > > >
> > >
> > > Certainly, it would be less confusing to the user to avoid suggestions
> > > regarding those two.
> > > I'm going to fix my code to avoid suggesting them in not C2x mode.
> > >
> > > Thank you for submitting the issue, I also would like to work on it.
> > >
> > > > The way we typically handle this is to attach FixIt hints to a note
> > > > instead of to the diagnostic. This way, automatic fixes aren't applied
> > > > (because there are multiple choices to pick from) but the user is still
> > > > able to apply whichever fix they want in an IDE or other tool. It might
> > > > be worth trying that approach (e.g., if there's only one candidate,
> > > > attach it to the warning, and if there are two or more, emit a warning
> > > > without a "did you mean" in it and use a new note for the fixit. e.g.,
> > > > ```
> > > > #elfindef // expected-warning {{invalid preprocessing directive}} \
> > > > expected-note {{did you mean '#elifdef'?}} \
> > > > expected-note {{did you mean '#elifndef'?}}
> > > > ```
> > > > WDYT?
> > >
> > > This is really cool, but don't you care about the redundancy of `did you
> > > mean` in terms of the llvm team culture?
> > > If not, I will implement notes like the above.
> > > Certainly, it would be less confusing to the user to avoid suggestions
> > > regarding those two. I'm going to fix my code to avoid suggesting them in
> > > not C2x mode.
> >
> > +1, thank you!
> >
> > > This is really cool, but don't you care about the redundancy of did you
> > > mean in terms of the llvm team culture? If not, I will implement notes
> > > like the above.
> >
> > I would care if the list were potentially unbounded (like, say, with
> > identifiers in general), but because we know this list will only have a max
> > of two entries on it in this case, it seems reasonable to me. I
> > double-checked with @erichkeane to see if he thought it would be an issue,
> > and he agreed that it being a fixed list makes it pretty reasonable.
> >
> > However, that discussion did raise a question -- why are there two
> > suggestions? elifdef requires a swap + delete and elifndef requires just a
> > swap, so we would have thought that it would have been the only option in
> > the list.
> With the implementation of Lev distances used in llvm, I could simply suggest
> `#elifdef` from `#elfidef` and `#elifndef` from `#elfindef`.
>
> So, in this situation, do you think that we still need to add two notes for
> conflicted distances?
No, let's skip the two note behavior. If we find ourselves with multiple
suggestions, we'll just leave off the "did you mean?" part of the diagnostic
entirely.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D124726/new/
https://reviews.llvm.org/D124726
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