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'?}}
----------------
erichkeane wrote:
> aaron.ballman wrote:
> > 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?
> Not particularly. I don't have a good hold of how much we want to suggest
> with the 'did you mean'. Line 9 and line 10 here are unfortunate, I would
> hope those would happen? Its unfortunate we don't have a way to figure out
> these common typos.
Yeah, ideally I want this to "do what I'm thinking" and make all three
situations work. :-D
================
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'?}}
----------------
erichkeane wrote:
> aaron.ballman wrote:
> > 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.
> Might I suggest we just emit the 'first' suggestion? This isn't really
> perfect, but I would think that our users put very little thought into it
> when we suggest the wrong thing.
Notionally that makes sense, but the situation I'm worried about is when users
pass `-fixit` to the compiler -- then it automatically does whatever, but we
have no idea whether that whatever is reasonable or not when we have more than
one option.
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