erichkeane 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'?}}
----------------
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.
================
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'?}}
----------------
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.
Repository:
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https://reviews.llvm.org/D124726/new/
https://reviews.llvm.org/D124726
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