[PATCH] Offer typo suggestions for 'using'.

Tue Jul 9 15:23:40 PDT 2013

That cleaned things up a bit. Now for the cases where the code used to
remove the using decl it instead suggests a fully-qualified
replacement to preserve syntax correctness while still allowing the
compilation to continue:

namespace using_suggestion_ty_dropped_specifier {
class AAA {}; // expected-note
{{'::using_suggestion_ty_dropped_specifier::AAA' declared here}}
namespace N { }
using N::AAA; // expected-error {{no member named 'AAA' in namespace
'using_suggestion_ty_dropped_specifier::N'; did you mean
'::using_suggestion_ty_dropped_specifier::AAA'?}}
}

On Tue, Jul 9, 2013 at 1:09 PM, Kaelyn Uhrain <rikka at google.com> wrote:
> The new patch looks pretty good except for one thing: the handling of a typo
> correction that removed the name qualifier.
>
> Right now in the case where the best correction is an unqualified name, the
> error message suggests replacing the qualified name with the unqualified one
> in the "using" statement but will sometimes include a FixIt to remove the
> entire "using" statement. Since a "using" statement with an unqualified name
> is not valid syntax, you need to either change the error message to suggest
> dropping the "using" statement in this situation, or you need to change
> UsingValidatorCCC::ValidateCandidate to exclude any correction candidates
> that would drop the qualifier. Since removing entire statements is a big
> stretch beyond typo correction (which just suggests alternate, potentially
> qualified, identifiers), I vote strongly for the latter option of rejecting
> candidates that would result in having an unqualified name in the "using"
> statement--which is to say, reject candidates where droppedSpecifier would
> be true, and in the diagnostic message just use a literal 0 since
> droppedSpecifier would never be true.
>
> As a minor nit, your change to Sema::BuildUsingDeclaration can be further
> simplified by dropping the "if" from "if (NamedDecl *ND =
> Corrected.getCorrectionDecl())" since UsingValidatorCCC rejects any
> candidate that does not have a NamedDecl. Once that "if" is gone you can
> drop the second "if (R.empty())" and just mark the UsingDecl as invalid,
> etc, if typo correction fails.
>
> On Tue, Jul 9, 2013 at 10:46 AM, Luke Zarko <zarko at google.com> wrote:
>>
>> Thanks for the feedback!
>>
>> 1- I've removed the guard.
>> 2- Done. I've also added a FixIt to remove using decls that typo
>> correction claims have unnecessary specifiers.
>> 3- Done; I believe I understand what droppedSpecifier means, but
>> there's a few tests I added in test/SemaCXX/using-decl-1.cpp that seem
>> to show that it's maybe not making all the corrections it might be
>> able to (is droppedSpecifier all-or-nothing?)
>>
>> On Mon, Jul 8, 2013 at 11:14 AM, Kaelyn Uhrain <rikka at google.com> wrote:
>> > Luke,
>> >
>> > I just looked through the patch and have a few questions/comments about
>> > it:
>> >
>> > 1) Why do you only perform typo correction when the scope is not NULL? I
>> > did
>> > not see any issues within tools/clang/test/ with the guard removed.
>> > Plus, as
>> > I mentioned on IRC, there is only one path in typo correction that
>> > dereferences the scope without checking it is not NULL, that path seems
>> > to
>> > be a hard-to-reach path and/or irrelevant in the context you are running
>> > it
>> > (iirc, it was only reached from a very ObjC-specific code path), and is
>> > most
>> > likely a bug in the code.
>> >
>> > 2) Is there a reason you aren't providing a fixit hint for the typo
>> > correction? If so, why can't one be provided? (And in the case that a
>> > fixit
>> > cannot be provided, you need to drop the declaration of CorrectedStr
>> > since
>> > it isn't being used.) If a fixit hint can be provided, please do and add
>> > a
>> > test for the fixit hint to an appropriate file under test/FixIt/;
>> > basically
>> > you just need to put one of your tests that offers a correction under
>> > there
>> > to make sure that the fixit hint provides the right substitution in the
>> > right place and doesn't introduce additional compilation errors.
>> >
>> > 3) You'll need to update your patch against clang HEAD and make sure
>> > your
>> > tests still run, since last week I submitted some typo correction
>> > changes
>> > and diag::err_no_member_suggest takes an additional argument to support
>> > dropping namespace qualifiers (look for declarations of "bool
>> > droppedSpecifier", e.g. in TryNamespaceTypoCorrection in SemaDeclCXX.cpp
>> > or
>> > in Sema::BuildCXXNestedNameSpecifier in SemaCXXScopeSpec.cpp, for
>> > examples
>> > of how to determine if the correction is dropping the name specifier but
>> > not
>> > changing the base identifier).
>> >
>> > Cheers,
>> > Kaelyn
>> >
>> >
>> > On Mon, Jul 8, 2013 at 10:28 AM, Luke Zarko <zarko at google.com> wrote:
>> >>
>> >> Ping--is there still something that needs to be done to this?
>> >>
>> >>
>> >> On Wed, Jun 26, 2013 at 3:04 PM, Luke Zarko <zarko at google.com> wrote:
>> >> > Thanks for looking it over!
>> >> >
>> >> > I've attached an updated patch with the indent fix (clang-format
>> >> > wanted the extra two spaces for some reason) and tests for
>> >> > IsTypeName/isa<TypeDecl> combinations. I moved the tests to
>> >> > using-decl-1.cpp; they seemed more appropriate there.
>> >> >
>> >> > It's unclear how to get into the IsInstantiation case, since the
>> >> > callers of BuildUsingDeclaration always seem to pass in 0 for Scope
>> >> > when they pass true for instantiation
>> >> > (TemplateDeclInstantiator::VisitUnresolvedUsingTypenameDecl,
>> >> > TemplateDeclInstantiator::VisitUnresolvedUsingValueDecl). Using
>> >> > getScopeForContext(CurContext) to try and get at a Scope when I need
>> >> > it for CorrectTypo returned null. UsingValidatorCCC's checks should
>> >> > be
>> >> > logically equivalent to the checks subsequent in the source file.
>> >> >
>> >> > On Wed, Jun 26, 2013 at 12:41 PM, Richard Smith
>> >> > <richard at metafoo.co.uk>
>> >> > wrote:
>> >> >> On Wed, Jun 26, 2013 at 12:35 PM, Luke Zarko <zarko at google.com>
>> >> >> wrote:
>> >> >>> I found a case where Clang doesn't yet help with typo correction:
>> >> >>>
>> >> >>> tests/base_using.cc:
>> >> >>>
>> >> >>> namespace Q { class AAA {}; }
>> >> >>> using Q::AAB;
>> >> >>>
>> >> >>> Before:
>> >> >>>
>> >> >>> tests/base_using.cc:2:10: error: no member named 'AAB' in namespace
>> >> >>> 'Q'
>> >> >>> using Q::AAB;
>> >> >>>       ~~~^
>> >> >>>
>> >> >>> After:
>> >> >>>
>> >> >>> tests/base_using.cc:2:10: error: no member named 'AAB' in namespace
>> >> >>> 'Q'; did you mean 'AAA'?
>> >> >>> using Q::AAB;
>> >> >>>       ~~~^
>> >> >>> tests/base_using.cc:1:21: note: 'AAA' declared here
>> >> >>> namespace Q { class AAA {}; }
>> >> >>>                     ^
>> >> >>
>> >> >> Code change looks good, but could do with more test coverage for the
>> >> >> type name / non-type-name / in instantiation cases.
>> >> >>
>> >> >> +        Diag(R.getNameLoc(), diag::err_no_member_suggest)
>> >> >> +            << NameInfo.getName() << LookupContext <<
>> >> >> CorrectedQuotedStr
>> >> >> +            << SS.getRange();
>> >> >>
>> >> >> We typically indent << only two spaces, not four (clang-format
>> >> >> bug?).
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>> >
>> >
>>
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