On 26 August 2013 23:22, Chandler Carruth <[email protected]> wrote:
> > On Mon, Aug 26, 2013 at 11:09 PM, Nick Lewycky <[email protected]>wrote: > >> On 26 August 2013 22:53, Chandler Carruth <[email protected]> wrote: >> >>> I think this case has more problems than just verbosity... >>> >>> On Mon, Aug 26, 2013 at 10:38 PM, Nick Lewycky <[email protected]>wrote: >>> >>>> a.cc:1:56: error: no template named 'Foox'; did you mean 'Foo'? >>>> template <typename T> class Foo {}; class Bar : public Foox {}; >>>> [point at 'Foox' suggest 'Foo'] >>>> >>> >>> Why does it assume Foox is a template? >>> >> >> It's already proven that it's not not-a-template. >> >> a.cc:1:29: note: 'Foo' declared here >>>> template <typename T> class Foo {}; class Bar : public Foox {}; >>>> [point at 'Foo'] >>>> a.cc:1:56: error: expected template argument list after template-id >>>> template <typename T> class Foo {}; class Bar : public Foox {}; >>>> [point at 'Foox'] >>>> >>> >>> And given that we then hit this error, why do we even consider the Foo >>> typo correction? Do we prefer that over a "Fooxie" class due to shorter >>> edit distance? That doesn't seem right. I would intuitively expect the lack >>> of "<..." to be a stronger signal than any edit distance, and thus >>> disqualify template-ids from the typo correction candidate set. >>> >> >> No. We only go down this patch after we've done a lookup and typo >> correction on non-templates, and found nothing. >> > > I'm suggesting that a missing header or exceeding the maximum edit > distance threshold seems just as plausible as using a template without > template arguments. I'm not claiming that I have some strong reason to > believe one interpretation or the other to be more likely, only that it > doesn't seem clear-cut in either direction to me. > ... if it can't find a template, then it doesn't mention templates: $ echo 'class Bar : public Foo {};' | llvm/Debug+Asserts/bin/clang -x c++ - <stdin>:1:20: error: expected class name class Bar : public Foo {}; ^ 1 error generated. $ echo 'template<typename T> class Fooa; class Foob {}; class Bar : public Foo {};' | llvm/Debug+Asserts/bin/clang -x c++ - <stdin>:1:68: error: unknown class name 'Foo'; did you mean 'Foob'? template<typename T> class Fooa; class Foob {}; class Bar : public Foo {}; ^~~ Foob <stdin>:1:40: note: 'Foob' declared here template<typename T> class Fooa; class Foob {}; class Bar : public Foo {}; ^ 1 error generated. Today, clang emits the exact same diagnostic "expected class name" even when you do have Foo declared as a template. That's the only thing I'm trying to fix, but it has this weird side-effect in that even asking Sema isTemplateName() causes does typo-correction, and when that typo-correction succeeds it issues this "no template" diagnostic. Nick
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