[PATCH v2 6/6] Wire up delayed typo correction to DiagnoseEmptyLookup and set up Sema::ActOnIdExpression to use the new functionality.
David Blaikie
dblaikie at gmail.com
Wed Nov 19 15:36:57 PST 2014
On Wed, Nov 19, 2014 at 11:03 AM, Kaelyn Takata <rikka at google.com> wrote:
>
>
> On Tue, Nov 18, 2014 at 10:50 AM, David Blaikie <dblaikie at gmail.com>
> wrote:
>
>> +cfe-commits
>>
>> Though I've had trouble applying the summary patch you posted - could you
>> rebase/repost? Sorry for the delays :/
>>
>
> No worries.
>
>>
>> On Tue, Nov 18, 2014 at 10:49 AM, David Blaikie <dblaikie at gmail.com>
>> wrote:
>>
>>>
>>>
>>> On Wed, Nov 5, 2014 at 1:10 PM, Kaelyn Takata <rikka at google.com> wrote:
>>>
>>>>
>>>>
>>>> On Tue, Nov 4, 2014 at 4:54 PM, David Blaikie <dblaikie at gmail.com>
>>>> wrote:
>>>>
>>>>> Could you post/send (on/off list, etc) an aggregate patch so I can
>>>>> play around with the behavior of this patch?
>>>>>
>>>>> Some superficial patch review
>>>>>
>>>>> lambda passed to CorrectDelayedTyposInExpr has 'else-after-return' -
>>>>> you could move the short block up to the top:
>>>>>
>>>>> if (!...CPlusPlus11)
>>>>> return this->VerifyIntegerConstantExpression(E);
>>>>> /* unindented the longer part of the code */
>>>>>
>>>>
>>>> Fixed. Thanks for catching that!
>>>>
>>>>>
>>>>> I'm slightly surprised at the indentation there too - I think
>>>>> clang-format has a special case for lambdas as the last function argument,
>>>>> where it won't indent them extra (so the "});" will be at the same level as
>>>>> the expression - maybe it only does that if you're not initializing a
>>>>> variable? Dunno.
>>>>>
>>>>
>>>> I think it was a quirk in the version of clang-format used to
>>>> originally format this several months ago; clang-format now formats it a
>>>> bit differently.
>>>>
>>>>>
>>>>> Do you need the 'this->' qualification in that lambda? I assume not.
>>>>> (& I usually favor just capture everything by reference [&] - but up to you
>>>>> on that, we're all still certainly feeling out how best to write C++11)
>>>>>
>>>>
>>>> I didn't think the implicit "this" could be used for accessing member
>>>> functions... I just learned something new. :) (Though "this" still needs to
>>>> be in the capture list--I didn't capture everything by reference because
>>>> the only variable that needed to be captured was "this".)
>>>>
>>>
>>> Sure - up to you. I usually don't even think about what's being captured
>>> and just write [&] by default. (this applies really well to functions that
>>> will only call the lambda within the function (not storing it away to call
>>> later - at which point you get into interesting lifetime situations, etc) -
>>> for those, it's trickier and depends on the lifetime of the things being
>>> captured as to whether to capture by ref or value, etc).
>>>
>>>
>>>>
>>>>> EmptyLookupTypoDiags::operator() - some {} on single-statement blocks
>>>>> (if (Ctx)/else)
>>>>> Might be worth inverting the if/following block - the if block is
>>>>> longer/nested than the tail block, so switching them around should reduce
>>>>> indentation, etc.
>>>>>
>>>>
>>>> Done and done.
>>>>
>>>>>
>>>>> std::string CorrectedStr(TC.getAsString(SemaRef.getLangOpts()));
>>>>>
>>>>> Prefer copy/move init rather than direct init:
>>>>>
>>>>> std::string CorrectedStr = TC.getAsString(SemaRef.getLangOpts());
>>>>>
>>>>
>>>> Changed.
>>>>
>>>>>
>>>>> Hmm - it might be nice to write EmptyLookupTypoDiags just as a single
>>>>> free function (taking all those members as parameters instead) then call
>>>>> that in a lambda - that way you don't have to write all the member
>>>>> state/ctor/etc logic?
>>>>>
>>>>
>>>> I had to capture variables by value instead of by reference to avoid
>>>> lifetime issues (and having 74 tests fail) and create a local variable so
>>>> the LookupResult didn't have to be captured since it cannot be copied, but
>>>> I did get it working as a static function and a lambda and the switch
>>>> resulted in a net change of 17 fewer lines (37 added, 54 deleted).
>>>>
>>>
>>> Cool cool.
>>>
>>>
>>>>
>>>>> lambda in ParseCaseStatement: I'd probably write "return
>>>>> ExprResult(...)" rather than explicitly specifying the return type. (do you
>>>>> even need to do either? If CorrectDelayedTyposInExpr is a template, then
>>>>> its return result should just implicitly convert to ExprResult in the
>>>>> caller, if it takes a std::function, that should still work too... - I can
>>>>> explain this more in person, perhaps.
>>>>>
>>>>
>>>> You're right, neither seem to be needed--though I thought I had added
>>>> the return type because of clang complaining without it.
>>>>
>>>>>
>>>>> Rather than goto in ParseCXXIdExpression, could that be a loop?
>>>>>
>>>>
>>>> The cleanest way I can see to write it as a loop would be to wrap it in
>>>> a "while (true) {...}" loop, and have an "if (Result.isInvalid() ||
>>>> Result.get()) break;" right before the (now unconditional) call to
>>>> UnconsumeToken. The only other way I can see to do the loop would require
>>>> checking "!Result.isInvalid() && !Result.get()" twice in a row, once to
>>>> know whether to call UnconsumeToken, and once in the do...while loop to
>>>> know whether to continue looping.
>>>>
>>>
>>> Hmm - fair point. I'd probably at least still write it using the
>>> while(true) loop rather than goto, just to demonstrate to the reader what
>>> kind of control flow is happening here more easily.
>>>
>>> As for other ways to write this... one alternative, which I wouldn't
>>> necessarily espouse as better than your suggested loop:
>>>
>>> bool first = true;
>>> do {
>>> if (!first)
>>> UnconsumeToken()
>>> first = false;
>>> ...
>>> } while (!Result.isInvalid() && !Result.get())
>>>
>>> Though calling '!Result.isInvalid() && !Result.get()' twice probably
>>> isn't the end of the world either, though certainly feels a bit off. Your
>>> suggestion of:
>>>
>>> while (true) {
>>> ...
>>> if (...)
>>> break;
>>> UnconsumeToken();
>>> }
>>>
>>> seems good. It's probably about as obvious as its going to get, I'd
>>> imagine. If the body of the loop is long, it might be more clear to pull it
>>> into a function and that'd make the loop's scope and purpose clearer.
>>>
>>
> I just remembered the other reason why I wrote this as a goto instead of a
> loop (and why the goto label is "retry"): the body of the "loop" should in
> most cases only be executed once, would only be executed a second time if
> there is an error and typo correction suggests a keyword, and should
> *never* be executed more than twice (i.e. the goto should only ever be
> called at most once) unless something has gone horribly, impossibly wrong
> ("wrong" being a typo was encountered, a keyword was suggested,
> substituting the keyword causes typo correction to be triggered again in
> the same spot and suggest a keyword again... a situation that shouldn't be
> possible and for which I'd be willing to add an assertion to prevent it
> from happening).
>
An assertion sounds good, in any case.
If it's only a single retry - perhaps breaking out the body of the loop
into a function that you call twice would make sense?
func()
if (failed)
func(other stuff)
assert(!failed)
?
>
>>>
>>>>>
>>>>> Hmm - why is the correction applied to the LHS/RHS of the binary
>>>>> expression, rather than waiting until the full expression is parsed?
>>>>>
>>>>
>>>> If you are referring to within ParseRHSOfBinaryExpression, it's because
>>>> any error in the RHS will cause the LHS to be replaced with an ExprError
>>>> without any typos in the LHS being diagnosed, so waiting until the full
>>>> expression is parsed causes typos to go undiagnosed if there are unrelated
>>>> parse errors in the full expression. This had been a bit of a pain to
>>>> figure out and track down why typo correction on certain full expressions
>>>> wasn't happening for part of the expression...
>>>>
>>>
>>> Hmm, that's interesting - I'd be curious to understand why that is, but
>>> I guess it's got a good reason.
>>>
>>
> I think it's because errors in the expression are communicated through the
> same channel as the expression itself: the ExprResult. So for something
> that combines multiple expressions into one (which it seems that
> ParseRHSOfBinaryExpression handles both parsing the RHS and combining the
> LHS and RHS), it can either return the subexpression tree or an
> ExprError.... which is fine up until something more needs to be done with
> the subexpression tree once an ExprError has been generated.
>
Hmm, OK - that makes sense. Could/should we then do the correction on the
LHS/RHS only when a failure is about to cause the expression to be thrown
out? (that way if there's no error... oh, but of course there'
>
>
>>
>>>
>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Wed, Oct 29, 2014 at 12:49 PM, Kaelyn Takata <rikka at google.com>
>>>>> wrote:
>>>>>
>>>>>>
>>>>>> Among other things, this eliminates at least one redundant error case
>>>>>> and allows recovery in several cases where it wasn't possible before
>>>>>> (e.g. correcting a mistyped static_cast<>).
>>>>>> ---
>>>>>> include/clang/Parse/Parser.h | 9 +++
>>>>>> include/clang/Sema/Sema.h | 4 +-
>>>>>> lib/Parse/ParseCXXInlineMethods.cpp | 1 +
>>>>>> lib/Parse/ParseDecl.cpp | 4 +-
>>>>>> lib/Parse/ParseDeclCXX.cpp | 2 +-
>>>>>> lib/Parse/ParseExpr.cpp | 30 +++++++---
>>>>>> lib/Parse/ParseExprCXX.cpp | 13 ++++-
>>>>>> lib/Parse/ParseObjc.cpp | 5 +-
>>>>>> lib/Parse/ParseOpenMP.cpp | 3 +-
>>>>>> lib/Parse/ParseStmt.cpp | 8 ++-
>>>>>> lib/Sema/SemaExpr.cpp | 110
>>>>>> ++++++++++++++++++++++++++++++++---
>>>>>> lib/Sema/SemaStmt.cpp | 19 ++++++
>>>>>> test/FixIt/fixit-unrecoverable.cpp | 4 +-
>>>>>> test/SemaCXX/typo-correction.cpp | 7 ++-
>>>>>> test/SemaTemplate/crash-10438657.cpp | 2 +-
>>>>>> 15 files changed, 189 insertions(+), 32 deletions(-)
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> cfe-commits mailing list
>>>>>> cfe-commits at cs.uiuc.edu
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>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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