[cfe-commits] [PATCH] Improved error-recovery for malformed declarations

[David Blaikie]

This generally looks good except that the last expected-error should
be on the following line (not great, since it doesn't appear at the
bad token, but nothing new there). Other than that - LGTM.

*vim users celebrate*

- David

On Wed, Apr 11, 2012 at 1:11 PM, Richard Smith <richard at metafoo.co.uk> wrote:
> Ping. A slightly modified patch is attached: the r_brace check got lost in
> some refactorings.
>
>
> On Tue, Apr 3, 2012 at 1:27 PM, Richard Smith <richard at metafoo.co.uk> wrote:
>>
>> Hi,
>>
>> Currently, after a malformed declaration, clang skips until it reaches an
>> unparenthesized '}' or ';'. One fairly common error (especially among vim
>> users) is for the first line of a file to have junk in it. This leads to
>> abysmal error recovery, where we skip all 'namespace { ... }' and 'extern
>> "C" { ... }' blocks and function definitions until we get to a top-level
>> semicolon (which often doesn't arrive until we're past all the #included
>> header files and somewhere in the main source file). We then produce a large
>> pile of incorrect diagnostics, because we have not seen any declarations
>> yet.
>>
>> The attached patch improves this situation by tweaking the recovery
>> heuristic as follows: we skip the shortest sequence of
>> brace/bracket/paren-balanced tokens which either ends with a semicolon or a
>> close brace[1] (and any following semicolon), or is followed by a namespace
>> definition at the start of a line.
>>
>> In my testing, this seems to be a strict improvement. Does this seem like
>> a reasonable change? I'm sure there are other places where this style of
>> recovery would be a better option than a simple SkipUntil(tok::r_brace), but
>> I don't have evidence of a specific common pattern of errors leading to poor
>> recovery elsewhere.
>>
>> Thanks!
>> Richard
>>
>> [1] If the close brace is followed by ',', '{' or 'try', we could be in
>> the initializer-list for a constructor, so we keep skipping.
>>
>>
>
>
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