[cfe-commits] [PATCH] PR4111, PR5925, PR13210: Make tentative parsing smarter in the presence of undeclared identifiers

[Sean Silva]

+      case ANK_TentativeDecl:
+      case ANK_TemplateName:
+        // These two shouldn't happen.
+      case ANK_Unresolved:
         break;

assert?

--Sean Silva

On Thu, Jun 28, 2012 at 1:49 PM, Richard Smith <richard at metafoo.co.uk> wrote:
> Hi,
>
> The attached patch makes tentative parsing try harder when it sees an
> undeclared identifier. In particular, it will try to typo-correct to a
> declared identifier or an appropriate keyword:
>
> int f(doulbe);
> int k = f(4.2);
>
> Was:
>
> <stdin>:1:7: error: use of undeclared identifier 'doulbe'
> int f(doulbe);
>       ^
> <stdin>:2:10: error: called object type 'int' is not a function or function
> pointer
> int k = f(4.2);
>         ~^
>
> Now:
>
> <stdin>:1:7: error: use of undeclared identifier 'doulbe'; did you mean
> 'double'?
> int f(doulbe);
>       ^~~~~~
>       double
>
> If typo-correction fails, it will continue disambiguating the declaration,
> in the hope that something later will resolve the error:
>
> int p = 0;
> int f(undeclared *p, int);
> int g(undeclared *p, 0);
> int *test(UnknownType *fool) { return 0; }
>
> Was:
>
> <stdin>:2:7: error: use of undeclared identifier 'undeclared'
> int f(undeclared *p, int);
>       ^
> <stdin>:3:7: error: use of undeclared identifier 'undeclared'
> int g(undeclared *p, 0);
>       ^
> <stdin>:4:11: error: use of undeclared identifier 'UnknownType'
> int *test(UnknownType *fool) { return 0; }
>           ^
> <stdin>:4:24: error: use of undeclared identifier 'fool'
> int *test(UnknownType *fool) { return 0; }
>                        ^
> <stdin>:4:29: error: expected ';' after top level declarator
> int *test(UnknownType *fool) { return 0; }
>                             ^
>                             ;
>
> Now:
>
> <stdin>:2:7: error: unknown type name 'undeclared'
> int f(undeclared *p, int);
>       ^
> <stdin>:3:7: error: use of undeclared identifier 'undeclared'
> int g(undeclared *p, 0);
>       ^
> <stdin>:4:11: error: unknown type name 'UnknownType'
> int *test(UnknownType *fool) { return 0; }
>           ^
>
> Additionally, this patch produces a tok::annot_primary_expr annotation when
> tentative parsing meets an identifier and resolves it as a non-type, in
> order to avoid the need to redo name lookup during the actual parse. This
> annotation token was previously only used by expression-statement /
> declaration-statement disambiguation.
>
> One small wrinkle with this approach is that tentative parsing needs to be
> aware of names which were declared earlier in the same parse. This is
> accomplished by maintaining a set of tentatively-declared identifiers on the
> parser (that is, names which it believes are going to be declared by the
> current point in the tentative parse, but which it hasn't told Sema about
> yet).
>
> This fixes at least PR4111, PR5925, and PR13210. I've tested this patch
> against a large pile of C++ code with no regressions.
>
> Please review!
>
> Thanks!
> Richard
>
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