[cfe-dev] [AST] how to check if a type is template specification type and get the template paramter?

[Yafei Liu via cfe-dev]

Hi Bruno, it works, are there suggestions saying that always using
Type::getAs<> rather than llvm::dyn_cast<>?

On Tue, Aug 4, 2020 at 7:32 PM Bruno Ricci <riccibrun at gmail.com> wrote:

> On 04/08/2020 12:08, Yafei Liu via cfe-dev wrote:
> > Hi, all.
> >
> > I want to check if a given `clang::Type` is a std::vector<xxx> and get
> the type of xxx.
> >
> > I tried this `if (const auto *tst =
> llvm::dyn_cast<clang::TemplateSpecializationType>(type)) {}` but the
> condition is always false, it seems that TemplateSpecializationType is not
> what I think it is.
> >
> > So can what I want be done?
>
> Assuming the template specialization type is not dependent (so you have a
> TemplateSpecializationType
> and not a DependentTemplateSpecializationType), use
> Type::getAs<TemplateSpecializationType> to
> look through sugar. Consider:
>
> namespace N {
>   template <typename T> struct S {};
> }
>
> using type = N::S<int>;
>
> The AST for the type alias declaration is:
>
> -TypeAliasDecl 0x559082acee80 <line:5:1, col:22> col:7 type
> 'N::S<int>':'N::S<int>'
>   `-ElaboratedType 0x559082acedc0 'N::S<int>' sugar
> <-------------------
>     `-TemplateSpecializationType 0x559082aced70 'S<int>' sugar S
>       |-TemplateArgument type 'int'
>       | `-BuiltinType 0x559082a882e0 'int'
>       `-RecordType 0x559082aced40 'N::S<int>'
>         `-ClassTemplateSpecialization 0x559082acec40 'S'
>
> >
> > _______________________________________________
> > cfe-dev mailing list
> > cfe-dev at lists.llvm.org
> > https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
> >
>
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