void added inline comments.
================
Comment at: clang/include/clang/AST/Designator.h:88
+ /// An array designator, e.g., "[42] = 0" and "[42 ... 50] = 1".
+ template <typename Ty> struct ArrayDesignatorInfo {
+ /// Location of the first and last index expression within the designated
----------------
rsmith wrote:
> void wrote:
> > void wrote:
> > > rsmith wrote:
> > > > Can we move the templating out from here to the whole `Designator` and
> > > > `Designation` classes? It shouldn't be possible to mix the two kinds in
> > > > the same `Designation`.
> > > Grr...My previous comment was eaten.
> > >
> > > I'll give it a shot.
> > >
> > > However, I'm a bit surprised at how designators are handled by Clang. I
> > > expected that a `Designation` would be an `Expr` with the `Designator`s
> > > being L-values (e.g. `MemberExpr`s / `ArraySubscriptExpr`s), but instead
> > > the `Designation` exists just long enough to be turned into an explicit
> > > initialization list. Is there a reason to do it that way instead of using
> > > expressions?
> > So it looks like moving the template outside of the class won't work. The
> > ability to switch between `Expr` and `unsigned` while retaining the same
> > overall type is hardwired into things like the `ASTImporter`.
> >
> > This is kind of a massive mess. Maybe we shouldn't even allow them to use
> > both `Expr` and `unsigned` but instead require them to use one or the
> > other? Maybe we could require `unsigned` with the understanding that the
> > `Expr` can be converted into a constant?
> I'm not understanding something. Currently the `ASTImporter` only deals with
> `DesignatedInitExpr::Designator`s , which only ever store integer indexes.
>
> Basically, today, we have two different classes:
> - A class that's specific to `DesignatedInitExpr`, and tracks array index
> expressions by storing the index of the expression within the
> `DesignatedInitExpr`'s list of children; this is also what `ASTImporter` can
> import, because it's the one that's used in the AST's representation.
> - A class that's specific to `Sema`'s processing that tracks array index
> expressions as `Expr*` instead.
>
> You want to refactor them to share code, which makes sense, because they are
> basically the same other than how they refer to expressions. (Not quite:
> `DesignatedInitExpr` can apparently refer to a field either as an
> `IdentifierInfo*` or as a `FieldDecl*`, whereas the `Sema` version always
> uses the `IdentifierInfo*` representation.)
>
> Each current user of one of these two classes uses only one of the two, which
> means they're either exclusively using integers to refer to expressions or
> exclusively using `Expr*`. So it seems to me that you should be able to
> update each user to use either `Designator<unsigned>` or `Designator<Expr*>`,
> depending on which class they used before.
>
> What am I missing?
I'm still allowing them to use a `Designator<unsigned>` / `Designator<Expr*>`
as they see fit, only it's hidden from them via the `Create` methods. I
personally find the use of two different versions (one using `unsigned` and one
using `Expr*`) completely baffling. Why can't they all use `Expr*`? Also the
`ASTImporter` only outputs the start of an array init range, which is at the
very least counter-intuitive. That's one of the issues I'd like to tackle with
follow-up patches, hopefully getting rid of the need for this template all
together. This does mean that in the interim a non-array range designator will
have extra `End` & `EllisisLoc` fields that aren't used, but that shouldn't be
too horrible, given that they'd be there anyway because of the union.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D140584/new/
https://reviews.llvm.org/D140584
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