saar.raz added inline comments.
================
Comment at: lib/Sema/SemaTemplateInstantiate.cpp:1021-1052
+ ExprResult TransformRequiresExpr(RequiresExpr *E) {
+ LocalInstantiationScope Scope(SemaRef, /*CombineWithOuterScope=*/true);
+ return TreeTransform<TemplateInstantiator>::TransformRequiresExpr(E);
+ }
+
+ bool TransformRequiresExprRequirements(ArrayRef<Requirement *> Reqs,
+ SmallVectorImpl<Requirement *> &Transformed) {
----------------
rsmith wrote:
> Do we really need to duplicate the `TreeTransform` code here, and add a
> representation for a requirement whose substitution failed, and so on?
>
> Possible alternative: create a `SFINAETrap` for the entire
> requires-expression, perform a `TreeTransform` of the whole thing, and if it
> fails, capture the diagnostic and build a `FailedRequiresExpr` node that
> stores the diagnostic and evaluates to `false`. (Under this model, a
> non-value-dependent `RequiresExpr` would always evaluate to `true`.) That
> should simplify this code, and the representations of `RequiresExpr` and
> `Requirements` (since you don't need to model "substitution failed" any more,
> nor conditionally store a diagnostic on a requirement).
>
> Are there cases where we want to retain more information than that? (I don't
> think there are, since you don't actually retain any useful information from
> the requirement that failed, other than the diagnostic itself, but maybe I've
> missed something.) The results of a successful substitution into some parts
> of a failed `RequiresExpr` don't really seem interesting.
Wouldn't it be interesting to store the successful requirements prior to the
failed ones? I imagine some tools might want this information
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D50360/new/
https://reviews.llvm.org/D50360
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