Perform access checking to private members in simple requirement.

> Dependent access checks.

Fixes: https://github.com/llvm/llvm-project/issues/53364

We previously ignored dependent access checks to private members.
These are visible only to the `RequiresExprBodyExpr` (through `PerformDependentDiagnositcs`) and not to the individual requirements.

---

> Non-dependent access checks.
Fixes: https://github.com/llvm/llvm-project/issues/53334
Access to members in a non-dependent context would always yield an
invalid expression. When it appears in a requires-expression, then this
is a hard error as this would always result in a substitution failure.

https://eel.is/c++draft/expr.prim.req#general-note-1
> Note 1: If a requires-expression contains invalid types or expressions in its requirements, and it does not appear within the declaration of a templated entity, then the program is ill-formed. — end note]
> If the substitution of template arguments into a requirement would always result in a substitution failure, the program is ill-formed; no diagnostic required.

The main issue here is the delaying of the diagnostics.
Use a `ParsingDeclRAIIObject` creates a separate diagnostic pool for diagnositcs associated to the `RequiresExprBodyDecl`.
This is important because dependent diagnostics should not be leaked/delayed to higher scopes (Eg. inside a template function or in a trailing requires). These dependent diagnostics must be attached to the `DeclContext` of the parameters of `RequiresExpr` (which is the `RequiresExprBodyDecl` in this case).
Non dependent diagnostics, on the other hand, should not delayed and surfaced as hard errors.

Differential Revision: https://reviews.llvm.org/D140547

1 files changed, 2 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaAccess.cpp b/clang/lib/Sema/SemaAccess.cpp
index 00d3efd..cbda624 100644
--- a/clang/lib/Sema/SemaAccess.cpp
+++ b/clang/lib/Sema/SemaAccess.cpp
@@ -1493,6 +1493,8 @@ void Sema::HandleDelayedAccessCheck(DelayedDiagnostic &DD, Decl *D) {
   } else if (TemplateDecl *TD = dyn_cast<TemplateDecl>(D)) {
     if (isa<DeclContext>(TD->getTemplatedDecl()))
       DC = cast<DeclContext>(TD->getTemplatedDecl());
+  } else if (auto *RD = dyn_cast<RequiresExprBodyDecl>(D)) {
+    DC = RD;
   }
 
   EffectiveContext EC(DC);