[clang] [Clang][NFC] Consolidate the parameter check for the `requires` expression parameter. (PR #110773)

[via cfe-commits]

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@@ -9519,15 +9519,28 @@ Sema::ActOnStartRequiresExpr(SourceLocation RequiresKWLoc,
       } else if (Param->getType().hasQualifiers()) {
         Diag(Param->getBeginLoc(), diag::err_void_param_qualified);
       }
-    }
-
-    if (Param->hasDefaultArg())
+    } else if (Param->hasDefaultArg()) {
       // C++2a [expr.prim.req] p4
       //     [...] A local parameter of a requires-expression shall not have a
       //     default argument. [...]
       Diag(Param->getDefaultArgRange().getBegin(),
            diag::err_requires_expr_local_parameter_default_argument);
-    // Ignore default argument and move on
+      // Ignore default argument and move on
+    } else if (Param->isExplicitObjectParameter()) {
+      // C++23 [dcl.fct]p6:
+      //   An explicit-object-parameter-declaration is a parameter-declaration
+      //   with a this specifier. An explicit-object-parameter-declaration
+      //   shall appear only as the first parameter-declaration of a
+      //   parameter-declaration-list of either:
+      //   - a member-declarator that declares a member function, or
+      //   - a lambda-declarator.
+      //
+      // The parameter-declaration-list of a requires-expression is not such
+      // a context.
+      Diag(Param->getExplicitObjectParamThisLoc(),
+           diag::err_requires_expr_explicit_object_parameter);
+      Param->setExplicitObjectParameterLoc(SourceLocation());
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c8ef wrote:

https://github.com/llvm/llvm-project/blob/e379094328e49731a606304f7e3559d4f1fa96f9/clang/lib/Sema/SemaType.cpp#L5175-L5179

I'm not entirely sure, but the check in function parameters do indeed perform this action.

https://github.com/llvm/llvm-project/pull/110773