From bb78a0b33496fb0140cec1a92a689505f53253b7 Mon Sep 17 00:00:00 2001
From: c8ef <c8ef@outlook.com>
Date: Tue, 1 Oct 2024 21:39:10 +0800
Subject: [PATCH] [clang] Fix the local parameter of void type inside the
 `Requires` expression. (#109831)

Fixes #109538.

In this patch, we introduce diagnostic for required expression
parameters in the same way as function parameters, fix the issue of
handling void type parameters, and align the behavior with GCC and other
compilers.
---
 clang/docs/ReleaseNotes.rst                      |  2 ++
 clang/lib/Sema/SemaExprCXX.cpp                   | 12 ++++++++++++
 .../expr.prim/expr.prim.req/requires-expr.cpp    | 16 +++++++++++++++-
 3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index a55a3b8687e4..7e64134f7eb1 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -362,6 +362,8 @@ Improvements to Clang's diagnostics
 
 - Clang now diagnoses cases where a dangling ``GSLOwner<GSLPointer>`` object is constructed, e.g. ``std::vector<string_view> v = {std::string()};`` (#GH100526).
 
+- Clang now diagnoses when a ``requires`` expression has a local parameter of void type, aligning with the function parameter (#GH109831).
+
 Improvements to Clang's time-trace
 ----------------------------------
 
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index ac3fe6ab8f9b..b30414a8a827 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -9509,6 +9509,18 @@ Sema::ActOnStartRequiresExpr(SourceLocation RequiresKWLoc,
   PushDeclContext(BodyScope, Body);
 
   for (ParmVarDecl *Param : LocalParameters) {
+    if (Param->getType()->isVoidType()) {
+      if (LocalParameters.size() > 1) {
+        Diag(Param->getBeginLoc(), diag::err_void_only_param);
+        Param->setType(Context.IntTy);
+      } else if (Param->getIdentifier()) {
+        Diag(Param->getBeginLoc(), diag::err_param_with_void_type);
+        Param->setType(Context.IntTy);
+      } else if (Param->getType().hasQualifiers()) {
+        Diag(Param->getBeginLoc(), diag::err_void_param_qualified);
+      }
+    }
+
     if (Param->hasDefaultArg())
       // C++2a [expr.prim.req] p4
       //     [...] A local parameter of a requires-expression shall not have a
diff --git a/clang/test/CXX/expr/expr.prim/expr.prim.req/requires-expr.cpp b/clang/test/CXX/expr/expr.prim/expr.prim.req/requires-expr.cpp
index 90a38292d15d..09f8f36d3c5b 100644
--- a/clang/test/CXX/expr/expr.prim/expr.prim.req/requires-expr.cpp
+++ b/clang/test/CXX/expr/expr.prim/expr.prim.req/requires-expr.cpp
@@ -65,4 +65,18 @@ template<typename T> requires requires { T::value; S<T>::s; }
 struct r4 { };
 
 using r4i = r4<int>;
-// expected-error@-1 {{constraints not satisfied for class template 'r4' [with T = int]}}
\ No newline at end of file
+// expected-error@-1 {{constraints not satisfied for class template 'r4' [with T = int]}}
+
+namespace GH109538 {
+static_assert(requires(void *t) { t; });
+static_assert(requires(void) { 42; });
+static_assert(requires(void t) { // expected-error {{argument may not have 'void' type}}
+  t;
+});
+static_assert(requires(void t, int a) {  // expected-error {{'void' must be the first and only parameter if specified}}
+  t;
+});
+static_assert(requires(const void) { // expected-error {{'void' as parameter must not have type qualifiers}}
+  42;
+});
+} // namespace GH109538