[clang] [clang] pointer to member with qualified-id closed in parantheses in unevaluated context should be invalid (PR #89713)

[via cfe-commits]

https://github.com/zwuis created https://github.com/llvm/llvm-project/pull/89713

clang don't check whether the operand of the & operator is enclosed in parantheses when pointer to member is formed in unevaluated context, for example:

```cpp
struct foo { int val; };

int main() { decltype(&(foo::val)) ptr; }
```

`decltype(&(foo::val))` should be invalid, but clang accepts it. This PR fixes this issue.

Fixes #40906.

>From f6fd1e5e5f42b3c72cb5aeaf9e6d4e91d5424bee Mon Sep 17 00:00:00 2001
From: YanzuoLiu <zwuis at outlook.com>
Date: Tue, 23 Apr 2024 14:56:12 +0800
Subject: [PATCH] Add missing check when making pointer to member

---
 clang/lib/Sema/SemaExpr.cpp                    | 11 +++++++++++
 .../CXX/expr/expr.unary/expr.unary.op/p3.cpp   | 18 +++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 5c861467bc1023..824667fb722365 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -14644,6 +14644,17 @@ QualType Sema::CheckAddressOfOperand(ExprResult &OrigOp, SourceLocation OpLoc) {
             return QualType();
           }
 
+          // C++11 [expr.unary.op] p4:
+          // A pointer to member is only formed when an explicit & is used and
+          // its operand is a qualified-id not enclosed in parentheses.
+          if (isa<ParenExpr>(OrigOp.get())) {
+            // `op->getEndLoc()` is the last part of the qualified-id.
+            // For example, "baz" in "foo::bar::baz".
+            Diag(op->getEndLoc(), diag::err_invalid_non_static_member_use)
+                << dcl->getDeclName() << op->getSourceRange();
+            return QualType();
+          }
+
           while (cast<RecordDecl>(Ctx)->isAnonymousStructOrUnion())
             Ctx = Ctx->getParent();
 
diff --git a/clang/test/CXX/expr/expr.unary/expr.unary.op/p3.cpp b/clang/test/CXX/expr/expr.unary/expr.unary.op/p3.cpp
index 08ab0ca56fb632..73d850a6839da7 100644
--- a/clang/test/CXX/expr/expr.unary/expr.unary.op/p3.cpp
+++ b/clang/test/CXX/expr/expr.unary/expr.unary.op/p3.cpp
@@ -1,5 +1,4 @@
 // RUN: %clang_cc1 -fsyntax-only %s -verify 
-// expected-no-diagnostics
 
 namespace rdar10544564 {
   // Check that we don't attempt to use an overloaded operator& when
@@ -27,3 +26,20 @@ namespace rdar10544564 {
   X (Y::*func_mem_ptr1)() = &Y::memfunc1;
   X (Y::*func_mem_ptr2)() = &Y::memfunc2;
 }
+
+namespace test2 {
+  struct A {
+    int val;
+    void func() {}
+  };
+
+  void test() {
+    decltype(&(A::val)) ptr1; // expected-error {{invalid use of non-static data member 'val'}}
+    int A::* ptr2 = &(A::val); // expected-error {{invalid use of non-static data member 'val'}}
+
+    // FIXME: Error messages in these cases are less than clear, we can do
+    // better.
+    int size = sizeof(&(A::func)); // expected-error {{call to non-static member function without an object argument}}
+    void (A::* ptr3)() = &(A::func); // expected-error {{call to non-static member function without an object argument}}
+  }
+}