[clang] [Clang] [Sema] Handle placeholders in '.*' expressions (PR #83103)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman updated https://github.com/llvm/llvm-project/pull/83103

>From 071b6287e89e4601d9e441978f0b4bd53e757c26 Mon Sep 17 00:00:00 2001
From: Sirraide <aeternalmail at gmail.com>
Date: Tue, 27 Feb 2024 06:19:05 +0100
Subject: [PATCH 1/3] [Clang] [Sema] Handle placeholders in '.*' expressions

---
 clang/lib/Sema/SemaOverload.cpp | 22 +++++++++++++++++-----
 clang/test/SemaCXX/gh53815.cpp  | 21 +++++++++++++++++++++
 2 files changed, 38 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/SemaCXX/gh53815.cpp

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index c46f6338a5a125..f4b67e7b469418 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -14474,6 +14474,23 @@ ExprResult Sema::CreateOverloadedBinOp(SourceLocation OpLoc,
                                        CurFPFeatureOverrides());
   }
 
+  // If this is the .* operator, which is not overloadable, just
+  // create a built-in binary operator.
+  if (Opc == BO_PtrMemD) {
+    auto CheckPlaceholder = [&](Expr *&Arg) {
+      ExprResult Res = CheckPlaceholderExpr(Arg);
+      if (!Res.isInvalid())
+        Arg = Res.get();
+      return Res.isInvalid();
+    };
+
+    // CreateBuiltinBinOp() doesn't like it if we tell it to create a '.*'
+    // expression that contains placeholders (in either the LHS or RHS).
+    if (CheckPlaceholder(Args[0]) || CheckPlaceholder(Args[1]))
+      return ExprError();
+    return CreateBuiltinBinOp(OpLoc, Opc, Args[0], Args[1]);
+  }
+
   // Always do placeholder-like conversions on the RHS.
   if (checkPlaceholderForOverload(*this, Args[1]))
     return ExprError();
@@ -14493,11 +14510,6 @@ ExprResult Sema::CreateOverloadedBinOp(SourceLocation OpLoc,
   if (Opc == BO_Assign && !Args[0]->getType()->isOverloadableType())
     return CreateBuiltinBinOp(OpLoc, Opc, Args[0], Args[1]);
 
-  // If this is the .* operator, which is not overloadable, just
-  // create a built-in binary operator.
-  if (Opc == BO_PtrMemD)
-    return CreateBuiltinBinOp(OpLoc, Opc, Args[0], Args[1]);
-
   // Build the overload set.
   OverloadCandidateSet CandidateSet(OpLoc, OverloadCandidateSet::CSK_Operator,
                                     OverloadCandidateSet::OperatorRewriteInfo(
diff --git a/clang/test/SemaCXX/gh53815.cpp b/clang/test/SemaCXX/gh53815.cpp
new file mode 100644
index 00000000000000..326c911c7bfaf5
--- /dev/null
+++ b/clang/test/SemaCXX/gh53815.cpp
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++20 %s
+// expected-no-diagnostics
+
+// Check that we don't crash due to forgetting to check for placeholders
+// in the RHS of '.*'.
+
+template <typename Fn>
+static bool has_explicitly_named_overload() {
+  return requires { Fn().*&Fn::operator(); };
+}
+
+int main() {
+  has_explicitly_named_overload<decltype([](auto){})>();
+}
+
+template <typename Fn>
+constexpr bool has_explicitly_named_overload_2() {
+  return requires { Fn().*&Fn::operator(); };
+}
+
+static_assert(!has_explicitly_named_overload_2<decltype([](auto){})>());

>From b39abdb1a5d083a59ce818748c0d130501467706 Mon Sep 17 00:00:00 2001
From: Sirraide <aeternalmail at gmail.com>
Date: Tue, 27 Feb 2024 18:35:22 +0100
Subject: [PATCH 2/3] [Clang] Update release notes

---
 clang/docs/ReleaseNotes.rst | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index c60c5682dbd826..7e16b9f0c67dbd 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -288,6 +288,8 @@ Bug Fixes to C++ Support
   templates when determining the primary template of an explicit specialization.
 - Fixed a crash in Microsoft compatibility mode where unqualified dependent base class
   lookup searches the bases of an incomplete class.
+- Fix a crash when an unresolved overload set is encountered on the RHS of a ``.*`` operator.
+  (`#53815 <https://github.com/llvm/llvm-project/issues/53815>`_)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

>From c52a0e91b9949c8ee4a13df11309b230d37ca933 Mon Sep 17 00:00:00 2001
From: Sirraide <aeternalmail at gmail.com>
Date: Tue, 27 Feb 2024 18:56:23 +0100
Subject: [PATCH 3/3] [NFC] Use isUsable() instead of isInvalid()

---
 clang/lib/Sema/SemaOverload.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 1b1252ba90e560..7d38043890ca20 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -14576,9 +14576,9 @@ ExprResult Sema::CreateOverloadedBinOp(SourceLocation OpLoc,
   if (Opc == BO_PtrMemD) {
     auto CheckPlaceholder = [&](Expr *&Arg) {
       ExprResult Res = CheckPlaceholderExpr(Arg);
-      if (!Res.isInvalid())
+      if (Res.isUsable())
         Arg = Res.get();
-      return Res.isInvalid();
+      return !Res.isUsable();
     };
 
     // CreateBuiltinBinOp() doesn't like it if we tell it to create a '.*'