[clang] [clang][bytecode] Fix assertion failure when returning function type (PR #180681)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

<details>
<summary>Changes</summary>

... as an rvalue. Which can't work, so reject.

---
Full diff: https://github.com/llvm/llvm-project/pull/180681.diff


2 Files Affected:

- (modified) clang/lib/AST/ByteCode/Pointer.cpp (+6) 
- (modified) clang/test/AST/ByteCode/invalid.cpp (+3) 


``````````diff
diff --git a/clang/lib/AST/ByteCode/Pointer.cpp b/clang/lib/AST/ByteCode/Pointer.cpp
index fb9202c6d66c8..c9eb6c9c986c5 100644
--- a/clang/lib/AST/ByteCode/Pointer.cpp
+++ b/clang/lib/AST/ByteCode/Pointer.cpp
@@ -937,6 +937,12 @@ std::optional<APValue> Pointer::toRValue(const Context &Ctx,
     llvm_unreachable("invalid value to return");
   };
 
+  // Can't return functions as rvalues.
+  if (ResultType->isFunctionType() || ResultType->isFunctionProtoType() ||
+      ResultType->isFunctionPointerType() ||
+      ResultType->isFunctionReferenceType())
+    return std::nullopt;
+
   // Invalid to read from.
   if (isDummy() || !isLive() || isPastEnd())
     return std::nullopt;
diff --git a/clang/test/AST/ByteCode/invalid.cpp b/clang/test/AST/ByteCode/invalid.cpp
index c8298fa2c2b9b..bd4b226815c9c 100644
--- a/clang/test/AST/ByteCode/invalid.cpp
+++ b/clang/test/AST/ByteCode/invalid.cpp
@@ -151,3 +151,6 @@ namespace NullRecord {
   };
   S2 s = S2();
 }
+
+/// Pointer::toRValue() of a function type.
+void foo() { *(void (*)()) ""; } // both-warning {{expression result unused}}

``````````

</details>


https://github.com/llvm/llvm-project/pull/180681