[clang] Preserve UDL nodes in RemoveNestedImmediateInvocation

clang/docs/ReleaseNotes.rst

@@ -290,6 +290,8 @@ Bug Fixes in This Version
   (`#67722 <https://github.com/llvm/llvm-project/issues/67722>`_).
 - Fixes a crash when instantiating a lambda with requires clause.
   (`#64462 <https://github.com/llvm/llvm-project/issues/64462>`_)
+- Fixes a regression where the ``UserDefinedLiteral`` was not properly preserved
+  while evaluating consteval functions. (`#63898 <https://github.com/llvm/llvm-project/issues/63898>`_).
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/Sema/SemaExpr.cpp

@@ -18468,7 +18468,10 @@ static void RemoveNestedImmediateInvocation(
       DRSet.erase(cast<DeclRefExpr>(E->getCallee()->IgnoreImplicit()));
       return Base::TransformCXXOperatorCallExpr(E);
     }
-    /// Base::TransformInitializer skip ConstantExpr so we need to visit them
+    /// Base::TransformUserDefinedLiteral doesn't preserve the
+    /// UserDefinedLiteral node.
+    ExprResult TransformUserDefinedLiteral(UserDefinedLiteral *E) { return E; }
+    /// Base::TransformInitializer skips ConstantExpr so we need to visit them
     /// here.
     ExprResult TransformInitializer(Expr *Init, bool NotCopyInit) {
       if (!Init)

clang/test/AST/ast-dump-udl-consteval.cpp

@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -xc++ -std=c++23 -ast-dump %s | FileCheck %s
+
+int inline consteval operator""_u32(unsigned long long val) {
+  return val;
+}
+
+void udl() {
+  (void)(0_u32 + 1_u32);
+}
+
+// CHECK: `-BinaryOperator {{.+}} <col:10, col:18> 'int' '+'
+// CHECK-NEXT: |-ConstantExpr {{.+}} <col:10> 'int'
+// CHECK-NEXT: | |-value: Int 0
+// CHECK-NEXT: | `-UserDefinedLiteral {{.+}} <col:10> 'int'
+// CHECK: `-ConstantExpr {{.+}} <col:18> 'int'
+// CHECK-NEXT:   |-value: Int 1
+// CHECK-NEXT:   `-UserDefinedLiteral {{.+}} <col:18> 'int'