[clang] [llvm] [mlir] [LLVM][MLIR] Treewide C++26/2d fixes (PR #223284)

[via llvm-commits]

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@@ -161,8 +161,9 @@ class FrontendAction {
 
   std::unique_ptr<ASTUnit> takeCurrentASTUnit();
 
+  void setCurrentInput(const FrontendInputFile &CurrentInput);
   void setCurrentInput(const FrontendInputFile &CurrentInput,
-                       std::unique_ptr<ASTUnit> AST = nullptr);
+                       std::unique_ptr<ASTUnit> AST);
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rdong8 wrote:

I added an overload that omits the extra `AST` arg entirely and is defined to call the 3-ary version out of line with a null `AST`.

https://github.com/llvm/llvm-project/pull/223284