[clang][NFC] Simplify implementation of IgnoreExprNodes

[localspook]

Using a fold instead of template recursion.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Victor Chernyakin (localspook)

Changes

Using a fold instead of template recursion.

---

Full diff: https://github.com/llvm/llvm-project/pull/164193.diff

1 Files Affected:

• (modified) clang/include/clang/AST/IgnoreExpr.h (+1-11)

diff --git a/clang/include/clang/AST/IgnoreExpr.h b/clang/include/clang/AST/IgnoreExpr.h
index 917bada61fa6f..bf098f3f09068 100644
--- a/clang/include/clang/AST/IgnoreExpr.h
+++ b/clang/include/clang/AST/IgnoreExpr.h
@@ -17,16 +17,6 @@
 #include "clang/AST/ExprCXX.h"
 
 namespace clang {
-namespace detail {
-/// Given an expression E and functions Fn_1,...,Fn_n : Expr * -> Expr *,
-/// Return Fn_n(...(Fn_1(E)))
-inline Expr *IgnoreExprNodesImpl(Expr *E) { return E; }
-template <typename FnTy, typename... FnTys>
-Expr *IgnoreExprNodesImpl(Expr *E, FnTy &&Fn, FnTys &&... Fns) {
-  return IgnoreExprNodesImpl(std::forward<FnTy>(Fn)(E),
-                             std::forward<FnTys>(Fns)...);
-}
-} // namespace detail
 
 /// Given an expression E and functions Fn_1,...,Fn_n : Expr * -> Expr *,
 /// Recursively apply each of the functions to E until reaching a fixed point.
@@ -35,7 +25,7 @@ template <typename... FnTys> Expr *IgnoreExprNodes(Expr *E, FnTys &&... Fns) {
   Expr *LastE = nullptr;
   while (E != LastE) {
     LastE = E;
-    E = detail::IgnoreExprNodesImpl(E, std::forward<FnTys>(Fns)...);
+    ((E = std::forward<FnTys>(Fns)(E)), ...);
   }
   return E;
 }

[cor3ntin]

Do we ever have more that 2 functions?
It might be simpler/faster to compile to just have

const Expr *IgnoreExprNodes(const Expr *E, const Expr*(*F)(const Expr*));
const Expr *IgnoreExprNodes(const Expr *E, const Expr*(*F1)(const Expr*),
                                                                                 const Expr*(*F2)(const Expr*)); 

[localspook]

We have this :D

llvm-project/clang/lib/AST/Expr.cpp

Lines 3203 to 3206 in 4d6f43d

	return IgnoreExprNodes(
	this, IgnoreImplicitSingleStep, IgnoreImplicitCastsExtraSingleStep,
	IgnoreParensOnlySingleStep, IgnoreImplicitConstructorSingleStep,
	IgnoreImplicitMemberCallSingleStep, IgnoreImplicitCallSingleStep);

[cor3ntin]

We have this :D

llvm-project/clang/lib/AST/Expr.cpp

Lines 3203 to 3206 in 4d6f43d

	return IgnoreExprNodes(
	this, IgnoreImplicitSingleStep, IgnoreImplicitCastsExtraSingleStep,
	IgnoreParensOnlySingleStep, IgnoreImplicitConstructorSingleStep,
	IgnoreImplicitMemberCallSingleStep, IgnoreImplicitCallSingleStep);

We could use an array of functions for that (and apply the array in reverse)