[PATCH] D132945: [clang] Skip re-building lambda expressions in parameters to consteval fns.

[Utkarsh Saxena via Phabricator via cfe-commits]

usaxena95 created this revision.
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usaxena95 requested review of this revision.
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Fixes: https://github.com/llvm/llvm-project/issues/56183
Fixes: https://github.com/llvm/llvm-project/issues/51695
Fixes: https://github.com/llvm/llvm-project/issues/50455


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D132945

Files:
  clang/docs/ReleaseNotes.rst
  clang/lib/Sema/SemaExpr.cpp
  clang/test/SemaCXX/cxx2a-consteval.cpp


Index: clang/test/SemaCXX/cxx2a-consteval.cpp
===================================================================
--- clang/test/SemaCXX/cxx2a-consteval.cpp
+++ clang/test/SemaCXX/cxx2a-consteval.cpp
@@ -939,3 +939,63 @@
 static_assert(max(1,2)==2);
 static_assert(mid(1,2,3)==2);
 } // namespace GH51182
+
+// https://github.com/llvm/llvm-project/issues/56183
+namespace GH56183 {
+consteval auto Foo(auto c) { return c; }
+consteval auto Bar(auto f) { return f(); }
+void test() {
+  constexpr auto x = Foo(Bar([] { return 'a'; }));
+  static_assert(x == 'a');
+}
+}  // namespace GH56183
+
+// https://github.com/llvm/llvm-project/issues/51695
+namespace GH51695 {
+// Original ========================================
+template <typename T>
+struct type_t {};
+
+template <typename...>
+struct list_t {};
+
+template <typename T, typename... Ts>
+consteval auto pop_front(list_t<T, Ts...>) -> auto {
+  return list_t<Ts...>{};
+}
+
+template <typename... Ts, typename F>
+consteval auto apply(list_t<Ts...>, F fn) -> auto {
+  return fn(type_t<Ts>{}...);
+}
+
+void test1() {
+  constexpr auto x = apply(pop_front(list_t<char, char>{}),
+                            []<typename... Us>(type_t<Us>...) { return 42; });
+  static_assert(x == 42);
+}
+// Reduced ========================================
+consteval bool zero() { return false; }
+
+template <typename F>
+consteval bool foo(bool, F f) {
+  return f();
+}
+
+void test2() {
+  constexpr auto x = foo(zero(), []() { return true; });
+  static_assert(x);
+}
+}  // namespace GH51695
+
+// https://github.com/llvm/llvm-project/issues/50455
+namespace GH50455 {
+void f() {
+  []() consteval { int i{}; }();
+  []() consteval { int i{}; ++i; }();
+}
+void g() {
+  (void)[](int i) consteval { return i; }(0);
+  (void)[](int i) consteval { return i; }(0);
+}
+}  // namespace GH50455
\ No newline at end of file
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -17598,6 +17598,7 @@
       DRSet.erase(E);
       return E;
     }
+    ExprResult TransformLambdaExpr(LambdaExpr *E) { return E; }
     bool AlwaysRebuild() { return false; }
     bool ReplacingOriginal() { return true; }
     bool AllowSkippingCXXConstructExpr() {
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -191,8 +191,12 @@
 
 - Correctly set expression evaluation context as 'immediate function context' in
   consteval functions.
-  This fixes `GH51182 <https://github.com/llvm/llvm-project/issues/51182>`
+  This fixes `GH51182 <https://github.com/llvm/llvm-project/issues/51182>`_.
 
+- Skip re-building lambda expressions when they appear as parameters to an immediate invocation.
+  This fixes `GH56183 <https://github.com/llvm/llvm-project/issues/56183>`_,
+  `GH51695 <https://github.com/llvm/llvm-project/issues/51695>`_,
+  `GH50455 <https://github.com/llvm/llvm-project/issues/50455>`_.
 
 C++2b Feature Support
 ^^^^^^^^^^^^^^^^^^^^^


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