[clang] [Clang][Parser] GH78524 (PR #80656)

[Younan Zhang via cfe-commits]

https://github.com/zyn0217 created https://github.com/llvm/llvm-project/pull/80656

Poking the CI.

>From 3ceeae611848b58f8d49c58295a625bdb052ac97 Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Mon, 5 Feb 2024 18:01:34 +0800
Subject: [PATCH] GH78524

---
 clang/lib/Parse/ParseExprCXX.cpp              |  6 ++++-
 .../Parser/cxx-concepts-requires-clause.cpp   | 27 +++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Parse/ParseExprCXX.cpp b/clang/lib/Parse/ParseExprCXX.cpp
index fd262ff31e661..5c374d2eb452d 100644
--- a/clang/lib/Parse/ParseExprCXX.cpp
+++ b/clang/lib/Parse/ParseExprCXX.cpp
@@ -1385,6 +1385,11 @@ ExprResult Parser::ParseLambdaExpressionAfterIntroducer(
       Diag(RAngleLoc,
            diag::err_lambda_template_parameter_list_empty);
     } else {
+      // We increase the template depth before recursing into a requires-clause.
+      // The abbreviated generic lambdas thereof could have different template
+      // depths, avoiding substituting into wrong template parameters during the
+      // satisfaction check.
+      ++CurTemplateDepthTracker;
       ExprResult RequiresClause;
       if (TryConsumeToken(tok::kw_requires)) {
         RequiresClause =
@@ -1396,7 +1401,6 @@ ExprResult Parser::ParseLambdaExpressionAfterIntroducer(
 
       Actions.ActOnLambdaExplicitTemplateParameterList(
           Intro, LAngleLoc, TemplateParams, RAngleLoc, RequiresClause);
-      ++CurTemplateDepthTracker;
     }
   }
 
diff --git a/clang/test/Parser/cxx-concepts-requires-clause.cpp b/clang/test/Parser/cxx-concepts-requires-clause.cpp
index 1ec1eefa12865..f268092728fdf 100644
--- a/clang/test/Parser/cxx-concepts-requires-clause.cpp
+++ b/clang/test/Parser/cxx-concepts-requires-clause.cpp
@@ -168,3 +168,30 @@ auto lambda4 = [] requires(sizeof(char) == 1){}; // expected-error {{expected bo
 #if __cplusplus <= 202002L
 // expected-warning at -2{{lambda without a parameter clause is a C++23 extension}}
 #endif
+
+namespace GH78524 {
+
+template <typename T> T Foo;
+
+template <typename T> auto C(Foo<T>);
+
+template <typename T> struct D {
+  decltype(T()(C<T>)) Type;
+};
+
+template <typename T, typename U> D<T> G(T, U) { return {}; }
+
+struct E {};
+
+void F() {
+  G([]<typename T>
+//     ~~~~~~~~~~ T: 0,0
+      requires requires { [](auto...) {}; }(T)
+//                           ~~~~ auto: 1,0
+    { return T(); },
+    E{});
+}
+
+int a = []<int=0> requires requires { [](auto){}; } { return 0; }();
+
+} // namespace GH78524