[Concepts] Fix incorrect DeclContext for transformed RequiresExprBodyDecl

We would assign the incorrect DeclContext when transforming the RequiresExprBodyDecl, causing incorrect
handling of 'this' inside RequiresExprBodyDecls (bug #45162).

Assign the current context as the DeclContext of the transformed decl.

(cherry picked from commit 9769e1ee9acc33638449b50ac394b5ee2d4efb60)

2 files changed, 14 insertions, 1 deletions

diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 805fe66..0305954 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -11303,7 +11303,7 @@ TreeTransform<Derived>::TransformRequiresExpr(RequiresExpr *E) {
       SemaRef, Sema::ExpressionEvaluationContext::Unevaluated);
 
   RequiresExprBodyDecl *Body = RequiresExprBodyDecl::Create(
-      getSema().Context, E->getBody()->getDeclContext(),
+      getSema().Context, getSema().CurContext,
       E->getBody()->getBeginLoc());
 
   Sema::ContextRAII SavedContext(getSema(), Body, /*NewThisContext*/false);
diff --git a/clang/test/SemaTemplate/instantiate-requires-expr.cpp b/clang/test/SemaTemplate/instantiate-requires-expr.cpp
index 927bc1b..ba82fc1 100644
--- a/clang/test/SemaTemplate/instantiate-requires-expr.cpp
+++ b/clang/test/SemaTemplate/instantiate-requires-expr.cpp
@@ -164,6 +164,19 @@ namespace expr_requirement {
   struct r3 {};
 
   using r3i = r3<int, unsigned int>; // expected-error{{constraints not satisfied for class template 'r3' [with Ts = <int, unsigned int>]}}
+
+  template<typename T>
+  struct r4 {
+      constexpr int foo() {
+        if constexpr (requires { this->invalid(); })
+          return 1;
+        else
+          return 0;
+      }
+
+      constexpr void invalid() requires false { }
+  };
+  static_assert(r4<int>{}.foo() == 0);
 }
 
 namespace nested_requirement {