[clang] [Clang] Fix a regression introduced by #140576 (PR #140859)

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https://github.com/cor3ntin updated https://github.com/llvm/llvm-project/pull/140859

>From 1e7330b89327ea02271d54349ab3b01b8a495805 Mon Sep 17 00:00:00 2001
From: Corentin Jabot <corentinjabot at gmail.com>
Date: Wed, 21 May 2025 09:12:52 +0200
Subject: [PATCH] [Clang] Fix a regression introduced by #140576

Lambda bodies should not be treated as subexpressions of the
enclosing scope.
---
 clang/lib/Sema/SemaExpr.cpp                         | 6 ++----
 clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp | 8 ++++++++
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index b18e83b605e4f..66dac21bf5818 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -17777,15 +17777,13 @@ void Sema::PushExpressionEvaluationContextForFunction(
     Current.InImmediateEscalatingFunctionContext =
         getLangOpts().CPlusPlus20 && FD->isImmediateEscalating();
 
-    if (isLambdaMethod(FD)) {
-      Current.InDiscardedStatement = Parent.isDiscardedStatementContext();
+    if (isLambdaMethod(FD))
       Current.InImmediateFunctionContext =
           FD->isConsteval() ||
           (isLambdaMethod(FD) && (Parent.isConstantEvaluated() ||
                                   Parent.isImmediateFunctionContext()));
-    } else {
+    else
       Current.InImmediateFunctionContext = FD->isConsteval();
-    }
   }
 }
 
diff --git a/clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp b/clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp
index 20125cc5d4a9c..ac21e36daf870 100644
--- a/clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp
+++ b/clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp
@@ -208,6 +208,14 @@ void test() {
 
     }
 }
+
+void regression() {
+  if constexpr (false) {
+    auto lam = []() { return 0; };
+    1 | lam(); // expected-warning {{unused}}
+  }
+}
+
 }
 
 #endif