[clang] [Clang] Do not inherit immediate-function context in lambda bodies (PR #214002)

[via cfe-commits]

https://github.com/term-est updated https://github.com/llvm/llvm-project/pull/214002

>From fcba5fc86df76161420027750f6fca5caae34e67 Mon Sep 17 00:00:00 2001
From: term-est <eurasia.sely at gmail.com>
Date: Tue, 4 Aug 2026 19:23:57 +0300
Subject: [PATCH 1/4] [clang] Linker regression with lambda NTTP containing
 consteval function call  #169139

---
 clang/lib/Sema/SemaLambda.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index bbe93f6ab8a40..91016e3523387 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -1601,6 +1601,9 @@ void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
   // cleanups from the enclosing full-expression.
   PushExpressionEvaluationContextForFunction(
       ExpressionEvaluationContext::PotentiallyEvaluated, LSI->CallOperator);
+
+  currentEvaluationContext().InImmediateFunctionContext =
+      LSI->CallOperator->isConsteval();
 }
 
 void Sema::ActOnLambdaError(SourceLocation StartLoc, Scope *CurScope,

>From acb12ac095020e2be17655cea25c50273087e64c Mon Sep 17 00:00:00 2001
From: term-est <eurasia.sely at gmail.com>
Date: Tue, 4 Aug 2026 21:26:58 +0300
Subject: [PATCH 2/4] Add a regression test.

---
 clang/test/CodeGen/consteval-lambda-nttp.cpp | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
 create mode 100644 clang/test/CodeGen/consteval-lambda-nttp.cpp

diff --git a/clang/test/CodeGen/consteval-lambda-nttp.cpp b/clang/test/CodeGen/consteval-lambda-nttp.cpp
new file mode 100644
index 0000000000000..71ff0c2d9013d
--- /dev/null
+++ b/clang/test/CodeGen/consteval-lambda-nttp.cpp
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-linux-gnu \
+// RUN:   -emit-llvm -o - %s | FileCheck %s
+
+consteval int foo() {
+  return 42;
+}
+
+template <auto Fn>
+int bar() {
+  return Fn();
+}
+
+int test() {
+  return bar<[] { return foo(); }>();
+}
+
+// CHECK-NOT: @_Z3foov
+// CHECK: define{{.*}} i32 @_Z4testv
+// CHECK-NOT: @_Z3foov
\ No newline at end of file

>From 54c9b7818eeaa5f35e4ea7b7120da1f45a202094 Mon Sep 17 00:00:00 2001
From: term-est <eurasia.sely at gmail.com>
Date: Tue, 4 Aug 2026 21:42:31 +0300
Subject: [PATCH 3/4] Add comments and fix formatting

---
 clang/lib/Sema/SemaLambda.cpp                | 2 ++
 clang/test/CodeGen/consteval-lambda-nttp.cpp | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index 91016e3523387..5960f8a26ae06 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -1602,6 +1602,8 @@ void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
   PushExpressionEvaluationContextForFunction(
       ExpressionEvaluationContext::PotentiallyEvaluated, LSI->CallOperator);
 
+  // A lambda body does not inherit the immediate-function context of the
+  // enclosing lambda-expression.
   currentEvaluationContext().InImmediateFunctionContext =
       LSI->CallOperator->isConsteval();
 }
diff --git a/clang/test/CodeGen/consteval-lambda-nttp.cpp b/clang/test/CodeGen/consteval-lambda-nttp.cpp
index 71ff0c2d9013d..19b0e7f23e3df 100644
--- a/clang/test/CodeGen/consteval-lambda-nttp.cpp
+++ b/clang/test/CodeGen/consteval-lambda-nttp.cpp
@@ -16,4 +16,4 @@ int test() {
 
 // CHECK-NOT: @_Z3foov
 // CHECK: define{{.*}} i32 @_Z4testv
-// CHECK-NOT: @_Z3foov
\ No newline at end of file
+// CHECK-NOT: @_Z3foov

>From 62df2318459e473c9ad715f13099565af147a3e6 Mon Sep 17 00:00:00 2001
From: term-est <eurasia.sely at gmail.com>
Date: Thu, 6 Aug 2026 05:55:05 +0300
Subject: [PATCH 4/4] Fix the issue in
 PushExpressionEvaluationContextForFunction instead

---
 clang/lib/Sema/SemaExpr.cpp   | 18 +++++++++++-------
 clang/lib/Sema/SemaLambda.cpp |  5 -----
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 59b8c9b60663c..fb17d029ea64a 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -18273,13 +18273,17 @@ void Sema::PushExpressionEvaluationContextForFunction(
     Current.InImmediateEscalatingFunctionContext =
         getLangOpts().CPlusPlus20 && FD->isImmediateEscalating();
 
-    if (isLambdaMethod(FD))
-      Current.InImmediateFunctionContext =
-          FD->isConsteval() ||
-          (isLambdaMethod(FD) && (Parent.isConstantEvaluated() ||
-                                  Parent.isImmediateFunctionContext()));
-    else
-      Current.InImmediateFunctionContext = FD->isConsteval();
+    const bool InheritParentImmediateContext =
+        isLambdaMethod(FD) && !isLambdaCallOperator(FD);
+
+    // A lambda call operator body is not a subexpression of the enclosing
+    // lambda-expression. Other lambda methods may be synthesized while
+    // processing the lambda and need to inherit the enclosing evaluation
+    // context.
+    Current.InImmediateFunctionContext =
+        FD->isConsteval() ||
+        (InheritParentImmediateContext &&
+         (Parent.isConstantEvaluated() || Parent.isImmediateFunctionContext()));
   }
 }
 
diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index 5960f8a26ae06..bbe93f6ab8a40 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -1601,11 +1601,6 @@ void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
   // cleanups from the enclosing full-expression.
   PushExpressionEvaluationContextForFunction(
       ExpressionEvaluationContext::PotentiallyEvaluated, LSI->CallOperator);
-
-  // A lambda body does not inherit the immediate-function context of the
-  // enclosing lambda-expression.
-  currentEvaluationContext().InImmediateFunctionContext =
-      LSI->CallOperator->isConsteval();
 }
 
 void Sema::ActOnLambdaError(SourceLocation StartLoc, Scope *CurScope,