[clang] [Clang] Only remove lambda scope after computing evaluation context (PR #154106)

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Mon Aug 18 05:22:07 PDT 2025 

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Younan Zhang (zyn0217)

<details>
<summary>Changes</summary>

The immediate evaluation context needs the lambda scope info to propagate some flags, however that LSI was removed in ActOnFinishFunctionBody which happened before rebuilding a lambda expression.

This also converts the wrapper function to default arguments as a drive-by fix.

Fixes https://github.com/llvm/llvm-project/issues/145776

---
Full diff: https://github.com/llvm/llvm-project/pull/154106.diff


6 Files Affected:

- (modified) clang/docs/ReleaseNotes.rst (+1) 
- (modified) clang/include/clang/Sema/Sema.h (+7-6) 
- (modified) clang/lib/Sema/SemaDecl.cpp (+4-7) 
- (modified) clang/lib/Sema/SemaLambda.cpp (+12-2) 
- (modified) clang/lib/Sema/TreeTransform.h (+4-7) 
- (modified) clang/test/SemaCXX/cxx2b-consteval-propagate.cpp (+16) 


``````````diff
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 9231f2cae9bfa..ca6fc663c9525 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -158,6 +158,7 @@ Bug Fixes to C++ Support
 - Diagnose binding a reference to ``*nullptr`` during constant evaluation. (#GH48665)
 - Suppress ``-Wdeprecated-declarations`` in implicitly generated functions. (#GH147293)
 - Fix a crash when deleting a pointer to an incomplete array (#GH150359).
+- Fixed a mismatched lambda scope bug when propagating up ``consteval`` within nested lambdas. (#GH145776)
 - Fix an assertion failure when expression in assumption attribute
   (``[[assume(expr)]]``) creates temporary objects.
 
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 5211373367677..160b0739b5aa2 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -4179,8 +4179,9 @@ class Sema final : public SemaBase {
   /// return statement in the scope of a variable has the same NRVO candidate,
   /// that candidate is an NRVO variable.
   void computeNRVO(Stmt *Body, sema::FunctionScopeInfo *Scope);
-  Decl *ActOnFinishFunctionBody(Decl *Decl, Stmt *Body);
-  Decl *ActOnFinishFunctionBody(Decl *Decl, Stmt *Body, bool IsInstantiation);
+  Decl *ActOnFinishFunctionBody(Decl *Decl, Stmt *Body,
+                                bool IsInstantiation = false,
+                                bool RetainFunctionScopeInfo = false);
   Decl *ActOnSkippedFunctionBody(Decl *Decl);
   void ActOnFinishInlineFunctionDef(FunctionDecl *D);
 
@@ -6873,23 +6874,23 @@ class Sema final : public SemaBase {
     assert(!ExprEvalContexts.empty() &&
            "Must be in an expression evaluation context");
     return ExprEvalContexts.back();
-  };
+  }
 
   ExpressionEvaluationContextRecord &currentEvaluationContext() {
     assert(!ExprEvalContexts.empty() &&
            "Must be in an expression evaluation context");
     return ExprEvalContexts.back();
-  };
+  }
 
   ExpressionEvaluationContextRecord &parentEvaluationContext() {
     assert(ExprEvalContexts.size() >= 2 &&
            "Must be in an expression evaluation context");
     return ExprEvalContexts[ExprEvalContexts.size() - 2];
-  };
+  }
 
   const ExpressionEvaluationContextRecord &parentEvaluationContext() const {
     return const_cast<Sema *>(this)->parentEvaluationContext();
-  };
+  }
 
   bool isAttrContext() const {
     return ExprEvalContexts.back().ExprContext ==
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index b5eb825eb52cc..4c8974b2e6c9a 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -16149,10 +16149,6 @@ Decl *Sema::ActOnSkippedFunctionBody(Decl *Decl) {
   return Decl;
 }
 
-Decl *Sema::ActOnFinishFunctionBody(Decl *D, Stmt *BodyArg) {
-  return ActOnFinishFunctionBody(D, BodyArg, /*IsInstantiation=*/false);
-}
-
 /// RAII object that pops an ExpressionEvaluationContext when exiting a function
 /// body.
 class ExitFunctionBodyRAII {
@@ -16223,8 +16219,8 @@ void Sema::CheckCoroutineWrapper(FunctionDecl *FD) {
     Diag(FD->getLocation(), diag::err_coroutine_return_type) << RD;
 }
 
-Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
-                                    bool IsInstantiation) {
+Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body, bool IsInstantiation,
+                                    bool RetainFunctionScopeInfo) {
   FunctionScopeInfo *FSI = getCurFunction();
   FunctionDecl *FD = dcl ? dcl->getAsFunction() : nullptr;
 
@@ -16681,7 +16677,8 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
   if (!IsInstantiation)
     PopDeclContext();
 
-  PopFunctionScopeInfo(ActivePolicy, dcl);
+  if (!RetainFunctionScopeInfo)
+    PopFunctionScopeInfo(ActivePolicy, dcl);
   // If any errors have occurred, clear out any temporaries that may have
   // been leftover. This ensures that these temporaries won't be picked up for
   // deletion in some later function.
diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index bc3c4b0addeba..eb6bc83cf861a 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -1968,12 +1968,13 @@ ExprResult Sema::BuildCaptureInit(const Capture &Cap,
 }
 
 ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body) {
-  LambdaScopeInfo LSI = *cast<LambdaScopeInfo>(FunctionScopes.back());
+  LambdaScopeInfo &LSI = *cast<LambdaScopeInfo>(FunctionScopes.back());
 
   if (LSI.CallOperator->hasAttr<SYCLKernelEntryPointAttr>())
     SYCL().CheckSYCLEntryPointFunctionDecl(LSI.CallOperator);
 
-  ActOnFinishFunctionBody(LSI.CallOperator, Body);
+  ActOnFinishFunctionBody(LSI.CallOperator, Body, /*IsInstantiation=*/false,
+                          /*RetainFunctionScopeInfo=*/true);
 
   return BuildLambdaExpr(StartLoc, Body->getEndLoc(), &LSI);
 }
@@ -2134,6 +2135,11 @@ ConstructFixItRangeForUnusedCapture(Sema &S, SourceRange CaptureRange,
 
 ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
                                  LambdaScopeInfo *LSI) {
+  // Copy the LSI before PopFunctionScopeInfo removes it.
+  // FIXME: This is dumb. Store the lambda information somewhere that outlives
+  // the call operator.
+  LambdaScopeInfo LSICopy = *LSI;
+  LSI = &LSICopy;
   // Collect information from the lambda scope.
   SmallVector<LambdaCapture, 4> Captures;
   SmallVector<Expr *, 4> CaptureInits;
@@ -2170,6 +2176,10 @@ ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
 
     PopExpressionEvaluationContext();
 
+    sema::AnalysisBasedWarnings::Policy WP =
+        AnalysisWarnings.getPolicyInEffectAt(EndLoc);
+    PopFunctionScopeInfo(&WP, LSI->CallOperator);
+
     // True if the current capture has a used capture or default before it.
     bool CurHasPreviousCapture = CaptureDefault != LCD_None;
     SourceLocation PrevCaptureLoc = CurHasPreviousCapture ?
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 5ff5fbf52ae25..c3893959c85bf 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -15791,12 +15791,9 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
     return ExprError();
   }
 
-  // Copy the LSI before ActOnFinishFunctionBody removes it.
-  // FIXME: This is dumb. Store the lambda information somewhere that outlives
-  // the call operator.
-  auto LSICopy = *LSI;
   getSema().ActOnFinishFunctionBody(NewCallOperator, Body.get(),
-                                    /*IsInstantiation*/ true);
+                                    /*IsInstantiation=*/true,
+                                    /*RetainFunctionScopeInfo=*/true);
   SavedContext.pop();
 
   // Recompute the dependency of the lambda so that we can defer the lambda call
@@ -15832,7 +15829,7 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
   // *after* the substitution in case we can't decide the dependency
   // so early, e.g. because we want to see if any of the *substituted*
   // parameters are dependent.
-  DependencyKind = getDerived().ComputeLambdaDependency(&LSICopy);
+  DependencyKind = getDerived().ComputeLambdaDependency(LSI);
   Class->setLambdaDependencyKind(DependencyKind);
   // Clean up the type cache created previously. Then, we re-create a type for
   // such Decl with the new DependencyKind.
@@ -15840,7 +15837,7 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
   getSema().Context.getTypeDeclType(Class);
 
   return getDerived().RebuildLambdaExpr(E->getBeginLoc(),
-                                        Body.get()->getEndLoc(), &LSICopy);
+                                        Body.get()->getEndLoc(), LSI);
 }
 
 template<typename Derived>
diff --git a/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp b/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
index c4cfd9398920a..6cf0e0251ab62 100644
--- a/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
+++ b/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
@@ -610,3 +610,19 @@ namespace GH135281 {
   void (*ff)() = f2<B>; // expected-note {{instantiation of function template specialization}}
 }
 #endif
+
+namespace GH145776 {
+
+void runtime_only() {}
+consteval void comptime_only() {}
+
+void fn() {
+  []() {
+    runtime_only();
+    []() {
+      &comptime_only;
+    }();
+  }();
+}
+
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/154106

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