[Clang] Fixes to immediate-escalating functions (#82281)

[steakhal]

• Consider that immediate escalating function can appear at global scope, fixing a crash

• Lambda conversion to function pointer was sometimes not performed in an immediate function context when it should be.

Fixes #82258

(cherry picked from commit baf6bd3)

[llvmbot]

@llvm/pr-subscribers-clang

Author: Balazs Benics (steakhal)

Changes

• Consider that immediate escalating function can appear at global scope, fixing a crash

• Lambda conversion to function pointer was sometimes not performed in an immediate function context when it should be.

Fixes #82258

(cherry picked from commit baf6bd3)

---

Full diff: https://github.com/llvm/llvm-project/pull/82609.diff

4 Files Affected:

• (modified) clang/docs/ReleaseNotes.rst (+5)
• (modified) clang/include/clang/Sema/Sema.h (+3-1)
• (modified) clang/lib/Sema/SemaExpr.cpp (+2-2)
• (modified) clang/test/SemaCXX/cxx2b-consteval-propagate.cpp (+26)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 93a67e7a895592..8697f1f3bbe9c2 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -1099,6 +1099,11 @@ Bug Fixes to C++ Support
 - Fix incorrect code generation caused by the object argument of ``static operator()`` and ``static operator[]`` calls not being evaluated.
   Fixes (`#67976 <https://github.com/llvm/llvm-project/issues/67976>`_)
 
+- Fix crash when using an immediate-escalated function at global scope.
+  (`#82258 <https://github.com/llvm/llvm-project/issues/82258>`_)
+- Correctly immediate-escalate lambda conversion functions.
+  (`#82258 <https://github.com/llvm/llvm-project/issues/82258>`_)
+
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
 - Fixed an import failure of recursive friend class template.
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 1f1cbd11ff7358..6adb8fb7966b3f 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -1090,7 +1090,9 @@ class Sema final {
       if (FD) {
         FD->setWillHaveBody(true);
         S.ExprEvalContexts.back().InImmediateFunctionContext =
-            FD->isImmediateFunction();
+            FD->isImmediateFunction() ||
+            S.ExprEvalContexts[S.ExprEvalContexts.size() - 2]
+                .isConstantEvaluated();
         S.ExprEvalContexts.back().InImmediateEscalatingFunctionContext =
             S.getLangOpts().CPlusPlus20 && FD->isImmediateEscalating();
       } else
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 0d9c087ed0cd19..4cce0abc231505 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -18294,7 +18294,6 @@ void Sema::CheckUnusedVolatileAssignment(Expr *E) {
 }
 
 void Sema::MarkExpressionAsImmediateEscalating(Expr *E) {
-  assert(!FunctionScopes.empty() && "Expected a function scope");
   assert(getLangOpts().CPlusPlus20 &&
          ExprEvalContexts.back().InImmediateEscalatingFunctionContext &&
          "Cannot mark an immediate escalating expression outside of an "
@@ -18311,7 +18310,8 @@ void Sema::MarkExpressionAsImmediateEscalating(Expr *E) {
   } else {
     assert(false && "expected an immediately escalating expression");
   }
-  getCurFunction()->FoundImmediateEscalatingExpression = true;
+  if (FunctionScopeInfo *FI = getCurFunction())
+    FI->FoundImmediateEscalatingExpression = true;
 }
 
 ExprResult Sema::CheckForImmediateInvocation(ExprResult E, FunctionDecl *Decl) {
diff --git a/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp b/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
index 531a6262287335..4a75392045d05a 100644
--- a/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
+++ b/clang/test/SemaCXX/cxx2b-consteval-propagate.cpp
@@ -368,3 +368,29 @@ vector<void> v{};
 // expected-note@-2 {{in call to 'vector()'}}
 
 }
+
+
+namespace GH82258 {
+
+template <class R, class Pred>
+constexpr auto none_of(R&& r, Pred pred) -> bool { return true; }
+
+struct info { int value; };
+consteval auto is_invalid(info i) -> bool { return false; }
+constexpr info types[] = { {1}, {3}, {5}};
+
+static_assert(none_of(
+    types,
+    +[](info i) consteval {
+        return is_invalid(i);
+    }
+));
+
+static_assert(none_of(
+    types,
+    []{
+        return is_invalid;
+    }()
+));
+
+}

[tstellar]

@cor3ntin @AaronBallman What do you think about backporting this?

[cor3ntin]

Makes sense to me!

[tstellar]

Merged a7a74ec