[PATCH] D119651: [clang] Fix evaluation context type for consteval function calls in instantiations

[Evgeny Shulgin via Phabricator via cfe-commits]

Izaron created this revision.
Izaron added reviewers: aaron.ballman, erichkeane, rsmith.
Izaron requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

When instantiating a VarDecl initializing sub-AST, the evaluation
context was only PotentiallyEvaluated, even if we are inside a consteval
function. It dictated clang to construct a redundant ConstantExpr node, which
could be not evaluable.

Fixes https://github.com/llvm/llvm-project/issues/51182
and https://github.com/llvm/llvm-project/issues/52648


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D119651

Files:
  clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
  clang/test/SemaCXX/cxx2a-consteval.cpp


Index: clang/test/SemaCXX/cxx2a-consteval.cpp
===================================================================
--- clang/test/SemaCXX/cxx2a-consteval.cpp
+++ clang/test/SemaCXX/cxx2a-consteval.cpp
@@ -613,6 +613,23 @@
 
 } // namespace unevaluated
 
+namespace templated {
+
+consteval int f(int v) {
+  return v;
+}
+
+template <typename T>
+consteval int g(T a) {
+  // Previously this call was rejected due to incorrect evaluation context type in instantiations. Now we show that this call is OK.
+  int n = f(a);
+  return n;
+}
+
+static_assert(g(100) == 100);
+
+} // namespace templated
+
 namespace PR50779 {
 struct derp {
   int b = 0;
Index: clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
===================================================================
--- clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -5326,8 +5326,13 @@
     Var->setImplicitlyInline();
 
   if (OldVar->getInit()) {
-    EnterExpressionEvaluationContext Evaluated(
-        *this, Sema::ExpressionEvaluationContext::PotentiallyEvaluated, Var);
+    ExpressionEvaluationContext Context =
+        ExpressionEvaluationContext::PotentiallyEvaluated;
+    // If current context is constant evaluated, the variable initializer
+    // context is also constant evaluated
+    if (isConstantEvaluated())
+      Context = ExpressionEvaluationContext::ConstantEvaluated;
+    EnterExpressionEvaluationContext Evaluated(*this, Context, Var);
 
     // Instantiate the initializer.
     ExprResult Init;


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D119651.408219.patch
Type: text/x-patch
Size: 1536 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20220212/0272ba6c/attachment.bin>