[PATCH] D48322: [Sema] Discarded statment should be an evaluatable context

[Erik Pilkington via Phabricator via cfe-commits]

erik.pilkington created this revision.
erik.pilkington added a reviewer: rsmith.

The constexpr evaluator was erroring out because these templates weren't defined. Despite being used in a discarded statement, we still need to constexpr evaluate them, which means that we need to instantiate them.

Fixes https://llvm.org/PR37585

Thanks!


Repository:
  rC Clang

https://reviews.llvm.org/D48322

Files:
  clang/lib/Sema/SemaExpr.cpp
  clang/test/SemaCXX/constant-expression-cxx1z.cpp


Index: clang/test/SemaCXX/constant-expression-cxx1z.cpp
===================================================================
--- clang/test/SemaCXX/constant-expression-cxx1z.cpp
+++ clang/test/SemaCXX/constant-expression-cxx1z.cpp
@@ -46,3 +46,16 @@
   const int &r = 0;
   constexpr int n = r;
 }
+
+namespace PR37585 {
+template <class T> struct S { static constexpr bool value = true; };
+template <class T> constexpr bool f() { return true; }
+template <class T> constexpr bool v = true;
+
+void test() {
+  if constexpr (true) {}
+  else if constexpr (f<int>()) {}
+  else if constexpr (S<int>::value) {}
+  else if constexpr (v<int>) {}
+}
+}
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -14143,13 +14143,13 @@
   switch (SemaRef.ExprEvalContexts.back().Context) {
     case Sema::ExpressionEvaluationContext::Unevaluated:
     case Sema::ExpressionEvaluationContext::UnevaluatedAbstract:
-    case Sema::ExpressionEvaluationContext::DiscardedStatement:
       // Expressions in this context are never evaluated.
       return false;
 
     case Sema::ExpressionEvaluationContext::UnevaluatedList:
     case Sema::ExpressionEvaluationContext::ConstantEvaluated:
     case Sema::ExpressionEvaluationContext::PotentiallyEvaluated:
+    case Sema::ExpressionEvaluationContext::DiscardedStatement:
       // Expressions in this context could be evaluated.
       return true;
 


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