1 files changed, 17 insertions, 3 deletions
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 7784126377..75b09cf218 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -15179,10 +15179,24 @@ bool Sema::DiagRuntimeBehavior(SourceLocation Loc, const Stmt *Statement,
     if (Statement && getCurFunctionOrMethodDecl()) {
       FunctionScopes.back()->PossiblyUnreachableDiags.
         push_back(sema::PossiblyUnreachableDiag(PD, Loc, Statement));
+      return true;
     }
-    else
-      Diag(Loc, PD);
-      
+
+    // The initializer of a constexpr variable or of the first declaration of a
+    // static data member is not syntactically a constant evaluated constant,
+    // but nonetheless is always required to be a constant expression, so we
+    // can skip diagnosing.
+    // FIXME: Using the mangling context here is a hack.
+    if (auto *VD = dyn_cast_or_null<VarDecl>(
+            ExprEvalContexts.back().ManglingContextDecl)) {
+      if (VD->isConstexpr() ||
+          (VD->isStaticDataMember() && VD->isFirstDecl() && !VD->isInline()))
+        break;
+      // FIXME: For any other kind of variable, we should build a CFG for its
+      // initializer and check whether the context in question is reachable.
+    }
+
+    Diag(Loc, PD);
     return true;
   }