Silence some MSVC warnings about not all control paths returning a value; NFC.

llvm-svn: 318809

clang-tools-extra/clangd/JSONExpr.cpp

@@ -519,6 +519,7 @@ bool operator==(const Expr &L, const Expr &R) {
   case Expr::Object:
     return *L.object() == *R.object();
   }
+  llvm_unreachable("Unknown expressiopn kind");
 }
 } // namespace json
 } // namespace clangd

clang-tools-extra/clangd/JSONExpr.h

@@ -162,6 +162,7 @@ public:
     case T_Array:
       return Array;
     }
+    llvm_unreachable("Unknown kind");
   }
 
   // Typed accessors return None/nullptr if the Expr is not of this type.