[Clangd] Disable ExtractVariable for all types of assignments

clang-tools-extra/trunk/clangd/refactor/tweaks/ExtractVariable.cpp

if (!N)
     return false;
   const clang::Expr *SelectedExpr = N->ASTNode.get<clang::Expr>();
   const SelectionTree::Node *TargetNode = N;
   if (!SelectedExpr)
     return false;
   // Extracting Exprs like a = 1 gives dummy = a = 1 which isn't useful.
   if (const BinaryOperator *BinOpExpr =
           dyn_cast_or_null<BinaryOperator>(SelectedExpr)) {
-    if (BinOpExpr->getOpcode() == BinaryOperatorKind::BO_Assign)
+    if (BinOpExpr->isAssignmentOp())
       return false;
   }
   // For function and member function DeclRefs, we look for a parent that is a
   // CallExpr
   if (const DeclRefExpr *DeclRef =
           dyn_cast_or_null<DeclRefExpr>(SelectedExpr)) {
     // Extracting just a variable isn't that useful.
     if (!isa<FunctionDecl>(DeclRef->getDecl()))

clang-tools-extra/trunk/clangd/unittests/TweakTests.cpp

void f(int b = [[1]]) {
           a = [[[[a]] +]] 1;
       // for loop
       for(int a = 1, b = 2, c = 3; a > [[b + c]]; [[a++]])
         a = [[a + 1]];
       // lambda
       auto lamb = [&[[a]], &[[b]]](int r = [[1]]) {return 1;}
       // assigment
       [[a = 5]];
+      [[a >>= 5]];
+      [[a *= 5]];
       // Variable DeclRefExpr
       a = [[b]];
       // label statement
       goto label;
       label:
         a = [[1]];
     }
   )cpp");