take optional chains into account when locating the left-most item in…

… an expression. (close #1256)

lib/utils/first_in_statement.js

@@ -1,6 +1,7 @@
 import {
     AST_Binary,
     AST_Conditional,
+    AST_Chain,
     AST_Dot,
     AST_Object,
     AST_Sequence,
@@ -23,6 +24,7 @@ function first_in_statement(stack) {
             (p instanceof AST_PrefixedTemplateString && p.prefix === node) ||
             (p instanceof AST_Dot && p.expression === node) ||
             (p instanceof AST_Sub && p.expression === node) ||
+            (p instanceof AST_Chain && p.expression === node) ||
             (p instanceof AST_Conditional && p.condition === node) ||
             (p instanceof AST_Binary && p.left === node) ||
             (p instanceof AST_UnaryPostfix && p.expression === node)
@@ -41,6 +43,7 @@ function left_is_object(node) {
     if (node.TYPE === "Call") return left_is_object(node.expression);
     if (node instanceof AST_PrefixedTemplateString) return left_is_object(node.prefix);
     if (node instanceof AST_Dot || node instanceof AST_Sub) return left_is_object(node.expression);
+    if (node instanceof AST_Chain) return left_is_object(node.expression);
     if (node instanceof AST_Conditional) return left_is_object(node.condition);
     if (node instanceof AST_Binary) return left_is_object(node.left);
     if (node instanceof AST_UnaryPostfix) return left_is_object(node.expression);