fix(no-this-assign-in-render): explicit left hand side traversal (#185)

The esquery we were using was too wide in that it would match a `.left`
at _any_ level.

This meant the following code would match:

```ts
render() {
  x = this.foo || 123;
}
```

As a `LogicalExpression` has a left just like an `AssignmentExpression`.

Since esquery doesn't support relative direct child selection (i.e.
using `:has(> foo)`), we are now selecting the left side node and
reporting on the parent instead.

src/rules/no-this-assign-in-render.ts

@@ -88,18 +88,18 @@ const rule: Rule.RuleModule = {
     }
 
     /**
-     * Assignment expression entered
+     * Left side of an assignment expr found
      *
-     * @param {ESTree.AssignmentExpression} node Node entered
+     * @param {Rule.Node} node Node entered
      * @return {void}
      */
-    function assignmentFound(node: ESTree.AssignmentExpression): void {
+    function assignmentFound(node: Rule.Node): void {
       if (!inRender) {
         return;
       }
 
       context.report({
-        node,
+        node: node.parent,
         messageId: 'noThis'
       });
     }
@@ -114,9 +114,9 @@ const rule: Rule.RuleModule = {
       MethodDefinition: (node: ESTree.Node): void =>
         methodEnter(node as ESTree.MethodDefinition),
       'MethodDefinition:exit': methodExit,
-      'AssignmentExpression:has(.left ThisExpression)': (
-        node: ESTree.Node
-      ): void => assignmentFound(node as ESTree.AssignmentExpression)
+      'AssignmentExpression > .left:has(ThisExpression)': (
+        node: Rule.Node
+      ): void => assignmentFound(node)
     };
   }
 };

src/test/rules/no-this-assign-in-render_test.ts

@@ -61,6 +61,12 @@ ruleTester.run('no-this-assign-in-render', rule, {
           let x;
           x = 5;
         }
+      }`,
+    `class Foo extends LitElement {
+        render() {
+          let x;
+          x = this.foo || 123;
+        }
       }`
   ],