Fix template-no-obsolete-elements: track element-level block params

The rule suppressed obsolete-element reports when the tag name shadows a
block param from a GlimmerBlockStatement (e.g. {{#let (...) as |marquee|}}).
It did not track element-level block params (<Comp as |marquee|>), so
inside an angle-bracket component the shadowing was ignored and the tag
was falsely reported. Push element block params on enter and pop on exit,
mirroring the existing GlimmerBlockStatement handling.

Author: johanrd

lib/rules/template-no-obsolete-elements.js

@@ -64,13 +64,21 @@ module.exports = {
         }
       },
       GlimmerElementNode(node) {
-        if (blockParamsInScope.includes(node.tag)) {
-          return;
-        }
-        if (obsolete.has(node.tag)) {
+        // Push element-level block params (e.g. <Comp as |param|>) before
+        // checking children. Pop on exit.
+        const elementParams = node.blockParams || [];
+        blockParamsInScope.push(...elementParams);
+
+        if (!blockParamsInScope.includes(node.tag) && obsolete.has(node.tag)) {
           context.report({ node, messageId: 'obsolete', data: { element: node.tag } });
         }
       },
+      'GlimmerElementNode:exit'(node) {
+        const elementParams = node.blockParams || [];
+        for (let i = 0; i < elementParams.length; i++) {
+          blockParamsInScope.pop();
+        }
+      },
     };
   },
 };

tests/lib/rules/template-no-obsolete-elements.js

@@ -11,6 +11,9 @@ ruleTester.run('template-no-obsolete-elements', rule, {
     `<template>{{#let (component 'whatever-here') as |plaintext|}}
       <plaintext />
     {{/let}}</template>`,
+    // Element-level block params (<Comp as |...|>) are now tracked
+    '<template><Comp as |plaintext|><plaintext /></Comp></template>',
+    '<template><Outer as |marquee|><marquee /></Outer></template>',
   ],
   invalid: [
     {