feat: update class-methods-use-this for class static blocks (#15298)

Updates the `class-methods-use-this` rule to account for class static blocks.

This only fixes false negatives where use of `this` in a class static block mistakenly counts as used `this` in the enclosing context.

The rule still correctly does not require that class static blocks use `this`.

Refs #15016

docs/rules/class-methods-use-this.md

@@ -83,6 +83,10 @@ class A {
     static foo() {
         // OK. static methods aren't expected to use this.
     }
+
+    static {
+        // OK. static blocks are exempt.
+    }
 }
 ```
 

lib/rules/class-methods-use-this.js

@@ -161,8 +161,17 @@ module.exports = {
             /*
              * Class field value are implicit functions.
              */
-            "PropertyDefinition:exit": popContext,
             "PropertyDefinition > *.key:exit": pushContext,
+            "PropertyDefinition:exit": popContext,
+
+            /*
+             * Class static blocks are implicit functions. They aren't required to use `this`,
+             * but we have to push context so that it captures any use of `this` in the static block
+             * separately from enclosing contexts, because static blocks have their own `this` and it
+             * shouldn't count as used `this` in enclosing contexts.
+             */
+            StaticBlock: pushContext,
+            "StaticBlock:exit": popContext,
 
             ThisExpression: markThisUsed,
             Super: markThisUsed,

tests/lib/rules/class-methods-use-this.js

@@ -41,7 +41,8 @@ ruleTester.run("class-methods-use-this", rule, {
         { code: "class A { #bar() {} }", options: [{ exceptMethods: ["#bar"] }], parserOptions: { ecmaVersion: 2022 } },
         { code: "class A { foo = function () {} }", options: [{ enforceForClassFields: false }], parserOptions: { ecmaVersion: 2022 } },
         { code: "class A { foo = () => {} }", options: [{ enforceForClassFields: false }], parserOptions: { ecmaVersion: 2022 } },
-        { code: "class A { foo() { return class { [this.foo] = 1 }; } }", parserOptions: { ecmaVersion: 2022 } }
+        { code: "class A { foo() { return class { [this.foo] = 1 }; } }", parserOptions: { ecmaVersion: 2022 } },
+        { code: "class A { static {} }", parserOptions: { ecmaVersion: 2022 } }
     ],
     invalid: [
         {
@@ -203,6 +204,13 @@ ruleTester.run("class-methods-use-this", rule, {
             errors: [
                 { messageId: "missingThis", data: { name: "method 'foo'" }, column: 11, endColumn: 15 }
             ]
+        },
+        {
+            code: "class A { foo () { return class { static { this; } } } }",
+            parserOptions: { ecmaVersion: 2022 },
+            errors: [
+                { messageId: "missingThis", data: { name: "method 'foo'" }, column: 11, endColumn: 15 }
+            ]
         }
     ]
 });