From df908fc63b809444db3b7689b12a298a8d48f66d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicol=C3=B2=20Ribaudo?= <nicolo.ribaudo@gmail.com>
Date: Tue, 27 Oct 2020 13:12:49 +0100
Subject: [PATCH] Mark `ThisExpression` and `Super` as `Purish` (#12251)

* Mark `ThisExpression` as `Purish`

The other purish types are functions and literals, so I
guess it means "it doesn't have side effects"

* Super & tests

* Fix tests
---
 packages/babel-traverse/test/scope.js               | 13 +++++++++++++
 packages/babel-types/src/definitions/core.js        |  4 ++--
 .../babel-types/src/validators/generated/index.js   |  2 ++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/packages/babel-traverse/test/scope.js b/packages/babel-traverse/test/scope.js
index 106c9631e6..f02089db6d 100644
--- a/packages/babel-traverse/test/scope.js
+++ b/packages/babel-traverse/test/scope.js
@@ -232,6 +232,19 @@ describe("scope", () => {
       expect(
         getPath("String.raw`foo`").get("body")[0].get("expression").isPure(),
       ).toBeTruthy();
+      expect(getPath("this").get("body.0.expression").isPure()).toBeTruthy();
+      expect(getPath("this.foo").get("body.0.expression").isPure()).toBeFalsy();
+      expect(
+        getPath("({ m() { super.foo } })")
+          .get("body.0.expression.properties.0.body.body.0.expression")
+          .isPure(),
+      ).toBeFalsy();
+      expect(
+        // This only tests "super", not "super.foo"
+        getPath("({ m() { super.foo } })")
+          .get("body.0.expression.properties.0.body.body.0.expression.object")
+          .isPure(),
+      ).toBeTruthy();
     });
 
     test("label", function () {
diff --git a/packages/babel-types/src/definitions/core.js b/packages/babel-types/src/definitions/core.js
index 51be45bfd7..57b45a17ba 100644
--- a/packages/babel-types/src/definitions/core.js
+++ b/packages/babel-types/src/definitions/core.js
@@ -980,7 +980,7 @@ defineType("SwitchStatement", {
 });
 
 defineType("ThisExpression", {
-  aliases: ["Expression"],
+  aliases: ["Expression", "Pureish"],
 });
 
 defineType("ThrowStatement", {
@@ -1785,7 +1785,7 @@ defineType("SpreadElement", {
 });
 
 defineType("Super", {
-  aliases: ["Expression"],
+  aliases: ["Expression", "Pureish"],
 });
 
 defineType("TaggedTemplateExpression", {
diff --git a/packages/babel-types/src/validators/generated/index.js b/packages/babel-types/src/validators/generated/index.js
index 2bf0ed62ea..2fb59235c3 100644
--- a/packages/babel-types/src/validators/generated/index.js
+++ b/packages/babel-types/src/validators/generated/index.js
@@ -3965,7 +3965,9 @@ export function isPureish(node: ?Object, opts?: Object): boolean {
     "NullLiteral" === nodeType ||
     "BooleanLiteral" === nodeType ||
     "RegExpLiteral" === nodeType ||
+    "ThisExpression" === nodeType ||
     "ArrowFunctionExpression" === nodeType ||
+    "Super" === nodeType ||
     "BigIntLiteral" === nodeType ||
     "DecimalLiteral" === nodeType ||
     (nodeType === "Placeholder" && "StringLiteral" === node.expectedNode)