Implement assumptions defined in the babel/rfcs#5 RFC

- `mutableTemplateObject` and `ignoreToPrimitiveHint` (#12408)
- `setClassMethods` (#12407)
- `setComputedProperties` (#12490)
- `ignoreFunctionLength` (#12491)
- `noDocumentAll` (#12481)
- `iterableIsArray` and `arrayLikeIsIterable` (#12489)
- `pureGetters` (#12504)
- `skipForOfIteratorClosing` (#12496)
- `objectRestNoSymbols`, `setSpreadProperties` and `pureGetters` (#12505)
- `noNewArrows` (#12613, #12793)
- `setPublicClassFields` and `privateFieldsAsProperties` (#12497)
- `constantReexports` and `enumerableModuleMeta` (#12618)
- `constantSuper`, `superIsCallableConstructor` and `noClassCalls` (#12726)

Co-authored-by: Justin Ridgewell <justin@ridgewell.name>
Co-authored-by: Huáng Jùnliàng <JLHwung@users.noreply.github.com>

packages/babel-plugin-transform-arrow-functions/test/fixtures/arrow-functions/spec-self-referential/options.json

@@ -1,7 +0,0 @@
-{
-  "plugins": [
-    "external-helpers",
-    ["transform-arrow-functions", { "spec": true }],
-    "transform-function-name"
-  ]
-}

packages/babel-plugin-transform-arrow-functions/test/fixtures/assumption-newableArrowFunctions-false/basic/input.js

@@ -0,0 +1,10 @@
+function foo() {
+  arr.map(x => x * x);
+  var f = (x, y) => x * y;
+  (function () {
+    return () => this;
+  })();
+  return {
+    g: () => this
+  }
+}

packages/babel-plugin-transform-arrow-functions/test/fixtures/assumption-newableArrowFunctions-false/basic/output.js

@@ -0,0 +1,29 @@
+function foo() {
+  var _this = this;
+
+  arr.map(function (x) {
+    babelHelpers.newArrowCheck(this, _this);
+    return x * x;
+  }.bind(this));
+
+  var f = function f(x, y) {
+    babelHelpers.newArrowCheck(this, _this);
+    return x * y;
+  }.bind(this);
+
+  (function () {
+    var _this2 = this;
+
+    return function () {
+      babelHelpers.newArrowCheck(this, _this2);
+      return this;
+    }.bind(this);
+  })();
+
+  return {
+    g: function g() {
+      babelHelpers.newArrowCheck(this, _this);
+      return this;
+    }.bind(this)
+  };
+}

packages/babel-plugin-transform-arrow-functions/test/fixtures/assumption-newableArrowFunctions-false/options.json

@@ -0,0 +1,6 @@
+{
+  "plugins": ["external-helpers", "transform-arrow-functions"],
+  "assumptions": {
+    "noNewArrows": false
+  }
+}

packages/babel-plugin-transform-arrow-functions/test/fixtures/spec/newableArrowFunction-default/input.js

@@ -0,0 +1 @@
+let a = () => 1;

packages/babel-plugin-transform-arrow-functions/test/fixtures/spec/newableArrowFunction-default/output.js

@@ -0,0 +1,6 @@
+var _this = this;
+
+let a = function a() {
+  babelHelpers.newArrowCheck(this, _this);
+  return 1;
+}.bind(this);

packages/babel-plugin-transform-arrow-functions/test/fixtures/spec/newableArrowFunction-vs-spec-false/input.js

@@ -0,0 +1 @@
+let a = () => 1;

packages/babel-plugin-transform-arrow-functions/test/fixtures/spec/newableArrowFunction-vs-spec-false/options.json

@@ -0,0 +1,9 @@
+{
+  "plugins": [
+    "external-helpers",
+    ["transform-arrow-functions", { "spec": false }]
+  ],
+  "assumptions": {
+    "noNewArrows": false
+  }
+}

packages/babel-plugin-transform-arrow-functions/test/fixtures/spec/newableArrowFunction-vs-spec-false/output.js

@@ -0,0 +1,6 @@
+var _this = this;
+
+let a = function a() {
+  babelHelpers.newArrowCheck(this, _this);
+  return 1;
+}.bind(this);

packages/babel-plugin-transform-arrow-functions/test/fixtures/spec/newableArrowFunction-vs-spec-true/input.js

@@ -0,0 +1 @@
+let a = () => 1;

packages/babel-plugin-transform-arrow-functions/test/fixtures/spec/newableArrowFunction-vs-spec-true/options.json

@@ -0,0 +1,9 @@
+{
+  "plugins": [
+    "external-helpers",
+    ["transform-arrow-functions", { "spec": true }]
+  ],
+  "assumptions": {
+    "noNewArrows": true
+  }
+}

packages/babel-plugin-transform-arrow-functions/test/fixtures/spec/newableArrowFunction-vs-spec-true/output.js

@@ -0,0 +1,3 @@
+let a = function () {
+  return 1;
+};