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-classes/test/fixtures/assumption-setClassMethods/literal-key/input.js

@@ -0,0 +1,5 @@
+class Foo {
+  "bar"() {
+
+  }
+}

packages/babel-plugin-transform-classes/test/fixtures/assumption-setClassMethods/literal-key/output.js

@@ -0,0 +1,13 @@
+var Foo = /*#__PURE__*/function () {
+  "use strict";
+
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+  }
+
+  var _proto = Foo.prototype;
+
+  _proto["bar"] = function bar() {};
+
+  return Foo;
+}();

packages/babel-plugin-transform-classes/test/fixtures/assumption-setClassMethods/method-return-type-annotation/input.js

@@ -0,0 +1,6 @@
+// @flow
+class C {
+  m(x: number): string {
+    return 'a';
+  }
+}

packages/babel-plugin-transform-classes/test/fixtures/assumption-setClassMethods/method-return-type-annotation/options.json

@@ -0,0 +1,10 @@
+{
+  "plugins": [
+    "external-helpers",
+    "transform-function-name",
+    ["transform-classes", { "loose": true }],
+    "transform-spread",
+    "transform-block-scoping",
+    "syntax-flow"
+  ]
+}

packages/babel-plugin-transform-classes/test/fixtures/assumption-setClassMethods/method-return-type-annotation/output.js

@@ -0,0 +1,14 @@
+// @flow
+var C = /*#__PURE__*/function () {
+  "use strict";
+
+  function C() {}
+
+  var _proto = C.prototype;
+
+  _proto.m = function m(x: number): string {
+    return 'a';
+  };
+
+  return C;
+}();

packages/babel-plugin-transform-classes/test/fixtures/assumption-setClassMethods/method-reuse-prototype/input.js

@@ -0,0 +1,5 @@
+class Test {
+  a() {}
+  static b() {}
+  c() {}
+}

packages/babel-plugin-transform-classes/test/fixtures/assumption-setClassMethods/method-reuse-prototype/output.js

@@ -0,0 +1,17 @@
+var Test = /*#__PURE__*/function () {
+  "use strict";
+
+  function Test() {
+    babelHelpers.classCallCheck(this, Test);
+  }
+
+  var _proto = Test.prototype;
+
+  _proto.a = function a() {};
+
+  Test.b = function b() {};
+
+  _proto.c = function c() {};
+
+  return Test;
+}();

packages/babel-plugin-transform-classes/test/fixtures/assumption-setClassMethods/options.json

@@ -0,0 +1,12 @@
+{
+  "plugins": [
+    ["external-helpers", { "helperVersion": "7.100.0" }],
+    "transform-function-name",
+    "transform-classes",
+    ["transform-spread", { "loose": true }],
+    "transform-block-scoping"
+  ],
+  "assumptions": {
+    "setClassMethods": true
+  }
+}

packages/babel-plugin-transform-classes/test/fixtures/assumption-setClassMethods/program-with-use-strict-directive/input.js

@@ -0,0 +1,7 @@
+"use strict";
+
+class Foo {
+    method() {
+        
+    }
+}

packages/babel-plugin-transform-classes/test/fixtures/assumption-setClassMethods/program-with-use-strict-directive/output.js

@@ -0,0 +1,13 @@
+"use strict";
+
+var Foo = /*#__PURE__*/function () {
+  function Foo() {
+    babelHelpers.classCallCheck(this, Foo);
+  }
+
+  var _proto = Foo.prototype;
+
+  _proto.method = function method() {};
+
+  return Foo;
+}();