fix #27258, don't allow dynamic set of a final field

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/classes.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// This library defines the operations that define and manipulate Dart
 /// classes.  Included in this are:
 ///   - Generics
 ///   - Class metadata
 ///   - Extension methods
 ///
@@ skipping 179 matching lines @@
 getGetterSig(value) => JS('', '#[#]', value, _getterSig);
 getSetterSig(value) => JS('', '#[#]', value, _setterSig);
 getStaticSig(value) => JS('', '#[#]', value, _staticSig);
 getStaticFieldSig(value) => JS('', '#[#]', value, _staticFieldSig);
 getStaticGetterSig(value) => JS('', '#[#]', value, _staticGetterSig);
 getStaticSetterSig(value) => JS('', '#[#]', value, _staticSetterSig);
 
 getGenericTypeCtor(value) => JS('', '#[#]', value, _genericTypeCtor);
 
 /// Get the type of a method from an object using the stored signature
-getType(obj) => JS(
-    '',
-    '''(() => {
-  return $obj == null ? $Object : $obj.__proto__.constructor;
-})()''');
+getType(obj) =>
+    JS('', '# == null ? # : #.__proto__.constructor', obj, Object, obj);
 
 bool isJsInterop(obj) {
   if (JS('bool', 'typeof # === "function"', obj)) {
     // A function is a Dart function if it has runtime type information.
     return _getRuntimeType(obj) == null;
   }
   // Primitive types are not JS interop types.
   if (JS('bool', 'typeof # !== "object"', obj)) return false;
 
   // Extension types are not considered JS interop types.
   // Note that it is still possible to call typed JS interop methods on
   // extension types but the calls must be statically typed.
   if (getExtensionType(obj) != null) return false;
   return JS('bool', '!($obj instanceof $Object)');
 }
 
 /// Get the type of a method from a type using the stored signature
-getMethodType(type, name) => JS(
-    '',
-    '''(() => {
-  let sigObj = $type[$_methodSig];
-  if (sigObj === void 0) return void 0;
-  return sigObj[$name];
-})()''');
+getMethodType(type, name) {
+  var m = JS('', '#[#]', type, _methodSig);
+  return m != null ? JS('', '#[#]', m, name) : null;
+}
 
-getFieldType(type, name) => JS(
-    '',
-    '''(() => {
-  let sigObj = $type[$_fieldSig];
-  if (sigObj === void 0) return void 0;
-  let fieldType = sigObj[$name];
-  // workaround to handle metadata.
-  return (fieldType instanceof Array) ? fieldType[0] : fieldType;
-})()''');
+/// Gets the type of the corresponding setter (this includes writable fields).
+getSetterType(type, name) {
+  var signature = JS('', '#[#]', type, _setterSig);
+  if (signature != null) {
+    var type = JS('', '#[#]', signature, name);
+    if (type != null) {
+      // TODO(jmesserly): it would be nice not to encode setters with a full
+      // function type.
+      return JS('', '#.args[0]', type);
+    }
+  }
+  signature = JS('', '#[#]', type, _fieldSig);
+  if (signature != null) {
+    var fieldInfo = JS('', '#[#]', signature, name);
+    if (fieldInfo != null && JS('bool', '!#.isFinal', fieldInfo)) {
+      return JS('', '#.type', fieldInfo);
+    }
+  }
+  return null;
+}
 
-getSetterType(type, name) => JS(
-    '',
-    '''(() => {
-  let sigObj = $type[$_setterSig];
-  if (sigObj === void 0) return void 0;
-  return sigObj[$name];
-})()''');
+finalFieldType(type, metadata) =>
+    JS('', '{ type: #, isFinal: true, metadata: # }', type, metadata);
+
+fieldType(type, metadata) =>
+    JS('', '{ type: #, isFinal: false, metadata: # }', type, metadata);
 
 /// Get the type of a constructor from a class using the stored signature
 /// If name is undefined, returns the type of the default constructor
 /// Returns undefined if the constructor is not found.
 classGetConstructorType(cls, name) => JS(
     '',
     '''(() => {
   if(!$name) $name = 'new';
   if ($cls === void 0) return void 0;
   if ($cls == null) return void 0;
@@ skipping 14 matching lines @@
     '',
     '''(() => {
   if ($f === void 0) $f = $obj[$name];
   // TODO(jmesserly): track the function's signature on the function, instead
   // of having to go back to the class?
   let sig = $getMethodType($getType($obj), $name);
 
   // JS interop case: do not bind this for compatibility with the dart2js
   // implementation where we cannot bind this reliably here until we trust
   // types more.
-  if (sig === void 0) return $f;
+  if (sig == null) return $f;
 
   $f = $f.bind($obj);
   $tag($f, sig);
   return $f;
 })()''');
 
 /// Instantiate a generic method.
 ///
 /// We need to apply the type arguments both to the function, as well as its
 /// associated function type.
 gbind(f, @rest typeArgs) {
   var result = JS('', '#.apply(null, #)', f, typeArgs);
   var sig = JS('', '#.instantiate(#)', _getRuntimeType(f), typeArgs);
   tag(result, sig);
   return result;
 }
 
 // Set up the method signature field on the constructor
-_setInstanceSignature(f, sigF, kind) => JS(
-    '',
-    '''(() => {
-  $defineMemoizedGetter($f, $kind, () => {
-    let sigObj = $sigF();
-    let proto = $f.__proto__;
-    // We need to set the root proto to null not undefined.
-    sigObj.__proto__ = ($kind in proto) ? proto[$kind] : null;
-    return sigObj;
-  });
-})()''');
+_setInstanceSignature(f, sigF, kind) => defineMemoizedGetter(
+    f,
+    kind,
+    JS(
+        '',
+        '''() => {
+          let sigObj = #();
+          let proto = #.__proto__;
+          // We need to set the root proto to null not undefined.
+          sigObj.__proto__ = (# in proto) ? proto[#] : null;
+          return sigObj;
+        }''',
+        sigF,
+        f,
+        kind,
+        kind));
 
 _setMethodSignature(f, sigF) => _setInstanceSignature(f, sigF, _methodSig);
 _setFieldSignature(f, sigF) => _setInstanceSignature(f, sigF, _fieldSig);
 _setGetterSignature(f, sigF) => _setInstanceSignature(f, sigF, _getterSig);
 _setSetterSignature(f, sigF) => _setInstanceSignature(f, sigF, _setterSig);
 
 // Set up the constructor signature field on the constructor
 _setConstructorSignature(f, sigF) =>
     JS('', '$defineMemoizedGetter($f, $_constructorSig, $sigF)');
 
@@ skipping 322 matching lines @@
     '''(() => {
   let values = [];
   for (var i = 0; i < $names.length; i++) {
     let value = $const_(new $enumClass(i));
     values.push(value);
     Object.defineProperty($enumClass, $names[i],
         { value: value, configurable: true });
   }
   $enumClass.values = $constList(values, $enumClass);
 })()''');