Deprecate the use of `Function` as a class.

pkg/analyzer/test/generated/hint_code_test.dart

 // Copyright (c) 2016, 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.
 
 library analyzer.test.generated.hint_code_test;
 
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/src/error/codes.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/parser.dart';
@@ skipping 926 matching lines @@
   A.named() {}
 }
 class B extends A {
   B() : super.named() {}
 }''');
     await computeAnalysisResult(source);
     assertErrors(source, [HintCode.DEPRECATED_MEMBER_USE]);
     verify([source]);
   }
 
+  test_deprecatedFunction_class() async {
+    Source source = addSource(r'''
+class Function {}
+''');
+    await computeAnalysisResult(source);
+    assertErrors(source, [HintCode.DEPRECATED_FUNCTION_CLASS_DECLARATION]);
+    verify([source]);
+  }
+
+  test_deprecatedFunction_extends() async {
+    Source source = addSource(r'''
+class A extends Function {}
+''');
+    await computeAnalysisResult(source);
+    assertErrors(source, [
+      HintCode.DEPRECATED_EXTENDS_FUNCTION,
+      StaticWarningCode.FUNCTION_WITHOUT_CALL
+    ]);
+    verify([source]);
+  }
+
+  test_deprecatedFunction_extends2() async {
+    Source source = addSource(r'''
+class Function {}
+class A extends Function {}
+''');
+    await computeAnalysisResult(source);
+    assertErrors(source, [
+      HintCode.DEPRECATED_FUNCTION_CLASS_DECLARATION,
+      HintCode.DEPRECATED_EXTENDS_FUNCTION
+    ]);
+    verify([source]);
+  }
+
+  test_deprecatedFunction_mixin() async {
+    Source source = addSource(r'''
+class A extends Object with Function {}
+''');
+    await computeAnalysisResult(source);
+    assertErrors(source, [
+      HintCode.DEPRECATED_MIXIN_FUNCTION,
+      StaticWarningCode.FUNCTION_WITHOUT_CALL
+    ]);
+    verify([source]);
+  }
+
+  test_deprecatedFunction_mixin2() async {
+    Source source = addSource(r'''
+class Function {}
+class A extends Object with Function {}
+''');
+    await computeAnalysisResult(source);
+    assertErrors(source, [
+      HintCode.DEPRECATED_FUNCTION_CLASS_DECLARATION,
+      HintCode.DEPRECATED_MIXIN_FUNCTION
+    ]);
+    verify([source]);
+  }
+
   test_divisionOptimization_double() async {
     Source source = addSource(r'''
 f(double x, double y) {
   var v = (x / y).toInt();
 }''');
     await computeAnalysisResult(source);
     assertErrors(source, [HintCode.DIVISION_OPTIMIZATION]);
     verify([source]);
   }
 
@@ skipping 3076 matching lines @@
   n() {
     var a = m(), b = m();
   }
 }''');
     await computeAnalysisResult(source);
     assertErrors(
         source, [HintCode.USE_OF_VOID_RESULT, HintCode.USE_OF_VOID_RESULT]);
     verify([source]);
   }
 }