Deprecate the use of `Function` as a class.

pkg/analyzer/test/generated/hint_code_test.dart

Index: pkg/analyzer/test/generated/hint_code_test.dart
diff --git a/pkg/analyzer/test/generated/hint_code_test.dart b/pkg/analyzer/test/generated/hint_code_test.dart
index 52b0febf25bf92c570fbce05e5e66a5dc5004015..013ffe281867cbdeca13e8d22ea0a64e127811ab 100644
--- a/pkg/analyzer/test/generated/hint_code_test.dart
+++ b/pkg/analyzer/test/generated/hint_code_test.dart
@@ -944,6 +944,65 @@ class B extends A {
     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) {