Add testing for constructor tearoffs constant rendering. (#2780)

* constructor tearoffs testing

* another construct that analyzer doesn't like

Author: jcollins-g

test/end2end/model_special_cases_test.dart

@@ -228,6 +228,49 @@ void main() {
         expect(referenceLookup(A, 'new'), equals(MatchingLinkResult(null)));
         expect(referenceLookup(At, 'new'), equals(MatchingLinkResult(null)));
       });
+
+      test('constant rendering', () {
+        TopLevelVariable aFunc,
+            aFuncParams,
+            aTearOffDefaultConstructor,
+            aTearOffNonDefaultConstructor,
+            aTearOffNonDefaultConstructorInt,
+            aTearOffDefaultConstructorArgs;
+        TopLevelVariable aTearOffDefaultConstructorTypedef;
+        aFunc =
+            constructorTearoffs.constants.firstWhere((c) => c.name == 'aFunc');
+        aFuncParams = constructorTearoffs.constants
+            .firstWhere((c) => c.name == 'aFuncParams');
+        aTearOffDefaultConstructor = constructorTearoffs.constants
+            .firstWhere((c) => c.name == 'aTearOffDefaultConstructor');
+        aTearOffNonDefaultConstructor = constructorTearoffs.constants
+            .firstWhere((c) => c.name == 'aTearOffNonDefaultConstructor');
+        aTearOffNonDefaultConstructorInt = constructorTearoffs.constants
+            .firstWhere((c) => c.name == 'aTearOffNonDefaultConstructorInt');
+        aTearOffDefaultConstructorArgs = constructorTearoffs.constants
+            .firstWhere((c) => c.name == 'aTearOffDefaultConstructorArgs');
+        aTearOffDefaultConstructorTypedef = constructorTearoffs.constants
+            .firstWhere((c) => c.name == 'aTearOffDefaultConstructorTypedef');
+
+        expect(aFunc.constantValue, equals('func'));
+        expect(aFuncParams.constantValue, equals('funcTypeParams'));
+        // Does not work @ analyzer 2.2
+        //expect(aFuncWithArgs.constantValue, equals('funcTypeParams<String, int>'));
+
+        expect(aTearOffDefaultConstructor.constantValue, equals('F.new'));
+        expect(aTearOffNonDefaultConstructor.constantValue,
+            equals('F.alternative'));
+        expect(aTearOffNonDefaultConstructorInt.constantValue,
+            equals('F<int>.alternative'));
+        expect(aTearOffDefaultConstructorArgs.constantValue,
+            equals('F<String>.new'));
+
+        expect(aTearOffDefaultConstructorTypedef.constantValue,
+            equals('Fstring.new'));
+        // Does not work @ analyzer 2.2
+        //expect(aTearOffDefaultConstructorArgsTypedef.constantValue,
+        //    equals('Ft<String>.new'));
+      });
     }, skip: !_constructorTearoffsAllowed.allows(utils.platformVersion));
   });
 

testing/test_package_experiments/lib/constructor_tearoffs.dart

@@ -46,6 +46,8 @@ class F<T> {
   F() {
     print('I too am a valid constructor invocation with this feature.');
   }
+
+  F.alternative() {}
 }
 
 typedef Ft = F;
@@ -59,3 +61,21 @@ typedef NotAClass = Function;
 /// Mixins don't have constructors either, so disallow `M.new`.
 mixin M<T> on C {
 }
+
+void func() {}
+void funcTypeParams<T extends String, U extends num>(T something, U different) {}
+
+const aFunc = func;
+const aFuncParams = funcTypeParams;
+// TODO(jcollins-g): does not work @ analyzer 2.2
+//const aFuncWithArgs = funcTypeParams<String, int>;
+
+const aTearOffDefaultConstructor = F.new;
+const aTearOffNonDefaultConstructor = F.alternative;
+const aTearOffNonDefaultConstructorInt = F<int>.alternative;
+const aTearOffDefaultConstructorArgs = F<String>.new;
+
+const aTearOffDefaultConstructorTypedef = Fstring.new;
+
+// TODO(jcollins-g): does not work @ analyzer 2.2
+//const aTearOffDefaultConstructorArgsTypedef = Ft<String>.new;