Handle cycles when infering static variables

pkg/analyzer/test/src/task/dart_test.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.
 
 library test.src.task.dart_test;
 
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/constant.dart';
 import 'package:analyzer/src/generated/element.dart';
@@ skipping 2111 matching lines @@
     VariableElement topLevel =
         getTopLevelVariable(unit, 'topLevel').name.staticElement;
     VariableElement field =
         getFieldInClass(unit, 'C', 'field').name.staticElement;
 
     computeResult(field, INFERRED_STATIC_VARIABLE);
     InterfaceType stringType = context.typeProvider.stringType;
     expect(topLevel.type, stringType);
     expect(field.type, stringType);
   }
+
+  void test_perform_cycle() {
+    AnalysisTarget source = newSource(
+        '/test.dart',
+        '''
+var piFirst = true;
+var pi = piFirst ? 3.14 : tau / 2;
+var tau = piFirst ? pi * 2 : 6.28;
+''');
+    computeResult(new LibrarySpecificUnit(source, source), RESOLVED_UNIT5);
+    CompilationUnit unit = outputs[RESOLVED_UNIT5];
+    VariableElement piFirst =
+        getTopLevelVariable(unit, 'piFirst').name.staticElement;
+    VariableElement pi = getTopLevelVariable(unit, 'pi').name.staticElement;
+    VariableElement tau = getTopLevelVariable(unit, 'tau').name.staticElement;
+
+    computeResult(piFirst, INFERRED_STATIC_VARIABLE);
+    expect(piFirst.type, context.typeProvider.boolType);
+    expect(pi.type.isDynamic, isTrue);
+    expect(tau.type.isDynamic, isTrue);
+  }
+
+  void test_perform_null() {
+    AnalysisTarget source = newSource(
+        '/test.dart',
+        '''
+var a = null;
+''');
+    computeResult(new LibrarySpecificUnit(source, source), RESOLVED_UNIT5);
+    CompilationUnit unit = outputs[RESOLVED_UNIT5];
+    VariableElement a = getTopLevelVariable(unit, 'a').name.staticElement;
+
+    computeResult(a, INFERRED_STATIC_VARIABLE);
+    expect(a.type.isDynamic, isTrue);
+  }
 }
 
 @reflectiveTest
 class LibraryErrorsReadyTaskTest extends _AbstractDartTaskTest {
   test_perform() {
     Source library = newSource(
         '/lib.dart',
         r'''
 library lib;
 part 'part1.dart';
@@ skipping 906 matching lines @@
   /**
    * Fill [errorListener] with [result] errors in the current [task].
    */
   void _fillErrorListener(ResultDescriptor<List<AnalysisError>> result) {
     List<AnalysisError> errors = task.outputs[result];
     expect(errors, isNotNull, reason: result.name);
     errorListener = new GatheringErrorListener();
     errorListener.addAll(errors);
   }
 }