Downwards inference. This adds support to the resolver for downwards

pkg/analyzer/test/utils.dart

 // Copyright (c) 2013, 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.utils;
 
+import 'package:analyzer/src/generated/ast.dart';
+import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/java_io.dart';
+import 'package:analyzer/src/generated/resolver.dart' show TypeProvider;
 import 'package:path/path.dart' as path;
 import 'package:unittest/unittest.dart';
 
 void initializeTestEnvironment() {
   groupSep = ' | ';
   JavaFile.pathContext = path.posix;
 }
+
+/** The type of an assertion which asserts properties of [T]s.
+ */
+typedef void Asserter<T>(T type);
+
+/** The type of a function which given an [S], builds an assertion over [T]s.
+ */
+typedef Asserter<T> AsserterBuilder<S, T>(S arg);
+
+/** The type of a function which given an [S0] and an S1, builds an assertion over [T]s.

[Jennifer Messerly, 2015/11/23 22:11:58]

long line (& a few below)

unfortunately dartfmt won't fix comments :(

[Leaf, 2015/12/01 21:49:12]

Done.

+ */
+typedef Asserter<T> AsserterBuilder2<S0, S1, T>(S0 arg0, S1 arg1);
+
+/** The type of a function which given an [R] returns an [AsserterBuilder] over
+ * [S]s and [T]s.  That is, it returns a function which given an [S], returns
+ * a function over [T]s.
+ */
+typedef AsserterBuilder<S, T> AsserterBuilderBuilder<R, S, T>(R arg);
+
+class AstFinder {

[scheglov, 2015/11/21 06:31:35]

Could you please move the methods of AstFinder into a separate library and make
them functions?
It seems that they have pretty unique names and may be easy to imported without
(or with) a prefix.

[Brian Wilkerson, 2015/11/21 16:12:22]

I'm not a fan of top-level functions; I'd actually prefer leaving it the way you
have it. So I guess it's your call.

[Leaf, 2015/11/24 19:32:12]

Hmm, I was really annoyed that moving these from local instance methods to
static methods in a separate class made all the lines really long, so I kind of
like Konstantin's suggestion.  Brian, how would you feel about them being in a
library that gets imported with a shorter prefix (e.g. finder.getClass, etc)?

[Brian Wilkerson, 2015/11/24 21:17:57]

It isn't my favorite solution, but I'm not going to object too loudly :-)

It seems like doing so is essentially the same as making them static methods on
an invisible class, except that every importer gets to choose the name of the
containing class. It works OK if implementors choose a consistent and meaningful
name, but if I see

  utils.getClass(...)

in one file and

  finder.getClass(...)

in another, it isn't obvious to me that it's the same function. But I'd be
surprised to find code like

  import '.../utils.dart' as AstFinder;

Of course, none of this would be a problem if we had a sensible (100 character)
line limit :-)

[Leaf, 2015/12/01 21:49:12]

Ok, leaving as is for now.

+  /**
+   * Return the declaration of the class with the given [className] in the given
+   * compilation [unit].
+   */
+  static ClassDeclaration getClass(CompilationUnit unit, String className) {
+    NodeList<CompilationUnitMember> unitMembers = unit.declarations;
+    for (CompilationUnitMember unitMember in unitMembers) {
+      if (unitMember is ClassDeclaration && unitMember.name.name == className) {
+        return unitMember;
+      }
+    }
+    fail('No class named $className in ${unit.element.source}');
+    return null;
+  }
+
+  /**
+   * Return the declaration of the constructor with the given [constructorName] in
+   * the class with the given [className] in the given compilation [unit].  If
+   * constructorName is null, return the default constructor;
+   */
+  static ConstructorDeclaration getConstructorInClass(
+      CompilationUnit unit, String className, String constructorName) {
+    ClassDeclaration unitMember = getClass(unit, className);
+    NodeList<ClassMember> classMembers = unitMember.members;
+    for (ClassMember classMember in classMembers) {
+      if (classMember is ConstructorDeclaration) {
+        if (classMember.name?.name == constructorName) {
+          return classMember;
+        }
+      }
+    }
+    fail('No constructor named $constructorName in $className');
+    return null;
+  }
+
+  /**
+   * Return the declaration of the field with the given [fieldName] in the class
+   * with the given [className] in the given compilation [unit].
+   */
+  static VariableDeclaration getFieldInClass(
+      CompilationUnit unit, String className, String fieldName) {
+    ClassDeclaration unitMember = getClass(unit, className);
+    NodeList<ClassMember> classMembers = unitMember.members;
+    for (ClassMember classMember in classMembers) {
+      if (classMember is FieldDeclaration) {
+        NodeList<VariableDeclaration> fields = classMember.fields.variables;
+        for (VariableDeclaration field in fields) {
+          if (field.name.name == fieldName) {
+            return field;
+          }
+        }
+      }
+    }
+    fail('No field named $fieldName in $className');
+    return null;
+  }
+
+  /**
+   * Return the declaration of the method with the given [methodName] in the
+   * class with the given [className] in the given compilation [unit].
+   */
+  static MethodDeclaration getMethodInClass(
+      CompilationUnit unit, String className, String methodName) {
+    ClassDeclaration unitMember = getClass(unit, className);
+    NodeList<ClassMember> classMembers = unitMember.members;
+    for (ClassMember classMember in classMembers) {
+      if (classMember is MethodDeclaration) {
+        if (classMember.name.name == methodName) {
+          return classMember;
+        }
+      }
+    }
+    fail('No method named $methodName in $className');
+    return null;
+  }
+
+  /**
+   * Return the statements in the body of a the method with the given
+   * [methodName] in the class with the given [className] in the given
+   * compilation [unit].
+   */
+  static List<Statement> getStatementsInMethod(
+      CompilationUnit unit, String className, String methodName) {
+    MethodDeclaration method = getMethodInClass(unit, className, methodName);
+    BlockFunctionBody body = method.body;
+    return body.block.statements;
+  }
+
+  /**
+   * Return the statements in the body of the top-level function with the given
+   * [functionName] in the given compilation [unit].
+   */
+  static List<Statement> getStatementsInTopLevelFunction(
+      CompilationUnit unit, String functionName) {
+    FunctionDeclaration function = getTopLevelFunction(unit, functionName);
+    BlockFunctionBody body = function.functionExpression.body;
+    return body.block.statements;
+  }
+
+  /**
+   * Return the declaration of the top-level function with the given
+   * [functionName] in the given compilation [unit].
+   */
+  static FunctionDeclaration getTopLevelFunction(
+      CompilationUnit unit, String functionName) {
+    NodeList<CompilationUnitMember> unitMembers = unit.declarations;
+    for (CompilationUnitMember unitMember in unitMembers) {
+      if (unitMember is FunctionDeclaration) {
+        if (unitMember.name.name == functionName) {
+          return unitMember;
+        }
+      }
+    }
+    fail('No toplevel function named $functionName found');
+    return null;
+  }
+
+  /**
+   * Return the declaration of the top-level variable with the given
+   * [variableName] in the given compilation [unit].
+   */
+  static VariableDeclaration getTopLevelVariable(
+      CompilationUnit unit, String variableName) {
+    NodeList<CompilationUnitMember> unitMembers = unit.declarations;
+    for (CompilationUnitMember unitMember in unitMembers) {
+      if (unitMember is TopLevelVariableDeclaration) {
+        NodeList<VariableDeclaration> variables =
+            unitMember.variables.variables;
+        for (VariableDeclaration variable in variables) {
+          if (variable.name.name == variableName) {
+            return variable;
+          }
+        }
+      }
+    }
+    fail('No toplevel variable named $variableName found');
+    return null;
+  }
+}
+
+/** Class for compositionally building up assertions on types
+ */
+class TypeAssertions {

[Jennifer Messerly, 2015/11/23 22:11:58]

note: it'd be slightly nicer to make these be Matchers, which have better
self-documenting error messages
https://www.dartdocs.org/documentation/matcher/0.12.0%2B1/matcher/Matcher-cla...

[Leaf, 2015/12/01 21:49:12]

Added TODO.  Nice to know 

+  /* Provides primitive types for basic type assertions */
+  final TypeProvider _typeProvider;
+
+  TypeAssertions(this._typeProvider);
+
+  /** Primitive assertion for the dynamic type */
+  Asserter<DartType> get isDynamic => isType(_typeProvider.dynamicType);
+
+  /** Primitive assertion for the int type */
+  Asserter<DartType> get isInt => isType(_typeProvider.intType);
+
+  /** Primitive assertion for the list type
+ */
+  Asserter<DartType> get isList => sameElement(_typeProvider.listType);
+
+  /** Primitive assertion for the map type
+ */
+  Asserter<DartType> get isMap => sameElement(_typeProvider.mapType);
+
+  /** Primitive assertion for the num type */
+  Asserter<DartType> get isNum => isType(_typeProvider.numType);
+
+  /** Primitive assertion for the string type */
+  Asserter<DartType> get isString => isType(_typeProvider.stringType);
+
+  /** Given a type, produce an assertion that a type has the same element.
+   */
+  Asserter<DartType> hasElement(Element element) =>
+      (DartType type) => expect(element, same(type.element));
+
+/** Given assertions for the argument and return types, produce an

[Brian Wilkerson, 2015/11/21 16:12:22]

Format the file?

[Leaf, 2015/12/01 21:49:12]

Filed https://github.com/dart-lang/dart_style/issues/472 .  :)

+   *  assertion over unary function types.
+   */
+  Asserter<DartType> isFunction2Of(
+          Asserter<DartType> argType, Asserter<DartType> returnType) =>
+      (DartType type) {
+        FunctionType fType = (type as FunctionType);
+        argType(fType.normalParameterTypes[0]);
+        returnType(fType.returnType);
+      };
+
+  /** Given an assertion for the base type and assertions over the type
+   * parameters, produce an assertion over instantations.
+   */
+  AsserterBuilder<List<Asserter<DartType>>, DartType> isInstantiationOf(
+          Asserter<DartType> baseAssert) =>
+      (List<Asserter<DartType>> argAsserts) => (DartType type) {
+            InterfaceType t = (type as InterfaceType);
+            baseAssert(t);
+            List<DartType> typeArguments = t.typeArguments;
+            expect(typeArguments, hasLength(argAsserts.length));
+            for (int i = 0; i < typeArguments.length; i++) {
+              argAsserts[i](typeArguments[i]);
+            }
+          };
+
+  /** Assert that a type is the List type, and that the given assertion holds
+   * over the type parameter.
+   */
+  Asserter<InterfaceType> isListOf(Asserter<DartType> argAssert) =>
+      isInstantiationOf(isList)([argAssert]);
+
+  /** Assert that a type is the Map type, and that the given assertions hold
+   * over the type parameters.
+   */
+  Asserter<InterfaceType> isMapOf(
+          Asserter<DartType> argAssert0, Asserter<DartType> argAssert1) =>
+      isInstantiationOf(isMap)([argAssert0, argAssert1]);
+
+  /** Assert that one type is the same as another
+   */
+  Asserter<DartType> isType(DartType argument) => (DartType t) {
+        expect(t, same(argument));
+      };
+
+  /** Given a type, produce an assertion that a type has the same element.
+   */
+  Asserter<DartType> sameElement(DartType elementType) =>
+      hasElement(elementType.element);
+}