Abstract over the type system.

pkg/analyzer/lib/src/generated/resolver.dart

Index: pkg/analyzer/lib/src/generated/resolver.dart
diff --git a/pkg/analyzer/lib/src/generated/resolver.dart b/pkg/analyzer/lib/src/generated/resolver.dart
index eb7bacf41f3cb4b8f571cb3feed09e9273cd051c..5c1f5774252482accc8cbedc2eadddd7e5d8740d 100644
--- a/pkg/analyzer/lib/src/generated/resolver.dart
+++ b/pkg/analyzer/lib/src/generated/resolver.dart
@@ -73,11 +73,16 @@ class BestPracticesVerifier extends RecursiveAstVisitor<Object> {
   final InterfaceType _futureNullType;
 
   /**
+   * The type system primitives
+   */
+  TypeSystem _typeSystem;
+
+  /**
    * Create a new instance of the [BestPracticesVerifier].
    *
    * @param errorReporter the error reporter
    */
-  BestPracticesVerifier(this._errorReporter, TypeProvider typeProvider)
+  BestPracticesVerifier(this._errorReporter, TypeProvider typeProvider, this._typeSystem)
       : _futureNullType = typeProvider.futureNullType;
 
   @override
@@ -304,7 +309,7 @@ class BestPracticesVerifier extends RecursiveAstVisitor<Object> {
     // Warning case: test static type information
     //
     if (actualStaticType != null && expectedStaticType != null) {
-      if (!actualStaticType.isAssignableTo(expectedStaticType)) {
+      if (!_typeSystem.isAssignableTo(actualStaticType, expectedStaticType)) {
         // A warning was created in the ErrorVerifier, return false, don't
         // create a hint when a warning has already been created.
         return false;
@@ -320,7 +325,7 @@ class BestPracticesVerifier extends RecursiveAstVisitor<Object> {
     DartType actualBestType =
         actualPropagatedType != null ? actualPropagatedType : actualStaticType;
     if (actualBestType != null && expectedBestType != null) {
-      if (!actualBestType.isAssignableTo(expectedBestType)) {
+      if (!_typeSystem.isAssignableTo(actualBestType, expectedBestType)) {
         _errorReporter.reportTypeErrorForNode(
             hintCode, expression, [actualBestType, expectedBestType]);
         return true;
@@ -519,14 +524,14 @@ class BestPracticesVerifier extends RecursiveAstVisitor<Object> {
         ? ErrorVerifier.getStaticType(lhs)
         : leftVariableElement.type;
     DartType staticRightType = ErrorVerifier.getStaticType(rhs);
-    if (!staticRightType.isAssignableTo(leftType)) {
+    if (!_typeSystem.isAssignableTo(staticRightType, leftType)) {
       // The warning was generated on this rhs
       return false;
     }
     // Test for, and then generate the hint
     DartType bestRightType = rhs.bestType;
     if (leftType != null && bestRightType != null) {
-      if (!bestRightType.isAssignableTo(leftType)) {
+      if (!_typeSystem.isAssignableTo(bestRightType, leftType)) {
         _errorReporter.reportTypeErrorForNode(
             HintCode.INVALID_ASSIGNMENT, rhs, [bestRightType, leftType]);
         return true;
@@ -593,7 +598,7 @@ class BestPracticesVerifier extends RecursiveAstVisitor<Object> {
     }
     // For async, give no hint if Future<Null> is assignable to the return
     // type.
-    if (body.isAsynchronous && _futureNullType.isAssignableTo(returnTypeType)) {
+    if (body.isAsynchronous && _typeSystem.isAssignableTo(_futureNullType, returnTypeType)) {
       return false;
     }
     // Check the block for a return statement, if not, create the hint
@@ -839,6 +844,11 @@ class ConstantVerifier extends RecursiveAstVisitor<Object> {
   final TypeProvider _typeProvider;
 
   /**
+   * The type system in use.
+   */
+  final TypeSystem _typeSystem;
+
+  /**
    * The set of variables declared using '-D' on the command line.
    */
   final DeclaredVariables declaredVariables;
@@ -874,7 +884,7 @@ class ConstantVerifier extends RecursiveAstVisitor<Object> {
    * @param errorReporter the error reporter by which errors will be reported
    */
   ConstantVerifier(this._errorReporter, this._currentLibrary,
-      this._typeProvider, this.declaredVariables) {
+                   this._typeProvider, this._typeSystem, this.declaredVariables) {
     this._boolType = _typeProvider.boolType;
     this._intType = _typeProvider.intType;
     this._numType = _typeProvider.numType;
@@ -1349,7 +1359,7 @@ class ConstantVerifier extends RecursiveAstVisitor<Object> {
     ErrorReporter subErrorReporter =
         new ErrorReporter(errorListener, _errorReporter.source);
     DartObjectImpl result = expression.accept(
-        new _ConstantVerifier_validateInitializerExpression(_typeProvider,
+        new _ConstantVerifier_validateInitializerExpression(_typeProvider, _typeSystem,
             subErrorReporter, this, parameterElements, declaredVariables));
     _reportErrors(errorListener.errors,
         CompileTimeErrorCode.NON_CONSTANT_VALUE_IN_INITIALIZER);
@@ -1475,11 +1485,16 @@ class DeadCodeVerifier extends RecursiveAstVisitor<Object> {
   final ErrorReporter _errorReporter;
 
   /**
+   *  The type system for this visitor
+   */
+  final TypeSystem _typeSystem;
+
+  /**
    * Create a new instance of the [DeadCodeVerifier].
    *
    * @param errorReporter the error reporter
    */
-  DeadCodeVerifier(this._errorReporter);
+  DeadCodeVerifier(this._errorReporter, this._typeSystem);
 
   @override
   Object visitBinaryExpression(BinaryExpression node) {
@@ -1644,7 +1659,7 @@ class DeadCodeVerifier extends RecursiveAstVisitor<Object> {
             }
           }
           for (DartType type in visitedTypes) {
-            if (currentType.isSubtypeOf(type)) {
+            if (_typeSystem.isSubtypeOf(currentType, type)) {
               CatchClause lastCatchClause = catchClauses[numOfCatchClauses - 1];
               int offset = catchClause.offset;
               int length = lastCatchClause.end - offset;
@@ -4775,7 +4790,7 @@ class HintGenerator {
     ErrorReporter errorReporter = new ErrorReporter(_errorListener, source);
     unit.accept(_usedImportedElementsVisitor);
     // dead code analysis
-    unit.accept(new DeadCodeVerifier(errorReporter));
+    unit.accept(new DeadCodeVerifier(errorReporter, _context.typeSystem));
     unit.accept(_usedLocalElementsVisitor);
     // dart2js analysis
     if (_enableDart2JSHints) {
@@ -4783,7 +4798,7 @@ class HintGenerator {
     }
     // Dart best practices
     unit.accept(
-        new BestPracticesVerifier(errorReporter, _context.typeProvider));
+        new BestPracticesVerifier(errorReporter, _context.typeProvider, _context.typeSystem));
     unit.accept(new OverrideVerifier(errorReporter, _manager));
     // Find to-do comments
     new ToDoFinder(errorReporter).findIn(unit);
@@ -6244,11 +6259,12 @@ class InheritanceManager {
               continue;
             }
             bool subtypeOfAllTypes = true;
+            TypeSystem typeSystem = _library.context.typeSystem;
             for (int j = 0;
                 j < numOfEltsWithMatchingNames && subtypeOfAllTypes;
                 j++) {
               if (i != j) {
-                if (!subtype.isSubtypeOf(executableElementTypes[j])) {
+                if (!typeSystem.isSubtypeOf(subtype, executableElementTypes[j])) {
                   subtypeOfAllTypes = false;
                   break;
                 }
@@ -7546,6 +7562,11 @@ class LibraryResolver {
   TypeProvider _typeProvider;
 
   /**
+   * The type system in use for the library
+   */
+  TypeSystem _typeSystem;
+
+  /**
    * A table mapping library sources to the information being maintained for those libraries.
    */
   HashMap<Source, Library> _libraryMap = new HashMap<Source, Library>();
@@ -7588,6 +7609,11 @@ class LibraryResolver {
   TypeProvider get typeProvider => _typeProvider;
 
   /**
+   * The type system in use.
+   */
+  TypeSystem get typeSystem => _typeSystem;
+
+  /**
    * Create an object to represent the information about the library defined by the compilation unit
    * with the given source.
    *
@@ -7672,6 +7698,7 @@ class LibraryResolver {
     }
     _buildDirectiveModels();
     _typeProvider = new TypeProviderImpl(coreElement, asyncElement);
+    _typeSystem = new TypeSystemImpl(typeProvider);
     _buildTypeHierarchies();
     //
     // Perform resolution and type analysis.
@@ -7750,6 +7777,7 @@ class LibraryResolver {
     }
     _buildDirectiveModels();
     _typeProvider = new TypeProviderImpl(coreElement, asyncElement);
+    _typeSystem = new TypeSystemImpl(typeProvider);
     _buildEnumMembers();
     _buildTypeHierarchies();
     //
@@ -8290,6 +8318,7 @@ class LibraryResolver {
                 errorReporter,
                 library.libraryElement,
                 _typeProvider,
+                _typeSystem,
                 analysisContext.declaredVariables);
             unit.accept(constantVerifier);
           } on AnalysisException catch (exception, stackTrace) {
@@ -8780,6 +8809,7 @@ class LibraryResolver2 {
               errorReporter,
               library.libraryElement,
               _typeProvider,
+              analysisContext.typeSystem,
               analysisContext.declaredVariables);
           ast.accept(constantVerifier);
         }
@@ -14730,6 +14760,12 @@ abstract class TypeSystem {
   DartType getLeastUpperBound(DartType type1, DartType type2);
 
   /**
+   * Return `true` if the [leftType] is assignable to the [rightType] (that is,
+   * if leftType <==> rightType).
+   */
+  bool isAssignableTo(DartType leftType, DartType rightType);
+
+  /**
    * Return `true` if the [leftType] is a subtype of the [rightType] (that is,
    * if leftType <: rightType).
    */
@@ -14825,6 +14861,11 @@ class TypeSystemImpl implements TypeSystem {
   }
 
   @override
+  bool isAssignableTo(DartType leftType, DartType rightType) {
+    return leftType.isAssignableTo(rightType);
+  }
+
+  @override
   bool isSubtypeOf(DartType leftType, DartType rightType) {
     return leftType.isSubtypeOf(rightType);
   }
@@ -15232,8 +15273,11 @@ class _ConstantVerifier_validateInitializerExpression extends ConstantVisitor {
 
   List<ParameterElement> parameterElements;
 
+  TypeSystem _typeSystem;
+
   _ConstantVerifier_validateInitializerExpression(
       TypeProvider typeProvider,
+      this._typeSystem,
       ErrorReporter errorReporter,
       this.verifier,
       this.parameterElements,
@@ -15251,19 +15295,19 @@ class _ConstantVerifier_validateInitializerExpression extends ConstantVisitor {
           if (type.isDynamic) {
             return new DartObjectImpl(
                 verifier._typeProvider.objectType, DynamicState.DYNAMIC_STATE);
-          } else if (type.isSubtypeOf(verifier._boolType)) {
+          } else if (_typeSystem.isSubtypeOf(type, verifier._boolType)) {
             return new DartObjectImpl(
                 verifier._typeProvider.boolType, BoolState.UNKNOWN_VALUE);
-          } else if (type.isSubtypeOf(verifier._typeProvider.doubleType)) {
+          } else if (_typeSystem.isSubtypeOf(type, verifier._typeProvider.doubleType)) {
             return new DartObjectImpl(
                 verifier._typeProvider.doubleType, DoubleState.UNKNOWN_VALUE);
-          } else if (type.isSubtypeOf(verifier._intType)) {
+          } else if (_typeSystem.isSubtypeOf(type, verifier._intType)) {
             return new DartObjectImpl(
                 verifier._typeProvider.intType, IntState.UNKNOWN_VALUE);
-          } else if (type.isSubtypeOf(verifier._numType)) {
+          } else if (_typeSystem.isSubtypeOf(type, verifier._numType)) {
             return new DartObjectImpl(
                 verifier._typeProvider.numType, NumState.UNKNOWN_VALUE);
-          } else if (type.isSubtypeOf(verifier._stringType)) {
+          } else if (_typeSystem.isSubtypeOf(type, verifier._stringType)) {
             return new DartObjectImpl(
                 verifier._typeProvider.stringType, StringState.UNKNOWN_VALUE);
           }