Split up TypeInferrer class.

pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart

Index: pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
diff --git a/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart b/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
index e32850006ba4975f8375ba40c568fa5d0fded9e3..caa08103a55fbb2c0c783274d018a83a1db49b85 100644
--- a/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
+++ b/pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart
@@ -3,101 +3,67 @@
 // BSD-style license that can be found in the LICENSE.md file.
 
 import 'package:front_end/src/base/instrumentation.dart';
-import 'package:front_end/src/dependency_walker.dart' as dependencyWalker;
-import 'package:kernel/ast.dart' show DartType, DynamicType, Member;
-import 'package:kernel/class_hierarchy.dart';
+import 'package:front_end/src/fasta/type_inference/type_inference_engine.dart';
+import 'package:kernel/ast.dart' show DartType, Member;
 import 'package:kernel/core_types.dart';
 
-/// Data structure for tracking dependencies between fields that require type
-/// inference.
+/// Keeps track of the local state for the type inference that occurs during
+/// compilation of a single method body or top level initializer.
 ///
-/// TODO(paulberry): see if it's possible to make this class more lightweight
-/// by changing the API so that the walker is passed to computeDependencies().
-/// (This should allow us to drop the _typeInferrer field).
-class FieldNode<F> extends dependencyWalker.Node<FieldNode<F>> {
-  final TypeInferrer _typeInferrer;
-
-  final F _field;
-
-  final dependencies = <FieldNode<F>>[];
-
-  FieldNode(this._typeInferrer, this._field);
-
-  @override
-  bool get isEvaluated => _typeInferrer.isFieldInferred(_field);
-
-  @override
-  List<FieldNode<F>> computeDependencies() {
-    return dependencies;
-  }
-}
-
-/// Abstract implementation of type inference which is independent of the
-/// underlying AST representation (but still uses DartType from kernel).
-///
-/// TODO(paulberry): would it make more sense to abstract away the
-/// representation of types as well?
+/// This class abstracts away the representation of the underlying AST using
+/// generic parameters.  TODO(paulberry): would it make more sense to abstract
+/// away the representation of types as well?
 ///
 /// Derived classes should set S, E, V, and F to the class they use to represent
 /// statements, expressions, variable declarations, and field declarations,
 /// respectively.
+///
+/// This class describes the interface for use by clients of type inference
+/// (e.g. BodyBuilder).  Derived classes should derive from [TypeInferrerImpl].
 abstract class TypeInferrer<S, E, V, F> {
-  final Instrumentation instrumentation;
-
-  final bool strongMode;
-
-  final fieldNodes = <FieldNode<F>>[];
-
-  CoreTypes coreTypes;
-
-  ClassHierarchy classHierarchy;
-
   /// The URI of the code for which type inference is currently being
   /// performed--this is used for testing.
-  String uri;
+  String get uri;
 
-  /// Indicates whether we are currently performing top level inference.
-  bool isTopLevel = false;
+  /// Gets the [FieldNode] corresponding to the given [readTarget], if any.
+  FieldNode<F> getFieldNodeForReadTarget(Member readTarget);
 
-  TypeInferrer(this.instrumentation, this.strongMode);
+  /// Performs type inference on the given [statement].
+  ///
+  /// Derived classes should override this method with logic that dispatches on
+  /// the statement type and calls the appropriate specialized "infer" method.
+  void inferStatement(S statement);
+}
 
-  /// Cleares the initializer of [field].
-  void clearFieldInitializer(F field);
+/// Derived class containing generic implementations of [TypeInferrerImpl].
+///
+/// This class contains as much of the implementation of type inference as
+/// possible without knowing the identity of the type parameters.  It defers to
+/// abstract methods for everything else.
+abstract class TypeInferrerImpl<S, E, V, F> extends TypeInferrer<S, E, V, F> {
+  @override
+  final String uri;
+
+  /// Indicates whether the construct we are currently performing inference for
+  /// is outside of a method body, and hence top level type inference rules
+  /// should apply.
+  final bool isTopLevel = false;
+
+  final CoreTypes coreTypes;
 
-  /// Creates a [FieldNode] to track dependencies of the given [field].
-  FieldNode<F> createFieldNode(F field);
+  final bool strongMode;
 
-  /// Gets the declared type of the given [field], or `null` if the type is
-  /// implicit.
-  DartType getFieldDeclaredType(F field);
+  final Instrumentation instrumentation;
 
-  /// Gets the list of top level type inference dependencies of the given
-  /// [field].
-  List<FieldNode<F>> getFieldDependencies(F field);
+  TypeInferrerImpl(TypeInferenceEngineImpl<F> engine, this.uri)
+      : coreTypes = engine.coreTypes,
+        strongMode = engine.strongMode,
+        instrumentation = engine.instrumentation;
 
   /// Gets the initializer for the given [field], or `null` if there is no
   /// initializer.
   E getFieldInitializer(F field);
 
-  /// Gets the [FieldNode] corresponding to the given [readTarget], if any.
-  FieldNode<F> getFieldNodeForReadTarget(Member readTarget);
-
-  /// Gets the character offset of the declaration of [field] within its
-  /// compilation unit.
-  int getFieldOffset(F field);
-
-  /// Gets the URI of the compilation unit the [field] is declared in.
-  String getFieldUri(F field);
-
-  /// Performs type inference on a method with the given method [body].
-  ///
-  /// [uri] is the URI of the file the method is contained in--this is used for
-  /// testing.
-  void inferBody(S body, Uri uri) {
-    this.uri = uri.toString();
-    inferStatement(body);
-  }
-
   /// Performs type inference on the given [expression].
   ///
   /// [typeContext] is the expected type of the expression, based on surrounding
@@ -109,42 +75,11 @@ abstract class TypeInferrer<S, E, V, F> {
   /// the expression type and calls the appropriate specialized "infer" method.
   DartType inferExpression(E expression, DartType typeContext, bool typeNeeded);
 
-  /// Performs type inference on the given [field].
-  void inferField(F field) {
-    var initializer = getFieldInitializer(field);
-    if (initializer != null) {
-      var type = getFieldDeclaredType(field);
-      uri = getFieldUri(field);
-      isTopLevel = true;
-      var inferredType = inferExpression(initializer, type, type == null);
-      if (type == null && strongMode) {
-        instrumentation?.record(
-            'topType',
-            Uri.parse(uri),
-            getFieldOffset(field),
-            new InstrumentationValueForType(inferredType));
-        setFieldInferredType(field, inferredType);
-      }
-      // TODO(paulberry): if type != null, then check that the type of the
-      // initializer is assignable to it.
-      // TODO(paulberry): the following is a hack so that outlines don't contain
-      // initializers.  But it means that we rebuild the initializers when doing
-      // a full compile.  There should be a better way.
-      clearFieldInitializer(field);
-    }
-  }
-
-  /// Makes a note that the given [field] is part of a circularity, so its type
-  /// can't be inferred.
-  void inferFieldCircular(F field) {
-    // TODO(paulberry): report the appropriate error.
-    if (getFieldDeclaredType(field) == null) {
-      var uri = getFieldUri(field);
-      instrumentation?.record('topType', Uri.parse(uri), getFieldOffset(field),
-          const InstrumentationValueLiteral('circular'));
-      setFieldInferredType(field, const DynamicType());
-    }
-  }
+  /// Performs type inference on the given [field]'s initializer expression.
+  ///
+  /// Derived classes should provide an implementation that calls
+  /// [inferExpression] for the given [field]'s initializer expression.
+  DartType inferFieldInitializer(F field, DartType type, bool typeNeeded);
 
   /// Performs the core type inference algorithm for integer literals.
   ///
@@ -154,12 +89,6 @@ abstract class TypeInferrer<S, E, V, F> {
     return typeNeeded ? coreTypes.intClass.rawType : null;
   }
 
-  /// Performs type inference on the given [statement].
-  ///
-  /// Derived classes should override this method with logic that dispatches on
-  /// the statement type and calls the appropriate specialized "infer" method.
-  void inferStatement(S statement);
-
   /// Performs the core type inference algorithm for static variable getters.
   ///
   /// [typeContext], [typeNeeded], and the return value behave as described in
@@ -190,45 +119,4 @@ abstract class TypeInferrer<S, E, V, F> {
       setType(inferredType);
     }
   }
-
-  /// Determines if top level type inference has been completed for [field].
-  bool isFieldInferred(F field);
-
-  /// Performs top level type inference for all fields that have been passed to
-  /// [recordField].
-  void performInitializerInference() {
-    for (var fieldNode in fieldNodes) {
-      if (fieldNode.isEvaluated) continue;
-      new _FieldWalker<F>().walk(fieldNode);
-    }
-  }
-
-  /// Records that the given [field] will need top level type inference.
-  void recordField(F field) {
-    fieldNodes.add(createFieldNode(field));
-  }
-
-  /// Stores [inferredType] as the inferred type of [field].
-  void setFieldInferredType(F field, DartType inferredType);
-}
-
-/// Subtype of [dependencyWalker.DependencyWalker] which is specialized to
-/// perform top level type inference.
-class _FieldWalker<F> extends dependencyWalker.DependencyWalker<FieldNode<F>> {
-  _FieldWalker();
-
-  @override
-  void evaluate(FieldNode<F> f) {
-    f._typeInferrer.inferField(f._field);
-  }
-
-  @override
-  void evaluateScc(List<FieldNode<F>> scc) {
-    for (var f in scc) {
-      f._typeInferrer.inferFieldCircular(f._field);
-    }
-    for (var f in scc) {
-      f._typeInferrer.inferField(f._field);
-    }
-  }
 }