Implement type inference for named function expressions.

pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart

 // Copyright (c) 2017, 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.
 
 /// This file declares a "shadow hierarchy" of concrete classes which extend
 /// the kernel class hierarchy, adding methods and fields needed by the
 /// BodyBuilder.
 ///
 /// Instances of these classes may be created using the factory methods in
 /// `ast_factory.dart`.
@@ skipping 1316 matching lines @@
 
   @override
   DartType _inferExpression(
       KernelTypeInferrer inferrer, DartType typeContext, bool typeNeeded) {
     return inferrer.inferMethodInvocation(
         this, receiver, fileOffset, _isImplicitCall, typeContext, typeNeeded,
         desugaredInvocation: this);
   }
 }
 
+/// Concrete shadow object representing a named function expression.
+///
+/// Named function expressions are not legal in Dart, but they are accepted by
+/// the parser and BodyBuilder for error recovery purposes.
+///
+/// A named function expression of the form `f() { ... }` is represented as the
+/// kernel expression:
+///
+///     let f = () { ... } in f
+class KernelNamedFunctionExpression extends Let implements KernelExpression {
+  KernelNamedFunctionExpression(VariableDeclaration variable, Expression body)
+      : super(variable, body);
+
+  @override
+  void _collectDependencies(KernelDependencyCollector collector) {
+    collector.collectDependencies(variable.initializer);
+  }
+
+  @override
+  DartType _inferExpression(
+      KernelTypeInferrer inferrer, DartType typeContext, bool typeNeeded) {
+    typeNeeded =
+        inferrer.listener.namedFunctionExpressionEnter(this, typeContext) ||
+            typeNeeded;
+    var inferredType =
+        inferrer.inferExpression(variable.initializer, typeContext, true);
+    if (inferrer.strongMode) variable.type = inferredType;
+    if (!typeNeeded) inferredType = null;
+    inferrer.listener.namedFunctionExpressionExit(this, inferredType);
+    return inferredType;
+  }
+}
+
 /// Shadow object for [Not].
 class KernelNot extends Not implements KernelExpression {
   KernelNot(Expression operand) : super(operand);
 
   @override
   void _collectDependencies(KernelDependencyCollector collector) {
     collector.collectDependencies(operand);
   }
 
   @override
@@ skipping 1115 matching lines @@
   accept(v) => unsupported("accept", -1, null);
 
   accept1(v, arg) => unsupported("accept1", -1, null);
 
   getStaticType(types) => unsupported("getStaticType", -1, null);
 
   transformChildren(v) => unsupported("transformChildren", -1, null);
 
   visitChildren(v) => unsupported("visitChildren", -1, null);
 }