Implement type inference for conventional for-loops.

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 691 matching lines @@
           variable.fileOffset,
           'type',
           new InstrumentationValueForType(inferredType));
       variable.type = inferredType;
     }
     inferrer.inferStatement(body);
     inferrer.listener.forInStatementExit(this);
   }
 }
 
+/// Concrete shadow object representing a classic for loop in kernel form.
+class KernelForStatement extends ForStatement implements KernelStatement {
+  KernelForStatement(List<VariableDeclaration> variables, Expression condition,
+      List<Expression> updates, Statement body)
+      : super(variables, condition, updates, body);
+
+  @override
+  void _inferStatement(KernelTypeInferrer inferrer) {
+    inferrer.listener.forStatementEnter(this);
+    variables.forEach(inferrer.inferStatement);
+    inferrer.inferExpression(
+        condition, inferrer.coreTypes.boolClass.rawType, false);
+    for (var update in updates) {
+      inferrer.inferExpression(update, null, false);
+    }
+    inferrer.inferStatement(body);
+    inferrer.listener.forStatementExit(this);
+  }
+}
+
 /// Concrete shadow object representing a local function declaration in kernel
 /// form.
 class KernelFunctionDeclaration extends FunctionDeclaration
     implements KernelStatement {
   bool _hasImplicitReturnType = false;
 
   KernelFunctionDeclaration(VariableDeclaration variable, FunctionNode function)
       : super(variable, function);
 
   @override
@@ skipping 1494 matching lines @@
   }
 
   transformChildren(v) {
     return internalError("Internal error: Unsupported operation.");
   }
 
   visitChildren(v) {
     return internalError("Internal error: Unsupported operation.");
   }
 }