Implement type inference for asserts in constructor initializers.

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

 // Copyright (c) 2016, 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 fasta.body_builder;
 
 import 'package:kernel/ast.dart'
     hide InvalidExpression, InvalidInitializer, InvalidStatement;
 
 import 'package:kernel/class_hierarchy.dart' show ClassHierarchy;
@@ skipping 2745 matching lines @@
     // Since kernel only has asserts in statment form, we convert it to an
     // expression by wrapping it in an anonymous function which we call
     // immediately.
     //
     // Additionally, kernel has no initializer that evaluates an expression,
     // but it does have `LocalInitializer` which requires a variable declartion.
     //
     // So we produce an initializer like this:
     //
     //    var #t0 = (() { statement; }) ()
-    return new LocalInitializer(new VariableDeclaration.forValue(
-        buildMethodInvocation(
+    return new KernelAssertInitializer(
+        new VariableDeclaration.forValue(buildMethodInvocation(
             new FunctionExpression(new FunctionNode(statement)),
             callName,
             new Arguments.empty(),
             statement.fileOffset,
             isConstantExpression: true,
-            isImplicitCall: true)));
+            isImplicitCall: true)),
+        statement);
   }
 
   @override
   void endYieldStatement(Token yieldToken, Token starToken, Token endToken) {
     debugEvent("YieldStatement");
     push(new KernelYieldStatement(popForValue(), isYieldStar: starToken != null)
       ..fileOffset = yieldToken.charOffset);
   }
 
   @override
@@ skipping 1016 matching lines @@
       return AsyncMarker.Async;
     } else {
       assert(identical(starToken.stringValue, "*"));
       return AsyncMarker.AsyncStar;
     }
   } else {
     return unhandled(asyncToken.lexeme, "asyncMarkerFromTokens",
         asyncToken.charOffset, null);
   }
 }