Convert ShadowNullLiteral to NullJudgment.

Change-Id: I5d38b16b0416f04255fa46c44a5aa89a15848a83
Reviewed-on: https://dart-review.googlesource.com/61100
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>

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

@@ -92,7 +92,7 @@ import 'kernel_shadow_ast.dart'
         ShadowLogicalExpression,
         ShadowMapLiteral,
         ShadowNot,
-        ShadowNullLiteral,
+        NullJudgment,
         ShadowRethrow,
         ShadowReturnStatement,
         ShadowStringConcatenation,
@@ -205,8 +205,8 @@ class Fangorn extends Forest<Expression, Statement, Token, Arguments> {
   }
 
   @override
-  ShadowNullLiteral literalNull(Token token) {
-    return new ShadowNullLiteral()..fileOffset = offsetForToken(token);
+  NullJudgment literalNull(Token token) {
+    return new NullJudgment()..fileOffset = offsetForToken(token);
   }
 
   @override

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

@@ -1827,7 +1827,7 @@ class ShadowNullAwarePropertyGet extends Let implements ExpressionJudgment {
 }
 
 /// Concrete shadow object representing a null literal in kernel form.
-class ShadowNullLiteral extends NullLiteral implements ExpressionJudgment {
+class NullJudgment extends NullLiteral implements ExpressionJudgment {
   DartType inferredType;
 
   @override
@@ -1835,7 +1835,7 @@ class ShadowNullLiteral extends NullLiteral implements ExpressionJudgment {
       ShadowTypeInferrer inferrer,
       Factory<Expression, Statement, Initializer, Type> factory,
       DartType typeContext) {
-    return inferrer.coreTypes.nullClass.rawType;
+    return inferredType = inferrer.coreTypes.nullClass.rawType;
   }
 }
 

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

@@ -73,7 +73,7 @@ import '../kernel/kernel_shadow_ast.dart'
         ShadowConstructorInvocation,
         ShadowField,
         ShadowMember,
-        ShadowNullLiteral,
+        NullJudgment,
         ShadowVariableDeclaration;
 
 import '../names.dart' show callName;
@@ -1203,7 +1203,7 @@ abstract class TypeInferrerImpl extends TypeInferrer {
         inferMetadataKeepingHelper(factory, parameter.annotations);
         if (i >= function.requiredParameterCount &&
             parameter.initializer == null) {
-          parameter.initializer = new ShadowNullLiteral()..parent = parameter;
+          parameter.initializer = new NullJudgment()..parent = parameter;
         }
         if (parameter.initializer != null) {
           inferExpression(
@@ -1213,7 +1213,7 @@ abstract class TypeInferrerImpl extends TypeInferrer {
       for (var parameter in function.namedParameters) {
         inferMetadataKeepingHelper(factory, parameter.annotations);
         if (parameter.initializer == null) {
-          parameter.initializer = new ShadowNullLiteral()..parent = parameter;
+          parameter.initializer = new NullJudgment()..parent = parameter;
         }
         inferExpression(factory, parameter.initializer, parameter.type, false);
       }