Support checked mode for return type.

sdk/lib/_internal/compiler/implementation/ssa/nodes.dart

 // Copyright (c) 2012, 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.
 
 part of ssa;
 
 abstract class HVisitor<R> {
   R visitAdd(HAdd node);
   R visitBailoutTarget(HBailoutTarget node);
   R visitBitAnd(HBitAnd node);
@@ skipping 853 matching lines @@
   // All isFunctions work on the propagated types.
   bool isArray(HTypeMap types) => types[this].isArray();
   bool isReadableArray(HTypeMap types) => types[this].isReadableArray();
   bool isMutableArray(HTypeMap types) => types[this].isMutableArray();
   bool isExtendableArray(HTypeMap types) => types[this].isExtendableArray();
   bool isFixedArray(HTypeMap types) => types[this].isFixedArray();
   bool isBoolean(HTypeMap types) => types[this].isBoolean();
   bool isInteger(HTypeMap types) => types[this].isInteger();
   bool isDouble(HTypeMap types) => types[this].isDouble();
   bool isNumber(HTypeMap types) => types[this].isNumber();
+  bool isNumberOrNull(HTypeMap types) => types[this].isNumberOrNull();
   bool isString(HTypeMap types) => types[this].isString();
   bool isTypeUnknown(HTypeMap types) => types[this].isUnknown();
   bool isIndexablePrimitive(HTypeMap types)
       => types[this].isIndexablePrimitive();
   bool isPrimitive(HTypeMap types) => types[this].isPrimitive();
   bool canBePrimitive(HTypeMap types) => types[this].canBePrimitive();
   bool canBeNull(HTypeMap types) => types[this].canBeNull();
 
   /**
    * This is the type the instruction is guaranteed to have. It does not
@@ skipping 237 matching lines @@
 
     HInstruction current = this;
     while (current != null) {
       if (identical(current, other)) return true;
       current = current.next;
     }
     return false;
   }
 
 
-  HInstruction convertType(Compiler compiler,
-                           Element sourceElement,
-                           int kind) {
-    DartType type = sourceElement.computeType(compiler);
+  HInstruction convertType(Compiler compiler, DartType type, int kind) {
     if (type == null) return this;
     if (identical(type.element, compiler.dynamicClass)) return this;
     if (identical(type.element, compiler.objectClass)) return this;
 
     // If the original can't be null, type conversion also can't produce null.
     bool canBeNull = this.guaranteedType.canBeNull();
     HType convertedType =
         new HType.fromBoundedType(type, compiler, canBeNull);
 
     // No need to convert if we know the instruction has
@@ skipping 1859 matching lines @@
   HBasicBlock get start => expression.start;
   HBasicBlock get end {
     // We don't create a switch block if there are no cases.
     assert(!statements.isEmpty);
     return statements.last.end;
   }
 
   bool accept(HStatementInformationVisitor visitor) =>
       visitor.visitSwitchInfo(this);
 }