Add another type JSPositiveInt to show a range analysis in the inferrer would be very beneficial :-…

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 visitBitAnd(HBitAnd node);
   R visitBitNot(HBitNot node);
@@ skipping 895 matching lines @@
     return !instructionType.isNullable
         && instructionType.satisfies(backend.jsUInt32Class, compiler);
   }
 
   bool isUInt31(Compiler compiler) {
     JavaScriptBackend backend = compiler.backend;
     return !instructionType.isNullable
         && instructionType.satisfies(backend.jsUInt31Class, compiler);
   }
 
+  bool isPositiveInteger(Compiler compiler) {
+    JavaScriptBackend backend = compiler.backend;
+    return !instructionType.isNullable
+        && instructionType.satisfies(backend.jsPositiveIntClass, compiler);
+  }
+
+  bool isPositiveIntegerOrNull(Compiler compiler) {
+    JavaScriptBackend backend = compiler.backend;
+    return instructionType.satisfies(backend.jsPositiveIntClass, compiler);
+  }
+
   bool isIntegerOrNull(Compiler compiler) {
     return instructionType.containsOnlyInt(compiler);
   }
 
   bool isNumber(Compiler compiler) {
     return instructionType.containsOnlyNum(compiler)
         && !instructionType.isNullable;
   }
 
   bool isNumberOrNull(Compiler compiler) {
@@ skipping 1904 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);
 }