Implement type inference for conventional for-loops.

pkg/front_end/testcases/implicit_scope_test.dart.strong.expect

 library;
 import self as self;
 import "dart:core" as core;
 import "package:expect/expect.dart" as exp;
 
 class ImplicitScopeTest extends core::Object {
   constructor •() → void
     : super core::Object::•()
     ;
   static method alwaysTrue() → core::bool {
     return 1.{core::num::+}(1).{core::num::==}(2);
   }
   static method testMain() → dynamic {
     core::String a = "foo";
     dynamic b;
     if(self::ImplicitScopeTest::alwaysTrue()) {
       dynamic a = "bar";
     }
     else {
       dynamic b = a;
     }
     exp::Expect::equals("foo", a);
     exp::Expect::equals(null, b);
     while (!self::ImplicitScopeTest::alwaysTrue()) {
       dynamic a = "bar";
       dynamic b = "baz";
     }
     exp::Expect::equals("foo", a);
     exp::Expect::equals(null, b);
-    for (core::int i = 0; i.<(10); i = i.+(1)) {
+    for (core::int i = 0; i.{core::num::<}(10); i = i.{core::num::+}(1)) {
       dynamic a = "bar";
       dynamic b = "baz";
     }
     exp::Expect::equals("foo", a);
     exp::Expect::equals(null, b);
     do {
       dynamic a = "bar";
       dynamic b = "baz";
     }
     while ("black".==("white"))
     exp::Expect::equals("foo", a);
     exp::Expect::equals(null, b);
   }
 }
 static method main() → dynamic {
   self::ImplicitScopeTest::testMain();
 }