Named constants are (usually) not null.

test/codegen/expect/sunflower/sunflower.js

 dart_library.library('sunflower', null, /* Imports */[
   'dart_sdk'
 ], function(exports, dart_sdk) {
   'use strict';
   const core = dart_sdk.core;
   const html = dart_sdk.html;
   const math = dart_sdk.math;
   const dart = dart_sdk.dart;
   const dartx = dart_sdk.dartx;
   const sunflower = Object.create(null);
   const circle = Object.create(null);
   const painter = Object.create(null);
   sunflower.SEED_RADIUS = 2;
   sunflower.SCALE_FACTOR = 4;
   sunflower.MAX_D = 300;
-  sunflower.centerX = dart.notNull(sunflower.MAX_D) / 2;
+  sunflower.centerX = sunflower.MAX_D / 2;
   sunflower.centerY = sunflower.centerX;
   sunflower.querySelector = function(selector) {
     return html.document[dartx.querySelector](selector);
   };
   dart.fn(sunflower.querySelector, html.Element, [core.String]);
   dart.defineLazy(sunflower, {
     get canvas() {
       return dart.as(sunflower.querySelector("#canvas"), html.CanvasElement);
     }
   });
@@ skipping 20 matching lines @@
   sunflower.seeds = 0;
   sunflower.main = function() {
     sunflower.slider[dartx.addEventListener]('change', dart.fn(e => sunflower.draw(), dart.void, [html.Event]));
     sunflower.draw();
   };
   dart.fn(sunflower.main, dart.void, []);
   sunflower.draw = function() {
     sunflower.seeds = core.int.parse(sunflower.slider[dartx.value]);
     sunflower.context[dartx.clearRect](0, 0, sunflower.MAX_D, sunflower.MAX_D);
     for (let i = 0; i < dart.notNull(sunflower.seeds); i++) {
-      let theta = i * dart.notNull(painter.TAU) / dart.notNull(sunflower.PHI);
-      let r = dart.notNull(math.sqrt(i)) * dart.notNull(sunflower.SCALE_FACTOR);
-      let x = dart.notNull(sunflower.centerX) + r * dart.notNull(math.cos(theta));
-      let y = dart.notNull(sunflower.centerY) - r * dart.notNull(math.sin(theta));
+      let theta = i * painter.TAU / dart.notNull(sunflower.PHI);
+      let r = dart.notNull(math.sqrt(i)) * sunflower.SCALE_FACTOR;
+      let x = sunflower.centerX + r * dart.notNull(math.cos(theta));
+      let y = sunflower.centerY - r * dart.notNull(math.sin(theta));
       new sunflower.SunflowerSeed(x, y, sunflower.SEED_RADIUS).draw(sunflower.context);
     }
     sunflower.notes[dartx.text] = `${sunflower.seeds} seeds`;
   };
   dart.fn(sunflower.draw, dart.void, []);
   circle.Circle = class Circle extends core.Object {
     Circle(x, y, radius) {
       this.x = x;
       this.y = y;
       this.radius = radius;
@@ skipping 27 matching lines @@
       super.Circle(x, y, radius);
       if (color != null) this.color = color;
     }
   };
   dart.setSignature(sunflower.SunflowerSeed, {
     constructors: () => ({SunflowerSeed: [sunflower.SunflowerSeed, [core.num, core.num, core.num], [core.String]]})
   });
   painter.ORANGE = "orange";
   painter.RED = "red";
   painter.BLUE = "blue";
-  painter.TAU = dart.notNull(math.PI) * 2;
+  painter.TAU = math.PI * 2;
   painter.querySelector = function(selector) {
     return html.document[dartx.querySelector](selector);
   };
   dart.fn(painter.querySelector, html.Element, [core.String]);
   dart.defineLazy(painter, {
     get canvas() {
       return dart.as(painter.querySelector("#canvas"), html.CanvasElement);
     }
   });
   dart.defineLazy(painter, {
     get context() {
       return dart.as(painter.canvas[dartx.getContext]('2d'), html.CanvasRenderingContext2D);
     }
   });
   // Exports:
   exports.sunflower = sunflower;
   exports.circle = circle;
   exports.painter = painter;
 });
 
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