feat(Parser): implement Parser

Add a simple parser implementation that supports only field reads.

modules/change_detection/test/parser/parser_spec.js

@@ -0,0 +1,38 @@
+import {ddescribe, describe, it, expect, beforeEach} from 'test_lib/test_lib';
+import {Parser} from 'change_detection/parser/parser';
+import {Lexer} from 'change_detection/parser/lexer';
+import {ClosureMap} from 'change_detection/parser/closure_map';
+
+class TestData {
+  constructor(a) {
+    this.a = a;
+  }
+}
+
+export function main() {
+  function td({a}) {
+    return new TestData(a);
+  }
+
+  describe("parser", () => {
+    describe("field access", () => {
+      var parser;
+
+      beforeEach(() => {
+        parser = new Parser(new Lexer(), new ClosureMap());
+      });
+
+      it("should parse field access",() => {
+        var exp = parser.parse("a");
+        var context = td({a: 999});
+        expect(exp.eval(context)).toEqual(999);
+      });
+
+      it("should parse nested field access",() => {
+        var exp = parser.parse("a.a");
+        var context = td({a: td({a: 999})});
+        expect(exp.eval(context)).toEqual(999);
+      });
+    });
+  });
+}