support the implicitCast tag (Closure Compiler only) (#605)

lib/jsdoc/tag/dictionary/definitions.js

@@ -882,6 +882,10 @@ exports.closureTags = {
     },
     final: cloneTagDef(baseTags.readonly),
     implements: cloneTagDef(baseTags.implements),
+    // Closure Compiler only
+    implicitcast: {
+        onTagged: ignore
+    },
     inheritdoc: cloneTagDef(baseTags.inheritdoc),
     interface: cloneTagDef(baseTags.interface, {
         canHaveName: false,

test/fixtures/implicitcasttag.js

@@ -0,0 +1,7 @@
+function Foo() {}
+
+/**
+ * @type {string}
+ * @implicitCast
+ */
+Foo.prototype.bar;

test/specs/tags/implicitcasttag.js

@@ -0,0 +1,42 @@
+'use strict';
+
+describe('@implicitCast tag', function() {
+    var env = require('jsdoc/env');
+    var logger = require('jsdoc/util/logger');
+
+    var allowUnknownTags = Boolean(env.conf.tags.allowUnknownTags);
+
+    beforeEach(function() {
+        env.conf.tags.allowUnknownTags = false;
+        spyOn(logger, 'error');
+    });
+
+    afterEach(function() {
+        jasmine.restoreTagDictionary();
+        env.conf.tags.allowUnknownTags = allowUnknownTags;
+    });
+
+    describe('JSDoc tags', function() {
+        beforeEach(function() {
+            jasmine.replaceTagDictionary('jsdoc');
+        });
+
+        it('should not recognize the @implicitCast tag', function() {
+            jasmine.getDocSetFromFile('test/fixtures/implicitcasttag.js');
+
+            expect(logger.error).toHaveBeenCalled();
+        });
+    });
+
+    describe('Closure Compiler tags', function() {
+        beforeEach(function() {
+            jasmine.replaceTagDictionary('closure');
+        });
+
+        it('should recognize the @implicitCast tag', function() {
+            jasmine.getDocSetFromFile('test/fixtures/implicitcasttag.js');
+
+            expect(logger.error).not.toHaveBeenCalled();
+        });
+    });
+});