docs(minerr): fill in error message descriptions

Errors I've documented so far:
- `$injector:cdep`
- `$injector:itkn`
- `$injector:modulerr`
- `$injector:nomod`
- `$injector:pget`
- `$injector:unpr`
- `ng:areq`
- `ng:cpi`
- `ng:cpws`
- `ngModel:noass`

Closes #3430

6 files changed, 113 insertions, 0 deletions

diff --git a/docs/content/error/injector/cdep.ngdoc b/docs/content/error/injector/cdep.ngdoc
index f4a9c909..0e9769c4 100644
--- a/docs/content/error/injector/cdep.ngdoc
+++ b/docs/content/error/injector/cdep.ngdoc
@@ -2,3 +2,25 @@
 @name $injector:cdep
 @fullName Circular Dependency
 @description
+
+This error occurs when the {@link api/angular.injector $injector} tries to get
+a service that depends on itself, either directly or indirectly. To fix this,
+construct your dependency chain such that there are no circular dependencies.
+
+For example:
+
+```
+angular.module('myApp', [])
+  .factory('myService', function (myService) {
+    // ...
+  })
+  .controller('MyCtrl', function ($scope, myService) {
+    // ...
+  });
+```
+
+When an instance of `MyCtrl` is created, the service `myService` will be created
+by the `$injector`. `myService` depends on itself, which causes the `$injector`
+to detect a circular dependency and throw the error.
+
+For more information, see the {@link guide/di Dependency Injection Guide}.
\ No newline at end of file
diff --git a/docs/content/error/injector/itkn.ngdoc b/docs/content/error/injector/itkn.ngdoc
index fab64696..5437dce7 100644
--- a/docs/content/error/injector/itkn.ngdoc
+++ b/docs/content/error/injector/itkn.ngdoc
@@ -2,3 +2,25 @@
 @name $injector:itkn
 @fullName Bad Injection Token
 @description
+
+This error occurs when using a bad token as a dependency injection annotation.
+Dependency injection annotation tokens should always be strings. Using any other
+type will cause this error to be thrown.
+
+Examples of code with bad injection tokens include:
+
+```
+var myCtrl = function ($scope, $http) { /* ... */ };
+myCtrl.$inject = ['$scope', 42];
+
+myAppModule.controller('MyCtrl', ['$scope', {}, function ($scope, $timeout) {
+  // ...
+}]);
+```
+
+The bad injection tokens are `42` in the first example and `{}` in the second.
+To avoid the error, always use string literals for dependency injection annotation
+tokens.
+
+For an explanation of what injection annotations are and how to use them, refer
+to the {@link guide/di Dependency Injection Guide}.
\ No newline at end of file
diff --git a/docs/content/error/injector/modulerr.ngdoc b/docs/content/error/injector/modulerr.ngdoc
index 5d2aa8f8..e9d77c18 100644
--- a/docs/content/error/injector/modulerr.ngdoc
+++ b/docs/content/error/injector/modulerr.ngdoc
@@ -2,3 +2,6 @@
 @name $injector:modulerr
 @fullName Module Error
 @description
+
+This error occurs when a module fails to load due to some exception. The error
+message above should provide additional context.
diff --git a/docs/content/error/injector/nomod.ngdoc b/docs/content/error/injector/nomod.ngdoc
index 6dd4c169..66e2a5ad 100644
--- a/docs/content/error/injector/nomod.ngdoc
+++ b/docs/content/error/injector/nomod.ngdoc
@@ -2,3 +2,25 @@
 @name $injector:nomod
 @fullName Module Unavailable
 @description
+
+This error occurs when trying to "re-open" a module that has not yet been defined.
+
+To define a new module, call {@link api/angular.module angular.module} with a name
+and an array of dependent modules, like so:
+
+```
+// When defining a module with no module dependencies,
+// the requires array should be defined and empty.
+var myApp = angular.module('myApp', []);
+```
+
+To retrieve a reference to the same module for further configuration, call
+`angular.module` without the `requires` array.
+
+```
+var myApp = angular.module('myApp');
+```
+
+Calling `angular.module` without the `requires` array when the module has not yet
+been defined causes this error to be thrown. To fix it, define your module with
+a name and an empty array, as in the first example above.
\ No newline at end of file
diff --git a/docs/content/error/injector/pget.ngdoc b/docs/content/error/injector/pget.ngdoc
index 3eca8d80..e296b8ae 100644
--- a/docs/content/error/injector/pget.ngdoc
+++ b/docs/content/error/injector/pget.ngdoc
@@ -2,3 +2,25 @@
 @name $injector:pget
 @fullName Provider Missing $get
 @description
+
+This error occurs when attempting to register a provider that does not have a
+`$get` method. For example:
+
+```
+function BadProvider() {} // No $get method!
+angular.module("myApp", [])
+  .provider('bad', BadProvider);  // this throws the error
+```
+
+To fix the error, fill in the `$get` method on the provider like so:
+
+```
+function GoodProvider() {
+  this.$get = angular.noop;
+}
+angular.module("myApp", [])
+  .provider('good', GoodProvider);
+```
+
+For more information, refer to the {@link api/AUTO.$provide#provider
+$provide.provider} api doc.
\ No newline at end of file
diff --git a/docs/content/error/injector/unpr.ngdoc b/docs/content/error/injector/unpr.ngdoc
index 5459711f..1b0faa8e 100644
--- a/docs/content/error/injector/unpr.ngdoc
+++ b/docs/content/error/injector/unpr.ngdoc
@@ -2,3 +2,25 @@
 @name $injector:unpr
 @fullName Unknown Provider
 @description
+
+This error results from the `$injector` being unable to resolve a required
+dependency. To fix this, make sure the dependency is defined and spelled
+correctly. For example:
+
+```
+angular.module('myApp', [])
+  .controller('myCtrl', ['myService', function (myService) {
+    // Do something with myService
+  }]);
+```
+
+This code will fail with `$injector:unpr` if `myService` is not defined. Making
+sure each dependency is defined will fix the problem.
+
+```
+angular.module('myApp', [])
+  .service('myService', function () { /* ... */ })
+  .controller('myCtrl', ['myService', function (myService) {
+    // Do something with myService
+  }]);
+```
\ No newline at end of file