chore(lint): disallow duplicate imports from a module

Closes #7859

modules/@angular/common/src/forms/directives/validators.ts

@@ -2,7 +2,6 @@ import {forwardRef, Attribute, Directive} from '@angular/core';
 import {NumberWrapper} from '../../facade/lang';
 import {Validators, NG_VALIDATORS} from '../validators';
 import {AbstractControl} from '../model';
-import * as modelModule from '../model';
 
 
 
@@ -23,7 +22,7 @@ import * as modelModule from '../model';
  * }
  * ```
  */
-export interface Validator { validate(c: modelModule.AbstractControl): {[key: string]: any}; }
+export interface Validator { validate(c: AbstractControl): {[key: string]: any}; }
 
 const REQUIRED = /*@ts2dart_const*/ Validators.required;
 

tslint.json

@@ -3,7 +3,7 @@
       "requireInternalWithUnderscore": true,
       "requireParameterType": true,
       "requireReturnType": true,
-      "duplicateModuleImport": false,
+      "duplicateModuleImport": true,
       "semicolon": true,
       "variable-name": false
     }