fix: address feedback

Author: crisbeto

src/demo-app/input/input-demo.html

@@ -64,8 +64,10 @@ <h4>Regular</h4>
 
       <md-input-container>
         <input mdInput placeholder="email" [formControl]="emailFormControl">
-        <md-error *ngIf="emailFormControl.errors['required']">This field is required</md-error>
-        <md-error *ngIf="emailFormControl.errors['pattern']">
+        <md-error *ngIf="emailFormControl.errors ? emailFormControl.errors['required'] : false">
+          This field is required
+        </md-error>
+        <md-error *ngIf="emailFormControl.errors ? emailFormControl.errors['pattern'] : false">
           Please enter a valid email address
         </md-error>
       </md-input-container>

src/lib/input/input-container.html

@@ -41,7 +41,7 @@
       <ng-content select="md-error, mat-error"></ng-content>
     </div>
 
-    <div *ngSwitchCase="'hint'" class="mat-input-hint-clearfix" [@transitionMessages]="_messageAnimationState">
+    <div *ngSwitchCase="'hint'" [@transitionMessages]="_messageAnimationState">
       <div *ngIf="hintLabel != ''" [attr.id]="_hintLabelId" class="mat-hint">{{hintLabel}}</div>
       <ng-content select="md-hint, mat-hint"></ng-content>
     </div>

src/lib/input/input-container.scss

@@ -228,6 +228,7 @@ $mat-input-underline-disabled-background-image:
   top: 100%;
   width: 100%;
   margin-top: -$mat-input-wrapper-spacing;
+  overflow: hidden; // prevents multi-line errors from overlapping the input
 }
 
 // The hint is shown below the underline. There can be
@@ -249,19 +250,6 @@ $mat-input-underline-disabled-background-image:
   }
 }
 
-// Clears the floats on the hints. Necessary for the `transform` animation to work.
-.mat-input-hint-clearfix {
-  &::before,
-  &::after {
-    content: '';
-    display: table;
-  }
-
-  &::after {
-    clear: both;
-  }
-}
-
 // Single errror message displayed beneath the input.
 .mat-input-error {
   display: block;

src/lib/input/input-container.ts

@@ -368,7 +368,7 @@ export class MdInputContainer implements AfterViewInit, AfterContentInit {
   }
 
   /** Determines whether to display hints, errors or no messages at all. */
-  _getDisplayedMessages(): 'error'|'hint'|'none' {
+  _getDisplayedMessages(): 'error' | 'hint' | 'none' {
     if (this._errorChildren.length > 0) {
       if (this._isErrorState()) {
         return 'error';