chore: fix compilation error in form field

Fixes a compilation error in the `matNativeControl` directive.

Author: crisbeto

src/lib/input/input.ts

@@ -185,7 +185,7 @@ export class MatInput extends _MatInputMixinBase implements MatFormFieldControl<
     // input element. To ensure that bindings for `type` work, we need to sync the setter
     // with the native property. Textarea elements don't support the type property or attribute.
     if (!this._isTextarea() && getSupportedInputTypes().has(this._type)) {
-      this._elementRef.nativeElement.type = this._type;
+      (this._elementRef.nativeElement as HTMLInputElement).type = this._type;
     }
   }
   protected _type = 'text';
@@ -221,7 +221,7 @@ export class MatInput extends _MatInputMixinBase implements MatFormFieldControl<
     'week'
   ].filter(t => getSupportedInputTypes().has(t));
 
-  constructor(protected _elementRef: ElementRef<HTMLInputElement>,
+  constructor(protected _elementRef: ElementRef<HTMLInputElement | HTMLSelectElement>,
               protected _platform: Platform,
               /** @docs-private */
               @Optional() @Self() public ngControl: NgControl,
@@ -372,8 +372,9 @@ export class MatInput extends _MatInputMixinBase implements MatFormFieldControl<
       // For a single-selection `<select>`, the label should float when the selected option has
       // a non-empty display value. For a `<select multiple>`, the label *always* floats to avoid
       // overlapping the label with the options.
-      const selectElement = this._elementRef.nativeElement;
-      return selectElement.multiple || !this.empty || selectElement.options[0].label ||
+      const selectElement = this._elementRef.nativeElement as HTMLSelectElement;
+
+      return selectElement.multiple || !this.empty || !!selectElement.options[0].label ||
           this.focused;
     } else {
       return this.focused || !this.empty;