Revert "fix(compiler): shouldn't throw when Symbol is used as DI token (

angular#13701)" (angular#15319)

This reverts commit 8b5c6b2.

This feature is not compatible with the `Injector.get` which now only 
takes `Type` or `InjectableToken`. `Symbol` is not a valid type.

Closes angular#15183

PR Close angular#15319

packages/compiler/src/compile_metadata.ts

@@ -80,8 +80,6 @@ function _sanitizeIdentifier(name: string): string {
 }
 
 let _anonymousTypeIndex = 0;
-let symbolId = 0;
-const symbolIds = new Map<Symbol, string>();
 
 export function identifierName(compileIdentifier: CompileIdentifierMetadata): string {
   if (!compileIdentifier || !compileIdentifier.reference) {
@@ -91,14 +89,6 @@ export function identifierName(compileIdentifier: CompileIdentifierMetadata): st
   if (ref instanceof StaticSymbol) {
     return ref.name;
   }
-  if (isSymbol(ref)) {
-    if (symbolIds.has(ref)) {
-      return symbolIds.get(ref);
-    }
-    const symbolStr = `_symbol_${_sanitizeIdentifier(ref.toString())}_${symbolId++}`;
-    symbolIds.set(ref, symbolStr);
-    return symbolStr;
-  }
   if (ref['__anonymousType']) {
     return ref['__anonymousType'];
   }
@@ -113,10 +103,6 @@ export function identifierName(compileIdentifier: CompileIdentifierMetadata): st
   return identifier;
 }
 
-function isSymbol(sym: any): sym is Symbol {
-  return typeof sym === 'symbol';
-}
-
 export function identifierModuleUrl(compileIdentifier: CompileIdentifierMetadata): string {
   const ref = compileIdentifier.reference;
   if (ref instanceof StaticSymbol) {

packages/compiler/test/integration_spec.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Component, Directive, Inject, Input} from '@angular/core';
+import {Component, Directive, Input} from '@angular/core';
 import {ComponentFixture, TestBed, async} from '@angular/core/testing';
 import {By} from '@angular/platform-browser/src/dom/debug/by';
 import {expect} from '@angular/platform-browser/testing/src/matchers';
@@ -38,31 +38,6 @@ export function main() {
          }));
     });
 
-    it('should not throw when Symbol is used as DI token', async(() => {
-         const SOME_SYMBOL = Symbol('Symbol');
-         const ANOTHER_SYMBOL = Symbol('Symbol');
-
-         @Component({selector: 'symbol', template: ''})
-         class CmpWithSymbol {
-           constructor(
-               @Inject(SOME_SYMBOL) public symbol: string,
-               @Inject(ANOTHER_SYMBOL) public anotherSymbol: string) {}
-         }
-
-         TestBed.configureTestingModule({
-           declarations: [CmpWithSymbol],
-           providers: [
-             {provide: SOME_SYMBOL, useValue: 'value'},
-             {provide: SOME_SYMBOL, useValue: 'override'},
-             {provide: ANOTHER_SYMBOL, useValue: 'another value'}
-           ]
-         });
-
-         const fixture = TestBed.createComponent(CmpWithSymbol);
-         fixture.detectChanges();
-         expect(fixture.componentInstance.symbol).toEqual('override');
-         expect(fixture.componentInstance.anotherSymbol).toEqual('another value');
-       }));
   });
 }