fix(compiler): emit correct type-check-blocks with TemplateRef's (#20463

)

The type-check block generated with `"fullTemplateTypeCheck"` was
invalid if the it contained a template ref as would be generated
using the `else` micro-syntax of `NgIf`.

Fixes: #19485

PR Close #20463

packages/compiler-cli/test/diagnostics/check_types_spec.ts

@@ -87,6 +87,23 @@ describe('ng type checker', () => {
     addTests({fullTemplateTypeCheck: true});
   });
 
+  describe('regressions', () => {
+    // #19485
+    it('should accept if else (TemplateRef)', () => {
+      accept(
+          {
+            'src/app.component.html': `
+              <div class="text-center" *ngIf="!person; else e">
+                No person supplied.
+              </div>
+              <ng-template #e>
+                Welcome {{person.name}}!
+              <ng-template>`
+          },
+          {fullTemplateTypeCheck: true});
+    });
+  });
+
   function addTests(config: {fullTemplateTypeCheck: boolean}) {
     function a(template: string) { accept({'src/app.component.html': template}, config); }
 
@@ -234,6 +251,7 @@ const QUICKSTART = {
   `,
   'src/app.module.ts': `
     import { NgModule }      from '@angular/core';
+    import { CommonModule }  from '@angular/common';
     import { AppComponent, APipe, ADirective }  from './app.component';
     import { LibDirective, LibPipe } from './lib';
 
@@ -246,7 +264,7 @@ const QUICKSTART = {
     @NgModule({
       declarations: [ AppComponent, APipe, ADirective ],
       bootstrap:    [ AppComponent ],
-      imports:      [ LibModule ]
+      imports:      [ LibModule, CommonModule ]
     })
     export class AppModule { }
   `

packages/compiler/src/aot/compiler.ts

@@ -206,11 +206,16 @@ export class AotCompiler {
       // and they also cause TypeScript to include these files into the program too,
       // which will make them part of the analyzedFiles.
       const externalReferences: StaticSymbol[] = [
+        // Add references that are available from all the modules and imports.
         ...ngModuleMeta.transitiveModule.directives.map(d => d.reference),
         ...ngModuleMeta.transitiveModule.pipes.map(d => d.reference),
         ...ngModuleMeta.importedModules.map(m => m.type.reference),
         ...ngModuleMeta.exportedModules.map(m => m.type.reference),
+
+        // Add references that might be inserted by the template compiler.
+        ...this._externalIdentifierReferences([Identifiers.TemplateRef, Identifiers.ElementRef]),
       ];
+
       const externalReferenceVars = new Map<any, string>();
       externalReferences.forEach((ref, typeIndex) => {
         if (this._host.isSourceFile(ref.filePath)) {
@@ -248,6 +253,17 @@ export class AotCompiler {
     }
   }
 
+  private _externalIdentifierReferences(references: o.ExternalReference[]): StaticSymbol[] {
+    const result: StaticSymbol[] = [];
+    for (let reference of references) {
+      const token = createTokenForExternalReference(this._reflector, reference);
+      if (token.identifier) {
+        result.push(token.identifier.reference);
+      }
+    }
+    return result;
+  }
+
   private _createTypeCheckBlock(
       ctx: OutputContext, componentId: string, moduleMeta: CompileNgModuleMetadata,
       compMeta: CompileDirectiveMetadata, directives: CompileIdentifierMetadata[],