fix(compiler): support event bindings in `fullTemplateTypeCheck` (#20490)

The type-check block now disables type checking event access instead
of generating a reference to an undefined variable.

PR Close #20490

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

@@ -14,13 +14,16 @@ import * as ts from 'typescript';
 
 import {TestSupport, expectNoDiagnostics, setup} from '../test_support';
 
+type MockFiles = {
+  [fileName: string]: string
+};
+
 describe('ng type checker', () => {
   let errorSpy: jasmine.Spy&((s: string) => void);
   let testSupport: TestSupport;
 
   function compileAndCheck(
-      mockDirs: {[fileName: string]: string}[],
-      overrideOptions: ng.CompilerOptions = {}): ng.Diagnostics {
+      mockDirs: MockFiles[], overrideOptions: ng.CompilerOptions = {}): ng.Diagnostics {
     testSupport.writeFiles(...mockDirs);
     const fileNames: string[] = [];
     mockDirs.forEach((dir) => {
@@ -40,13 +43,12 @@ describe('ng type checker', () => {
     testSupport = setup();
   });
 
-  function accept(
-      files: {[fileName: string]: string} = {}, overrideOptions: ng.CompilerOptions = {}) {
+  function accept(files: MockFiles = {}, overrideOptions: ng.CompilerOptions = {}) {
     expectNoDiagnostics({}, compileAndCheck([QUICKSTART, files], overrideOptions));
   }
 
   function reject(
-      message: string | RegExp, location: RegExp, files: {[fileName: string]: string},
+      message: string | RegExp, location: RegExp, files: MockFiles,
       overrideOptions: ng.CompilerOptions = {}) {
     const diagnostics = compileAndCheck([QUICKSTART, files], overrideOptions);
     if (!diagnostics || !diagnostics.length) {
@@ -79,6 +81,41 @@ describe('ng type checker', () => {
     });
   });
 
+  describe('regressions ', () => {
+    const a = (files: MockFiles, options: object = {}) => {
+      accept(files, {fullTemplateTypeCheck: true, ...options});
+    };
+
+    // #19905
+    it('should accept an event binding', () => {
+      a({
+        'src/app.component.ts': '',
+        'src/lib.ts': '',
+        'src/app.module.ts': `
+        import {NgModule, Component, Directive, HostListener} from '@angular/core';
+
+        @Component({
+          selector: 'comp',
+          template: '<div someDir></div>'
+        })
+        export class MainComp {}
+
+        @Directive({
+          selector: '[someDir]'
+        })
+        export class SomeDirective {
+          @HostListener('click', ['$event'])
+          onClick(event: any) {}
+        }
+
+        @NgModule({
+          declarations: [MainComp, SomeDirective],
+        })
+        export class MainModule {}`
+      });
+    });
+  });
+
   describe('with modified quickstart (fullTemplateTypeCheck: false)', () => {
     addTests({fullTemplateTypeCheck: false});
   });

packages/compiler/src/view_compiler/type_check_compiler.ts

@@ -69,6 +69,19 @@ interface Expression {
 
 const DYNAMIC_VAR_NAME = '_any';
 
+class TypeCheckLocalResolver implements LocalResolver {
+  getLocal(name: string): o.Expression|null {
+    if (name === EventHandlerVars.event.name) {
+      // References to the event should not be type-checked.
+      // TODO(chuckj): determine a better type for the event.
+      return o.variable(DYNAMIC_VAR_NAME);
+    }
+    return null;
+  }
+}
+
+const defaultResolver = new TypeCheckLocalResolver();
+
 class ViewBuilder implements TemplateAstVisitor, LocalResolver {
   private refOutputVars = new Map<string, OutputVarType>();
   private variables: VariableAst[] = [];
@@ -112,7 +125,7 @@ class ViewBuilder implements TemplateAstVisitor, LocalResolver {
     this.updates.forEach((expression) => {
       const {sourceSpan, context, value} = this.preprocessUpdateExpression(expression);
       const bindingId = `${bindingCount++}`;
-      const nameResolver = context === this.component ? this : null;
+      const nameResolver = context === this.component ? this : defaultResolver;
       const {stmts, currValExpr} = convertPropertyBinding(
           nameResolver, o.variable(this.getOutputVar(context)), value, bindingId);
       stmts.push(new o.ExpressionStatement(currValExpr));
@@ -122,7 +135,7 @@ class ViewBuilder implements TemplateAstVisitor, LocalResolver {
 
     this.actions.forEach(({sourceSpan, context, value}) => {
       const bindingId = `${bindingCount++}`;
-      const nameResolver = context === this.component ? this : null;
+      const nameResolver = context === this.component ? this : defaultResolver;
       const {stmts} = convertActionBinding(
           nameResolver, o.variable(this.getOutputVar(context)), value, bindingId);
       viewStmts.push(...stmts.map(