fix(compiler-cli): Produce diagnostic rather than crash when using invalid hostDirective (#48314)

Because the language service uses the compiler, we try to produce as
much useful information as possible rather than throwing hard errors.
Hard errors cause the compiler to crash. While this can be acceptable
when compiling a program as part of a regular build, this is undesirable
for the language service.

PR Close #48314

packages/compiler-cli/test/ngtsc/host_directives_spec.ts

@@ -451,6 +451,24 @@ runInEachFileSystem(() => {
         expect(messages).toEqual(['Host directive HostDir must be standalone']);
       });
 
+      it('should produce a diagnostic if a host directive is not a directive', () => {
+        env.write('test.ts', `
+          import {Directive, Pipe, Component, NgModule} from '@angular/core';
+
+          @Pipe({name: 'hostDir'})
+          export class HostDir {}
+
+          @Directive({
+            hostDirectives: [HostDir],
+          })
+          export class Dir {}
+        `);
+
+        const messages = env.driveDiagnostics().map(extractMessage);
+        expect(messages).toEqual(
+            ['HostDir must be a standalone directive to be used as a host directive']);
+      });
+
       it('should produce a diagnostic if a host directive is a component', () => {
         env.write('test.ts', `
           import {Directive, Component, NgModule} from '@angular/core';