fix(language-service): infer context type of structural directives (#35537) (#35561)

PR Close #35561

packages/language-service/test/diagnostics_spec.ts

@@ -286,6 +286,42 @@ describe('diagnostics', () => {
       expect(start).toBe(span.start);
       expect(length).toBe(span.length);
     });
+
+    it('report an unknown field in $implicit context', () => {
+      mockHost.override(TEST_TEMPLATE, `
+        <div *withContext="let myVar">
+          {{ ~{start-emb}myVar.missingField ~{end-emb}}}
+        </div>
+      `);
+      const diags = ngLS.getSemanticDiagnostics(TEST_TEMPLATE);
+      expect(diags.length).toBe(1);
+      const {messageText, start, length, category} = diags[0];
+      expect(category).toBe(ts.DiagnosticCategory.Error);
+      expect(messageText)
+          .toBe(
+              `Identifier 'missingField' is not defined. '{ implicitPerson: Person; }' does not contain such a member`, );
+      const span = mockHost.getLocationMarkerFor(TEST_TEMPLATE, 'emb');
+      expect(start).toBe(span.start);
+      expect(length).toBe(span.length);
+    });
+
+    it('report an unknown field in non implicit context', () => {
+      mockHost.override(TEST_TEMPLATE, `
+        <div *withContext="let myVar = nonImplicitPerson">
+          {{ ~{start-emb}myVar.missingField ~{end-emb}}}
+        </div>
+      `);
+      const diags = ngLS.getSemanticDiagnostics(TEST_TEMPLATE);
+      expect(diags.length).toBe(1);
+      const {messageText, start, length, category} = diags[0];
+      expect(category).toBe(ts.DiagnosticCategory.Error);
+      expect(messageText)
+          .toBe(
+              `Identifier 'missingField' is not defined. 'Person' does not contain such a member`, );
+      const span = mockHost.getLocationMarkerFor(TEST_TEMPLATE, 'emb');
+      expect(start).toBe(span.start);
+      expect(length).toBe(span.length);
+    });
   });
 
   // #17611

packages/language-service/test/project/app/main.ts

@@ -43,6 +43,7 @@ import * as ParsingCases from './parsing-cases';
     ParsingCases.StringModel,
     ParsingCases.TemplateReference,
     ParsingCases.TestComponent,
+    ParsingCases.WithContextDirective,
   ]
 })
 export class AppModule {

packages/language-service/test/project/app/parsing-cases.ts

@@ -127,6 +127,21 @@ export class CounterDirective implements OnChanges {
   }
 }
 
+interface WithContextDirectiveContext {
+  $implicit: {implicitPerson: Person;};
+  nonImplicitPerson: Person;
+}
+
+@Directive({selector: '[withContext]'})
+export class WithContextDirective {
+  constructor(_template: TemplateRef<WithContextDirectiveContext>) {}
+
+  static ngTemplateContextGuard(dir: WithContextDirective, ctx: unknown):
+      ctx is WithContextDirectiveContext {
+    return true;
+  }
+}
+
 /**
  * This Component provides the `test-comp` selector.
  */