fix(compiler-cli): resolve type of exported *ngIf variable. (#33016)

Currently, method `getVarDeclarations()` does not try to resolve the type of
exported variable from *ngIf directive. It always returns `any` type.
By resolving the real type of exported variable, it is now possible to use this
type information in language service and provide completions, go to definition
and quick info functionality in expressions that use exported variable.
Also language service will provide more accurate diagnostic errors during
development.

PR Close #33016

packages/compiler-cli/src/diagnostics/expression_diagnostics.ts

@@ -154,6 +154,19 @@ function refinedVariableType(
     }
   }
 
+  // Special case the ngIf directive ( *ngIf="data$ | async as variable" )
+  const ngIfDirective =
+      templateElement.directives.find(d => identifierName(d.directive.type) === 'NgIf');
+  if (ngIfDirective) {
+    const ngIfBinding = ngIfDirective.inputs.find(i => i.directiveName === 'ngIf');
+    if (ngIfBinding) {
+      const bindingType = new AstType(info.members, info.query, {}).getType(ngIfBinding.value);
+      if (bindingType) {
+        return bindingType;
+      }
+    }
+  }
+
   // We can't do better, return any
   return info.query.getBuiltinType(BuiltinType.Any);
 }