JoostK 40039d8068 fix(ivy): narrow NgIf context variables in template type checker (#35125)
When the `NgIf` directive is used in a template, its context variables
can be used to capture the bound value. This is typically used together
with a pipe or function call, where the resulting value is captured in a
context variable. There's two syntax forms available:

1. Binding to `NgIfContext.ngIf` using the `as` syntax:
```html
<span *ngIf="(user$ | async) as user">{{user.name}}</span>
```

2. Binding to `NgIfContext.$implicit` using the `let` syntax:
```html
<span *ngIf="user$ | async; let user">{{user.name}}</span>
```

Because of the semantics of `ngIf`, it is known that the captured
context variable is non-nullable, however the template type checker
would not consider them as such and still report errors when
`strictNullTypes` is enabled.

This commit updates `NgIf`'s context guard to make the types of the
context variables non-nullable, avoiding the issue.

Fixes #34572

PR Close #35125
2020-02-28 07:39:57 -08:00
..
2020-01-13 07:21:43 -08:00

Angular

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Usage information and reference details can be found in Angular documentation.

License: MIT