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JoostK 2a2744721b fix(compiler-cli): ensure literal types are retained when strictNullInputTypes is disabled (#38305 )

Consider the `NgModel` directive which has the `ngModelOptions` input:

```ts
class NgModel {
  @Input() ngModelOptions: { updateOn: 'blur'|'change'|'submit' };
}
```

In a template this may be set using an object literal as follows:

```html
<input ngModel [ngModelOptions]="{updateOn: 'blur'}">
```

This assignment should be accepted, as the object's type aligns with the
`ngModelOptions` input in `NgModel`. However, if the `strictNullInputTypes`
option is disabled this assignment would inadvertently produce an error:

```
Type '{ updateOn: string; }' is not assignable to type '{ updateOn: "blur"|"change"|"submit"; }'.
  Types of property 'updateOn' are incompatible.
    Type 'string' is not assignable to type '"blur"|"change"|"submit"'
```

This is due to the `'blur'` value being inferred to be of type `string`
instead of retaining its literal type. The non-null assertion operator
that is automatically inserted for input binding assignments when
`strictNullInputTypes` is disabled inhibits TypeScript from inferring
the string value as its literal type.

This commit fixes the issue by omitting the insertion of the non-null
operator for object literals and array literals.

PR Close #38305

2021-11-09 18:01:24 +00:00