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feat(compiler): allow ngIf to use the ngIf expression directly as a guard - #20972
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…uard Allows a directive to use the expression passed directly to a property as a guard instead of filtering the type through a type expression. This more accurately matches the intent of the ngIf usage of its template enabling better type inference. Moved NgIf to using this type of guard instead of a function guard. Closes: angular#20967
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You can preview c97ce64 at https://pr20972-c97ce64.ngbuilds.io/. |
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PullApprove broken, Misko approved. |
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Allows a directive to use the expression passed directly to a property
as a guard instead of filtering the type through a type guard function.
This more accurately matches the intent of the ngIf usage of its template
enabling better type inference.
Moved NgIf to using this type of guard instead of a function guard.
Closes: #20967
PR Type
What kind of change does this PR introduce?
What is the current behavior?
#20967
Using the type guard mechanism introduced in e7d9cb3 the following expression is not narrowed as expected.
because the type guard function only infers that the expression
!!personis true but does not further infer that implies person is notundefinedcausingperson.nameto report thatpersonmight beundefined.What is the new behavior?
The code generated for an
*ngIfuses the guard expression directly as the template guard instead of using a type guard function. This allows TypeScript to infer the correct types forpersonin the above example.Does this PR introduce a breaking change?