Structural directives can now specify a type guard that describes
what types can be inferred for an input expression inside the
directive's template.
NgIf was modified to declare an input guard on ngIf.
After this change, `fullTemplateTypeCheck` will infer that
usage of `ngIf` expression inside it's template is truthy.
For example, if a component has a property `person?: Person`
and a template of `<div *ngIf="person"> {{person.name}} </div>`
the compiler will no longer report that `person` might be null or
undefined.
The template compiler will generate code similar to,
```
if (NgIf.ngIfTypeGuard(instance.person)) {
instance.person.name
}
```
to validate the template's use of the interpolation expression.
Calling the type guard in this fashion allows TypeScript to infer
that `person` is non-null.
Fixes: #19756?
PR Close#20702
The errors produced when error were encountered while interpreting the
content of a directive was often incomprehencible. With this change
these kind of error messages should be easier to understand and diagnose.
PR Close#20459
Also adds auto upgrade from lower version based
on the .d.ts file (e.g. from version 3 to 4).
This is needed as we are now also capturing type aliases
in metadata files (and we rely on this),
see 6e3498ca8e.
- temporarily keeps the old sources under packages/tsc-wrapped
until the build scripts are changed to use compiler-cli everywhere.
- removes the compiler options `disableTransformerPipeline` that was introduced
in a previous beta of Angular 5, i.e. the transformer based compiler
is now always enabled.
PR Close#18966
Chuck Jazdzewski
Alex Eagle
Tobias Bosch
Matias Niemelä