173a1ac8e4
It's possible to pass a directive as an input to itself. Consider:
```html
<some-cmp #ref [value]="ref">
```
Since the template type-checker attempts to infer a type for `<some-cmp>`
using the values of its inputs, this creates a circular reference where the
type of the `value` input is used in its own inference:
```typescript
var _t0 = SomeCmp.ngTypeCtor({value: _t0});
```
Obviously, this doesn't work. To resolve this, the template type-checker
used to generate a `null!` expression when a reference would otherwise be
circular:
```typescript
var _t0 = SomeCmp.ngTypeCtor({value: null!});
```
This effectively asks TypeScript to infer a value for this context, and
works well to resolve this simple cycle. However, if the template
instead tries to use the circular value in a larger expression:
```html
<some-cmp #ref [value]="ref.prop">
```
The checker would generate:
```typescript
var _t0 = SomeCmp.ngTypeCtor({value: (null!).prop});
```
In this case, TypeScript can't figure out any way `null!` could have a
`prop` key, and so it infers `never` as the type. `(never).prop` is thus a
type error.
This commit implements a better fallback pattern for circular references to
directive types like this. Instead of generating a `null!` in place for the
reference, a type is inferred by calling the type constructor again with
`null!` as its input. This infers the widest possible type for the directive
which is then used to break the cycle:
```typescript
var _t0 = SomeCmp.ngTypeCtor(null!);
var _t1 = SomeCmp.ngTypeCtor({value: _t0.prop});
```
This has the desired effect of validating that `.prop` is legal for the
directive type (the type of `#ref`) while also avoiding a cycle.
Fixes #35372
Fixes #35603
Fixes #35522
PR Close #35622
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|---|---|---|
| .. | ||
| animations | ||
| bazel | ||
| benchpress | ||
| common | ||
| compiler | ||
| compiler-cli | ||
| core | ||
| docs | ||
| elements | ||
| examples | ||
| forms | ||
| http | ||
| language-service | ||
| localize | ||
| platform-browser | ||
| platform-browser-dynamic | ||
| platform-server | ||
| platform-webworker | ||
| platform-webworker-dynamic | ||
| private/testing | ||
| router | ||
| service-worker | ||
| upgrade | ||
| zone.js | ||
| BUILD.bazel | ||
| README.md | ||
| empty.ts | ||
| goog.d.ts | ||
| license-banner.txt | ||
| system.d.ts | ||
| tsconfig-build-no-strict.json | ||
| tsconfig-build.json | ||
| tsconfig-test.json | ||
| tsconfig.json | ||
| types.d.ts | ||
README.md
Angular
The sources for this package are in the main Angular repo. Please file issues and pull requests against that repo.
Usage information and reference details can be found in Angular documentation.
License: MIT