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c948128902
Consider a snippet like:
```
const x = directiveDef.inputs || EMPTY_OBJ
```
this currently results in `x` being inferred as just `{}`- ending up
turning of potential future assignment checks. This surfaced in the
`DirectiveDefinition` -> `DirectiveDef` conversion.
Note: This has the effect that assigning `EMPTY_OBJ` to a field of
anything would _always_ pass. It's questionable if this rather impacts
type-safety in a more negative way. There seem to be trade-offs in both
ways... Maybe worth considering just using `{}` directly as fallbacks in
some places, and treating this as an unique symbol?!
https://www.typescriptlang.org/play?#code/MYewdgzgLgBAHgLhmApgNxQJxgXhgbwF8YBDCZdLAbgCgbRJYAHJfGmDmAGxC6SkwBXFABoahAD6CwAExQAzAJaoZuZIK5dS5EmACeteuGgxBapjAkT4VIA
PR Close #53571
28 lines
1.1 KiB
TypeScript
28 lines
1.1 KiB
TypeScript
/**
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* @license
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* Copyright Google LLC All Rights Reserved.
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*
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* Use of this source code is governed by an MIT-style license that can be
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* found in the LICENSE file at https://angular.io/license
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*/
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import {initNgDevMode} from './ng_dev_mode';
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/**
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* This file contains reuseable "empty" symbols that can be used as default return values
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* in different parts of the rendering code. Because the same symbols are returned, this
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* allows for identity checks against these values to be consistently used by the framework
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* code.
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*/
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export const EMPTY_OBJ: never = {} as never;
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export const EMPTY_ARRAY: any[] = [];
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// freezing the values prevents any code from accidentally inserting new values in
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if ((typeof ngDevMode === 'undefined' || ngDevMode) && initNgDevMode()) {
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// These property accesses can be ignored because ngDevMode will be set to false
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// when optimizing code and the whole if statement will be dropped.
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// tslint:disable-next-line:no-toplevel-property-access
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Object.freeze(EMPTY_OBJ);
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// tslint:disable-next-line:no-toplevel-property-access
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Object.freeze(EMPTY_ARRAY);
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}
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