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19 April 2024, 08:24:33 UTC
Revision 874792dc43a70dc55c9b926807ca6bbcb5cafb9e authored by JoostK on 03 July 2020, 23:52:40 UTC, committed by Misko Hevery on 21 August 2020, 19:25:53 UTC 
feat(compiler): support unary operators for more accurate type checking (#37918)
 
Prior to this change, the unary + and - operators would be parsed as `x - 0`
and `0 - x` respectively. The runtime semantics of these expressions are
equivalent, however they may introduce inaccurate template type checking
errors as the literal type is lost, for example:

```ts
@Component({
  template: `<button [disabled]="isAdjacent(-1)"></button>`
})
export class Example {
  isAdjacent(direction: -1 | 1): boolean { return false; }
}
```

would incorrectly report a type-check error:

> error TS2345: Argument of type 'number' is not assignable to parameter
  of type '-1 | 1'.

Additionally, the translated expression for the unary + operator would be
considered as arithmetic expression with an incompatible left-hand side:

> error TS2362: The left-hand side of an arithmetic operation must be of
  type 'any', 'number', 'bigint' or an enum type.

To resolve this issues, the implicit transformation should be avoided.
This commit adds a new unary AST node to represent these expressions,
allowing for more accurate type-checking.

Fixes #20845
Fixes #36178

PR Close #37918
1 parent e7da404
History
Tip revision: 874792dc43a70dc55c9b926807ca6bbcb5cafb9e authored by JoostK on 03 July 2020, 23:52:40 UTC
feat(compiler): support unary operators for more accurate type checking (#37918)
Tip revision: 874792d
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