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
This commit is contained in:
JoostK
2020-07-04 01:52:40 +02:00
committed by Misko Hevery
parent e7da4040d6
commit 874792dc43
23 changed files with 313 additions and 23 deletions

View File

@ -1656,7 +1656,7 @@ Reference "#a" is defined several times ("<div #a></div><div [ERROR ->]#a></div>
expect(humanizeTplAst(parse('<div *ngIf="-1">', [ngIf]))).toEqual([
[EmbeddedTemplateAst],
[DirectiveAst, ngIf],
[BoundDirectivePropertyAst, 'ngIf', '0 - 1'],
[BoundDirectivePropertyAst, 'ngIf', '-1'],
[ElementAst, 'div'],
]);
});