fix(compiler): narrow the type of the aliased if block expression#51952
fix(compiler): narrow the type of the aliased if block expression#51952crisbeto wants to merge 1 commit intoangular:mainfrom
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What about this case? Where we alias the expr, but still use the expr and not the alias? @if (expr; as alias) {
{{expr}}
}Asking because of this comment Test in Ts playground
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That case isn't a problem since the generated code will always read the value off of the context: 
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My question was more for the TCB?
It looks like the TCB will always create the alias and use that one inside if. @if (expr; as alias) {
{{expr}}
{{alias}}
}would it generate this one? var _t1 = ((this).expr);
if (_t1) {
"" + ((this).expr); // this.expr will be catched ?
"" + _t1;
}IMO, the correct one would be sth like: var _t1 = ((this).expr);
if (_t1 && ((this).expr)) {
"" + ((this).expr);
"" + _t1;
} |
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Yes it would, but it's not worth the additional effort to deduplicate it since this is only used during type checking so we don't care about the size of the code. |
dylhunn
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Looks straightforward. Thanks for fixing this!
Currently the TCB for aliased `if` blocks looks something like this:
```
// Markup: `@if (expr; as alias) { {{alias}} }
if (block.condition) {
var alias = block.condition;
"" + alias;
}
```
The problem with this approach is that the type of `alias` won't be narrowed. This is something that `NgIf` currently supports.
These changes resolve the issue by emitting the variable outside the `if` block and using the variable reference instead:
```
// Markup: `@if (expr; as alias) { {{alias}} }
var alias = block.condition;
if (alias) {
"" + alias;
}
```
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This PR was merged into the repository by commit 02edb43. |
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…gular#51952) Currently the TCB for aliased `if` blocks looks something like this: ``` // Markup: `@if (expr; as alias) { {{alias}} } if (block.condition) { var alias = block.condition; "" + alias; } ``` The problem with this approach is that the type of `alias` won't be narrowed. This is something that `NgIf` currently supports. These changes resolve the issue by emitting the variable outside the `if` block and using the variable reference instead: ``` // Markup: `@if (expr; as alias) { {{alias}} } var alias = block.condition; if (alias) { "" + alias; } ``` PR Close angular#51952
Currently the TCB for aliased
ifblocks looks something like this:The problem with this approach is that the type of
aliaswon't be narrowed. This is something thatNgIfcurrently supports.These changes resolve the issue by emitting the variable outside the
ifblock and using the variable reference instead: