[compiler] Check TSAsExpression and TSNonNullExpression reorderability #33788
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josephsavona
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Jul 15, 2025
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Thanks for the PR! The changes make sense. A small nit on the test fixture. It would be nice to change this (lest someone say "but there's a test fixture that uses it, it must be allowed!"), but we can land as-is if you like.
| @@ -0,0 +1,8 @@ | |||
| export const Component = ({theme = localStorage.getItem('theme')!}) => { | |||
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I know it's just an example, but localStorage is a mutable data source that isn't safe to read from in a component.
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Thanks @josephsavona. I ammended my commit to remove the localStorage usage from the fixture. I was struggling to come up with a contrived example.
…lity The TSAsExpression and TSNonNullExpression nodes are supported by `lowerExpression()` but `isReorderableExpression()` does not check if they can be reordered.
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#33788) ## Summary The `TSAsExpression` and `TSNonNullExpression` nodes are supported by `lowerExpression()` but `isReorderableExpression()` does not check if they can be reordered. This PR updates `isReorderableExpression()` to handle these two node types by adding cases that fall through to the existing `TypeCastExpression` case. We ran `react-compiler-healthcheck` at scale on several of our repos and found dozens of `` (BuildHIR::node.lowerReorderableExpression) Expression type `TSAsExpression` cannot be safely reordered`` errors and a handful for `TSNonNullExpression`. ## How did you test this change? In this case I added two fixture tests DiffTrain build for [fe81314](fe81314)
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#33788) ## Summary The `TSAsExpression` and `TSNonNullExpression` nodes are supported by `lowerExpression()` but `isReorderableExpression()` does not check if they can be reordered. This PR updates `isReorderableExpression()` to handle these two node types by adding cases that fall through to the existing `TypeCastExpression` case. We ran `react-compiler-healthcheck` at scale on several of our repos and found dozens of `` (BuildHIR::node.lowerReorderableExpression) Expression type `TSAsExpression` cannot be safely reordered`` errors and a handful for `TSNonNullExpression`. ## How did you test this change? In this case I added two fixture tests DiffTrain build for [fe81314](fe81314)
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facebook#33788) ## Summary The `TSAsExpression` and `TSNonNullExpression` nodes are supported by `lowerExpression()` but `isReorderableExpression()` does not check if they can be reordered. This PR updates `isReorderableExpression()` to handle these two node types by adding cases that fall through to the existing `TypeCastExpression` case. We ran `react-compiler-healthcheck` at scale on several of our repos and found dozens of `` (BuildHIR::node.lowerReorderableExpression) Expression type `TSAsExpression` cannot be safely reordered`` errors and a handful for `TSNonNullExpression`. ## How did you test this change? In this case I added two fixture tests DiffTrain build for [fe81314](facebook@fe81314)
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facebook#33788) ## Summary The `TSAsExpression` and `TSNonNullExpression` nodes are supported by `lowerExpression()` but `isReorderableExpression()` does not check if they can be reordered. This PR updates `isReorderableExpression()` to handle these two node types by adding cases that fall through to the existing `TypeCastExpression` case. We ran `react-compiler-healthcheck` at scale on several of our repos and found dozens of `` (BuildHIR::node.lowerReorderableExpression) Expression type `TSAsExpression` cannot be safely reordered`` errors and a handful for `TSNonNullExpression`. ## How did you test this change? In this case I added two fixture tests DiffTrain build for [fe81314](facebook@fe81314)
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Summary
The
TSAsExpressionandTSNonNullExpressionnodes are supported bylowerExpression()butisReorderableExpression()does not check if they can be reordered. This PR updatesisReorderableExpression()to handle these two node types by adding cases that fall through to the existingTypeCastExpressioncase.We ran
react-compiler-healthcheckat scale on several of our repos and found dozens of(BuildHIR::node.lowerReorderableExpression) Expression type `TSAsExpression` cannot be safely reorderederrors and a handful forTSNonNullExpression.How did you test this change?
In this case I added two fixture tests