Regression in pattern matching optional fields. #7440
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Fixes #7400 Fix regression in pattern matching for optional fields. There's an optimisation where `{field: VariantCase}` is compiled to `field:VariantCase` instead of `field:Some(VariantCase)` to avoid generating code that handles undefined, since `VariantCase` is going to be a string. However, that optimisation happens early in the pattern matching compiler, and can end up interfering with other cases. For example, when `VariantCase` is the only case in a variant, and the following case is `_`, the compiler is induced in thinking that the variant case covers all cases, and the case for `_` is never generated. Similar behaviour happens when handling the last case of a variant followed by `_`.
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cristianoc
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May 8, 2025
| @@ -25,7 +25,11 @@ function decodeGroup(group) { | |||
| } | |||
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| function decodeNull(x) { | |||
| let tmp = x.field; | |||
| let match = x.field; | |||
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This has changed because dicts always add optional fields, and in this case it contains a json value, and one of the possible json values is undefined.
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Fixes #7400
Fix regression in pattern matching for optional fields.
There's an optimisation where
{field: VariantCase}is compiled tofield:VariantCaseinstead offield:Some(VariantCase)to avoid generating code that handles undefined, sinceVariantCaseis going to be a string. However, that optimisation happens early in the pattern matching compiler, and can end up interfering with other cases. For example, whenVariantCaseis the only case in a variant, and the following case is_, the compiler is induced in thinking that the variant case covers all cases, and the case for_is never generated. Similar behaviour happens when handling the last case of a variant followed by_.