Meta-issue for NNBD no-implicit-downcast and int/double operations. #725
Comments
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Here's a feature which is related to this request: Case functions (#148) are designed to make it possible to have a single function with multiple static typings, e.g., such that The point is that the function can have several "cases" in the body, and they are at the same time available for static selection (so we can make the choice to call a specific case at a given call site, which will give use good performance and tight typing), and the function still works as a whole (where the cases work basically like a regular type case statement) such that it can be invoked dynamically, torn off, etc. That approach would allow us to handle a number of cases that otherwise seem to call for special exceptions. |
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Is this resolved now with the num updates? |
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I believe so, with the analyzer having implemented this, we are done. |
The Dart
intanddoubletypes have special rules in the static type system which allows, effectively, limited overloading on the types of operations. For example ifxhas static typeintthenx + xhas static type int, even though the signature ofint.operator+isnum Function(num).Other operations are not special-cased and always return
num, but they always work in practice because of the implicit downcast fromnumto the type the user expects. For examplepowfromdart:mathalways returnnum, but it promises thatpow(2, 8)is an integer because both arguments are (positive) integers.When NNBD removes implicit downcast, some numeric operations will become much less usable in practice, and may require adding explicit downcasts in non-obvious places.
This issue tries to collect issues related to this in the hope that we can solve them in a unified way.
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