Swift: syntax ambiguity in generic constraints
| Originator: | d | ||
| Number: | rdar://23919603 | Date Originated: | 16-Dec-2015 03:27 PM |
| Status: | Open | Resolved: | |
| Product: | Developer Tools | Product Version: | Swift 2.1.1 |
| Classification: | Serious Bug | Reproducible: | Always |
Summary:
There’s an ambiguity case in Swift’s generic constraint syntax that happens when specifying more than one generic types, the first one needing to be constrained using `where`.
Long story short, the compiler interprets the second generic type as part of the `where` statement.
Steps to Reproduce:
```
protocol Protocol1 { }
protocol Protocol2 { }
class Class { }
class GenericClass<A: Class where A: Protocol1, B: Protocol2> {
}
```
Expected Results:
Swift interprets GenericClass<A, B>.
Actual Results:
Swift interprets GenericClass<A>, and throws an error because B is implicitly part of the `where` statement (which it shouldn’t).
Error: “Use of undeclared type B”
Comments
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