Allow generic signature superclass constraints to contain type parameters #1263
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| @@ -5,6 +5,12 @@ Swift 3 | |||
| * Curried function syntax has been removed, and now produces a compile-time | |||
| error. | |||
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| * Generic signatures can now contain superclass requirements with dependent types, | |||
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"Dependent types" might give people the wrong impression. 'Superclass requirements involving generic parameters' should be clearer.
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@DougGregor You're right, I believe some compiler_crashers regressed because I was overwriting Superclass. I didn't realize it was an instance variable (can we have mandatory 'this' in C++? Just kidding :-) ) |
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Just give your class a dependent template base class to get mandatory |
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| diag::recursive_superclass_constraint, | ||
| Superclass); | ||
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| superclass = Type(); |
…ontain type parameters There was a diagnostic to catch these, but it wasn't triggered reliably, and it sounds like users were already relying on this feature working in the few cases where it did. So instead, just map an archetype's superclass into context when building the archetype. Recursion is still not allowed and is diagnosed, for example <T, U where T : C<U>, U : C<T>>. Note that compiler_crashers_fixed/00022-no-stacktrace.swift no longer produces a diagnostic in Sema, despite the fact that the code is invalid. It does diagnose in IRGen when we map the type into context. Diagnosing in Sema requires fixing the declaration checker to correctly handle recursion through a generic signature. Right now, if recursion is detected, we bail out, but do not always diagnose. Alternatively, we could prohibit unbound generic types from appearing in generic signatures. This is a more principled fix for rdar://problem/24590570.
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@DougGregor, @jckarter Can you take a quick look?
This is NOT for Swift 2.2.