[cxx-interop] Work around crash in codegen when initializing C++ span #81030
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When initializing span with an UnsafePointer<Element>? we call into the generic initializer that we imported from the C++ templated constructor instead of the concrete initializer we have in the overlay that takes an UnsafePointer<Element> (non-optional). We cannot properly codegen for this generic initializer at the moment, so let's stop importing them since the user probably wanted to call the initializer from the overlay. We should come back later and fix the root cause. rdar://148961349
Xazax-hun
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ian-twilightcoder
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j-hui
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Apr 23, 2025
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… span Explanation: C++ templates are imported as Swift generics. Unfortunately, the codegen for some of the instantiations will crash codegen due to a confusion in how Swift pointer types are mapped back to their native counterparts. As a result, when a user is passing an UnsafePointer<Element>? to a C++ span constructor we got a crash. The user should never need the generic version of the initializer as we already have an initializer taking an UnsafePointer<Element> in the C++ overlay. This PR avoids importing the templated span constructors to work around this issue. Issue: rdar://148961349 Risk: Low, the fix is very targeted. Testing: Regression test added. Original PR: #81030 Reviewer: @j-hui
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When initializing span with an UnsafePointer? we call into the generic initializer that we imported from the C++ templated constructor instead of the concrete initializer we have in the overlay that takes an UnsafePointer (non-optional). We cannot properly codegen for this generic initializer at the moment, so let's stop importing them since the user probably wanted to call the initializer from the overlay.
We should come back later and fix the root cause.
rdar://148961349