Add `StaticString` implementation #31

MaxDesiatov · 2022-02-18T13:56:32Z

This implementation excludes a few properties that rely on precondition, which will be submitted as a separate PR.

MaxDesiatov · 2022-02-18T13:59:34Z

Sources/Core/UInt8.swift

+  }
+
+  @_transparent
+  public static func &= (lhs: inout UInt8, rhs: UInt8) {


These operators are required for StaticString flag checks. I'll move them to a corresponding numeric protocol conformance in a future PR.

MaxDesiatov · 2022-02-18T14:04:45Z

Build failure due to

StaticString.swift.obj : error LNK2019: 
unresolved external symbol swift_getTypeByMangledNameInContext referenced in function __swift_instantiateConcreteTypeFromMangledName

StaticString.swift.obj : error LNK2019: 
unresolved external symbol swift_getWitnessTable referenced in function $sSPys5UInt8VGSPyxGs8_PointersWl

StaticString.swift.obj : error LNK2019: 
unresolved external symbol swift_getTypeByMangledNameInContextInMetadataState referenced in function __swift_instantiateConcreteTypeFromMangledNameAbstract

$sSPys5UInt8VGSPyxGs8_PointersWl demangles to lazy protocol witness table accessor for type Swift.UnsafePointer<Swift.UInt8> and conformance Swift.UnsafePointer<A> : Swift._Pointer in Swift

I wonder if there's some way to specialize UnsafePointer<UInt8> to work around this?

MaxDesiatov · 2022-02-18T14:58:17Z

Tried to monomorphize that call to UnsafePointer(bitPattern:) by adding @inline(__always), but that didn't help, and @_specialize(exported: true, kind: full, where Pointee == UInt8) can apparently only be applied to generic functions?

MaxDesiatov · 2022-02-18T15:40:15Z

Ok, I removed utf8Start for now, but looks like code in OpaquePointer is still too complex for the release versions of the compiler 🤷‍♂️

compnerd · 2022-02-18T16:21:41Z

I tend to prefer that the changes are focused rather than a grab bag of changes. That makes it too difficult to focus on one thing. Please split this up accordingly.

Additionally, I'm not sure I want to add CMake toolchain configurations, especially the way that you have setup the cache file. It encodes much about the build environment. For example, I wish to build on Windows with MSVC 2022 to target ARM but that cache file doesn't work :) (or perhaps I want to build on exherbo Linux).

MaxDesiatov · 2022-02-18T16:25:05Z

I tend to prefer that the changes are focused rather than a grab bag of changes. That makes it too difficult to focus on one thing. Please split this up accordingly.

Sure, I can move out the .gitignore commit to a separate PR, but StaticString and pointer additions would have to be bundled, is that ok?

What about new metadata requirements, would you like utf8Start implementation to be postponed? This should not imply adding any Unicode/ICU dependencies, but apparently utf8Start is required to iterate over characters in StaticString for printing and such. And this raises a more general point of generics and metadata. Should we avoid generics altogether for now, and hide APIs requiring generics behind a flag? Is there any other way to prevent these dependencies on metadata symbols from being emitted?

compnerd · 2022-02-19T02:11:02Z

I think that we can split out the pointer changes, assertion changes, and static string changes. StaticString is definitely a type that I would like to see sooner rather than later, but splitting up the changes makes it easier to test.

As to the build failures, I don't think its the end of the world if we cannot support 5.4, but it would be nice to retain support for 5.5 - stable, development would be nice. If we cannot manage to do that, I'd be willing to settle for 5.6 + main.

Sources/Core/Policy.swift

compnerd · 2022-02-19T23:41:20Z

Sources/Core/CompilerProtocols.swift

 }
+
+public protocol _ExpressibleByBuiltinStringLiteral {
+  init(


Please don't break immediately after the (, prefer to bin-pack the arguments.

What column limit would you like to set? Would something like 100 or 120 work?

Sources/Core/CompilerProtocols.swift