Andrew Trick 1b72c7bbf6 SILGenCleanup: extend to handle trivial local var scopes ...

Improves OSSALifetimeCompletion to handle trivial variables when running from
SILGenCleanup. This only affects lifetime dependence diagnostics.

For the purpose of lifetime diagnostics, trivial local variables are only valid
within their lexical scope. Sadly, SILGen only know how to insert cleanup code
on normal function exits. SILGenCleanup relies on lifetime completion to fix
lifetimes on dead end paths.

  %var = move_value [var_decl]
  try_apply %f() : $..., normal bb1, error error
error:
  extend_lifetime %var <=== insert this
  unreachable

This allows Span to depend on local unsafe pointers AND be used within
throwing closures:

    _ = a.withUnsafeBufferPointer {
      let buffer = $0
      let view = Span(_unsafeElements: buffer)
      return view.withUnsafeBufferPointer(\.count)
    }

2025-01-23 12:42:43 -08:00

14 KiB

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