[MacPorts] #68036: lib2geom: build failure for 10.13: cannot use parentheses when declaring variable with deduced class template specialization type

[MacPorts]

#68036: lib2geom: build failure for 10.13: cannot use parentheses when declaring
variable with deduced class template specialization type
-------------------------+----------------------
  Reporter:  dyne2meter  |      Owner:  mascguy
      Type:  defect      |     Status:  assigned
  Priority:  Normal      |  Milestone:
 Component:  ports       |    Version:  2.8.1
Resolution:              |   Keywords:
      Port:  lib2geom    |
-------------------------+----------------------

Comment (by mascguy):

 A few observations from the log:

 * You have Xcode 10.1 installed, which includes the macOS 10.14 SDK. And
 since the latter targets 10.14 - while you're building ports to run on
 10.13 - that's not optimal. And indeed, it may cause unexpected issues,
 due to the version mismatch.
   * So I'd strongly recommend that you downgrade Xcode to the last release
 which includes a 10.13 SDK, which is 9.4.1.

 * As for the issue specifics: Based on some quick Googling, this may be a
 bug in the version of Clang shipped with Xcode 10.x.
   * So I suppose we can blacklist just Xcode Clang 10.x, to sidestep the
 issue.
   * I've also checked with upstream, and there doesn't appear to be a
 patch for this issue. Nor should it be necessary, as the code in question
 is correct, per the Cxx 2017 standard.

 So if you're in a hurry to get this fixed, downgrade to Xcode 9.4.1.

 Otherwise, I'll update the port to blacklist Xcode Clang 10.x. Though that
 may not happen until this evening, or over the weekend at the latest. (And
 by that time, buildbot binaries should be available for 10.13.)

-- 
Ticket URL: <https://trac.macports.org/ticket/68036#comment:5>
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