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Comment by cremno | Hacker News Reader

Making their preprocessor compliant with (modern) C and C++ standards is on their roadmap though (and two-phase lookup is too):

http://blogs.msdn.com/b/somasegar/archive/2014/06/03/first-p...

Also (nowadays) MS admits that their implementation of __VA_ARGS__ isn't compliant:

https://connect.microsoft.com/VisualStudio/Feedback/Details/...

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I'm not a big C++ user, nor terribly fond of the language in any case, but IMHO the "single-phase lookup" MSVC is doing for templates is conceptually much simpler to understand (and apparently implement) than the standard 2-phase: instantiating a template is literally a textual substitution, which is intuitively what I'd expect and understand templates to be.

With two-phase lookup errors in code that does not depend on template arguments are caught earlier (when the template is defined) than with one-phase lookup (when the template is instanciated). Which is why template code written for Visual Studio might not compile with a standard conforming compiler.

>instantiating a template is literally a textual substitution

I'm being pedantic here, but that's not quite the case. Example:

  template <typename T>
  void foo()
  {
    T t;
    ...
  }

  foo<int[2]>();

With simple textual substitution this would result in a syntax error, as

  int[2] t;

isn't valid C++ code.

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