[llvm-bugs] [Bug 48705] New: clang-format removes space in front of && in macro

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=48705

            Bug ID: 48705
           Summary: clang-format removes space in front of && in macro
           Product: clang
           Version: 11.0
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Formatter
          Assignee: unassignedclangbugs at nondot.org
          Reporter: barry.revzin at gmail.com
                CC: djasper at google.com, klimek at google.com,
                    llvm-bugs at lists.llvm.org

Consider the following example:

#include <type_traits>

template <typename T> inline constexpr bool check = true;

#define REQUIRES(...) std::enable_if_t<(__VA_ARGS__), int> = 0

template <typename T, REQUIRES(check<T> && check<T*>)>
void foo(T) { }

template <typename T, std::enable_if_t<(check<T> && check<T*>), int> = 0>
void bar(T) { }


The REQUIRES macro here allows for a nice way of writing constraints before
C++20. The foo and bar function templates here are just different ways of
writing the same thing, the macro just reads [quite a bit] nicer. 

With a .clang-format file consisting entirely of:
BasedOnStyle: Google

The above header gets formatted as:
#include <type_traits>

template <typename T>
inline constexpr bool check = true;

#define REQUIRES(...) std::enable_if_t<(__VA_ARGS__), int> = 0

template <typename T, REQUIRES(check<T>&& check<T*>)>
void foo(T) {}

template <typename T, std::enable_if_t<(check<T> && check<T*>), int> = 0>
void bar(T) {}

For foo, the && in the REQUIRES is moved over to the left... as if we're
declaring an rvalue reference of type check<T>. But in bar, the && stays spaced
out.

This should be formatted as:

template <typename T, REQUIRES(check<T> && check<T*>)>
void foo(T) {}

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