[PATCH] D27621: [clang-tidy] check to find declarations declaring more than one name

[Firat Kasmis via Phabricator via cfe-commits]

firolino created this revision.
firolino added reviewers: alexfh, aaron.ballman, klimek, malcolm.parsons.
firolino added a subscriber: cfe-commits.
Herald added subscribers: JDevlieghere, mgorny.

This check can be used to find declarations, which declare more than one name. 
It helps improving readability and prevents potential bugs caused by inattention
and C/C++ syntax specifics.

In addition, appropriate fix-it hints are provided and all user-intended 
indentation will be preserved. For example:

  {
    long ** lint1, lint2 = 0, * lint3, **linn;
  
    const int cx = 1, cy = 2;
  
    int const CS :: * pp = &CS::a, CS::* const qq = &CS::a;
  
    decltype(int()) declint1 = 5, declint2 = 3;
    
    typedef int ta, tb;
  }

will be transformed to:

  {
    long ** lint1;
    long lint2 = 0;
    long * lint3;
    long **linn;
    
    const int cx = 1;
    const int cy = 2;
    
    int const CS :: * pp = &CS::a;
    int const CS::* const qq = &CS::a;
    
    decltype(int()) declint1 = 5;
    decltype(int()) declint2 = 3;
    
    typdef int ta;
    typdef int tb;
  }

Only declarations within a compound statement are matched. Meaning, global declarations
and function parameters are not matched. Moreover, it does not match on the following:

  {
    class A { } Object1, Object2;
    
    for(int i = 0, j = 0;;);
  }

This check will be used for:

- CppCoreGuideline ES.10 <http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#a-nameres-name-oneaes10-declare-one-name-only-per-declaration>
- DCL04 <https://www.securecoding.cert.org/confluence/display/c/DCL04-C.+Do+not+declare+more+than+one+variable+per+declaration>

in the future and provide appropriate options for it.


https://reviews.llvm.org/D27621

Files:
  clang-tidy/readability/CMakeLists.txt
  clang-tidy/readability/OneNamePerDeclarationCheck.cpp
  clang-tidy/readability/OneNamePerDeclarationCheck.h
  clang-tidy/readability/ReadabilityTidyModule.cpp
  clang-tidy/utils/LexerUtils.cpp
  clang-tidy/utils/LexerUtils.h
  docs/clang-tidy/checks/list.rst
  docs/clang-tidy/checks/readability-one-name-per-declaration.rst
  test/clang-tidy/readability-one-name-per-declaration-complex.cpp
  test/clang-tidy/readability-one-name-per-declaration-modern.cpp
  test/clang-tidy/readability-one-name-per-declaration-simple.cpp

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