[cfe-commits] [PATCH] Pretty print identifiers even while suppressing specifiers

[Benoit Perrot]

Hello all,

On the following input code:

  for (int i = 42, k = 2097; false; )
    ;

Pretty printing only the init part of the "for" loop, gives the
following:

  int i = 42, = 2097

My understanding is that, when printing the "VarDecl" of the group
constituing the said init, the ones following the first are printed
with a policy asking to suppress specifiers (see "Decl::printGroup").
This policy reaches "TypePrinter::print()", which simply returns when
specifiers are suppressed - yet this method is also responsible of
displaying variable identifiers (kept in "PlaceHolder"):

  void TypePrinter::print(const Type *T, Qualifiers Quals, raw_ostream &OS,
                          StringRef PlaceHolder) {
    if (!T) {
      OS << "NULL TYPE";
      return;
    }

    if (Policy.SuppressSpecifiers && T->isSpecifierType())
      return;

    SaveAndRestore<bool> PHVal(HasEmptyPlaceHolder, PlaceHolder.empty());

    printBefore(T, Quals, OS);
    OS << PlaceHolder; // < Displays the identifier
    printAfter(T, Quals, OS);
  }

The following pretty printers are using "TypePrinter::print", and are
behaving in a manner that differs from what I was expecting after
reading the description of "PrintingPolicy::SuppressSpecifiers":

- "void DeclPrinter::VisitTypedefDecl(TypedefDecl *D)"

  Which on:
    typedef unsigned char foo_t;

  Outputs: (nothing is displayed)


  While I was expecting:
    foo_t

- "void DeclPrinter::VisitFunctionDecl(FunctionDecl *D)"

  On:
    void bar(int i);

  Outputs: (nothing is displayed - the prototype is entirely
  built internally - see implementation)


  While I was expecting:
    bar(int i)

- "void DeclPrinter::VisitVarDecl(VarDecl *D)"

  On:
    int x = 42;

  Outputs: (variable identifier is not displayed)
     = 42

  While it should have output (see initial problem):
    x = 42

If I am right, then "TypePrinter::print()" should be written:

  void TypePrinter::print(const Type *T, Qualifiers Quals, raw_ostream &OS,
                          StringRef PlaceHolder) {
    if (!T) {
      OS << "NULL TYPE";
      return;
    }

    SaveAndRestore<bool> PHVal(HasEmptyPlaceHolder, PlaceHolder.empty());

    printBefore(T, Quals, OS); // (returns immediately when suppressing
                               // specifiers, see implementation)
    OS << PlaceHolder;
    printAfter(T, Quals, OS);
  }

This fixes the initial problem (pretty printing variable declarations
of "for" loops), and gives the results I think was expected on "typedef"
and function declarations.

Attached herewith is a patch modifying "TypePrinter::print()" accordingly.

Regards,
-- 
Benoit PERROT
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