[cfe-dev] RFC: Adding a rename refactoring tool to clang

[Richard Smith]

On Fri, Jul 25, 2014 at 1:01 PM, Amin Shali <amshali at google.com> wrote:

> Folks,
>
> At Google we are working on a tool and set of APIs for refactoring C++
> programs based on LibTooling. Particularly, we have targeted rename
> refactoring for C++ as our first step.
>
> In our first iteration we want to offer two things:
> 1- A command line tool similar to clang-format which will semantically
> rename a symbol (specified by a position in a file) in a set of input files.
>

Do you intend to provide one command-line tool per refactoring, or one tool
that has subcommands for each operation? For command-line / scripting use,
it'd seem useful to also be able to specify a symbol by name (at least for
names that are not function-local). (For instance, say I want to rename all
*Decl classes in clang to *Declaration. I'd like to be able to perform a
semantic grep for those, then run them through a command-line rename tool.)

2- An API for doing the above task which can effectively be used to provide
> this functionality for any editor (Emacs, Vim, CodeMirror, etc.).
>
> == Renaming capabilities
> In the first iteration, we are offering the following features for the
> rename refactoring:
> === Supported C++ constructs:
>          - Global and local variables (including function arguments)
>          - Functions
>          - C and CXX record types (structs/unions/classes)
>            - For classes this includes renaming the constructor and
> destructor
>          - User defined types
>          - Enumerations (names and constants)
>          - Record member variables and methods
>          - Namespace specifiers
>          - Template parameters
>          - Lambda captures
>          - Overloaded operators
> === Unsupported C++ constructs:
>          - Macros
>          - Symbols in comments
>
> == Command line program
> === Current support:
>          - Input from stdin, output to stdout
>          - Input and output from/to disk
>          - Option to specify include path
>          - Option to predefine macros
> === Possible improvements:
>          - Multiple files from stdin
>          - Making backups of renamed files
>
> We think this tool should reside in clang-tools-extra.
>
> Please let us know what you think. Any comment and feedback is
> appreciated.
>

Do you have any thoughts on how to handle templates? For instance:

struct A { typedef int Foo; };
struct B { typedef char Foo; };
template<typename T> struct X { typename T::Foo bar; };
X<A> a;
X<B> b;

Suppose we want to rename A::Foo to A::Goo. Our obvious choices are:
1) Don't rename the use inside X; breaks X<A>.
2) Do rename the use inside X; breaks X<B>.
3) Rename the use inside X and the use inside B; will surprise users.
4) Report an error and refuse to rename A::Foo. Tell users they need to
rename B::Foo too. (And if the user requests that both are renamed at the
same time, do the right thing.)

I think option 4 is the best choice, but it might be a little tricky to get
right.

How do you intend to behave when renaming an entity shared by multiple
source files? That might influence the checks you're able to perform for
the above case.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20140725/b5fbdf0f/attachment.html>