[cfe-dev] clang refactoring/auto-completion support

"C. Bergström" cbergstrom at pathscale.com
Mon Sep 24 15:55:13 PDT 2012

We've hit a couple issues while using clang for 
refactoring/auto-completion tools

1. clang code completion -  There are two virtual methods within 
clang::CodeCompletionConsumer class. First is 
'ProcessCodeCompleteResults'. This methods is working quite well. But 
second - 'ProcessOverloadCandidates', which is providing functions 
overload candidates within function call context, is working very 
strange. This method is called /only /within context of calling free 
function. Example:\

void Foo();

void Bar()
    Foo(>|<); // Overload candidates are successfully provided and 
contain one item ('Foo()')

class Clazz
    Clazz(int, int);
    void Foo();
    void TestFn();

void Bar(Clazz& cls)
    cls.Foo(>|<); // Overload candidates aren't provided
    Class other(>|<); // The same.

void TestFn()
    Foo(>|<); // The same. Overload candidates aren't provided

Here ">|<" mark shows a current text caret position for which code 
completion is requested.
Is there missing functionality here?  (If so anyone interested to help 
us with this?)

2.   Here is a sample class:

class BaseClass : public SuperBaseClass
     BaseClass(int a);
     BaseClass(int a, int b);
     void SomeVirtualMethod(int a, int b = 10);
     void foo(int a, int b);
     void foo(double a);
     void foo(BaseClass *cls);


In the point marked with ">|<" suggestion list doesn't contain 
constructors of the 'BaseClass'. It's very strange.

3. AST building. We're looking to implement:
  - Create method declaration from usage
  - Create method declaration from definition

Both this features assume what source code (in initial state) contains 
an error and feature implementation fix this error in the corresponded 
way.  The problem is clang can't help us to analyze the line with such 

For example:

void Bar()
    int a, b;
    Foo(a, b); // There is no 'Foo' function within code yet

clang parser throws out the line with 'Foo' call from AST.  So we can't 
analyze nor type of symbol or type of arguments within this context.
My primary question is: can we add some special AST nodes into clang 
parser in order to handle such cases? In normal situation AST 
consumers/visitors will ignore such nodes but in case of refactoring we 
could extract some additional info from source code and have special 
handling for it.




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