[cfe-dev] clang-tidy: Tool for removing "this->" from source code?

[Kevin Funk]

Heya,

for familiarizing myself with writing custom tools for LibTooling I attempted to write a 
tool for removing (unnecessary) "this->" usage from source code.

Examples:

void inc() {
  this->counter++; // becomes: counter++;
}

Now there are a few cases where this would leave to different behaviour when just 
simply replacing "this->" by "" in source code, which is what I'd like to avoid:

Example:

void foo(bool b) {
  this->b = b; // would become: b = b; => self-assignment, BUG
}

void bar() {
  int num = this->num(); // would become: int num = num(); => compile-error
}

So, in other words, for a given expression like `this->$myid` to be replacable by just 
`$myid`, the name $myid must not be ambiguous from the context of the expression. 
(There might be other exceptions, but I'm just assuming this as my rule for now). In all 
other cases, I'd like to replace "this->" by "" in source code.

Now to the actual question: How to implement this via a clang-tidy tool?

Writing a AST matcher for getting to the expressions referencing `this` is trivial -- 
something like this:

  memberExpr(hasDescendant(thisExpr().bind("this"))).bind("member")

Now the part I'm struggling with is how to make sure the "member name" is a non-
ambiguous identifier from the current context so I can just strip "this->". How can I find 
out the accessible declarations (or just the ids) from the context of the expression 
referencing `this`? I'm missing API to get the clang::DeclContext, plus looking up 
declarations accessible from within this context.

Any ideas?

Any help appreciated,
Thanks!

-- 
Kevin Funk | kevin.funk at kdab.com | Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel. Germany +49-30-521325470, Sweden (HQ) +46-563-540090
KDAB - Qt Experts - Platform-independent software solutions
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