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

[Kevin Funk]

On Tuesday 09 June 2015 06:27:02 Wilhelm wrote:
> Hi Kevin,
> 
> be aware that there are cases in derived from template classes (eg.
> CRTP) where you can't remove "this" because it points to a depended name ...
> 
> Wilhelm

Good point, others in my team have already raised this issue. Will keep it in mind.

Thanks!

> Am 08.06.2015 um 13:54 schrieb 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 | kfunk at kde.org | http://kfunk.org
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