[PATCH] D18265: [clang-tidy] New: checker misc-assign-operator-return

Balogh, Ádám via cfe-commits cfe-commits at lists.llvm.org
Wed Apr 6 03:46:18 PDT 2016

baloghadamsoftware added inline comments.

Comment at: clang-tidy/misc/AssignOperatorCheck.cpp:63
@@ +62,3 @@
+  Finder->addMatcher(returnStmt(IsBadReturnStatement, hasAncestor(IsGoodAssign))
+                         .bind("returnStmt"),
sbenza wrote:
> baloghadamsoftware wrote:
> > sbenza wrote:
> > > I dislike these uses of hasAnscestor. They are kind of slow.
> > > But more importantly, they break with nested functions/types.
> > > This particular example is not checking that the return statement is from the assignment operator, only that it is within it. For example, it would match a lambda.
> > > I think this would trip the check:
> > > 
> > >     F& operator=(const F& o) {
> > >       std::copy_if(o.begin(), o.end(), begin(), [](V v) { return v > 0; });
> > >       return *this;
> > >     }
> > I can change it to hasDescendant if it is faster, but it does not solve the lambda problem. No solution for that comes to my mind with the existing matchers. Maybe a new matcher hasDescendantStatement could help which only traverses statements down the AST. Is this the right way to go?
> hasDescendant has the same problem has hasAnscestor.
> I think the best is to write a matcher like:
>     AST_MATCHER_P(ReturnStmt, forFunction, internal::Matcher<FunctionDecl>, InnerMatcher) {
>       ...
>     }
> In there we can find the right FunctionDecl that encloses the return statement and apply the matcher.
> This matcher seems like a good candidate to add to ASTMatchers.h
Maybe I am wrong, but your proposal also seems a bottom-up matcher which is slow. That is the reason I proposed a top-down matcher, e.g. hasDescendantStatement or something like this which is top-down and only traverses statements so it does not search in a lambda which is a declaration.


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