forward declaration not suggested for type returned from function

[firewave]

test.h

#include "s.h"

S f();

s.h

class S {};

Analyzing a file including test.h will not suggest a forward declaration which would be sufficient.

But if you are already using a forward declaration instead of the include it will report that everything is correct.

If the type is used as a function parameter it will suggest the forward declaration.

I am quite surprised but apparently it is legal: https://stackoverflow.com/questions/47817012/incomplete-types-as-function-parameters-and-return-values.

I am using include-what-you-use 0.22 on Manjaro Linux.

[bolshakov-a]

This is the default IWYU policy. Please read the docs: https://github.com/include-what-you-use/include-what-you-use/blob/master/docs/WhatIsAUse.md

I think it would be nice to add command-line flags to switch these policies off.

[firewave]

This is the default IWYU policy.

Interesting. This is basically the "mission statement" I was referring to in #1568 (comment).

I think it would be nice to add command-line flags to switch these policies off.

I second that.

I doubt that each author will properly express their intend. And even if that is covered in code reviews there might still be cases slipping through.

And with the function parameter case suggesting the forward declaration, depending on when you started to use include-what-you-use and the evolution of the code, you might end with either of the cases.

I think it would be nice to be able to enforce a certain policy for consistency across the code.

[firewave]

I think it would be nice to be able to enforce a certain policy for consistency across the code.

I think there should be three different policies: permissive (current / default), incomplete and full.

[firewave]

I think there should be three different policies: permissive (current / default), incomplete and full.

It could be more complex than that though as currently there are two different policies in place. They allow for either full or incomplete types if they are already being used and suggests the full type if a change is necessary.

So there would be more cases:

• incomplete - enforce usage of incomplete types
• full - enforce usage of full types
• suggest-incomplete - do not enforce and use incomplete types for suggestions (if necessary)
• suggest-full - do not enforce and use full types for suggestions (if necessary / current default)

[kimgr]

If you're interested in short term local solution, simply replace the include with a forward decl, and iwyu should interpret that according to its policy.