Guideline request: preferred signature for methods on small Copy types

[matklad]

Often I have small Copy types in the API:

struct TextRange { start: u32, end: u32 }

Every single time I wonder if I should write fn len(&self) -> u32 or fn len(self) -> u32. I think there's no major difference between the two, so a guideline would be helpful to avoid constantly thinking about minor differences.

&self:

• consistent with non-copy types
• may be more efficient if size_of::<Self> is large
• may screw up lifetime elision, if it picks lifetime from &self which should be irrelevant

self:

• stdlib does this for primitive types
• may be more efficient if size_of::<Self> is comparable to/smaller than usize
• is different the usual &self: I almost always type & automatically

[KodrAus]

I personally lean more towards self for copy types.