In the screenshot shown here:
VS code automatically added a tip line showing as "1 implementation" in the Rust code between line 14 and line 15.
My question is: how can I disable this gray tip line? and what is the official name for such tip lines inserted?
Assuming you're using rust-analyzer, in File | Settings | search for Rust Analyzer > Lens: Implementations and uncheck the box then restart VS Code.
The corresponding (boolean) JSON value is rust-analyzer.lens.implementations.
You can still find implementations by right clicking on the type anyway, so there's no real loss in setting it to false.
