unnecessary_wraps: do not include the whole body in the lint span

[samueltardieu]

Using the function declaration, by stripping the body, is enough to convey the lint message.

changelog: [unnecessary_wraps]: do not include the whole body in the lint span

Closes #14773

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[blyxyas]

I'm actually not sure about this one, only spanning the signature imo signifies that the issue is with the function signature, and really the too of the issue is with the returned expression.

Isn't there an option to like annotate several unconnected places with span_lint_then?

Something like:

error: the result is unnecessarily wrapped in an Option
  |
LL| fn my_func(args: &[usize]) -> Option<usize> {
  |                               ^^^^^^^^^^^^^
note: the only returns are from `Some` variants
 -> `return Some(ret)`
 -> `x.unwrap_or_else(|| Some(y))`
 -> (...the other branch ends)

Although each option should probably be truncated to guard against really big chains of maps and and_thens

[samueltardieu]

I'm actually not sure about this one, only spanning the signature imo signifies that the issue is with the function signature

That was the intent: if we assume the code is correct, then the issue is really with the function signature, which requires an Option or Result while it probably shouldn't. We wouldn't want to suggest that some code path would need to return None if this is not needed.

Though I agree that a note talking about only Some or Ok being returned would be definitely useful to add here. I'll see if pointing at them is doable without spamming the output.

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[rustbot]

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[samueltardieu]

Done. Example:

error: this function's return value is unnecessarily wrapped by `Option`
  --> tests/ui/unnecessary_wraps.rs:86:5
   |
LL |     fn func12() -> Option<i32> {
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
help: remove `Option` from the return type...
   |
LL -     fn func12() -> Option<i32> {
LL +     fn func12() -> i32 {
   |
help: ...and then remove the surrounding `Some()` from returning expressions
   |
LL -         Some(1)
LL +         1

@rustbot ready