Added warning for unused arithmetic expressions
The compiler now displays a warning when a binary arithmetic operation is evaluated but not used. This resolves#50124 by following the instructions outlined in the issue. The changes are as follows:
- Added new pattern matching for unused arithmetic expressions in `src/librustc_lint/unused.rs`
- Added `#[must_use]` attributes to the binary operation methods in `src/libcore/internal_macros.rs`
- Added `#[must_use]` attributes to the non-assigning binary operators in `src/libcore/ops/arith.rs`
Operator traits seem to be inconsistent regarding the right hand side
generic. Most default Rhs/RHS to Self, but a few omit this. This patch
modifies them all to default to Self. This should not have any backwards
compatibility issues because we are only enabling code that previously
wouldn't compile.
- filter error on the evaluated value of `Self`
- filter error on the evaluated value of the type arguments
- add argument to include custom note in diagnostic
- allow the parser to parse `Self` when processing attributes
- add custom message to binops
* fixed link typos and copy-paster errors
* rewrote Fn* explanations
* `RHS = Self` -> `RHS` is `Self` (added that to all applicable places as
well)
* fixed up some links
* s/MutDeref/DerefMut
* removed remaining superfluous `fn main()`s
* fixed some minor phrasings and factual errors and inaccuracies
std::ops docs: Fix phrasing and factual errors/inaccuracies
Part of #29365.
* Added "real" examples for `BitOrAssign`, `BitXorAssign`, `ShlAssign`,
and `ShrAssign`
* Rewrote method summary senteces to be in 3rd person singular
* Rephrased example introductions to be less redundant ("in this example"
etc.) and to not use "trivial"
* Removed superfluous explicit `fn main()`s in examples
* Added some missing periods
