Auto merge of rust-lang#115979 - GuillaumeGomez:rollup-06ujzgh, r=GuillaumeGomez

Rollup of 6 pull requests

Successful merges:

 - rust-lang#113383 (style-guide: Add section on bugs, and resolving bugs)
 - rust-lang#115499 (rustc_target/riscv: Fix passing of transparent unions with only one non-ZST member)
 - rust-lang#115801 (Detect cycle errors hidden by opaques during monomorphization)
 - rust-lang#115947 (Custom code classes in docs warning)
 - rust-lang#115957 (fix mismatched symbols)
 - rust-lang#115958 (explain mysterious addition in float minimum/maximum)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

core/src/num/f32.rs

@@ -957,6 +957,7 @@ impl f32 {
         } else if self == other {
             if self.is_sign_negative() && other.is_sign_positive() { self } else { other }
         } else {
+            // At least one input is NaN. Use `+` to perform NaN propagation and quieting.
             self + other
         }
     }

core/src/num/f64.rs

@@ -968,6 +968,7 @@ impl f64 {
         } else if self == other {
             if self.is_sign_negative() && other.is_sign_positive() { self } else { other }
         } else {
+            // At least one input is NaN. Use `+` to perform NaN propagation and quieting.
             self + other
         }
     }