Rollup merge of #104976 - WaffleLapkin:move_comments, r=cjgillot

Prefer doc comments over `//`-comments in compiler

Doc comments are generally nicer: they show up in the documentation, they are shown in IDEs when you hover other mentions of items, etc. Thus it makes sense to use them instead of `//`-comments.

compiler/rustc_save_analysis/src/lib.rs

@@ -94,7 +94,7 @@ impl<'tcx> SaveContext<'tcx> {
         }
     }
 
-    // Returns path to the compilation output (e.g., libfoo-12345678.rmeta)
+    /// Returns path to the compilation output (e.g., libfoo-12345678.rmeta)
     pub fn compilation_output(&self, crate_name: &str) -> PathBuf {
         let sess = &self.tcx.sess;
         // Save-analysis is emitted per whole session, not per each crate type
@@ -112,7 +112,7 @@ impl<'tcx> SaveContext<'tcx> {
         }
     }
 
-    // List external crates used by the current crate.
+    /// List external crates used by the current crate.
     pub fn get_external_crates(&self) -> Vec<ExternalCrateData> {
         let mut result = Vec::with_capacity(self.tcx.crates(()).len());