Auto merge of rust-lang#104507 - WaffleLapkin:asderefsyou, r=wesleywiser

Use `as_deref` in compiler (but only where it makes sense)

This simplifies some code :3

(there are some changes that are not exacly `as_deref`, but more like "clever `Option`/`Result` method use")

Author: bors

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -1637,7 +1637,7 @@ fn deny_equality_constraints(
                                     // Remove `Bar` from `Foo::Bar`.
                                     assoc_path.segments.pop();
                                     let len = assoc_path.segments.len() - 1;
-                                    let gen_args = args.as_ref().map(|p| (**p).clone());
+                                    let gen_args = args.as_deref().cloned();
                                     // Build `<Bar = RhsTy>`.
                                     let arg = AngleBracketedArg::Constraint(AssocConstraint {
                                         id: rustc_ast::node_id::DUMMY_NODE_ID,

compiler/rustc_builtin_macros/src/asm.rs

@@ -564,7 +564,7 @@ fn expand_preparsed_asm(ecx: &mut ExtCtxt<'_>, args: AsmArgs) -> Option<ast::Inl
         let template_snippet = ecx.source_map().span_to_snippet(template_sp).ok();
         template_strs.push((
             template_str,
-            template_snippet.as_ref().map(|s| Symbol::intern(s)),
+            template_snippet.as_deref().map(Symbol::intern),
             template_sp,
         ));
         let template_str = template_str.as_str();

compiler/rustc_builtin_macros/src/format_foreign/printf/tests.rs

@@ -100,7 +100,7 @@ fn test_iter() {
     let s = "The %d'th word %% is: `%.*s` %!\n";
     let subs: Vec<_> = iter_subs(s, 0).map(|sub| sub.translate().ok()).collect();
     assert_eq!(
-        subs.iter().map(|ms| ms.as_ref().map(|s| &s[..])).collect::<Vec<_>>(),
+        subs.iter().map(Option::as_deref).collect::<Vec<_>>(),
         vec![Some("{}"), None, Some("{:.*}"), None]
     );
 }

compiler/rustc_builtin_macros/src/format_foreign/shell/tests.rs

@@ -39,7 +39,7 @@ fn test_iter() {
     let s = "The $0'th word $$ is: `$WORD` $!\n";
     let subs: Vec<_> = iter_subs(s, 0).map(|sub| sub.translate().ok()).collect();
     assert_eq!(
-        subs.iter().map(|ms| ms.as_ref().map(|s| &s[..])).collect::<Vec<_>>(),
+        subs.iter().map(Option::as_deref).collect::<Vec<_>>(),
         vec![Some("{0}"), None, Some("{WORD}")]
     );
 }

compiler/rustc_codegen_cranelift/build_system/utils.rs

@@ -104,5 +104,5 @@ pub(crate) fn copy_dir_recursively(from: &Path, to: &Path) {
 }
 
 pub(crate) fn is_ci() -> bool {
-    env::var("CI").as_ref().map(|val| &**val) == Ok("true")
+    env::var("CI").as_deref() == Ok("true")
 }

compiler/rustc_codegen_cranelift/src/config.rs

@@ -2,7 +2,7 @@ use std::env;
 use std::str::FromStr;
 
 fn bool_env_var(key: &str) -> bool {
-    env::var(key).as_ref().map(|val| &**val) == Ok("1")
+    env::var(key).as_deref() == Ok("1")
 }
 
 /// The mode to use for compilation.

compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs

@@ -174,7 +174,7 @@ impl CoverageMapGenerator {
         counter_regions.sort_unstable_by_key(|(_counter, region)| *region);
         for (counter, region) in counter_regions {
             let CodeRegion { file_name, start_line, start_col, end_line, end_col } = *region;
-            let same_file = current_file_name.as_ref().map_or(false, |p| *p == file_name);
+            let same_file = current_file_name.map_or(false, |p| p == file_name);
             if !same_file {
                 if current_file_name.is_some() {
                     current_file_id += 1;

compiler/rustc_driver/src/lib.rs

@@ -318,7 +318,7 @@ fn run_compiler(
                             compiler.input(),
                             &*expanded_crate,
                             *ppm,
-                            compiler.output_file().as_ref().map(|p| &**p),
+                            compiler.output_file().as_deref(),
                         );
                         Ok(())
                     })?;
@@ -329,7 +329,7 @@ fn run_compiler(
                         compiler.input(),
                         &krate,
                         *ppm,
-                        compiler.output_file().as_ref().map(|p| &**p),
+                        compiler.output_file().as_deref(),
                     );
                 }
                 trace!("finished pretty-printing");
@@ -383,10 +383,7 @@ fn run_compiler(
                             &crate_name,
                             compiler.input(),
                             None,
-                            DumpHandler::new(
-                                compiler.output_dir().as_ref().map(|p| &**p),
-                                &crate_name,
-                            ),
+                            DumpHandler::new(compiler.output_dir().as_deref(), &crate_name),
                         )
                     });
                 }

compiler/rustc_errors/src/emitter.rs

@@ -248,7 +248,7 @@ pub trait Emitter: Translate {
         fluent_args: &FluentArgs<'_>,
     ) -> (MultiSpan, &'a [CodeSuggestion]) {
         let mut primary_span = diag.span.clone();
-        let suggestions = diag.suggestions.as_ref().map_or(&[][..], |suggestions| &suggestions[..]);
+        let suggestions = diag.suggestions.as_deref().unwrap_or(&[]);
         if let Some((sugg, rest)) = suggestions.split_first() {
             let msg = self.translate_message(&sugg.msg, fluent_args);
             if rest.is_empty() &&

compiler/rustc_hir_analysis/src/collect.rs

@@ -2157,7 +2157,7 @@ fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
         .emit();
     }
     let meta_item_list = attr.meta_item_list();
-    let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
+    let meta_item_list = meta_item_list.as_deref();
     let sole_meta_list = match meta_item_list {
         Some([item]) => item.literal(),
         Some(_) => {