Rollup merge of rust-lang#135826 - yotamofek:resolve-cleanups4, r=petrochenkov

Misc. `rustc_resolve` cleanups

Hopefully this PR should make `rustc_resolve` a bit cleaner.
Each commit here stands on its own. I tried to only include changes that are easy to review, and are a clear improvement. (but I'll be happy to revert any changes that turn out to be more controversial than I'd thought)

Best viewed with whitespace ignored 😁 (especially [these two commits](https://github.com/rust-lang/rust/pull/135826/files/a93616acf3118ef233027d74e8c636f9b79c342d..ae87d005bc92cbecc47b554e634d1bd3d22e1068?diff=unified&w=1))

Author: matthiaskrgr

Diff for: compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -645,10 +645,10 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                 let self_spans = items
                     .iter()
                     .filter_map(|(use_tree, _)| {
-                        if let ast::UseTreeKind::Simple(..) = use_tree.kind {
-                            if use_tree.ident().name == kw::SelfLower {
-                                return Some(use_tree.span);
-                            }
+                        if let ast::UseTreeKind::Simple(..) = use_tree.kind
+                            && use_tree.ident().name == kw::SelfLower
+                        {
+                            return Some(use_tree.span);
                         }
 
                         None
@@ -947,19 +947,19 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
         let imported_binding = self.r.import(binding, import);
         if parent == self.r.graph_root {
             let ident = ident.normalize_to_macros_2_0();
-            if let Some(entry) = self.r.extern_prelude.get(&ident) {
-                if expansion != LocalExpnId::ROOT && orig_name.is_some() && !entry.is_import() {
-                    self.r.dcx().emit_err(
-                        errors::MacroExpandedExternCrateCannotShadowExternArguments {
-                            span: item.span,
-                        },
-                    );
-                    // `return` is intended to discard this binding because it's an
-                    // unregistered ambiguity error which would result in a panic
-                    // caused by inconsistency `path_res`
-                    // more details: https://github.com/rust-lang/rust/pull/111761
-                    return;
-                }
+            if let Some(entry) = self.r.extern_prelude.get(&ident)
+                && expansion != LocalExpnId::ROOT
+                && orig_name.is_some()
+                && !entry.is_import()
+            {
+                self.r.dcx().emit_err(
+                    errors::MacroExpandedExternCrateCannotShadowExternArguments { span: item.span },
+                );
+                // `return` is intended to discard this binding because it's an
+                // unregistered ambiguity error which would result in a panic
+                // caused by inconsistency `path_res`
+                // more details: https://github.com/rust-lang/rust/pull/111761
+                return;
             }
             let entry = self
                 .r
@@ -1040,10 +1040,10 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                         span: item.span,
                     });
                 }
-                if let ItemKind::ExternCrate(Some(orig_name)) = item.kind {
-                    if orig_name == kw::SelfLower {
-                        self.r.dcx().emit_err(errors::MacroUseExternCrateSelf { span: attr.span });
-                    }
+                if let ItemKind::ExternCrate(Some(orig_name)) = item.kind
+                    && orig_name == kw::SelfLower
+                {
+                    self.r.dcx().emit_err(errors::MacroUseExternCrateSelf { span: attr.span });
                 }
                 let ill_formed = |span| {
                     self.r.dcx().emit_err(errors::BadMacroImport { span });
@@ -1179,14 +1179,12 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             return Some((MacroKind::Bang, item.ident, item.span));
         } else if ast::attr::contains_name(&item.attrs, sym::proc_macro_attribute) {
             return Some((MacroKind::Attr, item.ident, item.span));
-        } else if let Some(attr) = ast::attr::find_by_name(&item.attrs, sym::proc_macro_derive) {
-            if let Some(meta_item_inner) =
+        } else if let Some(attr) = ast::attr::find_by_name(&item.attrs, sym::proc_macro_derive)
+            && let Some(meta_item_inner) =
                 attr.meta_item_list().and_then(|list| list.get(0).cloned())
-            {
-                if let Some(ident) = meta_item_inner.ident() {
-                    return Some((MacroKind::Derive, ident, ident.span));
-                }
-            }
+            && let Some(ident) = meta_item_inner.ident()
+        {
+            return Some((MacroKind::Derive, ident, ident.span));
         }
         None
     }