Auto merge of #54756 - ljedrz:cleanup_middle, r=michaelwoerister

Cleanup rustc/middle

- improve allocations
- use `Cow<'static, str>` where applicable
- improve some patterns
- whitespace & formatting fixes

Author: bors

src/librustc/middle/dead.rs

@@ -131,12 +131,10 @@ impl<'a, 'tcx> MarkSymbolVisitor<'a, 'tcx> {
 
     fn mark_live_symbols(&mut self) {
         let mut scanned = FxHashSet();
-        while !self.worklist.is_empty() {
-            let id = self.worklist.pop().unwrap();
-            if scanned.contains(&id) {
+        while let Some(id) = self.worklist.pop() {
+            if !scanned.insert(id) {
                 continue
             }
-            scanned.insert(id);
 
             if let Some(ref node) = self.tcx.hir.find(id) {
                 self.live_symbols.insert(id);
@@ -212,7 +210,7 @@ impl<'a, 'tcx> Visitor<'tcx> for MarkSymbolVisitor<'a, 'tcx> {
     }
 
     fn visit_variant_data(&mut self, def: &'tcx hir::VariantData, _: ast::Name,
-                        _: &hir::Generics, _: ast::NodeId, _: syntax_pos::Span) {
+                          _: &hir::Generics, _: ast::NodeId, _: syntax_pos::Span) {
         let has_repr_c = self.repr_has_repr_c;
         let inherited_pub_visibility = self.inherited_pub_visibility;
         let live_fields = def.fields().iter().filter(|f| {
@@ -494,8 +492,8 @@ impl<'a, 'tcx> DeadVisitor<'a, 'tcx> {
                       ctor_id: Option<ast::NodeId>)
                       -> bool {
         if self.live_symbols.contains(&id)
-           || ctor_id.map_or(false,
-                             |ctor| self.live_symbols.contains(&ctor)) {
+           || ctor_id.map_or(false, |ctor| self.live_symbols.contains(&ctor))
+        {
             return true;
         }
         // If it's a type whose items are live, then it's live, too.

src/librustc/middle/dependency_format.rs

@@ -163,7 +163,7 @@ fn calculate_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                 let src = tcx.used_crate_source(cnum);
                 if src.rlib.is_some() { continue }
                 sess.err(&format!("crate `{}` required to be available in rlib format, \
-                                  but was not found in this form",
+                                   but was not found in this form",
                                   tcx.crate_name(cnum)));
             }
             return Vec::new();
@@ -247,13 +247,13 @@ fn calculate_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                     _ => "dylib",
                 };
                 sess.err(&format!("crate `{}` required to be available in {} format, \
-                                  but was not found in this form",
+                                   but was not found in this form",
                                   tcx.crate_name(cnum), kind));
             }
         }
     }
 
-    return ret;
+    ret
 }
 
 fn add_library(tcx: TyCtxt<'_, '_, '_>,

src/librustc/middle/entry.rs

@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-
 use hir::map as hir_map;
 use hir::def_id::{CRATE_DEF_INDEX};
 use session::{config, Session};
@@ -131,7 +130,7 @@ fn find_item(item: &Item, ctxt: &mut EntryContext<'_, '_>, at_root: bool) {
                 ctxt.attr_main_fn = Some((item.id, item.span));
             } else {
                 struct_span_err!(ctxt.session, item.span, E0137,
-                          "multiple functions with a #[main] attribute")
+                                 "multiple functions with a #[main] attribute")
                 .span_label(item.span, "additional #[main] function")
                 .span_label(ctxt.attr_main_fn.unwrap().1, "first #[main] function")
                 .emit();
@@ -141,11 +140,8 @@ fn find_item(item: &Item, ctxt: &mut EntryContext<'_, '_>, at_root: bool) {
             if ctxt.start_fn.is_none() {
                 ctxt.start_fn = Some((item.id, item.span));
             } else {
-                struct_span_err!(
-                    ctxt.session, item.span, E0138,
-                    "multiple 'start' functions")
-                    .span_label(ctxt.start_fn.unwrap().1,
-                                "previous `start` function here")
+                struct_span_err!(ctxt.session, item.span, E0138, "multiple 'start' functions")
+                    .span_label(ctxt.start_fn.unwrap().1, "previous `start` function here")
                     .span_label(item.span, "multiple `start` functions")
                     .emit();
             }

src/librustc/middle/exported_symbols.rs

@@ -35,12 +35,8 @@ impl_stable_hash_for!(enum self::SymbolExportLevel {
 
 impl SymbolExportLevel {
     pub fn is_below_threshold(self, threshold: SymbolExportLevel) -> bool {
-        if threshold == SymbolExportLevel::Rust {
-            // We export everything from Rust dylibs
-            true
-        } else {
-            self == SymbolExportLevel::C
-        }
+        threshold == SymbolExportLevel::Rust // export everything from Rust dylibs
+          || self == SymbolExportLevel::C
     }
 }
 

src/librustc/middle/expr_use_visitor.rs

@@ -321,7 +321,7 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
                     region::Scope {
                         id: body.value.hir_id.local_id,
                         data: region::ScopeData::Node
-                    }));
+                }));
             let arg_cmt = Rc::new(self.mc.cat_rvalue(
                 arg.hir_id,
                 arg.pat.span,
@@ -402,20 +402,20 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
                 self.walk_expr(&subexpr)
             }
 
-            hir::ExprKind::Unary(hir::UnDeref, ref base) => {      // *base
+            hir::ExprKind::Unary(hir::UnDeref, ref base) => { // *base
                 self.select_from_expr(&base);
             }
 
-            hir::ExprKind::Field(ref base, _) => {         // base.f
+            hir::ExprKind::Field(ref base, _) => { // base.f
                 self.select_from_expr(&base);
             }
 
-            hir::ExprKind::Index(ref lhs, ref rhs) => {       // lhs[rhs]
+            hir::ExprKind::Index(ref lhs, ref rhs) => { // lhs[rhs]
                 self.select_from_expr(&lhs);
                 self.consume_expr(&rhs);
             }
 
-            hir::ExprKind::Call(ref callee, ref args) => {    // callee(args)
+            hir::ExprKind::Call(ref callee, ref args) => { // callee(args)
                 self.walk_callee(expr, &callee);
                 self.consume_exprs(args);
             }
@@ -801,10 +801,8 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
             self.walk_pat(discr_cmt.clone(), &pat, mode);
         }
 
-        if let Some(ref guard) = arm.guard {
-            match guard {
-                hir::Guard::If(ref e) => self.consume_expr(e),
-            }
+        if let Some(hir::Guard::If(ref e)) = arm.guard {
+            self.consume_expr(e)
         }
 
         self.consume_expr(&arm.body);
@@ -826,12 +824,13 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
                                cmt_discr: mc::cmt<'tcx>,
                                pat: &hir::Pat,
                                mode: &mut TrackMatchMode) {
-        debug!("determine_pat_move_mode cmt_discr={:?} pat={:?}", cmt_discr,
-               pat);
+        debug!("determine_pat_move_mode cmt_discr={:?} pat={:?}", cmt_discr, pat);
+
         return_if_err!(self.mc.cat_pattern(cmt_discr, pat, |cmt_pat, pat| {
             if let PatKind::Binding(..) = pat.node {
-                let bm = *self.mc.tables.pat_binding_modes().get(pat.hir_id)
-                                                          .expect("missing binding mode");
+                let bm = *self.mc.tables.pat_binding_modes()
+                                        .get(pat.hir_id)
+                                        .expect("missing binding mode");
                 match bm {
                     ty::BindByReference(..) =>
                         mode.lub(BorrowingMatch),

src/librustc/middle/intrinsicck.rs

@@ -107,7 +107,7 @@ impl<'a, 'tcx> ExprVisitor<'a, 'tcx> {
                 }
                 Err(LayoutError::Unknown(bad)) => {
                     if bad == ty {
-                        "this type's size can vary".to_string()
+                        "this type's size can vary".to_owned()
                     } else {
                         format!("size can vary because of {}", bad)
                     }
@@ -117,7 +117,7 @@ impl<'a, 'tcx> ExprVisitor<'a, 'tcx> {
         };
 
         struct_span_err!(self.tcx.sess, span, E0512,
-            "transmute called with types of different sizes")
+                         "transmute called with types of different sizes")
             .note(&format!("source type: {} ({})", from, skeleton_string(from, sk_from)))
             .note(&format!("target type: {} ({})", to, skeleton_string(to, sk_to)))
             .emit();

src/librustc/middle/lang_items.rs

@@ -39,7 +39,6 @@ macro_rules! language_item_table {
         $( $variant:ident, $name:expr, $method:ident; )*
     ) => {
 
-
 enum_from_u32! {
     #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
     pub enum LangItem {
@@ -145,8 +144,8 @@ impl<'a, 'tcx> LanguageItemCollector<'a, 'tcx> {
 
     fn collect_item(&mut self, item_index: usize, item_def_id: DefId) {
         // Check for duplicates.
-        match self.items.items[item_index] {
-            Some(original_def_id) if original_def_id != item_def_id => {
+        if let Some(original_def_id) = self.items.items[item_index] {
+            if original_def_id != item_def_id {
                 let name = LangItem::from_u32(item_index as u32).unwrap().name();
                 let mut err = match self.tcx.hir.span_if_local(item_def_id) {
                     Some(span) => struct_span_err!(
@@ -161,17 +160,13 @@ impl<'a, 'tcx> LanguageItemCollector<'a, 'tcx> {
                             name)),
                 };
                 if let Some(span) = self.tcx.hir.span_if_local(original_def_id) {
-                    span_note!(&mut err, span,
-                               "first defined here.");
+                    span_note!(&mut err, span, "first defined here.");
                 } else {
                     err.note(&format!("first defined in crate `{}`.",
                                       self.tcx.crate_name(original_def_id.krate)));
                 }
                 err.emit();
             }
-            _ => {
-                // OK.
-            }
         }
 
         // Matched.
@@ -194,7 +189,7 @@ pub fn extract(attrs: &[ast::Attribute]) -> Option<(Symbol, Span)> {
         }
     }
 
-    return None;
+    None
 }
 
 pub fn collect<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) -> LanguageItems {

src/librustc/middle/lib_features.rs

@@ -128,8 +128,8 @@ impl<'a, 'tcx> LibFeatureCollector<'a, 'tcx> {
                 let msg = format!(
                     "feature `{}` is declared {}, but was previously declared {}",
                     feature,
-                    if since.is_some() { "stable"} else { "unstable" },
-                    if since.is_none() { "stable"} else { "unstable" },
+                    if since.is_some() { "stable" } else { "unstable" },
+                    if since.is_none() { "stable" } else { "unstable" },
                 );
                 self.tcx.sess.struct_span_err_with_code(span, &msg,
                     DiagnosticId::Error("E0711".into())).emit();