Rollup merge of #54717 - ljedrz:cleanup_ty_p1, r=davidtwco

Cleanup rustc/ty part 1

Part 2 will follow soon; I wouldn't want these changes to rot too quickly.

- improve stack shifting and remove related allocations
- move a faster early return up
- improve allocations
- use Cow<str> where applicable
- simplify common patterns
- whitespace fixes

Author: pietroalbini

src/librustc/ty/codec.rs

@@ -178,19 +178,19 @@ pub fn decode_predicates<'a, 'tcx, D>(decoder: &mut D)
     Ok(ty::GenericPredicates {
         parent: Decodable::decode(decoder)?,
         predicates: (0..decoder.read_usize()?).map(|_| {
-                // Handle shorthands first, if we have an usize > 0x80.
-                let predicate = if decoder.positioned_at_shorthand() {
-                    let pos = decoder.read_usize()?;
-                    assert!(pos >= SHORTHAND_OFFSET);
-                    let shorthand = pos - SHORTHAND_OFFSET;
-
-                    decoder.with_position(shorthand, ty::Predicate::decode)
-                } else {
-                    ty::Predicate::decode(decoder)
-                }?;
-                Ok((predicate, Decodable::decode(decoder)?))
-            })
-            .collect::<Result<Vec<_>, _>>()?,
+            // Handle shorthands first, if we have an usize > 0x80.
+            let predicate = if decoder.positioned_at_shorthand() {
+                let pos = decoder.read_usize()?;
+                assert!(pos >= SHORTHAND_OFFSET);
+                let shorthand = pos - SHORTHAND_OFFSET;
+
+                decoder.with_position(shorthand, ty::Predicate::decode)
+            } else {
+                ty::Predicate::decode(decoder)
+            }?;
+            Ok((predicate, Decodable::decode(decoder)?))
+        })
+        .collect::<Result<Vec<_>, _>>()?,
     })
 }
 
@@ -267,7 +267,7 @@ pub fn decode_const<'a, 'tcx, D>(decoder: &mut D)
 
 #[inline]
 pub fn decode_allocation<'a, 'tcx, D>(decoder: &mut D)
-                                 -> Result<&'tcx Allocation, D::Error>
+    -> Result<&'tcx Allocation, D::Error>
     where D: TyDecoder<'a, 'tcx>,
           'tcx: 'a,
 {

src/librustc/ty/context.rs

@@ -190,8 +190,8 @@ impl<'gcx: 'tcx, 'tcx> CtxtInterners<'tcx> {
             // types/regions in the global interner
             if local as *const _ as usize == global as *const _ as usize {
                 bug!("Attempted to intern `{:?}` which contains \
-                    inference types/regions in the global type context",
-                    &ty_struct);
+                      inference types/regions in the global type context",
+                     &ty_struct);
             }
 
             // Don't be &mut TyS.
@@ -272,9 +272,9 @@ fn validate_hir_id_for_typeck_tables(local_id_root: Option<DefId>,
 
                     bug!("node {} with HirId::owner {:?} cannot be placed in \
                           TypeckTables with local_id_root {:?}",
-                          tcx.hir.node_to_string(node_id),
-                          DefId::local(hir_id.owner),
-                          local_id_root)
+                         tcx.hir.node_to_string(node_id),
+                         DefId::local(hir_id.owner),
+                         local_id_root)
                 });
             }
         } else {
@@ -540,16 +540,13 @@ impl<'tcx> TypeckTables<'tcx> {
     }
 
     pub fn node_id_to_type(&self, id: hir::HirId) -> Ty<'tcx> {
-        match self.node_id_to_type_opt(id) {
-            Some(ty) => ty,
-            None => {
-                bug!("node_id_to_type: no type for node `{}`",
-                    tls::with(|tcx| {
-                        let id = tcx.hir.hir_to_node_id(id);
-                        tcx.hir.node_to_string(id)
-                    }))
-            }
-        }
+        self.node_id_to_type_opt(id).unwrap_or_else(||
+            bug!("node_id_to_type: no type for node `{}`",
+                 tls::with(|tcx| {
+                     let id = tcx.hir.hir_to_node_id(id);
+                     tcx.hir.node_to_string(id)
+                 }))
+        )
     }
 
     pub fn node_id_to_type_opt(&self, id: hir::HirId) -> Option<Ty<'tcx>> {
@@ -686,7 +683,7 @@ impl<'tcx> TypeckTables<'tcx> {
     }
 
     pub fn pat_adjustments_mut(&mut self)
-                           -> LocalTableInContextMut<'_, Vec<Ty<'tcx>>> {
+                               -> LocalTableInContextMut<'_, Vec<Ty<'tcx>>> {
         LocalTableInContextMut {
             local_id_root: self.local_id_root,
             data: &mut self.pat_adjustments,
@@ -1199,8 +1196,8 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             let hir_id = hir.node_to_hir_id(k);
             let map = trait_map.entry(hir_id.owner).or_default();
             Lrc::get_mut(map).unwrap()
-                            .insert(hir_id.local_id,
-                                    Lrc::new(StableVec::new(v)));
+                             .insert(hir_id.local_id,
+                                     Lrc::new(StableVec::new(v)));
         }
 
         let gcx = &GlobalCtxt {
@@ -2188,7 +2185,6 @@ macro_rules! sty_debug_print {
                 };
                 $(let mut $variant = total;)*
 
-
                 for &Interned(t) in tcx.interners.type_.borrow().iter() {
                     let variant = match t.sty {
                         ty::Bool | ty::Char | ty::Int(..) | ty::Uint(..) |
@@ -2207,7 +2203,7 @@ macro_rules! sty_debug_print {
                 }
                 println!("Ty interner             total           ty region  both");
                 $(println!("    {:18}: {uses:6} {usespc:4.1}%, \
-{ty:4.1}% {region:5.1}% {both:4.1}%",
+                            {ty:4.1}% {region:5.1}% {both:4.1}%",
                            stringify!($variant),
                            uses = $variant.total,
                            usespc = $variant.total as f64 * 100.0 / total.total as f64,
@@ -2216,7 +2212,7 @@ macro_rules! sty_debug_print {
                            both = $variant.both_infer as f64 * 100.0  / total.total as f64);
                   )*
                 println!("                  total {uses:6}        \
-{ty:4.1}% {region:5.1}% {both:4.1}%",
+                          {ty:4.1}% {region:5.1}% {both:4.1}%",
                          uses = total.total,
                          ty = total.ty_infer as f64 * 100.0  / total.total as f64,
                          region = total.region_infer as f64 * 100.0  / total.total as f64,
@@ -2653,7 +2649,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         }
 
     pub fn mk_closure(self, closure_id: DefId, closure_substs: ClosureSubsts<'tcx>)
-                                          -> Ty<'tcx> {
+                      -> Ty<'tcx> {
         self.mk_ty(Closure(closure_id, closure_substs))
     }
 
@@ -2686,8 +2682,8 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     }
 
     pub fn mk_ty_param(self,
-                    index: u32,
-                    name: InternedString) -> Ty<'tcx> {
+                       index: u32,
+                       name: InternedString) -> Ty<'tcx> {
         self.mk_ty(Param(ParamTy { idx: index, name: name }))
     }
 

src/librustc/ty/error.rs

@@ -10,6 +10,7 @@
 
 use hir::def_id::DefId;
 use ty::{self, BoundRegion, Region, Ty, TyCtxt};
+use std::borrow::Cow;
 use std::fmt;
 use rustc_target::spec::abi;
 use syntax::ast;
@@ -71,7 +72,7 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         use self::TypeError::*;
         fn report_maybe_different(f: &mut fmt::Formatter<'_>,
-                                  expected: String, found: String) -> fmt::Result {
+                                  expected: &str, found: &str) -> fmt::Result {
             // A naive approach to making sure that we're not reporting silly errors such as:
             // (expected closure, found closure).
             if expected == found {
@@ -126,15 +127,15 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
                        br)
             }
             Sorts(values) => ty::tls::with(|tcx| {
-                report_maybe_different(f, values.expected.sort_string(tcx),
-                                       values.found.sort_string(tcx))
+                report_maybe_different(f, &values.expected.sort_string(tcx),
+                                       &values.found.sort_string(tcx))
             }),
             Traits(values) => ty::tls::with(|tcx| {
                 report_maybe_different(f,
-                                       format!("trait `{}`",
-                                               tcx.item_path_str(values.expected)),
-                                       format!("trait `{}`",
-                                               tcx.item_path_str(values.found)))
+                                       &format!("trait `{}`",
+                                                tcx.item_path_str(values.expected)),
+                                       &format!("trait `{}`",
+                                                tcx.item_path_str(values.found)))
             }),
             IntMismatch(ref values) => {
                 write!(f, "expected `{:?}`, found `{:?}`",
@@ -162,8 +163,8 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
                        values.found)
             },
             ExistentialMismatch(ref values) => {
-                report_maybe_different(f, format!("trait `{}`", values.expected),
-                                       format!("trait `{}`", values.found))
+                report_maybe_different(f, &format!("trait `{}`", values.expected),
+                                       &format!("trait `{}`", values.found))
             }
             OldStyleLUB(ref err) => {
                 write!(f, "{}", err)
@@ -173,22 +174,22 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
 }
 
 impl<'a, 'gcx, 'lcx, 'tcx> ty::TyS<'tcx> {
-    pub fn sort_string(&self, tcx: TyCtxt<'a, 'gcx, 'lcx>) -> String {
+    pub fn sort_string(&self, tcx: TyCtxt<'a, 'gcx, 'lcx>) -> Cow<'static, str> {
         match self.sty {
             ty::Bool | ty::Char | ty::Int(_) |
-            ty::Uint(_) | ty::Float(_) | ty::Str | ty::Never => self.to_string(),
-            ty::Tuple(ref tys) if tys.is_empty() => self.to_string(),
+            ty::Uint(_) | ty::Float(_) | ty::Str | ty::Never => self.to_string().into(),
+            ty::Tuple(ref tys) if tys.is_empty() => self.to_string().into(),
 
-            ty::Adt(def, _) => format!("{} `{}`", def.descr(), tcx.item_path_str(def.did)),
-            ty::Foreign(def_id) => format!("extern type `{}`", tcx.item_path_str(def_id)),
+            ty::Adt(def, _) => format!("{} `{}`", def.descr(), tcx.item_path_str(def.did)).into(),
+            ty::Foreign(def_id) => format!("extern type `{}`", tcx.item_path_str(def_id)).into(),
             ty::Array(_, n) => {
                 match n.assert_usize(tcx) {
-                    Some(n) => format!("array of {} elements", n),
-                    None => "array".to_string(),
+                    Some(n) => format!("array of {} elements", n).into(),
+                    None => "array".into(),
                 }
             }
-            ty::Slice(_) => "slice".to_string(),
-            ty::RawPtr(_) => "*-ptr".to_string(),
+            ty::Slice(_) => "slice".into(),
+            ty::RawPtr(_) => "*-ptr".into(),
             ty::Ref(region, ty, mutbl) => {
                 let tymut = ty::TypeAndMut { ty, mutbl };
                 let tymut_string = tymut.to_string();
@@ -199,39 +200,39 @@ impl<'a, 'gcx, 'lcx, 'tcx> ty::TyS<'tcx> {
                     format!("{}reference", match mutbl {
                         hir::Mutability::MutMutable => "mutable ",
                         _ => ""
-                    })
+                    }).into()
                 } else {
-                    format!("&{}", tymut_string)
+                    format!("&{}", tymut_string).into()
                 }
             }
-            ty::FnDef(..) => "fn item".to_string(),
-            ty::FnPtr(_) => "fn pointer".to_string(),
+            ty::FnDef(..) => "fn item".into(),
+            ty::FnPtr(_) => "fn pointer".into(),
             ty::Dynamic(ref inner, ..) => {
-                inner.principal().map_or_else(|| "trait".to_string(),
-                    |p| format!("trait {}", tcx.item_path_str(p.def_id())))
+                inner.principal().map_or_else(|| "trait".into(),
+                    |p| format!("trait {}", tcx.item_path_str(p.def_id())).into())
             }
-            ty::Closure(..) => "closure".to_string(),
-            ty::Generator(..) => "generator".to_string(),
-            ty::GeneratorWitness(..) => "generator witness".to_string(),
-            ty::Tuple(..) => "tuple".to_string(),
-            ty::Infer(ty::TyVar(_)) => "inferred type".to_string(),
-            ty::Infer(ty::IntVar(_)) => "integral variable".to_string(),
-            ty::Infer(ty::FloatVar(_)) => "floating-point variable".to_string(),
+            ty::Closure(..) => "closure".into(),
+            ty::Generator(..) => "generator".into(),
+            ty::GeneratorWitness(..) => "generator witness".into(),
+            ty::Tuple(..) => "tuple".into(),
+            ty::Infer(ty::TyVar(_)) => "inferred type".into(),
+            ty::Infer(ty::IntVar(_)) => "integral variable".into(),
+            ty::Infer(ty::FloatVar(_)) => "floating-point variable".into(),
             ty::Infer(ty::CanonicalTy(_)) |
-            ty::Infer(ty::FreshTy(_)) => "fresh type".to_string(),
-            ty::Infer(ty::FreshIntTy(_)) => "fresh integral type".to_string(),
-            ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".to_string(),
-            ty::Projection(_) => "associated type".to_string(),
-            ty::UnnormalizedProjection(_) => "non-normalized associated type".to_string(),
+            ty::Infer(ty::FreshTy(_)) => "fresh type".into(),
+            ty::Infer(ty::FreshIntTy(_)) => "fresh integral type".into(),
+            ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".into(),
+            ty::Projection(_) => "associated type".into(),
+            ty::UnnormalizedProjection(_) => "non-normalized associated type".into(),
             ty::Param(ref p) => {
                 if p.is_self() {
-                    "Self".to_string()
+                    "Self".into()
                 } else {
-                    "type parameter".to_string()
+                    "type parameter".into()
                 }
             }
-            ty::Opaque(..) => "opaque type".to_string(),
-            ty::Error => "type error".to_string(),
+            ty::Opaque(..) => "opaque type".into(),
+            ty::Error => "type error".into(),
         }
     }
 }
@@ -251,20 +252,19 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                     db.note("no two closures, even if identical, have the same type");
                     db.help("consider boxing your closure and/or using it as a trait object");
                 }
-                match (&values.found.sty, &values.expected.sty) { // Issue #53280
-                    (ty::Infer(ty::IntVar(_)), ty::Float(_)) => {
-                        if let Ok(snippet) = self.sess.source_map().span_to_snippet(sp) {
-                            if snippet.chars().all(|c| c.is_digit(10) || c == '-' || c == '_') {
-                                db.span_suggestion_with_applicability(
-                                    sp,
-                                    "use a float literal",
-                                    format!("{}.0", snippet),
-                                    Applicability::MachineApplicable
-                                );
-                            }
+                if let (ty::Infer(ty::IntVar(_)), ty::Float(_)) =
+                       (&values.found.sty, &values.expected.sty) // Issue #53280
+                {
+                    if let Ok(snippet) = self.sess.source_map().span_to_snippet(sp) {
+                        if snippet.chars().all(|c| c.is_digit(10) || c == '-' || c == '_') {
+                            db.span_suggestion_with_applicability(
+                                sp,
+                                "use a float literal",
+                                format!("{}.0", snippet),
+                                Applicability::MachineApplicable
+                            );
                         }
-                    },
-                    _ => {}
+                    }
                 }
             },
             OldStyleLUB(err) => {

src/librustc/ty/flags.rs

@@ -62,9 +62,7 @@ impl FlagComputation {
         let outer_exclusive_binder = computation.outer_exclusive_binder;
         if outer_exclusive_binder > ty::INNERMOST {
             self.add_exclusive_binder(outer_exclusive_binder.shifted_out(1));
-        } else {
-            // otherwise, this binder captures nothing
-        }
+        } // otherwise, this binder captures nothing
     }
 
     fn add_sty(&mut self, st: &ty::TyKind<'_>) {

src/librustc/ty/inhabitedness/def_id_forest.rs

@@ -66,12 +66,7 @@ impl<'a, 'gcx, 'tcx> DefIdForest {
                     tcx: TyCtxt<'a, 'gcx, 'tcx>,
                     id: DefId) -> bool
     {
-        for root_id in self.root_ids.iter() {
-            if tcx.is_descendant_of(id, *root_id) {
-                return true;
-            }
-        }
-        false
+        self.root_ids.iter().any(|root_id| tcx.is_descendant_of(id, *root_id))
     }
 
     /// Calculate the intersection of a collection of forests.
@@ -92,11 +87,7 @@ impl<'a, 'gcx, 'tcx> DefIdForest {
             }
             ret.root_ids.extend(old_ret.drain());
 
-            for id in next_forest.root_ids {
-                if ret.contains(tcx, id) {
-                    next_ret.push(id);
-                }
-            }
+            next_ret.extend(next_forest.root_ids.into_iter().filter(|&id| ret.contains(tcx, id)));
 
             mem::swap(&mut next_ret, &mut ret.root_ids);
             next_ret.drain();
@@ -112,11 +103,7 @@ impl<'a, 'gcx, 'tcx> DefIdForest {
         let mut ret = DefIdForest::empty();
         let mut next_ret = SmallVec::new();
         for next_forest in iter {
-            for id in ret.root_ids.drain() {
-                if !next_forest.contains(tcx, id) {
-                    next_ret.push(id);
-                }
-            }
+            next_ret.extend(ret.root_ids.drain().filter(|&id| !next_forest.contains(tcx, id)));
 
             for id in next_forest.root_ids {
                 if !next_ret.contains(&id) {