Rollup merge of rust-lang#54788 - ljedrz:cleanup_rustc_mir, r=oli-obk

A handful of cleanups for rustc/mir

- use the "regular" `into()` instead of `graphviz::IntoCow` in `mod.rs`
- `format!("{}", x)` > `x.to_string()`
- remove one unnecessary `String` allocation
- shorten the logic of one loop
- `assert!(x == y)` > `assert_eq!(x, y)`
- whitespace & formatting fixes

r? @oli-obk

src/librustc/mir/interpret/value.rs

@@ -171,7 +171,7 @@ impl<'tcx> Scalar {
     pub fn from_uint(i: impl Into<u128>, size: Size) -> Self {
         let i = i.into();
         debug_assert_eq!(truncate(i, size), i,
-                    "Unsigned value {} does not fit in {} bits", i, size.bits());
+                         "Unsigned value {} does not fit in {} bits", i, size.bits());
         Scalar::Bits { bits: i, size: size.bytes() as u8 }
     }
 
@@ -181,7 +181,7 @@ impl<'tcx> Scalar {
         // `into` performed sign extension, we have to truncate
         let truncated = truncate(i as u128, size);
         debug_assert_eq!(sign_extend(truncated, size) as i128, i,
-                    "Signed value {} does not fit in {} bits", i, size.bits());
+                         "Signed value {} does not fit in {} bits", i, size.bits());
         Scalar::Bits { bits: truncated, size: size.bytes() as u8 }
     }
 

src/librustc/mir/mod.rs

@@ -12,7 +12,6 @@
 //!
 //! [rustc guide]: https://rust-lang-nursery.github.io/rustc-guide/mir/index.html
 
-use graphviz::IntoCow;
 use hir::def::CtorKind;
 use hir::def_id::DefId;
 use hir::{self, HirId, InlineAsm};
@@ -327,22 +326,20 @@ impl<'tcx> Mir<'tcx> {
         if idx < stmts.len() {
             &stmts[idx].source_info
         } else {
-            assert!(idx == stmts.len());
+            assert_eq!(idx, stmts.len());
             &block.terminator().source_info
         }
     }
 
     /// Check if `sub` is a sub scope of `sup`
     pub fn is_sub_scope(&self, mut sub: SourceScope, sup: SourceScope) -> bool {
-        loop {
-            if sub == sup {
-                return true;
-            }
+        while sub != sup {
             match self.source_scopes[sub].parent_scope {
                 None => return false,
                 Some(p) => sub = p,
             }
         }
+        true
     }
 
     /// Return the return type, it always return first element from `local_decls` array
@@ -526,9 +523,7 @@ impl BorrowKind {
     pub fn allows_two_phase_borrow(&self) -> bool {
         match *self {
             BorrowKind::Shared | BorrowKind::Shallow | BorrowKind::Unique => false,
-            BorrowKind::Mut {
-                allow_two_phase_borrow,
-            } => allow_two_phase_borrow,
+            BorrowKind::Mut { allow_two_phase_borrow } => allow_two_phase_borrow,
         }
     }
 }
@@ -1574,42 +1569,42 @@ impl<'tcx> TerminatorKind<'tcx> {
                         };
                         fmt_const_val(&mut s, &c).unwrap();
                         s.into()
-                    }).chain(iter::once(String::from("otherwise").into()))
+                    }).chain(iter::once("otherwise".into()))
                     .collect()
             }
             Call {
                 destination: Some(_),
                 cleanup: Some(_),
                 ..
-            } => vec!["return".into_cow(), "unwind".into_cow()],
+            } => vec!["return".into(), "unwind".into()],
             Call {
                 destination: Some(_),
                 cleanup: None,
                 ..
-            } => vec!["return".into_cow()],
+            } => vec!["return".into()],
             Call {
                 destination: None,
                 cleanup: Some(_),
                 ..
-            } => vec!["unwind".into_cow()],
+            } => vec!["unwind".into()],
             Call {
                 destination: None,
                 cleanup: None,
                 ..
             } => vec![],
-            Yield { drop: Some(_), .. } => vec!["resume".into_cow(), "drop".into_cow()],
-            Yield { drop: None, .. } => vec!["resume".into_cow()],
+            Yield { drop: Some(_), .. } => vec!["resume".into(), "drop".into()],
+            Yield { drop: None, .. } => vec!["resume".into()],
             DropAndReplace { unwind: None, .. } | Drop { unwind: None, .. } => {
-                vec!["return".into_cow()]
+                vec!["return".into()]
             }
             DropAndReplace {
                 unwind: Some(_), ..
             }
             | Drop {
                 unwind: Some(_), ..
-            } => vec!["return".into_cow(), "unwind".into_cow()],
+            } => vec!["return".into(), "unwind".into()],
             Assert { cleanup: None, .. } => vec!["".into()],
-            Assert { .. } => vec!["success".into_cow(), "unwind".into_cow()],
+            Assert { .. } => vec!["success".into(), "unwind".into()],
             FalseEdges {
                 ref imaginary_targets,
                 ..

src/librustc/mir/mono.rs

@@ -325,7 +325,7 @@ impl<'a, 'gcx: 'tcx, 'tcx: 'a> CodegenUnitNameBuilder<'a, 'gcx, 'tcx> {
                 String::new()
             };
 
-            let crate_disambiguator = format!("{}", tcx.crate_disambiguator(cnum));
+            let crate_disambiguator = tcx.crate_disambiguator(cnum).to_string();
             // Using a shortened disambiguator of about 40 bits
             format!("{}.{}{}",
                 tcx.crate_name(cnum),

src/librustc/mir/tcx.rs

@@ -87,8 +87,8 @@ impl<'a, 'gcx, 'tcx> PlaceTy<'tcx> {
                         assert!(index < adt_def.variants.len());
                         assert_eq!(adt_def, adt_def1);
                         PlaceTy::Downcast { adt_def,
-                                             substs,
-                                             variant_index: index }
+                                            substs,
+                                            variant_index: index }
                     }
                     _ => {
                         bug!("cannot downcast non-ADT type: `{:?}`", self)
@@ -151,7 +151,7 @@ impl<'tcx> Place<'tcx> {
                     }
                 },
                 _ => None,
-            }
+            }
             _ => None,
         }
     }
@@ -255,9 +255,9 @@ impl<'tcx> Operand<'tcx> {
 
 impl<'tcx> BinOp {
       pub fn ty<'a, 'gcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>,
-                    lhs_ty: Ty<'tcx>,
-                    rhs_ty: Ty<'tcx>)
-                    -> Ty<'tcx> {
+                          lhs_ty: Ty<'tcx>,
+                          rhs_ty: Ty<'tcx>)
+                          -> Ty<'tcx> {
         // FIXME: handle SIMD correctly
         match self {
             &BinOp::Add | &BinOp::Sub | &BinOp::Mul | &BinOp::Div | &BinOp::Rem |