Auto merge of #59276 - oli-obk:cleanups, r=eddyb

Cleanup (pretty) printing of `ty::Const`

r? @eddyb

addresses https://github.com/rust-lang/rust/pull/59178/files/5cd28066214a4a255bac6655c20bf05cb95730fd#r266243236 and https://github.com/rust-lang/rust/pull/59178/files/5cd28066214a4a255bac6655c20bf05cb95730fd#r266243336

Author: bors

.gitignore

@@ -12,7 +12,7 @@ __pycache__/
 .project
 .settings/
 .valgrindrc
-.vscode/
+.vscode
 .favorites.json
 /*-*-*-*/
 /*-*-*/

src/librustc/infer/error_reporting/mod.rs

@@ -462,6 +462,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
             type Region = !;
             type Type = !;
             type DynExistential = !;
+            type Const = !;
 
             fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx> {
                 self.tcx
@@ -488,6 +489,13 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 Err(NonTrivialPath)
             }
 
+            fn print_const(
+                self,
+                _ct: &'tcx ty::Const<'tcx>,
+            ) -> Result<Self::Const, Self::Error> {
+                Err(NonTrivialPath)
+            }
+
             fn path_crate(
                 self,
                 cnum: CrateNum,

src/librustc/infer/freshen.rs

@@ -260,7 +260,7 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for TypeFreshener<'a, 'gcx, 'tcx> {
 
             ConstValue::Param(_) |
             ConstValue::Scalar(_) |
-            ConstValue::Slice(..) |
+            ConstValue::Slice { .. } |
             ConstValue::ByRef(..) |
             ConstValue::Unevaluated(..) => {}
         }

src/librustc/lint/context.rs

@@ -791,6 +791,7 @@ impl<'a, 'tcx> LateContext<'a, 'tcx> {
             type Region = ();
             type Type = ();
             type DynExistential = ();
+            type Const = ();
 
             fn tcx<'a>(&'a self) -> TyCtxt<'a, 'tcx, 'tcx> {
                 self.tcx
@@ -807,7 +808,14 @@ impl<'a, 'tcx> LateContext<'a, 'tcx> {
             fn print_dyn_existential(
                 self,
                 _predicates: &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
-                ) -> Result<Self::DynExistential, Self::Error> {
+            ) -> Result<Self::DynExistential, Self::Error> {
+                Ok(())
+            }
+
+            fn print_const(
+                self,
+                _ct: &'tcx ty::Const<'tcx>,
+            ) -> Result<Self::Const, Self::Error> {
                 Ok(())
             }
 

src/librustc/mir/interpret/error.rs

@@ -38,7 +38,7 @@ impl ErrorHandled {
 }
 
 pub type ConstEvalRawResult<'tcx> = Result<RawConst<'tcx>, ErrorHandled>;
-pub type ConstEvalResult<'tcx> = Result<ty::Const<'tcx>, ErrorHandled>;
+pub type ConstEvalResult<'tcx> = Result<&'tcx ty::Const<'tcx>, ErrorHandled>;
 
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable)]
 pub struct ConstEvalErr<'tcx> {

src/librustc/mir/interpret/value.rs

@@ -35,14 +35,12 @@ pub enum ConstValue<'tcx> {
     /// Not using the enum `Value` to encode that this must not be `Undef`.
     Scalar(Scalar),
 
-    /// Used only for slices and strings (`&[T]`, `&str`, `*const [T]`, `*mut str`, `Box<str>`,
-    /// etc.).
-    ///
-    /// Empty slices don't necessarily have an address backed by an `AllocId`, thus we also need to
-    /// enable integer pointers. The `Scalar` type covers exactly those two cases. While we could
-    /// create dummy-`AllocId`s, the additional code effort for the conversions doesn't seem worth
-    /// it.
-    Slice(Scalar, u64),
+    /// Used only for `&[u8]` and `&str`
+    Slice {
+        data: &'tcx Allocation,
+        start: usize,
+        end: usize,
+    },
 
     /// An allocation together with a pointer into the allocation.
     /// Invariant: the pointer's `AllocId` resolves to the allocation.
@@ -54,7 +52,7 @@ pub enum ConstValue<'tcx> {
 }
 
 #[cfg(target_arch = "x86_64")]
-static_assert_size!(ConstValue<'_>, 40);
+static_assert_size!(ConstValue<'_>, 32);
 
 impl<'tcx> ConstValue<'tcx> {
     #[inline]
@@ -65,7 +63,7 @@ impl<'tcx> ConstValue<'tcx> {
             ConstValue::Placeholder(_) |
             ConstValue::ByRef(..) |
             ConstValue::Unevaluated(..) |
-            ConstValue::Slice(..) => None,
+            ConstValue::Slice { .. } => None,
             ConstValue::Scalar(val) => Some(val),
         }
     }
@@ -79,14 +77,6 @@ impl<'tcx> ConstValue<'tcx> {
     pub fn try_to_ptr(&self) -> Option<Pointer> {
         self.try_to_scalar()?.to_ptr().ok()
     }
-
-    #[inline]
-    pub fn new_slice(
-        val: Scalar,
-        len: u64,
-    ) -> Self {
-        ConstValue::Slice(val, len)
-    }
 }
 
 /// A `Scalar` represents an immediate, primitive value existing outside of a

src/librustc/mir/mod.rs

@@ -9,8 +9,6 @@ use crate::hir::def_id::DefId;
 use crate::hir::{self, InlineAsm as HirInlineAsm};
 use crate::mir::interpret::{ConstValue, InterpError, Scalar};
 use crate::mir::visit::MirVisitable;
-use rustc_apfloat::ieee::{Double, Single};
-use rustc_apfloat::Float;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::graph::dominators::{dominators, Dominators};
 use rustc_data_structures::graph::{self, GraphPredecessors, GraphSuccessors};
@@ -21,13 +19,13 @@ use rustc_macros::HashStable;
 use crate::rustc_serialize::{self as serialize};
 use smallvec::SmallVec;
 use std::borrow::Cow;
-use std::fmt::{self, Debug, Formatter, Write};
+use std::fmt::{self, Debug, Formatter, Write, Display};
 use std::iter::FusedIterator;
 use std::ops::{Index, IndexMut};
 use std::slice;
 use std::vec::IntoIter;
 use std::{iter, mem, option, u32};
-use syntax::ast::{self, Name};
+use syntax::ast::Name;
 use syntax::symbol::{InternedString, Symbol};
 use syntax_pos::{Span, DUMMY_SP};
 use crate::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
@@ -1662,28 +1660,25 @@ impl<'tcx> TerminatorKind<'tcx> {
                 switch_ty,
                 ..
             } => {
-                let size = ty::tls::with(|tcx| {
+                ty::tls::with(|tcx| {
                     let param_env = ty::ParamEnv::empty();
                     let switch_ty = tcx.lift_to_global(&switch_ty).unwrap();
-                    tcx.layout_of(param_env.and(switch_ty)).unwrap().size
-                });
-                values
-                    .iter()
-                    .map(|&u| {
-                        let mut s = String::new();
-                        let c = ty::Const {
-                            val: ConstValue::Scalar(
-                                Scalar::Bits {
-                                    bits: u,
-                                    size: size.bytes() as u8,
-                                }.into(),
-                            ),
-                            ty: switch_ty,
-                        };
-                        fmt_const_val(&mut s, c).unwrap();
-                        s.into()
-                    }).chain(iter::once("otherwise".into()))
-                    .collect()
+                    let size = tcx.layout_of(param_env.and(switch_ty)).unwrap().size;
+                    values
+                        .iter()
+                        .map(|&u| {
+                            tcx.mk_const(ty::Const {
+                                val: ConstValue::Scalar(
+                                    Scalar::Bits {
+                                        bits: u,
+                                        size: size.bytes() as u8,
+                                    }.into(),
+                                ),
+                                ty: switch_ty,
+                            }).to_string().into()
+                        }).chain(iter::once("otherwise".into()))
+                        .collect()
+                })
             }
             Call {
                 destination: Some(_),
@@ -2331,9 +2326,7 @@ impl<'tcx> Operand<'tcx> {
             span,
             ty,
             user_ty: None,
-            literal: tcx.mk_const(
-                ty::Const::zero_sized(ty),
-            ),
+            literal: ty::Const::zero_sized(tcx, ty),
         })
     }
 
@@ -2827,67 +2820,15 @@ newtype_index! {
 
 impl<'tcx> Debug for Constant<'tcx> {
     fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
-        write!(fmt, "const ")?;
-        fmt_const_val(fmt, *self.literal)
-    }
-}
-/// Write a `ConstValue` in a way closer to the original source code than the `Debug` output.
-pub fn fmt_const_val(f: &mut impl Write, const_val: ty::Const<'_>) -> fmt::Result {
-    use crate::ty::TyKind::*;
-    let value = const_val.val;
-    let ty = const_val.ty;
-    // print some primitives
-    if let ConstValue::Scalar(Scalar::Bits { bits, .. }) = value {
-        match ty.sty {
-            Bool if bits == 0 => return write!(f, "false"),
-            Bool if bits == 1 => return write!(f, "true"),
-            Float(ast::FloatTy::F32) => return write!(f, "{}f32", Single::from_bits(bits)),
-            Float(ast::FloatTy::F64) => return write!(f, "{}f64", Double::from_bits(bits)),
-            Uint(ui) => return write!(f, "{:?}{}", bits, ui),
-            Int(i) => {
-                let bit_width = ty::tls::with(|tcx| {
-                    let ty = tcx.lift_to_global(&ty).unwrap();
-                    tcx.layout_of(ty::ParamEnv::empty().and(ty))
-                        .unwrap()
-                        .size
-                        .bits()
-                });
-                let shift = 128 - bit_width;
-                return write!(f, "{:?}{}", ((bits as i128) << shift) >> shift, i);
-            }
-            Char => return write!(f, "{:?}", ::std::char::from_u32(bits as u32).unwrap()),
-            _ => {}
-        }
+        write!(fmt, "{}", self)
     }
-    // print function definitions
-    if let FnDef(did, _) = ty.sty {
-        return write!(f, "{}", def_path_str(did));
-    }
-    // print string literals
-    if let ConstValue::Slice(ptr, len) = value {
-        if let Scalar::Ptr(ptr) = ptr {
-            if let Ref(_, &ty::TyS { sty: Str, .. }, _) = ty.sty {
-                return ty::tls::with(|tcx| {
-                    let alloc = tcx.alloc_map.lock().get(ptr.alloc_id);
-                    if let Some(interpret::AllocKind::Memory(alloc)) = alloc {
-                        assert_eq!(len as usize as u64, len);
-                        let slice =
-                            &alloc.bytes[(ptr.offset.bytes() as usize)..][..(len as usize)];
-                        let s = ::std::str::from_utf8(slice).expect("non utf8 str from miri");
-                        write!(f, "{:?}", s)
-                    } else {
-                        write!(f, "pointer to erroneous constant {:?}, {:?}", ptr, len)
-                    }
-                });
-            }
-        }
-    }
-    // just raw dump everything else
-    write!(f, "{:?} : {}", value, ty)
 }
 
-fn def_path_str(def_id: DefId) -> String {
-    ty::tls::with(|tcx| tcx.def_path_str(def_id))
+impl<'tcx> Display for Constant<'tcx> {
+    fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
+        write!(fmt, "const ")?;
+        write!(fmt, "{}", self.literal)
+    }
 }
 
 impl<'tcx> graph::DirectedGraph for Mir<'tcx> {

src/librustc/traits/project.rs

@@ -412,7 +412,6 @@ impl<'a, 'b, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for AssociatedTypeNormalizer<'a,
                         };
                         if let Ok(evaluated) = tcx.const_eval(param_env.and(cid)) {
                             let substs = tcx.lift_to_global(&substs).unwrap();
-                            let evaluated = tcx.mk_const(evaluated);
                             let evaluated = evaluated.subst(tcx, substs);
                             return evaluated;
                         }
@@ -426,7 +425,7 @@ impl<'a, 'b, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for AssociatedTypeNormalizer<'a,
                                 promoted: None
                             };
                             if let Ok(evaluated) = tcx.const_eval(param_env.and(cid)) {
-                                return tcx.mk_const(evaluated);
+                                return evaluated;
                             }
                         }
                     }

src/librustc/traits/query/normalize.rs

@@ -202,7 +202,6 @@ impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for QueryNormalizer<'cx, 'gcx, 'tcx
                         };
                         if let Ok(evaluated) = tcx.const_eval(param_env.and(cid)) {
                             let substs = tcx.lift_to_global(&substs).unwrap();
-                            let evaluated = tcx.mk_const(evaluated);
                             let evaluated = evaluated.subst(tcx, substs);
                             return evaluated;
                         }
@@ -216,7 +215,7 @@ impl<'cx, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for QueryNormalizer<'cx, 'gcx, 'tcx
                                 promoted: None,
                             };
                             if let Ok(evaluated) = tcx.const_eval(param_env.and(cid)) {
-                                return tcx.mk_const(evaluated);
+                                return evaluated;
                             }
                         }
                     }

src/librustc/ty/context.rs

@@ -24,7 +24,7 @@ use crate::middle::lang_items;
 use crate::middle::resolve_lifetime::{self, ObjectLifetimeDefault};
 use crate::middle::stability;
 use crate::mir::{self, Mir, interpret, ProjectionKind};
-use crate::mir::interpret::{ConstValue, Allocation};
+use crate::mir::interpret::{ConstValue, Allocation, Scalar};
 use crate::ty::subst::{Kind, InternalSubsts, SubstsRef, Subst};
 use crate::ty::ReprOptions;
 use crate::traits;
@@ -1000,7 +1000,10 @@ impl<'tcx> CommonConsts<'tcx> {
         };
 
         CommonConsts {
-            err: mk_const(ty::Const::zero_sized(types.err)),
+            err: mk_const(ty::Const {
+                val: ConstValue::Scalar(Scalar::Bits { bits: 0, size: 0 }),
+                ty: types.err,
+            }),
         }
     }
 }
@@ -1822,14 +1825,6 @@ nop_list_lift!{ProjectionKind => ProjectionKind}
 // this is the impl for `&'a InternalSubsts<'a>`
 nop_list_lift!{Kind<'a> => Kind<'tcx>}
 
-impl<'a, 'tcx> Lift<'tcx> for &'a mir::interpret::Allocation {
-    type Lifted = &'tcx mir::interpret::Allocation;
-    fn lift_to_tcx<'b, 'gcx>(&self, tcx: TyCtxt<'b, 'gcx, 'tcx>) -> Option<Self::Lifted> {
-        assert!(tcx.global_arenas.const_allocs.in_arena(*self as *const _));
-        Some(unsafe { mem::transmute(*self) })
-    }
-}
-
 pub mod tls {
     use super::{GlobalCtxt, TyCtxt, ptr_eq};
 
@@ -2594,9 +2589,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 
     #[inline]
     pub fn mk_array(self, ty: Ty<'tcx>, n: u64) -> Ty<'tcx> {
-        self.mk_ty(Array(ty, self.mk_const(
-            ty::Const::from_usize(self.global_tcx(), n)
-        )))
+        self.mk_ty(Array(ty, ty::Const::from_usize(self.global_tcx(), n)))
     }
 
     #[inline]