Rollup merge of rust-lang#62927 - RalfJung:panic, r=oli-obk

use PanicMessage in MIR, kill InterpError::description

r? @oli-obk @eddyb
Cc @saleemjaffer rust-lang/const-eval#4

src/librustc/mir/mod.rs

@@ -7,7 +7,7 @@
 use crate::hir::def::{CtorKind, Namespace};
 use crate::hir::def_id::DefId;
 use crate::hir::{self, InlineAsm as HirInlineAsm};
-use crate::mir::interpret::{ConstValue, PanicMessage, InterpError::Panic, Scalar};
+use crate::mir::interpret::{ConstValue, PanicMessage, Scalar};
 use crate::mir::visit::MirVisitable;
 use crate::rustc_serialize as serialize;
 use crate::ty::adjustment::PointerCast;
@@ -3152,13 +3152,16 @@ impl<'tcx> TypeFoldable<'tcx> for Terminator<'tcx> {
                 }
             }
             Assert { ref cond, expected, ref msg, target, cleanup } => {
-                let msg = if let Panic(PanicMessage::BoundsCheck { ref len, ref index }) = *msg {
-                    Panic(PanicMessage::BoundsCheck {
-                        len: len.fold_with(folder),
-                        index: index.fold_with(folder),
-                    })
-                } else {
-                    msg.clone()
+                use PanicMessage::*;
+                let msg = match msg {
+                    BoundsCheck { ref len, ref index } =>
+                        BoundsCheck {
+                            len: len.fold_with(folder),
+                            index: index.fold_with(folder),
+                        },
+                    Panic { .. } | Overflow(_) | OverflowNeg | DivisionByZero | RemainderByZero |
+                    GeneratorResumedAfterReturn | GeneratorResumedAfterPanic =>
+                        msg.clone(),
                 };
                 Assert { cond: cond.fold_with(folder), expected, msg, target, cleanup }
             }
@@ -3197,10 +3200,14 @@ impl<'tcx> TypeFoldable<'tcx> for Terminator<'tcx> {
             }
             Assert { ref cond, ref msg, .. } => {
                 if cond.visit_with(visitor) {
-                    if let Panic(PanicMessage::BoundsCheck { ref len, ref index }) = *msg {
-                        len.visit_with(visitor) || index.visit_with(visitor)
-                    } else {
-                        false
+                    use PanicMessage::*;
+                    match msg {
+                        BoundsCheck { ref len, ref index } =>
+                            len.visit_with(visitor) || index.visit_with(visitor),
+                        Panic { .. } | Overflow(_) | OverflowNeg |
+                        DivisionByZero | RemainderByZero |
+                        GeneratorResumedAfterReturn | GeneratorResumedAfterPanic =>
+                            false
                     }
                 } else {
                     false

src/librustc/mir/visit.rs

@@ -514,11 +514,16 @@ macro_rules! make_mir_visitor {
             fn super_assert_message(&mut self,
                                     msg: & $($mutability)? AssertMessage<'tcx>,
                                     location: Location) {
-                use crate::mir::interpret::InterpError::*;
-                use crate::mir::interpret::PanicMessage::BoundsCheck;
-                if let Panic(BoundsCheck { len, index }) = msg {
-                    self.visit_operand(len, location);
-                    self.visit_operand(index, location);
+                use crate::mir::interpret::PanicMessage::*;
+                match msg {
+                    BoundsCheck { len, index } => {
+                        self.visit_operand(len, location);
+                        self.visit_operand(index, location);
+                    }
+                    Panic { .. } | Overflow(_) | OverflowNeg | DivisionByZero | RemainderByZero |
+                    GeneratorResumedAfterReturn | GeneratorResumedAfterPanic => {
+                        // Nothing to visit
+                    }
                 }
             }
 

src/librustc_codegen_ssa/mir/block.rs

@@ -2,7 +2,7 @@ use rustc::middle::lang_items;
 use rustc::ty::{self, Ty, TypeFoldable, Instance};
 use rustc::ty::layout::{self, LayoutOf, HasTyCtxt, FnTypeExt};
 use rustc::mir::{self, Place, PlaceBase, Static, StaticKind};
-use rustc::mir::interpret::{InterpError, PanicMessage};
+use rustc::mir::interpret::PanicMessage;
 use rustc_target::abi::call::{ArgType, FnType, PassMode, IgnoreMode};
 use rustc_target::spec::abi::Abi;
 use crate::base;
@@ -368,7 +368,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         // checked operation, just a comparison with the minimum
         // value, so we have to check for the assert message.
         if !bx.check_overflow() {
-            if let InterpError::Panic(PanicMessage::OverflowNeg) = *msg {
+            if let PanicMessage::OverflowNeg = *msg {
                 const_cond = Some(expected);
             }
         }
@@ -402,8 +402,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         let col = bx.const_u32(loc.col.to_usize() as u32 + 1);
 
         // Put together the arguments to the panic entry point.
-        let (lang_item, args) = match *msg {
-            InterpError::Panic(PanicMessage::BoundsCheck { ref len, ref index }) => {
+        let (lang_item, args) = match msg {
+            PanicMessage::BoundsCheck { ref len, ref index } => {
                 let len = self.codegen_operand(&mut bx, len).immediate();
                 let index = self.codegen_operand(&mut bx, index).immediate();
 

src/librustc_mir/borrow_check/mod.rs

@@ -733,8 +733,8 @@ impl<'cx, 'tcx> DataflowResultsConsumer<'cx, 'tcx> for MirBorrowckCtxt<'cx, 'tcx
                 cleanup: _,
             } => {
                 self.consume_operand(loc, (cond, span), flow_state);
-                use rustc::mir::interpret::{InterpError::Panic, PanicMessage};
-                if let Panic(PanicMessage::BoundsCheck { ref len, ref index }) = *msg {
+                use rustc::mir::interpret::PanicMessage;
+                if let PanicMessage::BoundsCheck { ref len, ref index } = *msg {
                     self.consume_operand(loc, (len, span), flow_state);
                     self.consume_operand(loc, (index, span), flow_state);
                 }

src/librustc_mir/borrow_check/nll/invalidation.rs

@@ -207,8 +207,8 @@ impl<'cx, 'tcx> Visitor<'tcx> for InvalidationGenerator<'cx, 'tcx> {
                 cleanup: _,
             } => {
                 self.consume_operand(location, cond);
-                use rustc::mir::interpret::{InterpError::Panic, PanicMessage::BoundsCheck};
-                if let Panic(BoundsCheck { ref len, ref index }) = *msg {
+                use rustc::mir::interpret::PanicMessage;
+                if let PanicMessage::BoundsCheck { ref len, ref index } = *msg {
                     self.consume_operand(location, len);
                     self.consume_operand(location, index);
                 }

src/librustc_mir/borrow_check/nll/type_check/mod.rs

@@ -28,7 +28,7 @@ use rustc::infer::canonical::QueryRegionConstraints;
 use rustc::infer::outlives::env::RegionBoundPairs;
 use rustc::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime, NLLRegionVariableOrigin};
 use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
-use rustc::mir::interpret::{InterpError::Panic, ConstValue, PanicMessage};
+use rustc::mir::interpret::{ConstValue, PanicMessage};
 use rustc::mir::tcx::PlaceTy;
 use rustc::mir::visit::{PlaceContext, Visitor, NonMutatingUseContext};
 use rustc::mir::*;
@@ -1606,7 +1606,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     span_mirbug!(self, term, "bad Assert ({:?}, not bool", cond_ty);
                 }
 
-                if let Panic(PanicMessage::BoundsCheck { ref len, ref index }) = *msg {
+                if let PanicMessage::BoundsCheck { ref len, ref index } = *msg {
                     if len.ty(body, tcx) != tcx.types.usize {
                         span_mirbug!(self, len, "bounds-check length non-usize {:?}", len)
                     }

src/librustc_mir/build/expr/as_place.rs

@@ -4,7 +4,7 @@ use crate::build::expr::category::Category;
 use crate::build::ForGuard::{OutsideGuard, RefWithinGuard};
 use crate::build::{BlockAnd, BlockAndExtension, Builder};
 use crate::hair::*;
-use rustc::mir::interpret::{InterpError::Panic, PanicMessage::BoundsCheck};
+use rustc::mir::interpret::{PanicMessage::BoundsCheck};
 use rustc::mir::*;
 use rustc::ty::{CanonicalUserTypeAnnotation, Variance};
 
@@ -105,10 +105,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     ),
                 );
 
-                let msg = Panic(BoundsCheck {
+                let msg = BoundsCheck {
                     len: Operand::Move(len),
                     index: Operand::Copy(Place::from(idx)),
-                });
+                };
                 let success = this.assert(block, Operand::Move(lt), true, msg, expr_span);
                 success.and(slice.index(idx))
             }

src/librustc_mir/build/expr/as_rvalue.rs

@@ -7,7 +7,7 @@ use crate::build::expr::category::{Category, RvalueFunc};
 use crate::build::{BlockAnd, BlockAndExtension, Builder};
 use crate::hair::*;
 use rustc::middle::region;
-use rustc::mir::interpret::{InterpError::Panic, PanicMessage};
+use rustc::mir::interpret::PanicMessage;
 use rustc::mir::*;
 use rustc::ty::{self, CanonicalUserTypeAnnotation, Ty, UpvarSubsts};
 use syntax_pos::Span;
@@ -101,7 +101,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         block,
                         Operand::Move(is_min),
                         false,
-                        Panic(PanicMessage::OverflowNeg),
+                        PanicMessage::OverflowNeg,
                         expr_span,
                     );
                 }
@@ -401,7 +401,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             let val = result_value.clone().field(val_fld, ty);
             let of = result_value.field(of_fld, bool_ty);
 
-            let err = Panic(PanicMessage::Overflow(op));
+            let err = PanicMessage::Overflow(op);
 
             block = self.assert(block, Operand::Move(of), false, err, span);
 
@@ -411,11 +411,12 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 // Checking division and remainder is more complex, since we 1. always check
                 // and 2. there are two possible failure cases, divide-by-zero and overflow.
 
-                let (zero_err, overflow_err) = if op == BinOp::Div {
-                    (Panic(PanicMessage::DivisionByZero), Panic(PanicMessage::Overflow(op)))
+                let zero_err = if op == BinOp::Div {
+                    PanicMessage::DivisionByZero
                 } else {
-                    (Panic(PanicMessage::RemainderByZero), Panic(PanicMessage::Overflow(op)))
+                    PanicMessage::RemainderByZero
                 };
+                let overflow_err = PanicMessage::Overflow(op);
 
                 // Check for / 0
                 let is_zero = self.temp(bool_ty, span);

src/librustc_mir/interpret/terminator.rs

@@ -7,7 +7,7 @@ use syntax::source_map::Span;
 use rustc_target::spec::abi::Abi;
 
 use super::{
-    InterpResult, PointerArithmetic, InterpError, Scalar, PanicMessage,
+    InterpResult, PointerArithmetic, InterpError, Scalar,
     InterpCx, Machine, Immediate, OpTy, ImmTy, PlaceTy, MPlaceTy, StackPopCleanup, FnVal,
 };
 
@@ -135,28 +135,31 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     self.goto_block(Some(target))?;
                 } else {
                     // Compute error message
-                    use rustc::mir::interpret::InterpError::*;
-                    return match *msg {
-                        Panic(PanicMessage::BoundsCheck { ref len, ref index }) => {
+                    use rustc::mir::interpret::PanicMessage::*;
+                    return match msg {
+                        BoundsCheck { ref len, ref index } => {
                             let len = self.read_immediate(self.eval_operand(len, None)?)
                                 .expect("can't eval len").to_scalar()?
                                 .to_bits(self.memory().pointer_size())? as u64;
                             let index = self.read_immediate(self.eval_operand(index, None)?)
                                 .expect("can't eval index").to_scalar()?
                                 .to_bits(self.memory().pointer_size())? as u64;
-                            err!(Panic(PanicMessage::BoundsCheck { len, index }))
+                            err!(Panic(BoundsCheck { len, index }))
                         }
-                        Panic(PanicMessage::Overflow(op)) =>
-                            Err(Panic(PanicMessage::Overflow(op)).into()),
-                        Panic(PanicMessage::OverflowNeg) =>
-                            Err(Panic(PanicMessage::OverflowNeg).into()),
-                        Panic(PanicMessage::DivisionByZero) =>
-                            Err(Panic(PanicMessage::DivisionByZero).into()),
-                        Panic(PanicMessage::RemainderByZero) =>
-                            Err(Panic(PanicMessage::RemainderByZero).into()),
-                        GeneratorResumedAfterReturn |
-                        GeneratorResumedAfterPanic => unimplemented!(),
-                        _ => bug!(),
+                        Overflow(op) =>
+                            err!(Panic(Overflow(*op))),
+                        OverflowNeg =>
+                            err!(Panic(OverflowNeg)),
+                        DivisionByZero =>
+                            err!(Panic(DivisionByZero)),
+                        RemainderByZero =>
+                            err!(Panic(RemainderByZero)),
+                        GeneratorResumedAfterReturn =>
+                            err!(Panic(GeneratorResumedAfterReturn)),
+                        GeneratorResumedAfterPanic =>
+                            err!(Panic(GeneratorResumedAfterPanic)),
+                        Panic { .. } =>
+                            bug!("`Panic` variant cannot occur in MIR"),
                     };
                 }
             }

src/librustc_mir/transform/const_prop.rs

@@ -13,7 +13,7 @@ use rustc::mir::{
 use rustc::mir::visit::{
     Visitor, PlaceContext, MutatingUseContext, MutVisitor, NonMutatingUseContext,
 };
-use rustc::mir::interpret::{InterpError::Panic, Scalar, GlobalId, InterpResult, PanicMessage};
+use rustc::mir::interpret::{Scalar, GlobalId, InterpResult, InterpError, PanicMessage};
 use rustc::ty::{self, Instance, ParamEnv, Ty, TyCtxt};
 use syntax_pos::{Span, DUMMY_SP};
 use rustc::ty::subst::InternalSubsts;
@@ -314,8 +314,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                     | HeapAllocNonPowerOfTwoAlignment(_)
                     | Unreachable
                     | ReadFromReturnPointer
-                    | GeneratorResumedAfterReturn
-                    | GeneratorResumedAfterPanic
                     | ReferencedConstant
                     | InfiniteLoop
                     => {
@@ -595,7 +593,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                     )
                 } else {
                     if overflow {
-                        let err = Panic(PanicMessage::Overflow(op)).into();
+                        let err = InterpError::Panic(PanicMessage::Overflow(op)).into();
                         let _: Option<()> = self.use_ecx(source_info, |_| Err(err));
                         return None;
                     }
@@ -809,7 +807,7 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
         self.super_terminator(terminator, location);
         let source_info = terminator.source_info;
         match &mut terminator.kind {
-            TerminatorKind::Assert { expected, msg, ref mut cond, .. } => {
+            TerminatorKind::Assert { expected, ref msg, ref mut cond, .. } => {
                 if let Some(value) = self.eval_operand(&cond, source_info) {
                     trace!("assertion on {:?} should be {:?}", value, expected);
                     let expected = ScalarMaybeUndef::from(Scalar::from_bool(*expected));
@@ -831,13 +829,13 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
                             .hir()
                             .as_local_hir_id(self.source.def_id())
                             .expect("some part of a failing const eval must be local");
-                        use rustc::mir::interpret::InterpError::*;
                         let msg = match msg {
-                            Panic(PanicMessage::Overflow(_)) |
-                            Panic(PanicMessage::OverflowNeg) |
-                            Panic(PanicMessage::DivisionByZero) |
-                            Panic(PanicMessage::RemainderByZero) => msg.description().to_owned(),
-                            Panic(PanicMessage::BoundsCheck { ref len, ref index }) => {
+                            PanicMessage::Overflow(_) |
+                            PanicMessage::OverflowNeg |
+                            PanicMessage::DivisionByZero |
+                            PanicMessage::RemainderByZero =>
+                                msg.description().to_owned(),
+                            PanicMessage::BoundsCheck { ref len, ref index } => {
                                 let len = self
                                     .eval_operand(len, source_info)
                                     .expect("len must be const");

src/librustc_mir/transform/generator.rs

@@ -1016,7 +1016,7 @@ fn create_generator_resume_function<'tcx>(
 
     let mut cases = create_cases(body, &transform, |point| Some(point.resume));
 
-    use rustc::mir::interpret::InterpError::{
+    use rustc::mir::interpret::PanicMessage::{
         GeneratorResumedAfterPanic,
         GeneratorResumedAfterReturn,
     };