Rollup merge of rust-lang#60951 - saleemjaffer:mir_better_error_enum, r=oli-obk

more specific errors in src/librustc/mir/interpret/error.rs

Implements [this](rust-lang/const-eval#4)

Author: Mark-Simulacrum

src/librustc/mir/interpret/error.rs

@@ -228,6 +228,24 @@ impl<'tcx> From<InterpError<'tcx, u64>> for InterpErrorInfo<'tcx> {
 
 pub type AssertMessage<'tcx> = InterpError<'tcx, mir::Operand<'tcx>>;
 
+#[derive(Clone, RustcEncodable, RustcDecodable, HashStable)]
+pub enum PanicMessage<O> {
+    Panic {
+        msg: Symbol,
+        line: u32,
+        col: u32,
+        file: Symbol,
+    },
+    BoundsCheck {
+        len: O,
+        index: O,
+    },
+    Overflow(mir::BinOp),
+    OverflowNeg,
+    DivisionByZero,
+    RemainderByZero,
+}
+
 #[derive(Clone, RustcEncodable, RustcDecodable, HashStable)]
 pub enum InterpError<'tcx, O> {
     /// This variant is used by machines to signal their own errors that do not
@@ -266,11 +284,6 @@ pub enum InterpError<'tcx, O> {
     Unimplemented(String),
     DerefFunctionPointer,
     ExecuteMemory,
-    BoundsCheck { len: O, index: O },
-    Overflow(mir::BinOp),
-    OverflowNeg,
-    DivisionByZero,
-    RemainderByZero,
     Intrinsic(String),
     InvalidChar(u128),
     StackFrameLimitReached,
@@ -298,12 +311,7 @@ pub enum InterpError<'tcx, O> {
     HeapAllocZeroBytes,
     HeapAllocNonPowerOfTwoAlignment(u64),
     Unreachable,
-    Panic {
-        msg: Symbol,
-        line: u32,
-        col: u32,
-        file: Symbol,
-    },
+    Panic(PanicMessage<O>),
     ReadFromReturnPointer,
     PathNotFound(Vec<String>),
     UnimplementedTraitSelection,
@@ -369,8 +377,6 @@ impl<'tcx, O> InterpError<'tcx, O> {
                 "tried to dereference a function pointer",
             ExecuteMemory =>
                 "tried to treat a memory pointer as a function pointer",
-            BoundsCheck{..} =>
-                "array index out of bounds",
             Intrinsic(..) =>
                 "intrinsic failed",
             NoMirFor(..) =>
@@ -422,8 +428,32 @@ impl<'tcx, O> InterpError<'tcx, O> {
                 two",
             Unreachable =>
                 "entered unreachable code",
-            Panic { .. } =>
+            Panic(PanicMessage::Panic{..}) =>
                 "the evaluated program panicked",
+            Panic(PanicMessage::BoundsCheck{..}) =>
+                "array index out of bounds",
+            Panic(PanicMessage::Overflow(mir::BinOp::Add)) =>
+                "attempt to add with overflow",
+            Panic(PanicMessage::Overflow(mir::BinOp::Sub)) =>
+                "attempt to subtract with overflow",
+            Panic(PanicMessage::Overflow(mir::BinOp::Mul)) =>
+                "attempt to multiply with overflow",
+            Panic(PanicMessage::Overflow(mir::BinOp::Div)) =>
+                "attempt to divide with overflow",
+            Panic(PanicMessage::Overflow(mir::BinOp::Rem)) =>
+                "attempt to calculate the remainder with overflow",
+            Panic(PanicMessage::OverflowNeg) =>
+                "attempt to negate with overflow",
+            Panic(PanicMessage::Overflow(mir::BinOp::Shr)) =>
+                "attempt to shift right with overflow",
+            Panic(PanicMessage::Overflow(mir::BinOp::Shl)) =>
+                "attempt to shift left with overflow",
+            Panic(PanicMessage::Overflow(op)) =>
+                bug!("{:?} cannot overflow", op),
+            Panic(PanicMessage::DivisionByZero) =>
+                "attempt to divide by zero",
+            Panic(PanicMessage::RemainderByZero) =>
+                "attempt to calculate the remainder with a divisor of zero",
             ReadFromReturnPointer =>
                 "tried to read from the return pointer",
             PathNotFound(_) =>
@@ -436,17 +466,6 @@ impl<'tcx, O> InterpError<'tcx, O> {
                 "encountered overly generic constant",
             ReferencedConstant =>
                 "referenced constant has errors",
-            Overflow(mir::BinOp::Add) => "attempt to add with overflow",
-            Overflow(mir::BinOp::Sub) => "attempt to subtract with overflow",
-            Overflow(mir::BinOp::Mul) => "attempt to multiply with overflow",
-            Overflow(mir::BinOp::Div) => "attempt to divide with overflow",
-            Overflow(mir::BinOp::Rem) => "attempt to calculate the remainder with overflow",
-            OverflowNeg => "attempt to negate with overflow",
-            Overflow(mir::BinOp::Shr) => "attempt to shift right with overflow",
-            Overflow(mir::BinOp::Shl) => "attempt to shift left with overflow",
-            Overflow(op) => bug!("{:?} cannot overflow", op),
-            DivisionByZero => "attempt to divide by zero",
-            RemainderByZero => "attempt to calculate the remainder with a divisor of zero",
             GeneratorResumedAfterReturn => "generator resumed after completion",
             GeneratorResumedAfterPanic => "generator resumed after panicking",
             InfiniteLoop =>
@@ -493,8 +512,6 @@ impl<'tcx, O: fmt::Debug> fmt::Debug for InterpError<'tcx, O> {
                     callee_ty, caller_ty),
             FunctionArgCountMismatch =>
                 write!(f, "tried to call a function with incorrect number of arguments"),
-            BoundsCheck { ref len, ref index } =>
-                write!(f, "index out of bounds: the len is {:?} but the index is {:?}", len, index),
             ReallocatedWrongMemoryKind(ref old, ref new) =>
                 write!(f, "tried to reallocate memory from {} to {}", old, new),
             DeallocatedWrongMemoryKind(ref old, ref new) =>
@@ -518,8 +535,10 @@ impl<'tcx, O: fmt::Debug> fmt::Debug for InterpError<'tcx, O> {
                 write!(f, "incorrect alloc info: expected size {} and align {}, \
                            got size {} and align {}",
                     size.bytes(), align.bytes(), size2.bytes(), align2.bytes()),
-            Panic { ref msg, line, col, ref file } =>
+            Panic(PanicMessage::Panic { ref msg, line, col, ref file }) =>
                 write!(f, "the evaluated program panicked at '{}', {}:{}:{}", msg, file, line, col),
+            Panic(PanicMessage::BoundsCheck { ref len, ref index }) =>
+                write!(f, "index out of bounds: the len is {:?} but the index is {:?}", len, index),
             InvalidDiscriminant(val) =>
                 write!(f, "encountered invalid enum discriminant {}", val),
             Exit(code) =>

src/librustc/mir/interpret/mod.rs

@@ -12,7 +12,7 @@ mod pointer;
 
 pub use self::error::{
     InterpErrorInfo, InterpResult, InterpError, AssertMessage, ConstEvalErr, struct_error,
-    FrameInfo, ConstEvalRawResult, ConstEvalResult, ErrorHandled,
+    FrameInfo, ConstEvalRawResult, ConstEvalResult, ErrorHandled, PanicMessage
 };
 
 pub use self::value::{Scalar, ScalarMaybeUndef, RawConst, ConstValue};

src/librustc/mir/interpret/pointer.rs

@@ -5,7 +5,7 @@ use crate::ty::layout::{self, HasDataLayout, Size};
 use rustc_macros::HashStable;
 
 use super::{
-    AllocId, InterpResult,
+    AllocId, InterpResult, PanicMessage
 };
 
 /// Used by `check_in_alloc` to indicate context of check
@@ -76,13 +76,13 @@ pub trait PointerArithmetic: layout::HasDataLayout {
     #[inline]
     fn offset<'tcx>(&self, val: u64, i: u64) -> InterpResult<'tcx, u64> {
         let (res, over) = self.overflowing_offset(val, i);
-        if over { err!(Overflow(mir::BinOp::Add)) } else { Ok(res) }
+        if over { err!(Panic(PanicMessage::Overflow(mir::BinOp::Add))) } else { Ok(res) }
     }
 
     #[inline]
     fn signed_offset<'tcx>(&self, val: u64, i: i64) -> InterpResult<'tcx, u64> {
         let (res, over) = self.overflowing_signed_offset(val, i128::from(i));
-        if over { err!(Overflow(mir::BinOp::Add)) } else { Ok(res) }
+        if over { err!(Panic(PanicMessage::Overflow(mir::BinOp::Add))) } else { Ok(res) }
     }
 }
 

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, InterpError, Scalar};
+use crate::mir::interpret::{ConstValue, PanicMessage, InterpError::Panic, Scalar};
 use crate::mir::visit::MirVisitable;
 use crate::rustc_serialize as serialize;
 use crate::ty::adjustment::PointerCast;
@@ -3152,11 +3152,11 @@ impl<'tcx> TypeFoldable<'tcx> for Terminator<'tcx> {
                 }
             }
             Assert { ref cond, expected, ref msg, target, cleanup } => {
-                let msg = if let InterpError::BoundsCheck { ref len, ref index } = *msg {
-                    InterpError::BoundsCheck {
+                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()
                 };
@@ -3197,7 +3197,7 @@ impl<'tcx> TypeFoldable<'tcx> for Terminator<'tcx> {
             }
             Assert { ref cond, ref msg, .. } => {
                 if cond.visit_with(visitor) {
-                    if let InterpError::BoundsCheck { ref len, ref index } = *msg {
+                    if let Panic(PanicMessage::BoundsCheck { ref len, ref index }) = *msg {
                         len.visit_with(visitor) || index.visit_with(visitor)
                     } else {
                         false

src/librustc/mir/visit.rs

@@ -515,7 +515,8 @@ macro_rules! make_mir_visitor {
                                     msg: & $($mutability)? AssertMessage<'tcx>,
                                     location: Location) {
                 use crate::mir::interpret::InterpError::*;
-                if let BoundsCheck { len, index } = msg {
+                use crate::mir::interpret::PanicMessage::BoundsCheck;
+                if let Panic(BoundsCheck { len, index }) = msg {
                     self.visit_operand(len, location);
                     self.visit_operand(index, location);
                 }

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;
+use rustc::mir::interpret::{InterpError, 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 mir::interpret::InterpError::OverflowNeg = *msg {
+            if let InterpError::Panic(PanicMessage::OverflowNeg) = *msg {
                 const_cond = Some(expected);
             }
         }
@@ -403,7 +403,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
         // Put together the arguments to the panic entry point.
         let (lang_item, args) = match *msg {
-            InterpError::BoundsCheck { ref len, ref index } => {
+            InterpError::Panic(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::BoundsCheck;
-                if let BoundsCheck { ref len, ref index } = *msg {
+                use rustc::mir::interpret::{InterpError::Panic, PanicMessage};
+                if let Panic(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::BoundsCheck;
-                if let BoundsCheck { ref len, ref index } = *msg {
+                use rustc::mir::interpret::{InterpError::Panic, PanicMessage::BoundsCheck};
+                if let Panic(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::BoundsCheck, ConstValue};
+use rustc::mir::interpret::{InterpError::Panic, 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 BoundsCheck { ref len, ref index } = *msg {
+                if let Panic(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::BoundsCheck;
+use rustc::mir::interpret::{InterpError::Panic, PanicMessage::BoundsCheck};
 use rustc::mir::*;
 use rustc::ty::{CanonicalUserTypeAnnotation, Variance};
 
@@ -105,10 +105,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     ),
                 );
 
-                let msg = BoundsCheck {
+                let msg = Panic(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;
+use rustc::mir::interpret::{InterpError::Panic, 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,
-                        InterpError::OverflowNeg,
+                        Panic(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 = InterpError::Overflow(op);
+            let err = Panic(PanicMessage::Overflow(op));
 
             block = self.assert(block, Operand::Move(of), false, err, span);
 
@@ -412,9 +412,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 // and 2. there are two possible failure cases, divide-by-zero and overflow.
 
                 let (zero_err, overflow_err) = if op == BinOp::Div {
-                    (InterpError::DivisionByZero, InterpError::Overflow(op))
+                    (Panic(PanicMessage::DivisionByZero), Panic(PanicMessage::Overflow(op)))
                 } else {
-                    (InterpError::RemainderByZero, InterpError::Overflow(op))
+                    (Panic(PanicMessage::RemainderByZero), Panic(PanicMessage::Overflow(op)))
                 };
 
                 // Check for / 0

src/librustc_mir/interpret/intrinsics.rs

@@ -7,7 +7,7 @@ use rustc::ty;
 use rustc::ty::layout::{LayoutOf, Primitive, Size};
 use rustc::mir::BinOp;
 use rustc::mir::interpret::{
-    InterpResult, InterpError, Scalar,
+    InterpResult, InterpError, Scalar, PanicMessage,
 };
 
 use super::{
@@ -261,7 +261,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             let file = Symbol::intern(self.read_str(file_place)?);
             let line = self.read_scalar(line.into())?.to_u32()?;
             let col = self.read_scalar(col.into())?.to_u32()?;
-            return Err(InterpError::Panic { msg, file, line, col }.into());
+            return Err(InterpError::Panic(PanicMessage::Panic { msg, file, line, col }).into());
         } else if Some(def_id) == self.tcx.lang_items().begin_panic_fn() {
             assert!(args.len() == 2);
             // &'static str, &(&'static str, u32, u32)
@@ -279,7 +279,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             let file = Symbol::intern(self.read_str(file_place)?);
             let line = self.read_scalar(line.into())?.to_u32()?;
             let col = self.read_scalar(col.into())?.to_u32()?;
-            return Err(InterpError::Panic { msg, file, line, col }.into());
+            return Err(InterpError::Panic(PanicMessage::Panic { msg, file, line, col }).into());
         } else {
             return Ok(false);
         }

src/librustc_mir/interpret/operator.rs

@@ -2,7 +2,7 @@ use rustc::mir;
 use rustc::ty::{self, layout::TyLayout};
 use syntax::ast::FloatTy;
 use rustc_apfloat::Float;
-use rustc::mir::interpret::{InterpResult, Scalar};
+use rustc::mir::interpret::{InterpResult, PanicMessage, Scalar};
 
 use super::{InterpCx, PlaceTy, Immediate, Machine, ImmTy};
 
@@ -173,8 +173,8 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 return Ok((Scalar::from_bool(op(&l, &r)), false));
             }
             let op: Option<fn(i128, i128) -> (i128, bool)> = match bin_op {
-                Div if r == 0 => return err!(DivisionByZero),
-                Rem if r == 0 => return err!(RemainderByZero),
+                Div if r == 0 => return err!(Panic(PanicMessage::DivisionByZero)),
+                Rem if r == 0 => return err!(Panic(PanicMessage::RemainderByZero)),
                 Div => Some(i128::overflowing_div),
                 Rem => Some(i128::overflowing_rem),
                 Add => Some(i128::overflowing_add),
@@ -231,8 +231,8 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     Add => u128::overflowing_add,
                     Sub => u128::overflowing_sub,
                     Mul => u128::overflowing_mul,
-                    Div if r == 0 => return err!(DivisionByZero),
-                    Rem if r == 0 => return err!(RemainderByZero),
+                    Div if r == 0 => return err!(Panic(PanicMessage::DivisionByZero)),
+                    Rem if r == 0 => return err!(Panic(PanicMessage::RemainderByZero)),
                     Div => u128::overflowing_div,
                     Rem => u128::overflowing_rem,
                     _ => bug!(),