Suppress "erroneous constant used" for constants tainted by errors

When constant evaluation fails because its MIR is tainted by errors,
suppress note indicating that erroneous constant was used, since those
errors have to be fixed regardless of the constant being used or not.

Author: tmiasko

compiler/rustc_const_eval/src/const_eval/error.rs

@@ -169,14 +169,14 @@ impl<'tcx> ConstEvalErr<'tcx> {
                 // See <https://github.com/rust-lang/rust/pull/63152>.
                 let mut err = struct_error(tcx, &self.error.to_string());
                 self.decorate(&mut err, decorate);
-                ErrorHandled::Reported(err.emit())
+                ErrorHandled::Reported(err.emit().into())
             }
             _ => {
                 // Report as hard error.
                 let mut err = struct_error(tcx, message);
                 err.span_label(self.span, self.error.to_string());
                 self.decorate(&mut err, decorate);
-                ErrorHandled::Reported(err.emit())
+                ErrorHandled::Reported(err.emit().into())
             }
         }
     }

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -382,7 +382,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
                         rustc_span::DUMMY_SP,
                         "This is likely a const item that is missing from its impl",
                     );
-                    throw_inval!(AlreadyReported(guar));
+                    throw_inval!(AlreadyReported(guar.into()));
                 } else {
                     // `find_mir_or_eval_fn` checks that this is a const fn before even calling us,
                     // so this should be unreachable.

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -7,7 +7,7 @@ use either::{Either, Left, Right};
 use rustc_hir::{self as hir, def_id::DefId, definitions::DefPathData};
 use rustc_index::IndexVec;
 use rustc_middle::mir;
-use rustc_middle::mir::interpret::{ErrorHandled, InterpError};
+use rustc_middle::mir::interpret::{ErrorHandled, InterpError, ReportedErrorInfo};
 use rustc_middle::ty::layout::{
     self, FnAbiError, FnAbiOfHelpers, FnAbiRequest, LayoutError, LayoutOf, LayoutOfHelpers,
     TyAndLayout,
@@ -470,7 +470,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         };
         // do not continue if typeck errors occurred (can only occur in local crate)
         if let Some(err) = body.tainted_by_errors {
-            throw_inval!(AlreadyReported(err));
+            throw_inval!(AlreadyReported(ReportedErrorInfo::tainted_by_errors(err)));
         }
         Ok(body)
     }
@@ -517,7 +517,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             Ok(None) => throw_inval!(TooGeneric),
 
             // FIXME(eddyb) this could be a bit more specific than `AlreadyReported`.
-            Err(error_reported) => throw_inval!(AlreadyReported(error_reported)),
+            Err(error_reported) => throw_inval!(AlreadyReported(error_reported.into())),
         }
     }
 
@@ -905,7 +905,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         query(self.tcx.at(span.unwrap_or_else(|| self.cur_span()))).map_err(|err| {
             match err {
                 ErrorHandled::Reported(err) => {
-                    if let Some(span) = span {
+                    if !err.is_tainted_by_errors() && let Some(span) = span {
                         // To make it easier to figure out where this error comes from, also add a note at the current location.
                         self.tcx.sess.span_note_without_error(span, "erroneous constant used");
                     }

compiler/rustc_const_eval/src/interpret/operand.rs

@@ -595,7 +595,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             // FIXME(generic_const_exprs): `ConstKind::Expr` should be able to be evaluated
             ty::ConstKind::Expr(_) => throw_inval!(TooGeneric),
             ty::ConstKind::Error(reported) => {
-                throw_inval!(AlreadyReported(reported))
+                throw_inval!(AlreadyReported(reported.into()))
             }
             ty::ConstKind::Unevaluated(uv) => {
                 let instance = self.resolve(uv.def, uv.substs)?;

compiler/rustc_infer/src/infer/mod.rs

@@ -1533,7 +1533,7 @@ impl<'tcx> InferCtxt<'tcx> {
             if let Some(ct) = tcx.thir_abstract_const(unevaluated.def)? {
                 let ct = tcx.expand_abstract_consts(ct.subst(tcx, substs));
                 if let Err(e) = ct.error_reported() {
-                    return Err(ErrorHandled::Reported(e));
+                    return Err(ErrorHandled::Reported(e.into()));
                 } else if ct.has_non_region_infer() || ct.has_non_region_param() {
                     return Err(ErrorHandled::TooGeneric);
                 } else {

compiler/rustc_middle/src/mir/interpret/error.rs

@@ -15,15 +15,49 @@ use std::{any::Any, backtrace::Backtrace, fmt};
 pub enum ErrorHandled {
     /// Already reported an error for this evaluation, and the compilation is
     /// *guaranteed* to fail. Warnings/lints *must not* produce `Reported`.
-    Reported(ErrorGuaranteed),
+    Reported(ReportedErrorInfo),
     /// Don't emit an error, the evaluation failed because the MIR was generic
     /// and the substs didn't fully monomorphize it.
     TooGeneric,
 }
 
 impl From<ErrorGuaranteed> for ErrorHandled {
-    fn from(err: ErrorGuaranteed) -> ErrorHandled {
-        ErrorHandled::Reported(err)
+    #[inline]
+    fn from(error: ErrorGuaranteed) -> ErrorHandled {
+        ErrorHandled::Reported(error.into())
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
+pub struct ReportedErrorInfo {
+    error: ErrorGuaranteed,
+    is_tainted_by_errors: bool,
+}
+
+impl ReportedErrorInfo {
+    #[inline]
+    pub fn tainted_by_errors(error: ErrorGuaranteed) -> ReportedErrorInfo {
+        ReportedErrorInfo { is_tainted_by_errors: true, error }
+    }
+
+    /// Returns true if evaluation failed because MIR was tainted by errors.
+    #[inline]
+    pub fn is_tainted_by_errors(self) -> bool {
+        self.is_tainted_by_errors
+    }
+}
+
+impl From<ErrorGuaranteed> for ReportedErrorInfo {
+    #[inline]
+    fn from(error: ErrorGuaranteed) -> ReportedErrorInfo {
+        ReportedErrorInfo { is_tainted_by_errors: false, error }
+    }
+}
+
+impl Into<ErrorGuaranteed> for ReportedErrorInfo {
+    #[inline]
+    fn into(self) -> ErrorGuaranteed {
+        self.error
     }
 }
 
@@ -89,7 +123,7 @@ fn print_backtrace(backtrace: &Backtrace) {
 
 impl From<ErrorGuaranteed> for InterpErrorInfo<'_> {
     fn from(err: ErrorGuaranteed) -> Self {
-        InterpError::InvalidProgram(InvalidProgramInfo::AlreadyReported(err)).into()
+        InterpError::InvalidProgram(InvalidProgramInfo::AlreadyReported(err.into())).into()
     }
 }
 
@@ -125,7 +159,7 @@ pub enum InvalidProgramInfo<'tcx> {
     /// Resolution can fail if we are in a too generic context.
     TooGeneric,
     /// Abort in case errors are already reported.
-    AlreadyReported(ErrorGuaranteed),
+    AlreadyReported(ReportedErrorInfo),
     /// An error occurred during layout computation.
     Layout(layout::LayoutError<'tcx>),
     /// An error occurred during FnAbi computation: the passed --target lacks FFI support
@@ -144,7 +178,7 @@ impl fmt::Display for InvalidProgramInfo<'_> {
         use InvalidProgramInfo::*;
         match self {
             TooGeneric => write!(f, "encountered overly generic constant"),
-            AlreadyReported(ErrorGuaranteed { .. }) => {
+            AlreadyReported(_) => {
                 write!(
                     f,
                     "an error has already been reported elsewhere (this should not usually be printed)"

compiler/rustc_middle/src/mir/interpret/mod.rs

@@ -120,8 +120,8 @@ use crate::ty::{self, Instance, Ty, TyCtxt};
 pub use self::error::{
     struct_error, CheckInAllocMsg, ErrorHandled, EvalToAllocationRawResult, EvalToConstValueResult,
     EvalToValTreeResult, InterpError, InterpErrorInfo, InterpResult, InvalidProgramInfo,
-    MachineStopType, ResourceExhaustionInfo, ScalarSizeMismatch, UndefinedBehaviorInfo,
-    UninitBytesAccess, UnsupportedOpInfo,
+    MachineStopType, ReportedErrorInfo, ResourceExhaustionInfo, ScalarSizeMismatch,
+    UndefinedBehaviorInfo, UninitBytesAccess, UnsupportedOpInfo,
 };
 
 pub use self::value::{get_slice_bytes, ConstAlloc, ConstValue, Scalar};

compiler/rustc_middle/src/mir/interpret/queries.rs

@@ -61,7 +61,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 self.const_eval_global_id(param_env, cid, span)
             }
             Ok(None) => Err(ErrorHandled::TooGeneric),
-            Err(error_reported) => Err(ErrorHandled::Reported(error_reported)),
+            Err(err) => Err(ErrorHandled::Reported(err.into())),
         }
     }
 
@@ -110,7 +110,7 @@ impl<'tcx> TyCtxt<'tcx> {
                 })
             }
             Ok(None) => Err(ErrorHandled::TooGeneric),
-            Err(error_reported) => Err(ErrorHandled::Reported(error_reported)),
+            Err(err) => Err(ErrorHandled::Reported(err.into())),
         }
     }
 

compiler/rustc_middle/src/mir/mod.rs

@@ -2342,7 +2342,7 @@ impl<'tcx> ConstantKind<'tcx> {
                 match tcx.const_eval_resolve(param_env, uneval, None) {
                     Ok(val) => Self::Val(val, ty),
                     Err(ErrorHandled::TooGeneric) => self,
-                    Err(ErrorHandled::Reported(guar)) => Self::Ty(tcx.const_error(ty, guar)),
+                    Err(ErrorHandled::Reported(guar)) => Self::Ty(tcx.const_error(ty, guar.into())),
                 }
             }
         }

compiler/rustc_middle/src/ty/consts/kind.rs

@@ -245,7 +245,7 @@ impl<'tcx> ConstKind<'tcx> {
                         // can leak through `val` into the const we return.
                         Ok(val) => Some(Ok(EvalResult::ValTree(val?))),
                         Err(ErrorHandled::TooGeneric) => None,
-                        Err(ErrorHandled::Reported(e)) => Some(Err(e)),
+                        Err(ErrorHandled::Reported(e)) => Some(Err(e.into())),
                     }
                 }
                 EvalMode::Mir => {
@@ -256,7 +256,7 @@ impl<'tcx> ConstKind<'tcx> {
                         // can leak through `val` into the const we return.
                         Ok(val) => Some(Ok(EvalResult::ConstVal(val))),
                         Err(ErrorHandled::TooGeneric) => None,
-                        Err(ErrorHandled::Reported(e)) => Some(Err(e)),
+                        Err(ErrorHandled::Reported(e)) => Some(Err(e.into())),
                     }
                 }
             }