require an ErrorGuaranteed to taint infcx with errors

compiler/rustc_borrowck/src/lib.rs

@@ -197,7 +197,7 @@ fn do_mir_borrowck<'tcx>(
     // Gather the upvars of a closure, if any.
     let tables = tcx.typeck_opt_const_arg(def);
     if let Some(e) = tables.tainted_by_errors {
-        infcx.set_tainted_by_errors();
+        infcx.set_tainted_by_errors(e);
         errors.set_tainted_by_errors(e);
     }
     let upvars: Vec<_> = tables

compiler/rustc_borrowck/src/nll.rs

@@ -303,7 +303,10 @@ pub(crate) fn compute_regions<'cx, 'tcx>(
 
     if !nll_errors.is_empty() {
         // Suppress unhelpful extra errors in `infer_opaque_types`.
-        infcx.set_tainted_by_errors();
+        infcx.set_tainted_by_errors(infcx.tcx.sess.delay_span_bug(
+            body.span,
+            "`compute_regions` tainted `infcx` with errors but did not emit any errors",
+        ));
     }
 
     let remapped_opaque_tys = regioncx.infer_opaque_types(&infcx, opaque_type_values);

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -115,7 +115,7 @@ pub trait AstConv<'tcx> {
     /// (e.g., resolve) that is translated into a ty-error. This is
     /// used to help suppress derived errors typeck might otherwise
     /// report.
-    fn set_tainted_by_errors(&self);
+    fn set_tainted_by_errors(&self, e: ErrorGuaranteed);
 
     fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
 }
@@ -2620,8 +2620,12 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 }
             }
             Res::Err => {
-                self.set_tainted_by_errors();
+                let e = self
-                self.tcx().ty_error()
+                    .tcx()
+                    .sess
+                    .delay_span_bug(path.span, "path with `Res:Err` but no error emitted");
+                self.set_tainted_by_errors(e);
+                self.tcx().ty_error_with_guaranteed(e)
             }
             _ => span_bug!(span, "unexpected resolution: {:?}", path.res),
         }

compiler/rustc_hir_analysis/src/collect.rs

@@ -518,7 +518,7 @@ impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
         ty
     }
 
-    fn set_tainted_by_errors(&self) {
+    fn set_tainted_by_errors(&self, _: ErrorGuaranteed) {
         // There's no obvious place to track this, so just let it go.
     }
 

compiler/rustc_hir_typeck/src/coercion.rs

@@ -1544,7 +1544,9 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
                 // Mark that we've failed to coerce the types here to suppress
                 // any superfluous errors we might encounter while trying to
                 // emit or provide suggestions on how to fix the initial error.
-                fcx.set_tainted_by_errors();
+                fcx.set_tainted_by_errors(
+                    fcx.tcx.sess.delay_span_bug(cause.span, "coercion error but no error emitted"),
+                );
                 let (expected, found) = if label_expression_as_expected {
                     // In the case where this is a "forced unit", like
                     // `break`, we want to call the `()` "expected"

compiler/rustc_hir_typeck/src/demand.rs

@@ -154,7 +154,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             Err(e) => e,
         };
 
-        self.set_tainted_by_errors();
+        self.set_tainted_by_errors(self.tcx.sess.delay_span_bug(
+            expr.span,
+            "`TypeError` when attempting coercion but no error emitted",
+        ));
         let expr = expr.peel_drop_temps();
         let cause = self.misc(expr.span);
         let expr_ty = self.resolve_vars_with_obligations(checked_ty);

compiler/rustc_hir_typeck/src/expr.rs

@@ -527,12 +527,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             self.resolve_ty_and_res_fully_qualified_call(qpath, expr.hir_id, expr.span);
         let ty = match res {
             Res::Err => {
-                self.set_tainted_by_errors();
+                let e =
-                tcx.ty_error()
+                    self.tcx.sess.delay_span_bug(qpath.span(), "`Res::Err` but no error emitted");
+                self.set_tainted_by_errors(e);
+                tcx.ty_error_with_guaranteed(e)
             }
             Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
-                report_unexpected_variant_res(tcx, res, qpath, expr.span);
+                let e = report_unexpected_variant_res(tcx, res, qpath, expr.span);
-                tcx.ty_error()
+                tcx.ty_error_with_guaranteed(e)
             }
             _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, expr.hir_id).0,
         };
@@ -1962,7 +1964,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expr_span: Span,
     ) {
         if variant.is_recovered() {
-            self.set_tainted_by_errors();
+            self.set_tainted_by_errors(
+                self.tcx
+                    .sess
+                    .delay_span_bug(expr_span, "parser recovered but no error was emitted"),
+            );
             return;
         }
         let mut err = self.err_ctxt().type_error_struct_with_diag(

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -140,8 +140,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         debug!("write_ty({:?}, {:?}) in fcx {}", id, self.resolve_vars_if_possible(ty), self.tag());
         self.typeck_results.borrow_mut().node_types_mut().insert(id, ty);
 
-        if ty.references_error() {
+        if let Err(e) = ty.error_reported() {
-            self.set_tainted_by_errors();
+            self.set_tainted_by_errors(e);
         }
     }
 
@@ -1148,9 +1148,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 explicit_late_bound = ExplicitLateBound::Yes;
             }
 
-            if let Err(GenericArgCountMismatch { reported: Some(_), .. }) = arg_count.correct {
+            if let Err(GenericArgCountMismatch { reported: Some(e), .. }) = arg_count.correct {
                 infer_args_for_err.insert(index);
-                self.set_tainted_by_errors(); // See issue #53251.
+                self.set_tainted_by_errors(e); // See issue #53251.
             }
         }
 

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -512,8 +512,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             tys.into_iter().any(|ty| ty.references_error() || ty.is_ty_var())
         }
 
-        self.set_tainted_by_errors();
         let tcx = self.tcx;
+        // FIXME: taint after emitting errors and pass through an `ErrorGuaranteed`
+        self.set_tainted_by_errors(
+            tcx.sess.delay_span_bug(call_span, "no errors reported for args"),
+        );
 
         // Get the argument span in the context of the call span so that
         // suggestions and labels are (more) correct when an arg is a
@@ -1208,7 +1211,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let (def, ty) = self.finish_resolving_struct_path(qpath, path_span, hir_id);
         let variant = match def {
             Res::Err => {
-                self.set_tainted_by_errors();
+                self.set_tainted_by_errors(
+                    self.tcx.sess.delay_span_bug(path_span, "`Res::Err` but no error emitted"),
+                );
                 return None;
             }
             Res::Def(DefKind::Variant, _) => match ty.kind() {

compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs

@@ -4,6 +4,7 @@ mod checks;
 mod suggestions;
 
 pub use _impl::*;
+use rustc_errors::ErrorGuaranteed;
 pub use suggestions::*;
 
 use crate::coercion::DynamicCoerceMany;
@@ -289,8 +290,8 @@ impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
         }
     }
 
-    fn set_tainted_by_errors(&self) {
+    fn set_tainted_by_errors(&self, e: ErrorGuaranteed) {
-        self.infcx.set_tainted_by_errors()
+        self.infcx.set_tainted_by_errors(e)
     }
 
     fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {

compiler/rustc_hir_typeck/src/lib.rs

@@ -53,7 +53,7 @@ use crate::check::check_fn;
 use crate::coercion::DynamicCoerceMany;
 use crate::gather_locals::GatherLocalsVisitor;
 use rustc_data_structures::unord::UnordSet;
-use rustc_errors::{struct_span_err, MultiSpan};
+use rustc_errors::{struct_span_err, ErrorGuaranteed, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def::Res;
 use rustc_hir::intravisit::Visitor;
@@ -428,7 +428,12 @@ impl<'tcx> EnclosingBreakables<'tcx> {
     }
 }
 
-fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, qpath: &hir::QPath<'_>, span: Span) {
+fn report_unexpected_variant_res(
+    tcx: TyCtxt<'_>,
+    res: Res,
+    qpath: &hir::QPath<'_>,
+    span: Span,
+) -> ErrorGuaranteed {
     struct_span_err!(
         tcx.sess,
         span,
@@ -437,7 +442,7 @@ fn report_unexpected_variant_res(tcx: TyCtxt<'_>, res: Res, qpath: &hir::QPath<'
         res.descr(),
         rustc_hir_pretty::qpath_to_string(qpath),
     )
-    .emit();
+    .emit()
 }
 
 /// Controls whether the arguments are tupled. This is used for the call

compiler/rustc_hir_typeck/src/pat.rs

@@ -839,12 +839,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let (res, opt_ty, segments) = path_resolution;
         match res {
             Res::Err => {
-                self.set_tainted_by_errors();
+                let e = tcx.sess.delay_span_bug(qpath.span(), "`Res::Err` but no error emitted");
-                return tcx.ty_error();
+                self.set_tainted_by_errors(e);
+                return tcx.ty_error_with_guaranteed(e);
             }
             Res::Def(DefKind::AssocFn | DefKind::Ctor(_, CtorKind::Fictive | CtorKind::Fn), _) => {
-                report_unexpected_variant_res(tcx, res, qpath, pat.span);
+                let e = report_unexpected_variant_res(tcx, res, qpath, pat.span);
-                return tcx.ty_error();
+                return tcx.ty_error_with_guaranteed(e);
             }
             Res::SelfCtor(..)
             | Res::Def(
@@ -985,9 +986,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         ti: TopInfo<'tcx>,
     ) -> Ty<'tcx> {
         let tcx = self.tcx;
-        let on_error = || {
+        let on_error = |e| {
             for pat in subpats {
-                self.check_pat(pat, tcx.ty_error(), def_bm, ti);
+                self.check_pat(pat, tcx.ty_error_with_guaranteed(e), def_bm, ti);
             }
         };
         let report_unexpected_res = |res: Res| {
@@ -1014,36 +1015,39 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     err.span_label(pat.span, "not a tuple variant or struct");
                 }
             }
-            err.emit();
+            let e = err.emit();
-            on_error();
+            on_error(e);
+            e
         };
 
         // Resolve the path and check the definition for errors.
         let (res, opt_ty, segments) =
             self.resolve_ty_and_res_fully_qualified_call(qpath, pat.hir_id, pat.span);
         if res == Res::Err {
-            self.set_tainted_by_errors();
+            let e = tcx.sess.delay_span_bug(pat.span, "`Res:Err` but no error emitted");
-            on_error();
+            self.set_tainted_by_errors(e);
-            return self.tcx.ty_error();
+            on_error(e);
+            return tcx.ty_error_with_guaranteed(e);
         }
 
         // Type-check the path.
         let (pat_ty, res) =
             self.instantiate_value_path(segments, opt_ty, res, pat.span, pat.hir_id);
         if !pat_ty.is_fn() {
-            report_unexpected_res(res);
+            let e = report_unexpected_res(res);
-            return tcx.ty_error();
+            return tcx.ty_error_with_guaranteed(e);
         }
 
         let variant = match res {
             Res::Err => {
-                self.set_tainted_by_errors();
+                let e = tcx.sess.delay_span_bug(pat.span, "`Res::Err` but no error emitted");
-                on_error();
+                self.set_tainted_by_errors(e);
-                return tcx.ty_error();
+                on_error(e);
+                return tcx.ty_error_with_guaranteed(e);
             }
             Res::Def(DefKind::AssocConst | DefKind::AssocFn, _) => {
-                report_unexpected_res(res);
+                let e = report_unexpected_res(res);
-                return tcx.ty_error();
+                return tcx.ty_error_with_guaranteed(e);
             }
             Res::Def(DefKind::Ctor(_, CtorKind::Fn), _) => tcx.expect_variant_res(res),
             _ => bug!("unexpected pattern resolution: {:?}", res),
@@ -1082,9 +1086,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         } else {
             // Pattern has wrong number of fields.
-            self.e0023(pat.span, res, qpath, subpats, &variant.fields, expected, had_err);
+            let e = self.e0023(pat.span, res, qpath, subpats, &variant.fields, expected, had_err);
-            on_error();
+            on_error(e);
-            return tcx.ty_error();
+            return tcx.ty_error_with_guaranteed(e);
         }
         pat_ty
     }
@@ -1098,7 +1102,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         fields: &'tcx [ty::FieldDef],
         expected: Ty<'tcx>,
         had_err: bool,
-    ) {
+    ) -> ErrorGuaranteed {
         let subpats_ending = pluralize!(subpats.len());
         let fields_ending = pluralize!(fields.len());
 
@@ -1245,7 +1249,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         }
 
-        err.emit();
+        err.emit()
     }
 
     fn check_pat_tuple(

compiler/rustc_infer/src/infer/mod.rs

@@ -34,7 +34,7 @@ pub use rustc_middle::ty::IntVarValue;
 use rustc_middle::ty::{self, GenericParamDefKind, InferConst, Ty, TyCtxt};
 use rustc_middle::ty::{ConstVid, FloatVid, IntVid, TyVid};
 use rustc_span::symbol::Symbol;
-use rustc_span::{Span, DUMMY_SP};
+use rustc_span::Span;
 
 use std::cell::{Cell, RefCell};
 use std::fmt;
@@ -1224,8 +1224,9 @@ impl<'tcx> InferCtxt<'tcx> {
 
         if self.tcx.sess.err_count() > self.err_count_on_creation {
             // errors reported since this infcx was made
-            self.set_tainted_by_errors();
+            let e = self.tcx.sess.has_errors().unwrap();
-            return self.tainted_by_errors.get();
+            self.set_tainted_by_errors(e);
+            return Some(e);
         }
 
         None
@@ -1233,11 +1234,9 @@ impl<'tcx> InferCtxt<'tcx> {
 
     /// Set the "tainted by errors" flag to true. We call this when we
     /// observe an error from a prior pass.
-    pub fn set_tainted_by_errors(&self) {
+    pub fn set_tainted_by_errors(&self, e: ErrorGuaranteed) {
-        debug!("set_tainted_by_errors()");
+        debug!("set_tainted_by_errors(ErrorGuaranteed)");
-        self.tainted_by_errors.set(Some(
+        self.tainted_by_errors.set(Some(e));
-            self.tcx.sess.delay_span_bug(DUMMY_SP, "`InferCtxt` incorrectly tainted by errors"),
-        ));
     }
 
     pub fn skip_region_resolution(&self) {

compiler/rustc_infer/src/infer/sub.rs

@@ -116,9 +116,9 @@ impl<'tcx> TypeRelation<'tcx> for Sub<'_, '_, 'tcx> {
                 Ok(a)
             }
 
-            (&ty::Error(_), _) | (_, &ty::Error(_)) => {
+            (&ty::Error(e), _) | (_, &ty::Error(e)) => {
-                infcx.set_tainted_by_errors();
+                infcx.set_tainted_by_errors(e);
-                Ok(self.tcx().ty_error())
+                Ok(self.tcx().ty_error_with_guaranteed(e))
             }
 
             (&ty::Opaque(a_def_id, _), &ty::Opaque(b_def_id, _)) if a_def_id == b_def_id => {

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -532,9 +532,12 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         root_obligation: &PredicateObligation<'tcx>,
         error: &SelectionError<'tcx>,
     ) {
-        self.set_tainted_by_errors();
         let tcx = self.tcx;
         let mut span = obligation.cause.span;
+        // FIXME: statically guarantee this by tainting after the diagnostic is emitted
+        self.set_tainted_by_errors(
+            tcx.sess.delay_span_bug(span, "`report_selection_error` did not emit an error"),
+        );
 
         let mut err = match *error {
             SelectionError::Unimplemented => {