typeck: taint if errors found during writeback

If any type added to the `TypeckResults` references an error then set
tainted by errors. By doing this, const eval can be skipped on bodies
that reference errors which would make const eval ICE.

Signed-off-by: David Wood <david@davidtw.co>

Author: davidtwco

compiler/rustc_hir_typeck/messages.ftl

@@ -94,5 +94,8 @@ hir_typeck_suggest_ptr_null_mut = consider using `core::ptr::null_mut` instead
 hir_typeck_union_pat_dotdot = `..` cannot be used in union patterns
 
 hir_typeck_union_pat_multiple_fields = union patterns should have exactly one field
+
+hir_typeck_writeback_found_err = found type error in writeback
+
 hir_typeck_yield_expr_outside_of_generator =
     yield expression outside of generator literal

compiler/rustc_hir_typeck/src/writeback.rs

@@ -2,7 +2,7 @@
 // unresolved type variables and replaces "ty_var" types with their
 // substitutions.
 
-use crate::FnCtxt;
+use crate::{fluent_generated as fluent, FnCtxt};
 use hir::def_id::LocalDefId;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{ErrorGuaranteed, StashKey};
@@ -134,13 +134,34 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
         self.fcx.tcx
     }
 
+    /// Checks if `ty` contains a `ty::Error` (i.e. `ty.references_error()`), but peering into
+    /// function signatures and ADTs.
+    fn deep_references_error(&self, ty: Ty<'tcx>) -> bool {
+        ty.references_error() || {
+            match ty.kind() {
+                ty::Adt(adt, substs) => {
+                    adt.all_fields().any(|field| field.ty(self.tcx(), substs).references_error())
+                }
+                ty::FnDef(..) => ty.fn_sig(self.tcx()).references_error(),
+                _ => false,
+            }
+        }
+    }
+
     fn write_ty_to_typeck_results(&mut self, hir_id: hir::HirId, ty: Ty<'tcx>) {
         debug!("write_ty_to_typeck_results({:?}, {:?})", hir_id, ty);
         assert!(
             !ty.has_infer() && !ty.has_placeholders() && !ty.has_free_regions(),
             "{ty} can't be put into typeck results"
         );
         self.typeck_results.node_types_mut().insert(hir_id, ty);
+        if self.deep_references_error(ty) {
+            self.typeck_results.tainted_by_errors = Some(
+                self.tcx()
+                    .sess
+                    .delay_span_bug(rustc_span::DUMMY_SP, fluent::hir_typeck_writeback_found_err),
+            );
+        }
     }
 
     // Hacky hack: During type-checking, we treat *all* operators

tests/ui/consts/issue-112824-type-mismatch-type-error-1.rs

@@ -0,0 +1,19 @@
+pub struct Opcode(pub u8);
+
+pub struct Opcode2 {
+    s: &'a S,
+    //~^ ERROR cannot find type `S` in this scope [E0412]
+    //~^^ ERROR use of undeclared lifetime name `'a` [E0261]
+}
+
+impl Opcode2 {
+    pub const OP2: Opcode2 = Opcode2 { s: Opcode(0x1) };
+}
+
+pub fn example2(msg_type: Opcode2) -> impl FnMut(&[u8]) {
+    move |i| match msg_type {
+        Opcode2::OP2 => unimplemented!(),
+    }
+}
+
+fn main() {}

tests/ui/consts/issue-112824-type-mismatch-type-error-1.stderr

@@ -0,0 +1,23 @@
+error[E0261]: use of undeclared lifetime name `'a`
+  --> $DIR/issue-112824-type-mismatch-type-error-1.rs:4:9
+   |
+LL | pub struct Opcode2 {
+   |                   - help: consider introducing lifetime `'a` here: `<'a>`
+LL |     s: &'a S,
+   |         ^^ undeclared lifetime
+
+error[E0412]: cannot find type `S` in this scope
+  --> $DIR/issue-112824-type-mismatch-type-error-1.rs:4:12
+   |
+LL |     s: &'a S,
+   |            ^ not found in this scope
+   |
+help: you might be missing a type parameter
+   |
+LL | pub struct Opcode2<S> {
+   |                   +++
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0261, E0412.
+For more information about an error, try `rustc --explain E0261`.

tests/ui/consts/issue-112824-type-mismatch-type-error.rs

@@ -0,0 +1,17 @@
+pub struct Opcode(pub u8);
+
+pub struct Opcode2(&'a S);
+//~^ ERROR cannot find type `S` in this scope [E0412]
+//~^^ ERROR use of undeclared lifetime name `'a` [E0261]
+
+impl Opcode2 {
+    pub const OP2: Opcode2 = Opcode2(Opcode(0x1));
+}
+
+pub fn example2(msg_type: Opcode2) -> impl FnMut(&[u8]) {
+    move |i| match msg_type {
+        Opcode2::OP2 => unimplemented!(),
+    }
+}
+
+fn main() {}

tests/ui/consts/issue-112824-type-mismatch-type-error.stderr

@@ -0,0 +1,23 @@
+error[E0261]: use of undeclared lifetime name `'a`
+  --> $DIR/issue-112824-type-mismatch-type-error.rs:3:21
+   |
+LL | pub struct Opcode2(&'a S);
+   |                   - ^^ undeclared lifetime
+   |                   |
+   |                   help: consider introducing lifetime `'a` here: `<'a>`
+
+error[E0412]: cannot find type `S` in this scope
+  --> $DIR/issue-112824-type-mismatch-type-error.rs:3:24
+   |
+LL | pub struct Opcode2(&'a S);
+   |                        ^ not found in this scope
+   |
+help: you might be missing a type parameter
+   |
+LL | pub struct Opcode2<S>(&'a S);
+   |                   +++
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0261, E0412.
+For more information about an error, try `rustc --explain E0261`.