Also consider TAIT to be uncomputable if the MIR body is tainted

rust-lang · Oct 30, 2023 · 48491c1 · 48491c1
1 parent e6e931d
commit 48491c1
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Showing 3 changed files with 42 additions and 3 deletions.
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -183,9  183,17 @@ impl TaitConstraintLocator<'_> {
         };
 
         // Use borrowck to get the type with unerased regions.
-        let concrete_opaque_types = &self.tcx.mir_borrowck(item_def_id).concrete_opaque_types;
-        debug!(?concrete_opaque_types);
-        if let Some(&concrete_type) = concrete_opaque_types.get(&self.def_id) {
         let borrowck_results = &self.tcx.mir_borrowck(item_def_id);
 
         // If the body was tainted, then assume the opaque may have been constrained and just set it to error.
         if let Some(guar) = borrowck_results.tainted_by_errors {
             self.found =
                 Some(ty::OpaqueHiddenType { span: DUMMY_SP, ty: Ty::new_error(self.tcx, guar) });
             return;
         }
 
         debug!(?borrowck_results.concrete_opaque_types);
         if let Some(&concrete_type) = borrowck_results.concrete_opaque_types.get(&self.def_id) {
             debug!(?concrete_type, "found constraint");
             if let Some(prev) = &mut self.found {
                 if concrete_type.ty != prev.ty && !(concrete_type, prev.ty).references_error() {

diff --git a/tests/ui/type-alias-impl-trait/unconstrained-due-to-bad-pattern.rs b/tests/ui/type-alias-impl-trait/unconstrained-due-to-bad-pattern.rs
@@ -0,0  1,14 @@
 #![feature(type_alias_impl_trait)]
 
 type Tait = impl Copy;
 // Make sure that this TAIT isn't considered unconstrained...
 
 fn empty_opaque() -> Tait {
     if false {
         match empty_opaque() {}
         //~^ ERROR non-empty
     }
     0u8
 }
 
 fn main() {}
diff --git a/tests/ui/type-alias-impl-trait/unconstrained-due-to-bad-pattern.stderr b/tests/ui/type-alias-impl-trait/unconstrained-due-to-bad-pattern.stderr
@@ -0,0  1,17 @@
 error[E0004]: non-exhaustive patterns: type `Tait` is non-empty
   --> $DIR/unconstrained-due-to-bad-pattern.rs:8:15
    |
 LL |         match empty_opaque() {}
    |               ^^^^^^^^^^^^^^
    |
    = note: the matched value is of type `Tait`
 help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern as shown
    |
 LL ~         match empty_opaque() {
 LL               _ => todo!(),
 LL           }
    |
 
 error: aborting due to previous error
 
 For more information about this error, try `rustc --explain E0004`.