Fail candidate assembly for erroneous types

Trait predicates for types which have errors may still evaluate to OK leading to downstream ICEs. Now we return a selection error for such types in candidate assembly and thereby prevent such issues
rust-lang · Apr 13, 2024 · 2783775 · 2783775
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diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -87,6 +87,12 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             } else if lang_items.sized_trait() == Some(def_id) {
                 // Sized is never implementable by end-users, it is
                 // always automatically computed.
+
+                // Error type cannot possibly implement `Sized` (fixes #123154)
+                if let ty::Error(_) = obligation.predicate.skip_binder().self_ty().kind() {
+                    return Err(SelectionError::Unimplemented);
+                }
+
                 let sized_conditions = self.sized_conditions(obligation);
                 self.assemble_builtin_bound_candidates(sized_conditions, &mut candidates);
             } else if lang_items.unsize_trait() == Some(def_id) {

diff --git a/compiler/rustc_ty_utils/src/ty.rs b/compiler/rustc_ty_utils/src/ty.rs
@@ -91,8 +91,8 @@ fn adt_sized_constraint<'tcx>(
     let tail_ty = tcx.type_of(tail_def.did).instantiate_identity();
 
     let constraint_ty = sized_constraint_for_ty(tcx, tail_ty)?;
-    if constraint_ty.references_error() {
-        return None;
+    if let Err(guar) = constraint_ty.error_reported() {
+        return Some(ty::EarlyBinder::bind(Ty::new_error(tcx, guar)));
     }
 
     // perf hack: if there is a `constraint_ty: Sized` bound, then we know

diff --git a/tests/ui/associated-inherent-types/issue-109071.no_gate.stderr b/tests/ui/associated-inherent-types/issue-109071.no_gate.stderr
@@ -43,7 +43,35 @@ LL |     type Item = &[T];
    = help: add `#![feature(inherent_associated_types)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error: aborting due to 4 previous errors
+error[E0223]: ambiguous associated type
+  --> $DIR/issue-109071.rs:15:22
+   |
+LL |     fn T() -> Option<Self::Item> {}
+   |                      ^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: use fully-qualified syntax
+   |
+LL |     fn T() -> Option<<Windows<T> as IntoAsyncIterator>::Item> {}
+   |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+LL |     fn T() -> Option<<Windows<T> as IntoIterator>::Item> {}
+   |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error[E0223]: ambiguous associated type
+  --> $DIR/issue-109071.rs:15:22
+   |
+LL |     fn T() -> Option<Self::Item> {}
+   |                      ^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: use fully-qualified syntax
+   |
+LL |     fn T() -> Option<<Windows<T> as IntoAsyncIterator>::Item> {}
+   |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+LL |     fn T() -> Option<<Windows<T> as IntoIterator>::Item> {}
+   |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error: aborting due to 6 previous errors
 
 Some errors have detailed explanations: E0107, E0223, E0637, E0658.
 For more information about an error, try `rustc --explain E0107`.
diff --git a/tests/ui/associated-inherent-types/issue-109071.rs b/tests/ui/associated-inherent-types/issue-109071.rs
@@ -14,6 +14,8 @@ impl<T> Windows { //~ ERROR: missing generics for struct `Windows`
 impl<T> Windows<T> {
     fn T() -> Option<Self::Item> {}
     //~^ ERROR: ambiguous associated type
+    //~| ERROR: ambiguous associated type
+    //~| ERROR: ambiguous associated type
 }
 
 fn main() {}
diff --git a/tests/ui/associated-inherent-types/issue-109071.with_gate.stderr b/tests/ui/associated-inherent-types/issue-109071.with_gate.stderr
@@ -33,7 +33,35 @@ LL |     fn T() -> Option<<Windows<T> as IntoAsyncIterator>::Item> {}
 LL |     fn T() -> Option<<Windows<T> as IntoIterator>::Item> {}
    |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-error: aborting due to 3 previous errors
+error[E0223]: ambiguous associated type
+  --> $DIR/issue-109071.rs:15:22
+   |
+LL |     fn T() -> Option<Self::Item> {}
+   |                      ^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: use fully-qualified syntax
+   |
+LL |     fn T() -> Option<<Windows<T> as IntoAsyncIterator>::Item> {}
+   |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+LL |     fn T() -> Option<<Windows<T> as IntoIterator>::Item> {}
+   |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error[E0223]: ambiguous associated type
+  --> $DIR/issue-109071.rs:15:22
+   |
+LL |     fn T() -> Option<Self::Item> {}
+   |                      ^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: use fully-qualified syntax
+   |
+LL |     fn T() -> Option<<Windows<T> as IntoAsyncIterator>::Item> {}
+   |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+LL |     fn T() -> Option<<Windows<T> as IntoIterator>::Item> {}
+   |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error: aborting due to 5 previous errors
 
 Some errors have detailed explanations: E0107, E0223, E0637.
 For more information about an error, try `rustc --explain E0107`.
diff --git a/tests/ui/closures/issue-78720.rs b/tests/ui/closures/issue-78720.rs
@@ -1,6 +1,5 @@
 fn server() -> impl {
     //~^ ERROR at least one trait must be specified
-    //~| ERROR type annotations needed
     ().map2(|| "")
 }
 

diff --git a/tests/ui/closures/issue-78720.stderr b/tests/ui/closures/issue-78720.stderr
@@ -5,7 +5,7 @@ LL | fn server() -> impl {
    |                ^^^^
 
 error[E0412]: cannot find type `F` in this scope
-  --> $DIR/issue-78720.rs:14:12
+  --> $DIR/issue-78720.rs:13:12
    |
 LL |     _func: F,
    |            ^
@@ -22,14 +22,8 @@ help: you might be missing a type parameter
 LL | struct Map2<Segment2, F> {
    |                     +++
 
-error[E0282]: type annotations needed
-  --> $DIR/issue-78720.rs:1:16
-   |
-LL | fn server() -> impl {
-   |                ^^^^ cannot infer type
-
 error[E0308]: mismatched types
-  --> $DIR/issue-78720.rs:8:39
+  --> $DIR/issue-78720.rs:7:39
    |
 LL |     fn map2<F>(self, f: F) -> Map2<F> {}
    |                                       ^^ expected `Map2<F>`, found `()`
@@ -38,7 +32,7 @@ LL |     fn map2<F>(self, f: F) -> Map2<F> {}
            found unit type `()`
 
 error[E0277]: the size for values of type `Self` cannot be known at compilation time
-  --> $DIR/issue-78720.rs:8:16
+  --> $DIR/issue-78720.rs:7:16
    |
 LL |     fn map2<F>(self, f: F) -> Map2<F> {}
    |                ^^^^ doesn't have a size known at compile-time
@@ -53,7 +47,7 @@ help: function arguments must have a statically known size, borrowed types alway
 LL |     fn map2<F>(&self, f: F) -> Map2<F> {}
    |                +
 
-error: aborting due to 5 previous errors
+error: aborting due to 4 previous errors
 
-Some errors have detailed explanations: E0277, E0282, E0308, E0412.
+Some errors have detailed explanations: E0277, E0308, E0412.
 For more information about an error, try `rustc --explain E0277`.
diff --git a/tests/ui/const-generics/const-arg-type-arg-misordered.rs b/tests/ui/const-generics/const-arg-type-arg-misordered.rs
@@ -2,6 +2,7 @@ type Array<T, const N: usize> = [T; N];
 
 fn foo<const N: usize>() -> Array<N, ()> {
     //~^ ERROR constant provided when a type was expected
+    //~| ERROR constant provided when a type was expected
     unimplemented!()
 }
 

diff --git a/tests/ui/const-generics/const-arg-type-arg-misordered.stderr b/tests/ui/const-generics/const-arg-type-arg-misordered.stderr
@@ -4,6 +4,14 @@ error[E0747]: constant provided when a type was expected
 LL | fn foo<const N: usize>() -> Array<N, ()> {
    |                                   ^
 
-error: aborting due to 1 previous error
+error[E0747]: constant provided when a type was expected
+  --> $DIR/const-arg-type-arg-misordered.rs:3:35
+   |
+LL | fn foo<const N: usize>() -> Array<N, ()> {
+   |                                   ^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0747`.
diff --git a/tests/ui/const-generics/generic_const_exprs/issue-102768.rs b/tests/ui/const-generics/generic_const_exprs/issue-102768.rs
@@ -13,6 +13,10 @@ const _: () = {
     //~| ERROR associated type takes 0 generic arguments but 1 generic argument
     //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
     //~| ERROR associated type takes 0 generic arguments but 1 generic argument
+    //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
+    //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
+    //~| ERROR associated type takes 0 generic arguments but 1 generic argument
+    //~| ERROR associated type takes 0 generic arguments but 1 generic argument
     //~| ERROR `X` cannot be made into an object
 };
 

diff --git a/tests/ui/const-generics/generic_const_exprs/issue-102768.stderr b/tests/ui/const-generics/generic_const_exprs/issue-102768.stderr
@@ -107,7 +107,71 @@ LL |     type Y<'a>;
    |          ^ ...because it contains the generic associated type `Y`
    = help: consider moving `Y` to another trait
 
-error: aborting due to 7 previous errors
+error[E0107]: associated type takes 1 lifetime argument but 0 lifetime arguments were supplied
+  --> $DIR/issue-102768.rs:9:30
+   |
+LL |     fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
+   |                              ^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/issue-102768.rs:5:10
+   |
+LL |     type Y<'a>;
+   |          ^ --
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: add missing lifetime argument
+   |
+LL |     fn f2<'a>(arg: Box<dyn X<Y<'_, 1> = &'a ()>>) {}
+   |                                +++
+
+error[E0107]: associated type takes 0 generic arguments but 1 generic argument was supplied
+  --> $DIR/issue-102768.rs:9:30
+   |
+LL |     fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
+   |                              ^--- help: remove these generics
+   |                              |
+   |                              expected 0 generic arguments
+   |
+note: associated type defined here, with 0 generic parameters
+  --> $DIR/issue-102768.rs:5:10
+   |
+LL |     type Y<'a>;
+   |          ^
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error[E0107]: associated type takes 1 lifetime argument but 0 lifetime arguments were supplied
+  --> $DIR/issue-102768.rs:9:30
+   |
+LL |     fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
+   |                              ^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/issue-102768.rs:5:10
+   |
+LL |     type Y<'a>;
+   |          ^ --
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: add missing lifetime argument
+   |
+LL |     fn f2<'a>(arg: Box<dyn X<Y<'_, 1> = &'a ()>>) {}
+   |                                +++
+
+error[E0107]: associated type takes 0 generic arguments but 1 generic argument was supplied
+  --> $DIR/issue-102768.rs:9:30
+   |
+LL |     fn f2<'a>(arg: Box<dyn X<Y<1> = &'a ()>>) {}
+   |                              ^--- help: remove these generics
+   |                              |
+   |                              expected 0 generic arguments
+   |
+note: associated type defined here, with 0 generic parameters
+  --> $DIR/issue-102768.rs:5:10
+   |
+LL |     type Y<'a>;
+   |          ^
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 11 previous errors
 
 Some errors have detailed explanations: E0038, E0107.
 For more information about an error, try `rustc --explain E0038`.
diff --git a/tests/ui/const_prop/ice-type-mismatch-when-copying-112824.rs b/tests/ui/const_prop/ice-type-mismatch-when-copying-112824.rs
@@ -13,7 +13,6 @@ impl Opcode2 {
 pub fn example2(msg_type: Opcode2) -> impl FnMut(&[u8]) {
     move |i| match msg_type {
         Opcode2::OP2 => unimplemented!(),
-        //~^ ERROR could not evaluate constant pattern
     }
 }
 

diff --git a/tests/ui/const_prop/ice-type-mismatch-when-copying-112824.stderr b/tests/ui/const_prop/ice-type-mismatch-when-copying-112824.stderr
@@ -17,13 +17,7 @@ help: you might be missing a type parameter
 LL | pub struct Opcode2<S>(&'a S);
    |                   +++
 
-error: could not evaluate constant pattern
-  --> $DIR/ice-type-mismatch-when-copying-112824.rs:15:9
-   |
-LL |         Opcode2::OP2 => unimplemented!(),
-   |         ^^^^^^^^^^^^
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 Some errors have detailed explanations: E0261, E0412.
 For more information about an error, try `rustc --explain E0261`.
diff --git a/tests/ui/consts/const-eval/ice-unsized-struct-const-eval-123154.rs b/tests/ui/consts/const-eval/ice-unsized-struct-const-eval-123154.rs
@@ -0,0 +1,15 @@
+// Regression test for #123154
+
+struct AA {
+    pub data: [&usize]
+    //~^ ERROR missing lifetime specifier
+}
+
+impl AA {
+    const fn new() -> Self { }
+    //~^ ERROR mismatched types
+}
+
+static ST: AA = AA::new();
+
+fn main() {}
diff --git a/tests/ui/consts/const-eval/ice-unsized-struct-const-eval-123154.stderr b/tests/ui/consts/const-eval/ice-unsized-struct-const-eval-123154.stderr
@@ -0,0 +1,24 @@
+error[E0106]: missing lifetime specifier
+  --> $DIR/ice-unsized-struct-const-eval-123154.rs:4:16
+   |
+LL |     pub data: [&usize]
+   |                ^ expected named lifetime parameter
+   |
+help: consider introducing a named lifetime parameter
+   |
+LL ~ struct AA<'a> {
+LL ~     pub data: [&'a usize]
+   |
+
+error[E0308]: mismatched types
+  --> $DIR/ice-unsized-struct-const-eval-123154.rs:9:23
+   |
+LL |     const fn new() -> Self { }
+   |              ---      ^^^^ expected `AA`, found `()`
+   |              |
+   |              implicitly returns `()` as its body has no tail or `return` expression
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0106, E0308.
+For more information about an error, try `rustc --explain E0106`.
diff --git a/tests/ui/generic-associated-types/gat-in-trait-path-undeclared-lifetime.rs b/tests/ui/generic-associated-types/gat-in-trait-path-undeclared-lifetime.rs
@@ -8,5 +8,7 @@ fn main() {
     //~| ERROR: binding for associated type `Y` references lifetime
     //~| ERROR: binding for associated type `Y` references lifetime
     //~| ERROR: binding for associated type `Y` references lifetime
+    //~| ERROR: binding for associated type `Y` references lifetime
+    //~| ERROR: binding for associated type `Y` references lifetime
     //~| ERROR: the trait `X` cannot be made into an object
 }
diff --git a/tests/ui/generic-associated-types/gat-in-trait-path-undeclared-lifetime.stderr b/tests/ui/generic-associated-types/gat-in-trait-path-undeclared-lifetime.stderr
@@ -51,7 +51,23 @@ LL |   type Y<'x>;
    |        ^ ...because it contains the generic associated type `Y`
    = help: consider moving `Y` to another trait
 
-error: aborting due to 5 previous errors
+error[E0582]: binding for associated type `Y` references lifetime `'a`, which does not appear in the trait input types
+  --> $DIR/gat-in-trait-path-undeclared-lifetime.rs:6:33
+   |
+LL |   fn _f(arg : Box<dyn for<'a> X<Y<'x> = &'a [u32]>>) {}
+   |                                 ^^^^^^^^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error[E0582]: binding for associated type `Y` references lifetime `'a`, which does not appear in the trait input types
+  --> $DIR/gat-in-trait-path-undeclared-lifetime.rs:6:33
+   |
+LL |   fn _f(arg : Box<dyn for<'a> X<Y<'x> = &'a [u32]>>) {}
+   |                                 ^^^^^^^^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 7 previous errors
 
 Some errors have detailed explanations: E0038, E0261, E0582.
 For more information about an error, try `rustc --explain E0038`.
diff --git a/tests/ui/generic-associated-types/gat-trait-path-parenthesised-args.rs b/tests/ui/generic-associated-types/gat-trait-path-parenthesised-args.rs
@@ -11,6 +11,11 @@ fn foo<'a>(arg: Box<dyn X<Y('a) = &'a ()>>) {}
   //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
   //~| ERROR associated type takes 0 generic arguments but 1 generic argument
   //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
+  //~| ERROR associated type takes 0 generic arguments but 1 generic argument
+  //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
+  //~| ERROR associated type takes 0 generic arguments but 1 generic argument
+  //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
+  //~| ERROR at least one trait is required
   //~| ERROR at least one trait is required
   //~| ERROR: the trait `X` cannot be made into an object
 
@@ -20,6 +25,8 @@ fn bar<'a>(arg: Box<dyn X<Y() = ()>>) {}
   //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
   //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
   //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
+  //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
+  //~| ERROR associated type takes 1 lifetime argument but 0 lifetime arguments
   //~| ERROR: the trait `X` cannot be made into an object
 
 fn main() {}