Allow type_of to return partially non-error types if the type was already tainted

18 files changed, 174 insertions, 51 deletions

diff --git a/compiler/rustc_hir_analysis/src/collect/type_of.rs b/compiler/rustc_hir_analysis/src/collect/type_of.rs
index ed942cc50bb..bc57b234555 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of.rs
@@ -502,7 +502,9 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_
             bug!("unexpected sort of node in type_of(): {:?}", x);
         }
     };
-    if let Err(e) = icx.check_tainted_by_errors() {
+    if let Err(e) = icx.check_tainted_by_errors()
+        && !output.references_error()
+    {
         ty::EarlyBinder::bind(Ty::new_error(tcx, e))
     } else {
         ty::EarlyBinder::bind(output)
diff --git a/tests/ui/associated-inherent-types/issue-109071.rs b/tests/ui/associated-inherent-types/issue-109071.rs
index 29eef081a32..97803ae7191 100644
--- a/tests/ui/associated-inherent-types/issue-109071.rs
+++ b/tests/ui/associated-inherent-types/issue-109071.rs
@@ -13,7 +13,7 @@ impl<T> Windows { //~ ERROR: missing generics for struct `Windows`
 
 impl<T> Windows<T> {
     fn T() -> Option<Self::Item> {}
-    //~^ ERROR: ambiguous associated type
+    //[no_gate]~^ 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
index a7d17e2d5eb..1324cb9bb9b 100644
--- a/tests/ui/associated-inherent-types/issue-109071.with_gate.stderr
+++ b/tests/ui/associated-inherent-types/issue-109071.with_gate.stderr
@@ -20,20 +20,7 @@ help: add missing generic argument
 LL | impl<T> Windows<T> {
    |                +++
 
-error[E0223]: ambiguous associated type
-  --> $DIR/issue-109071.rs:15:22
-   |
-LL |     fn T() -> Option<Self::Item> {}
-   |                      ^^^^^^^^^^
-   |
-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 3 previous errors
+error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0107, E0223, E0637.
+Some errors have detailed explanations: E0107, E0637.
 For more information about an error, try `rustc --explain E0107`.
diff --git a/tests/ui/const-generics/issues/issue-71381.full.stderr b/tests/ui/const-generics/issues/issue-71381.full.stderr
index 5d780074696..b6460e0017f 100644
--- a/tests/ui/const-generics/issues/issue-71381.full.stderr
+++ b/tests/ui/const-generics/issues/issue-71381.full.stderr
@@ -7,7 +7,7 @@ LL |     pub fn call_me<Args: Sized, const IDX: usize, const FN: unsafe extern "
    = note: type parameters may not be used in the type of const parameters
 
 error[E0770]: the type of const parameters must not depend on other generic parameters
-  --> $DIR/issue-71381.rs:22:40
+  --> $DIR/issue-71381.rs:23:40
    |
 LL |         const FN: unsafe extern "C" fn(Args),
    |                                        ^^^^ the type must not depend on the parameter `Args`
diff --git a/tests/ui/const-generics/issues/issue-71381.min.stderr b/tests/ui/const-generics/issues/issue-71381.min.stderr
index 5d780074696..e16d3b7a8a4 100644
--- a/tests/ui/const-generics/issues/issue-71381.min.stderr
+++ b/tests/ui/const-generics/issues/issue-71381.min.stderr
@@ -7,13 +7,29 @@ LL |     pub fn call_me<Args: Sized, const IDX: usize, const FN: unsafe extern "
    = note: type parameters may not be used in the type of const parameters
 
 error[E0770]: the type of const parameters must not depend on other generic parameters
-  --> $DIR/issue-71381.rs:22:40
+  --> $DIR/issue-71381.rs:23:40
    |
 LL |         const FN: unsafe extern "C" fn(Args),
    |                                        ^^^^ the type must not depend on the parameter `Args`
    |
    = note: type parameters may not be used in the type of const parameters
 
-error: aborting due to 2 previous errors
+error: using function pointers as const generic parameters is forbidden
+  --> $DIR/issue-71381.rs:14:61
+   |
+LL |     pub fn call_me<Args: Sized, const IDX: usize, const FN: unsafe extern "C" fn(Args)>(&self) {
+   |                                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: the only supported types are integers, `bool` and `char`
+
+error: using function pointers as const generic parameters is forbidden
+  --> $DIR/issue-71381.rs:23:19
+   |
+LL |         const FN: unsafe extern "C" fn(Args),
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: the only supported types are integers, `bool` and `char`
+
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0770`.
diff --git a/tests/ui/const-generics/issues/issue-71381.rs b/tests/ui/const-generics/issues/issue-71381.rs
index 7f2e14944e2..e472ef31fcd 100644
--- a/tests/ui/const-generics/issues/issue-71381.rs
+++ b/tests/ui/const-generics/issues/issue-71381.rs
@@ -13,6 +13,7 @@ unsafe extern "C" fn pass(args: PassArg) {
 impl Test {
     pub fn call_me<Args: Sized, const IDX: usize, const FN: unsafe extern "C" fn(Args)>(&self) {
         //~^ ERROR: the type of const parameters must not depend on other generic parameters
+        //[min]~^^ ERROR: using function pointers as const generic parameters is forbidden
         self.0 = Self::trampiline::<Args, IDX, FN> as _
     }
 
@@ -21,6 +22,7 @@ impl Test {
         const IDX: usize,
         const FN: unsafe extern "C" fn(Args),
         //~^ ERROR: the type of const parameters must not depend on other generic parameters
+        //[min]~^^ ERROR: using function pointers as const generic parameters is forbidden
     >(
         args: Args,
     ) {
diff --git a/tests/ui/const-generics/issues/issue-71611.min.stderr b/tests/ui/const-generics/issues/issue-71611.min.stderr
index 6f6a9fc21a6..b01936f4d25 100644
--- a/tests/ui/const-generics/issues/issue-71611.min.stderr
+++ b/tests/ui/const-generics/issues/issue-71611.min.stderr
@@ -6,6 +6,14 @@ LL | fn func<A, const F: fn(inner: A)>(outer: A) {
    |
    = note: type parameters may not be used in the type of const parameters
 
-error: aborting due to 1 previous error
+error: using function pointers as const generic parameters is forbidden
+  --> $DIR/issue-71611.rs:5:21
+   |
+LL | fn func<A, const F: fn(inner: A)>(outer: A) {
+   |                     ^^^^^^^^^^^^
+   |
+   = note: the only supported types are integers, `bool` and `char`
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0770`.
diff --git a/tests/ui/const-generics/issues/issue-71611.rs b/tests/ui/const-generics/issues/issue-71611.rs
index 0e0c08146b2..c6c1e267171 100644
--- a/tests/ui/const-generics/issues/issue-71611.rs
+++ b/tests/ui/const-generics/issues/issue-71611.rs
@@ -4,6 +4,7 @@
 
 fn func<A, const F: fn(inner: A)>(outer: A) {
     //~^ ERROR: the type of const parameters must not depend on other generic parameters
+    //[min]~| ERROR: using function pointers as const generic parameters is forbidden
     F(outer);
 }
 
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
index a41a159c1fd..09f7e2ba5b1 100644
--- a/tests/ui/const_prop/ice-type-mismatch-when-copying-112824.rs
+++ b/tests/ui/const_prop/ice-type-mismatch-when-copying-112824.rs
@@ -13,6 +13,7 @@ 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
index d95a8861230..9442eac0cf5 100644
--- a/tests/ui/const_prop/ice-type-mismatch-when-copying-112824.stderr
+++ b/tests/ui/const_prop/ice-type-mismatch-when-copying-112824.stderr
@@ -17,7 +17,13 @@ help: you might be missing a type parameter
 LL | pub struct Opcode2<S>(&'a S);
    |                   +++
 
-error: aborting due to 2 previous errors
+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
 
 Some errors have detailed explanations: E0261, E0412.
 For more information about an error, try `rustc --explain E0261`.
diff --git a/tests/ui/generic-associated-types/issue-71176.rs b/tests/ui/generic-associated-types/issue-71176.rs
index f0e162d825f..e58b6f6091e 100644
--- a/tests/ui/generic-associated-types/issue-71176.rs
+++ b/tests/ui/generic-associated-types/issue-71176.rs
@@ -9,6 +9,9 @@ impl Provider for () {
 struct Holder<B> {
   inner: Box<dyn Provider<A = B>>,
   //~^ ERROR: missing generics for associated type
+  //~| ERROR: missing generics for associated type
+  //~| ERROR: missing generics for associated type
+  //~| ERROR: the trait `Provider` cannot be made into an object
 }
 
 fn main() {
diff --git a/tests/ui/generic-associated-types/issue-71176.stderr b/tests/ui/generic-associated-types/issue-71176.stderr
index ed837f34753..a1913bb618b 100644
--- a/tests/ui/generic-associated-types/issue-71176.stderr
+++ b/tests/ui/generic-associated-types/issue-71176.stderr
@@ -14,6 +14,57 @@ help: add missing lifetime argument
 LL |   inner: Box<dyn Provider<A<'a> = B>>,
    |                            ++++
 
-error: aborting due to 1 previous error
+error[E0107]: missing generics for associated type `Provider::A`
+  --> $DIR/issue-71176.rs:10:27
+   |
+LL |   inner: Box<dyn Provider<A = B>>,
+   |                           ^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/issue-71176.rs:2:10
+   |
+LL |     type A<'a>;
+   |          ^ --
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: add missing lifetime argument
+   |
+LL |   inner: Box<dyn Provider<A<'a> = B>>,
+   |                            ++++
+
+error[E0107]: missing generics for associated type `Provider::A`
+  --> $DIR/issue-71176.rs:10:27
+   |
+LL |   inner: Box<dyn Provider<A = B>>,
+   |                           ^ expected 1 lifetime argument
+   |
+note: associated type defined here, with 1 lifetime parameter: `'a`
+  --> $DIR/issue-71176.rs:2:10
+   |
+LL |     type A<'a>;
+   |          ^ --
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: add missing lifetime argument
+   |
+LL |   inner: Box<dyn Provider<A<'a> = B>>,
+   |                            ++++
+
+error[E0038]: the trait `Provider` cannot be made into an object
+  --> $DIR/issue-71176.rs:10:14
+   |
+LL |   inner: Box<dyn Provider<A = B>>,
+   |              ^^^^^^^^^^^^^^^^^^^ `Provider` cannot be made into an object
+   |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/issue-71176.rs:2:10
+   |
+LL | trait Provider {
+   |       -------- this trait cannot be made into an object...
+LL |     type A<'a>;
+   |          ^ ...because it contains the generic associated type `A`
+   = help: consider moving `A` to another trait
+   = help: only type `()` implements the trait, consider using it directly instead
+
+error: aborting due to 4 previous errors
 
-For more information about this error, try `rustc --explain E0107`.
+Some errors have detailed explanations: E0038, E0107.
+For more information about an error, try `rustc --explain E0038`.
diff --git a/tests/ui/layout/issue-84108.rs b/tests/ui/layout/issue-84108.rs
index 425da65b990..974d5310f6b 100644
--- a/tests/ui/layout/issue-84108.rs
+++ b/tests/ui/layout/issue-84108.rs
@@ -8,6 +8,9 @@ static FOO: (dyn AsRef<OsStr>, u8) = ("hello", 42);
 
 const BAR: (&Path, [u8], usize) = ("hello", [], 42);
 //~^ ERROR cannot find type `Path` in this scope
+//~| ERROR the size for values of type `[u8]` cannot be known at compilation time
+//~| ERROR the size for values of type `[u8]` cannot be known at compilation time
+//~| ERROR mismatched types
 
 static BAZ: ([u8], usize) = ([], 0);
 //~^ ERROR the size for values of type `[u8]` cannot be known at compilation time
diff --git a/tests/ui/layout/issue-84108.stderr b/tests/ui/layout/issue-84108.stderr
index 6c168cc5fa8..8ddce285e23 100644
--- a/tests/ui/layout/issue-84108.stderr
+++ b/tests/ui/layout/issue-84108.stderr
@@ -21,7 +21,35 @@ LL + use std::path::Path;
    |
 
 error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
-  --> $DIR/issue-84108.rs:12:13
+  --> $DIR/issue-84108.rs:9:12
+   |
+LL | const BAR: (&Path, [u8], usize) = ("hello", [], 42);
+   |            ^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u8]`
+   = note: only the last element of a tuple may have a dynamically sized type
+
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+  --> $DIR/issue-84108.rs:9:12
+   |
+LL | const BAR: (&Path, [u8], usize) = ("hello", [], 42);
+   |            ^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u8]`
+   = note: only the last element of a tuple may have a dynamically sized type
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-84108.rs:9:45
+   |
+LL | const BAR: (&Path, [u8], usize) = ("hello", [], 42);
+   |                                             ^^ expected `[u8]`, found `[_; 0]`
+   |
+   = note: expected slice `[u8]`
+              found array `[_; 0]`
+
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+  --> $DIR/issue-84108.rs:15:13
    |
 LL | static BAZ: ([u8], usize) = ([], 0);
    |             ^^^^^^^^^^^^^ doesn't have a size known at compile-time
@@ -30,7 +58,7 @@ LL | static BAZ: ([u8], usize) = ([], 0);
    = note: only the last element of a tuple may have a dynamically sized type
 
 error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
-  --> $DIR/issue-84108.rs:12:13
+  --> $DIR/issue-84108.rs:15:13
    |
 LL | static BAZ: ([u8], usize) = ([], 0);
    |             ^^^^^^^^^^^^^ doesn't have a size known at compile-time
@@ -40,7 +68,7 @@ LL | static BAZ: ([u8], usize) = ([], 0);
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error[E0308]: mismatched types
-  --> $DIR/issue-84108.rs:12:30
+  --> $DIR/issue-84108.rs:15:30
    |
 LL | static BAZ: ([u8], usize) = ([], 0);
    |                              ^^ expected `[u8]`, found `[_; 0]`
@@ -48,7 +76,7 @@ LL | static BAZ: ([u8], usize) = ([], 0);
    = note: expected slice `[u8]`
               found array `[_; 0]`
 
-error: aborting due to 5 previous errors
+error: aborting due to 8 previous errors
 
 Some errors have detailed explanations: E0277, E0308, E0412.
 For more information about an error, try `rustc --explain E0277`.
diff --git a/tests/ui/lifetimes/unusual-rib-combinations.rs b/tests/ui/lifetimes/unusual-rib-combinations.rs
index 3bc87b9d480..0708a00d371 100644
--- a/tests/ui/lifetimes/unusual-rib-combinations.rs
+++ b/tests/ui/lifetimes/unusual-rib-combinations.rs
@@ -2,9 +2,8 @@ struct S<'a>(&'a u8);
 fn foo() {}
 
 // Paren generic args in AnonConst
-fn a() -> [u8; foo::()] {
-//~^ ERROR parenthesized type parameters may only be used with a `Fn` trait
-//~| ERROR mismatched types
+fn a() -> [u8; foo()] {
+    //~^ ERROR mismatched types
     panic!()
 }
 
@@ -26,5 +25,6 @@ fn d<const C: S>() {}
 trait Foo<'a> {}
 struct Bar<const N: &'a (dyn for<'a> Foo<'a>)>;
 //~^ ERROR the type of const parameters must not depend on other generic parameters
+//~| ERROR `&dyn for<'a> Foo<'a>` is forbidden as the type of a const generic parameter
 
 fn main() {}
diff --git a/tests/ui/lifetimes/unusual-rib-combinations.stderr b/tests/ui/lifetimes/unusual-rib-combinations.stderr
index 2857fc72ea1..70f06b4be60 100644
--- a/tests/ui/lifetimes/unusual-rib-combinations.stderr
+++ b/tests/ui/lifetimes/unusual-rib-combinations.stderr
@@ -1,11 +1,11 @@
 error[E0106]: missing lifetime specifier
-  --> $DIR/unusual-rib-combinations.rs:22:15
+  --> $DIR/unusual-rib-combinations.rs:21:15
    |
 LL | fn d<const C: S>() {}
    |               ^ expected named lifetime parameter
 
 error[E0770]: the type of const parameters must not depend on other generic parameters
-  --> $DIR/unusual-rib-combinations.rs:27:22
+  --> $DIR/unusual-rib-combinations.rs:26:22
    |
 LL | struct Bar<const N: &'a (dyn for<'a> Foo<'a>)>;
    |                      ^^ the type must not depend on the parameter `'a`
@@ -13,25 +13,19 @@ LL | struct Bar<const N: &'a (dyn for<'a> Foo<'a>)>;
    = note: lifetime parameters may not be used in the type of const parameters
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/unusual-rib-combinations.rs:5:16
-   |
-LL | fn a() -> [u8; foo::()] {
-   |                ^^^^^^^ only `Fn` traits may use parentheses
-
-error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/unusual-rib-combinations.rs:12:15
+  --> $DIR/unusual-rib-combinations.rs:11:15
    |
 LL | fn b<const C: u8()>() {}
    |               ^^^^ only `Fn` traits may use parentheses
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/unusual-rib-combinations.rs:16:10
+  --> $DIR/unusual-rib-combinations.rs:15:10
    |
 LL | fn c<T = u8()>() {}
    |          ^^^^ only `Fn` traits may use parentheses
 
 error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
-  --> $DIR/unusual-rib-combinations.rs:16:6
+  --> $DIR/unusual-rib-combinations.rs:15:6
    |
 LL | fn c<T = u8()>() {}
    |      ^^^^^^^^
@@ -43,14 +37,11 @@ LL | fn c<T = u8()>() {}
 error[E0308]: mismatched types
   --> $DIR/unusual-rib-combinations.rs:5:16
    |
-LL | fn a() -> [u8; foo::()] {
-   |                ^^^^^^^ expected `usize`, found fn item
-   |
-   = note: expected type `usize`
-           found fn item `fn() {foo}`
+LL | fn a() -> [u8; foo()] {
+   |                ^^^^^ expected `usize`, found `()`
 
 error: `S<'_>` is forbidden as the type of a const generic parameter
-  --> $DIR/unusual-rib-combinations.rs:22:15
+  --> $DIR/unusual-rib-combinations.rs:21:15
    |
 LL | fn d<const C: S>() {}
    |               ^
@@ -61,6 +52,18 @@ help: add `#![feature(adt_const_params)]` to the crate attributes to enable more
 LL + #![feature(adt_const_params)]
    |
 
+error: `&dyn for<'a> Foo<'a>` is forbidden as the type of a const generic parameter
+  --> $DIR/unusual-rib-combinations.rs:26:21
+   |
+LL | struct Bar<const N: &'a (dyn for<'a> Foo<'a>)>;
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: the only supported types are integers, `bool` and `char`
+help: add `#![feature(adt_const_params)]` to the crate attributes to enable more complex and user defined types
+   |
+LL + #![feature(adt_const_params)]
+   |
+
 error: aborting due to 8 previous errors
 
 Some errors have detailed explanations: E0106, E0214, E0308, E0770.
diff --git a/tests/ui/parser/issues/issue-103748-ICE-wrong-braces.rs b/tests/ui/parser/issues/issue-103748-ICE-wrong-braces.rs
index f6aa39df27d..1c28c0632fa 100644
--- a/tests/ui/parser/issues/issue-103748-ICE-wrong-braces.rs
+++ b/tests/ui/parser/issues/issue-103748-ICE-wrong-braces.rs
@@ -5,3 +5,4 @@ struct Apple((Apple, Option(Banana ? Citron)));
 //~| ERROR expected one of `)` or `,`, found `Citron`
 //~| ERROR cannot find type `Citron` in this scope [E0412]
 //~| ERROR parenthesized type parameters may only be used with a `Fn` trait [E0214]
+//~| ERROR `Apple` has infinite size
diff --git a/tests/ui/parser/issues/issue-103748-ICE-wrong-braces.stderr b/tests/ui/parser/issues/issue-103748-ICE-wrong-braces.stderr
index 71d2d7b7975..b0d8b03ae08 100644
--- a/tests/ui/parser/issues/issue-103748-ICE-wrong-braces.stderr
+++ b/tests/ui/parser/issues/issue-103748-ICE-wrong-braces.stderr
@@ -34,7 +34,18 @@ help: use angle brackets instead
 LL | struct Apple((Apple, Option<Banana ? Citron>));
    |                            ~               ~
 
-error: aborting due to 4 previous errors
+error[E0072]: recursive type `Apple` has infinite size
+  --> $DIR/issue-103748-ICE-wrong-braces.rs:3:1
+   |
+LL | struct Apple((Apple, Option(Banana ? Citron)));
+   | ^^^^^^^^^^^^  ----- recursive without indirection
+   |
+help: insert some indirection (e.g., a `Box`, `Rc`, or `&`) to break the cycle
+   |
+LL | struct Apple((Box<Apple>, Option(Banana ? Citron)));
+   |               ++++     +
+
+error: aborting due to 5 previous errors
 
-Some errors have detailed explanations: E0214, E0412.
-For more information about an error, try `rustc --explain E0214`.
+Some errors have detailed explanations: E0072, E0214, E0412.
+For more information about an error, try `rustc --explain E0072`.