Rollup merge of #65627 - varkor:const-generics-forbid-non-structural_match, r=petrochenkov

Forbid non-`structural_match` types in const generics

Fixes https://github.com/rust-lang/rust/issues/60286.

7 files changed, 45 insertions, 24 deletions

diff --git a/src/test/rustdoc/const-generics/const-impl.rs b/src/test/rustdoc/const-generics/const-impl.rs
index 85ee6d3376b..2d506787b3b 100644
--- a/src/test/rustdoc/const-generics/const-impl.rs
+++ b/src/test/rustdoc/const-generics/const-impl.rs
@@ -4,6 +4,7 @@
 
 #![crate_name = "foo"]
 
+#[derive(PartialEq, Eq)]
 pub enum Order {
     Sorted,
     Unsorted,
diff --git a/src/test/ui/const-generics/const-param-type-depends-on-type-param-ungated.rs b/src/test/ui/const-generics/const-param-type-depends-on-type-param-ungated.rs
index af5e8f49754..78bd549ba79 100644
--- a/src/test/ui/const-generics/const-param-type-depends-on-type-param-ungated.rs
+++ b/src/test/ui/const-generics/const-param-type-depends-on-type-param-ungated.rs
@@ -1,6 +1,6 @@
 use std::marker::PhantomData;
 
 struct B<T, const N: T>(PhantomData<[T; N]>); //~ ERROR const generics are unstable
-//~^ ERROR const parameters cannot depend on type parameters
+//~^ ERROR the types of const generic parameters must derive `PartialEq` and `Eq`
 
 fn main() {}
diff --git a/src/test/ui/const-generics/const-param-type-depends-on-type-param-ungated.stderr b/src/test/ui/const-generics/const-param-type-depends-on-type-param-ungated.stderr
index c659074a091..a2872ab982d 100644
--- a/src/test/ui/const-generics/const-param-type-depends-on-type-param-ungated.stderr
+++ b/src/test/ui/const-generics/const-param-type-depends-on-type-param-ungated.stderr
@@ -1,9 +1,3 @@
-error[E0671]: const parameters cannot depend on type parameters
-  --> $DIR/const-param-type-depends-on-type-param-ungated.rs:3:22
-   |
-LL | struct B<T, const N: T>(PhantomData<[T; N]>);
-   |                      ^ const parameter depends on type parameter
-
 error[E0658]: const generics are unstable
   --> $DIR/const-param-type-depends-on-type-param-ungated.rs:3:19
    |
@@ -13,7 +7,13 @@ LL | struct B<T, const N: T>(PhantomData<[T; N]>);
    = note: for more information, see https://github.com/rust-lang/rust/issues/44580
    = help: add `#![feature(const_generics)]` to the crate attributes to enable
 
+error[E0741]: the types of const generic parameters must derive `PartialEq` and `Eq`
+  --> $DIR/const-param-type-depends-on-type-param-ungated.rs:3:22
+   |
+LL | struct B<T, const N: T>(PhantomData<[T; N]>);
+   |                      ^ `T` doesn't derive both `PartialEq` and `Eq`
+
 error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0658, E0671.
+Some errors have detailed explanations: E0658, E0741.
 For more information about an error, try `rustc --explain E0658`.
diff --git a/src/test/ui/const-generics/const-param-type-depends-on-type-param.rs b/src/test/ui/const-generics/const-param-type-depends-on-type-param.rs
index 28e0d6c2bb7..b76209571b0 100644
--- a/src/test/ui/const-generics/const-param-type-depends-on-type-param.rs
+++ b/src/test/ui/const-generics/const-param-type-depends-on-type-param.rs
@@ -7,7 +7,6 @@
 // details.
 
 pub struct Dependent<T, const X: T>([(); X]);
-//~^ ERROR const parameters cannot depend on type parameters
-//~^^ ERROR parameter `T` is never used
+//~^ ERROR the types of const generic parameters must derive `PartialEq` and `Eq`
 
 fn main() {}
diff --git a/src/test/ui/const-generics/const-param-type-depends-on-type-param.stderr b/src/test/ui/const-generics/const-param-type-depends-on-type-param.stderr
index db14f9c9bf6..c9d6db7e2c2 100644
--- a/src/test/ui/const-generics/const-param-type-depends-on-type-param.stderr
+++ b/src/test/ui/const-generics/const-param-type-depends-on-type-param.stderr
@@ -1,9 +1,3 @@
-error[E0671]: const parameters cannot depend on type parameters
-  --> $DIR/const-param-type-depends-on-type-param.rs:9:34
-   |
-LL | pub struct Dependent<T, const X: T>([(); X]);
-   |                                  ^ const parameter depends on type parameter
-
 warning: the feature `const_generics` is incomplete and may cause the compiler to crash
   --> $DIR/const-param-type-depends-on-type-param.rs:1:12
    |
@@ -12,15 +6,12 @@ LL | #![feature(const_generics)]
    |
    = note: `#[warn(incomplete_features)]` on by default
 
-error[E0392]: parameter `T` is never used
-  --> $DIR/const-param-type-depends-on-type-param.rs:9:22
+error[E0741]: the types of const generic parameters must derive `PartialEq` and `Eq`
+  --> $DIR/const-param-type-depends-on-type-param.rs:9:34
    |
 LL | pub struct Dependent<T, const X: T>([(); X]);
-   |                      ^ unused parameter
-   |
-   = help: consider removing `T`, referring to it in a field, or using a marker such as `std::marker::PhantomData`
+   |                                  ^ `T` doesn't derive both `PartialEq` and `Eq`
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-Some errors have detailed explanations: E0392, E0671.
-For more information about an error, try `rustc --explain E0392`.
+For more information about this error, try `rustc --explain E0741`.
diff --git a/src/test/ui/const-generics/forbid-non-structural_match-types.rs b/src/test/ui/const-generics/forbid-non-structural_match-types.rs
new file mode 100644
index 00000000000..7bc4f3986eb
--- /dev/null
+++ b/src/test/ui/const-generics/forbid-non-structural_match-types.rs
@@ -0,0 +1,13 @@
+#![feature(const_generics)]
+//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
+
+#[derive(PartialEq, Eq)]
+struct A;
+
+struct B<const X: A>; // ok
+
+struct C;
+
+struct D<const X: C>; //~ ERROR the types of const generic parameters must derive
+
+fn main() {}
diff --git a/src/test/ui/const-generics/forbid-non-structural_match-types.stderr b/src/test/ui/const-generics/forbid-non-structural_match-types.stderr
new file mode 100644
index 00000000000..0fd9e0599e8
--- /dev/null
+++ b/src/test/ui/const-generics/forbid-non-structural_match-types.stderr
@@ -0,0 +1,17 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/forbid-non-structural_match-types.rs:1:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0741]: the types of const generic parameters must derive `PartialEq` and `Eq`
+  --> $DIR/forbid-non-structural_match-types.rs:11:19
+   |
+LL | struct D<const X: C>;
+   |                   ^ `C` doesn't derive both `PartialEq` and `Eq`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0741`.