loosen ordering restricts for const_generics_defaults

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -754,7 +754,7 @@ fn validate_generic_param_order(
             GenericParamKind::Type { default: _ } => (ParamKindOrd::Type, ident),
             GenericParamKind::Const { ref ty, kw_span: _, default: _ } => {
                 let ty = pprust::ty_to_string(ty);
-                let unordered = sess.features_untracked().const_generics;
+                let unordered = sess.features_untracked().unordered_const_ty_params();
                 (ParamKindOrd::Const { unordered }, Some(format!("const {}: {}", param.ident, ty)))
             }
         };

compiler/rustc_feature/src/active.rs

@@ -63,6 +63,10 @@ macro_rules! declare_features {
                     _ => panic!("`{}` was not listed in `declare_features`", feature),
                 }
             }
+
+            pub fn unordered_const_ty_params(&self) -> bool {
+                self.const_generics || self.const_generics_defaults
+            }
         }
     };
 }

compiler/rustc_hir/src/hir.rs

@@ -296,7 +296,9 @@ impl GenericArg<'_> {
         match self {
             GenericArg::Lifetime(_) => ast::ParamKindOrd::Lifetime,
             GenericArg::Type(_) => ast::ParamKindOrd::Type,
-            GenericArg::Const(_) => ast::ParamKindOrd::Const { unordered: feats.const_generics },
+            GenericArg::Const(_) => {
+                ast::ParamKindOrd::Const { unordered: feats.unordered_const_ty_params() }
+            }
         }
     }
 }

compiler/rustc_middle/src/ty/generics.rs

@@ -36,7 +36,7 @@ impl GenericParamDefKind {
             GenericParamDefKind::Lifetime => ast::ParamKindOrd::Lifetime,
             GenericParamDefKind::Type { .. } => ast::ParamKindOrd::Type,
             GenericParamDefKind::Const { .. } => {
-                ast::ParamKindOrd::Const { unordered: tcx.features().const_generics }
+                ast::ParamKindOrd::Const { unordered: tcx.features().unordered_const_ty_params() }
             }
         }
     }

compiler/rustc_typeck/src/astconv/generics.rs

@@ -286,7 +286,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                                                         ParamKindOrd::Const {
                                                             unordered: tcx
                                                                 .features()
-                                                                .const_generics,
+                                                                .unordered_const_ty_params(),
                                                         }
                                                     }
                                                 },
@@ -309,7 +309,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                                             GenericArg::Lifetime(_) => ParamKindOrd::Lifetime,
                                             GenericArg::Type(_) => ParamKindOrd::Type,
                                             GenericArg::Const(_) => ParamKindOrd::Const {
-                                                unordered: tcx.features().const_generics,
+                                                unordered: tcx
+                                                    .features()
+                                                    .unordered_const_ty_params(),
                                             },
                                         }),
                                         Some(&format!(

src/test/ui/const-generics/defaults/auxiliary/const_defaulty.rs

@@ -1,4 +1,4 @@
-#![feature(const_generics)]
+#![cfg_attr(full, feature(const_generics))]
 #![feature(const_generics_defaults)]
 #![allow(incomplete_features)]
 

src/test/ui/const-generics/defaults/complex-generic-default-expr.full.stderr

@@ -1,5 +1,5 @@
 error[E0277]: the size for values of type `T` cannot be known at compilation time
-  --> $DIR/complex-generic-default-expr.rs:6:62
+  --> $DIR/complex-generic-default-expr.rs:9:62
    |
 LL | struct Bar<T, const TYPE_SIZE: usize = { std::mem::size_of::<T>() }>(T);
    |            -                                                 ^ doesn't have a size known at compile-time

src/test/ui/const-generics/defaults/complex-generic-default-expr.min.stderr

@@ -0,0 +1,20 @@
+error: generic parameters may not be used in const operations
+  --> $DIR/complex-generic-default-expr.rs:6:47
+   |
+LL | struct Foo<const N: usize, const M: usize = { N + 1 }>;
+   |                                               ^ cannot perform const operation using `N`
+   |
+   = help: const parameters may only be used as standalone arguments, i.e. `N`
+   = help: use `#![feature(const_generics)]` and `#![feature(const_evaluatable_checked)]` to allow generic const expressions
+
+error: generic parameters may not be used in const operations
+  --> $DIR/complex-generic-default-expr.rs:9:62
+   |
+LL | struct Bar<T, const TYPE_SIZE: usize = { std::mem::size_of::<T>() }>(T);
+   |                                                              ^ cannot perform const operation using `T`
+   |
+   = note: type parameters may not be used in const expressions
+   = help: use `#![feature(const_generics)]` and `#![feature(const_evaluatable_checked)]` to allow generic const expressions
+
+error: aborting due to 2 previous errors
+

src/test/ui/const-generics/defaults/complex-generic-default-expr.rs

@@ -1,9 +1,13 @@
-#![feature(const_generics, const_generics_defaults)]
+// revisions: full min
+#![cfg_attr(full, feature(const_generics))]
+#![feature(const_generics_defaults)]
 #![allow(incomplete_features)]
 
 struct Foo<const N: usize, const M: usize = { N + 1 }>;
+//[min]~^ ERROR generic parameters may not be used in const operations
 
 struct Bar<T, const TYPE_SIZE: usize = { std::mem::size_of::<T>() }>(T);
-//~^ ERROR the size for values of type `T` cannot be known at compilation time 
+//[min]~^ ERROR generic parameters may not be used in const operations
+//[full]~^^ ERROR the size for values of type `T` cannot be known at compilation time 
 
 fn main() {}

src/test/ui/const-generics/defaults/const-default.rs

@@ -1,6 +1,6 @@
 // run-pass
-
-#![feature(const_generics)]
+// revisions: full min
+#![cfg_attr(full, feature(const_generics))]
 #![feature(const_generics_defaults)]
 #![allow(incomplete_features)]
 

src/test/ui/const-generics/defaults/default-on-impl.full.stderr

@@ -1,5 +1,5 @@
 error: defaults for const parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
-  --> $DIR/default-on-impl.rs:6:12
+  --> $DIR/default-on-impl.rs:8:12
    |
 LL | impl<const N: usize = 1> Foo<N> {}
    |            ^

src/test/ui/const-generics/defaults/default-on-impl.min.stderr

@@ -0,0 +1,8 @@
+error: defaults for const parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
+  --> $DIR/default-on-impl.rs:8:12
+   |
+LL | impl<const N: usize = 1> Foo<N> {}
+   |            ^
+
+error: aborting due to previous error
+

src/test/ui/const-generics/defaults/default-on-impl.rs

@@ -1,4 +1,6 @@
-#![feature(const_generics, const_generics_defaults)]
+// revisions: full min
+#![cfg_attr(full, feature(const_generics))]
+#![feature(const_generics_defaults)]
 #![allow(incomplete_features)]
 
 struct Foo<const N: usize>;

src/test/ui/const-generics/defaults/external.rs

@@ -1,5 +1,7 @@
 // aux-build:const_defaulty.rs
 // check-pass
+// revisions: full min
+#![cfg_attr(full, feature(const_generics))]
 #![feature(const_generics_defaults)]
 #![allow(incomplete_features)]
 

src/test/ui/const-generics/defaults/intermixed-lifetime.full.stderr

@@ -1,5 +1,5 @@
 error: lifetime parameters must be declared prior to const parameters
-  --> $DIR/intermixed-lifetime.rs:6:28
+  --> $DIR/intermixed-lifetime.rs:7:28
    |
 LL | struct Foo<const N: usize, 'a, T = u32>(&'a (), T);
    |           -----------------^^---------- help: reorder the parameters: lifetimes, then consts and types: `<'a, const N: usize, T = u32>`

src/test/ui/const-generics/defaults/intermixed-lifetime.min.stderr

@@ -1,26 +1,14 @@
 error: lifetime parameters must be declared prior to const parameters
-  --> $DIR/intermixed-lifetime.rs:6:28
+  --> $DIR/intermixed-lifetime.rs:7:28
    |
 LL | struct Foo<const N: usize, 'a, T = u32>(&'a (), T);
-   |           -----------------^^---------- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T = u32, const N: usize>`
+   |           -----------------^^---------- help: reorder the parameters: lifetimes, then types, then consts: `<'a, const N: usize, T = u32>`
 
-error: type parameters must be declared prior to const parameters
-  --> $DIR/intermixed-lifetime.rs:6:32
-   |
-LL | struct Foo<const N: usize, 'a, T = u32>(&'a (), T);
-   |           ---------------------^------- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T = u32, const N: usize>`
-
-error: lifetime parameters must be declared prior to const parameters
+error: lifetime parameters must be declared prior to type parameters
   --> $DIR/intermixed-lifetime.rs:10:37
    |
 LL | struct Bar<const N: usize, T = u32, 'a>(&'a (), T);
-   |           --------------------------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T = u32, const N: usize>`
+   |           --------------------------^^- help: reorder the parameters: lifetimes, then types, then consts: `<'a, const N: usize, T = u32>`
 
-error: type parameters must be declared prior to const parameters
-  --> $DIR/intermixed-lifetime.rs:10:28
-   |
-LL | struct Bar<const N: usize, T = u32, 'a>(&'a (), T);
-   |           -----------------^----------- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T = u32, const N: usize>`
-
-error: aborting due to 4 previous errors
+error: aborting due to 2 previous errors
 

src/test/ui/const-generics/defaults/intermixed-lifetime.rs

@@ -1,15 +1,13 @@
-// revisions: full min
 // Checks that lifetimes cannot be interspersed between consts and types.
+// revisions: full min
 #![cfg_attr(full, feature(const_generics))]
-#![cfg_attr(full, allow(incomplete_features))]
+#![feature(const_generics_defaults)]
+#![allow(incomplete_features)]
 
 struct Foo<const N: usize, 'a, T = u32>(&'a (), T);
 //~^ Error lifetime parameters must be declared prior to const parameters
-//[min]~^^ Error type parameters must be declared prior to const parameters
 
 struct Bar<const N: usize, T = u32, 'a>(&'a (), T);
-//[full]~^ Error lifetime parameters must be declared prior to type parameters
-//[min]~^^ Error type parameters must be declared prior to const parameters
-//[min]~| Error lifetime parameters must be declared prior to const parameters
+//~^ Error lifetime parameters must be declared prior to type parameters
 
 fn main() {}

src/test/ui/const-generics/defaults/mismatch.full.stderr

@@ -1,5 +1,5 @@
 error[E0308]: mismatched types
-  --> $DIR/mismatch.rs:11:28
+  --> $DIR/mismatch.rs:12:28
    |
 LL |     let e: Example::<13> = ();
    |            -------------   ^^ expected struct `Example`, found `()`
@@ -7,7 +7,7 @@ LL |     let e: Example::<13> = ();
    |            expected due to this
 
 error[E0308]: mismatched types
-  --> $DIR/mismatch.rs:13:34
+  --> $DIR/mismatch.rs:14:34
    |
 LL |     let e: Example2::<u32, 13> = ();
    |            -------------------   ^^ expected struct `Example2`, found `()`
@@ -18,7 +18,7 @@ LL |     let e: Example2::<u32, 13> = ();
            found unit type `()`
 
 error[E0308]: mismatched types
-  --> $DIR/mismatch.rs:15:34
+  --> $DIR/mismatch.rs:16:34
    |
 LL |     let e: Example3::<13, u32> = ();
    |            -------------------   ^^ expected struct `Example3`, found `()`
@@ -29,7 +29,7 @@ LL |     let e: Example3::<13, u32> = ();
            found unit type `()`
 
 error[E0308]: mismatched types
-  --> $DIR/mismatch.rs:17:28
+  --> $DIR/mismatch.rs:18:28
    |
 LL |     let e: Example3::<7> = ();
    |            -------------   ^^ expected struct `Example3`, found `()`
@@ -40,7 +40,7 @@ LL |     let e: Example3::<7> = ();
            found unit type `()`
 
 error[E0308]: mismatched types
-  --> $DIR/mismatch.rs:21:28
+  --> $DIR/mismatch.rs:22:28
    |
 LL |     let e: Example4::<7> = ();
    |            -------------   ^^ expected struct `Example4`, found `()`

src/test/ui/const-generics/defaults/mismatch.min.stderr

@@ -0,0 +1,52 @@
+error[E0308]: mismatched types
+  --> $DIR/mismatch.rs:12:28
+   |
+LL |     let e: Example::<13> = ();
+   |            -------------   ^^ expected struct `Example`, found `()`
+   |            |
+   |            expected due to this
+
+error[E0308]: mismatched types
+  --> $DIR/mismatch.rs:14:34
+   |
+LL |     let e: Example2::<u32, 13> = ();
+   |            -------------------   ^^ expected struct `Example2`, found `()`
+   |            |
+   |            expected due to this
+   |
+   = note: expected struct `Example2`
+           found unit type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/mismatch.rs:16:34
+   |
+LL |     let e: Example3::<13, u32> = ();
+   |            -------------------   ^^ expected struct `Example3`, found `()`
+   |            |
+   |            expected due to this
+   |
+   = note: expected struct `Example3`
+           found unit type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/mismatch.rs:18:28
+   |
+LL |     let e: Example3::<7> = ();
+   |            -------------   ^^ expected struct `Example3`, found `()`
+   |            |
+   |            expected due to this
+   |
+   = note: expected struct `Example3<7_usize>`
+           found unit type `()`
+
+error[E0308]: mismatched types
+  --> $DIR/mismatch.rs:22:28
+   |
+LL |     let e: Example4::<7> = ();
+   |            -------------   ^^ expected struct `Example4`, found `()`
+   |            |
+   |            expected due to this
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/const-generics/defaults/mismatch.rs

@@ -1,4 +1,5 @@
-#![feature(const_generics)]
+// revisions: full min
+#![cfg_attr(full, feature(const_generics))]
 #![feature(const_generics_defaults)]
 #![allow(incomplete_features)]
 

src/test/ui/const-generics/defaults/pretty-printing-ast.stdout

@@ -18,4 +18,3 @@ fn foo<const SIZE : usize = 5>() { }
 
 struct Range<const FROM : usize = 0, const LEN : usize = 0, const TO : usize =
              FROM>;
-

src/test/ui/const-generics/defaults/repr-c-issue-82792.rs

@@ -6,7 +6,7 @@
 #![allow(incomplete_features)]
 
 #[repr(C)]
-pub struct Loaf<T: Sized, const N: usize = 1usize> {
+pub struct Loaf<T: Sized, const N: usize = 1> {
     head: [T; N],
     slice: [T],
 }

src/test/ui/const-generics/defaults/simple-defaults.min.stderr

@@ -1,8 +0,0 @@
-error: type parameters must be declared prior to const parameters
-  --> $DIR/simple-defaults.rs:8:40
-   |
-LL | struct FixedOutput<'a, const N: usize, T=u32> {
-   |                   ---------------------^----- help: reorder the parameters: lifetimes, then types, then consts: `<'a, T = u32, const N: usize>`
-
-error: aborting due to previous error
-

src/test/ui/const-generics/defaults/simple-defaults.rs

@@ -1,12 +1,12 @@
-// [full] run-pass
-// revisions: min full
-// Checks some basic test cases for defaults.
+// run-pass
+// Checks that type param defaults are allowed after const params.
+// revisions: full min
 #![cfg_attr(full, feature(const_generics))]
-#![cfg_attr(full, allow(incomplete_features))]
+#![feature(const_generics_defaults)]
+#![allow(incomplete_features)]
 #![allow(dead_code)]
 
 struct FixedOutput<'a, const N: usize, T=u32> {
-    //[min]~^ ERROR type parameters must be declared prior to const parameters
     out: &'a [T; N],
 }
 

src/test/ui/const-generics/defaults/type-default-const-param-name.rs

@@ -1,5 +1,7 @@
 // check-pass
-#![feature(const_generics, const_generics_defaults)]
+// revisions: full min
+#![cfg_attr(full, feature(const_generics))]
+#![feature(const_generics_defaults)]
 #![allow(incomplete_features)]
 
 struct N;

src/test/ui/const-generics/defaults/wrong-order.full.stderr

@@ -1,19 +1,8 @@
 error: generic parameters with a default must be trailing
-  --> $DIR/wrong-order.rs:4:10
+  --> $DIR/wrong-order.rs:6:10
    |
 LL | struct A<T = u32, const N: usize> {
    |          ^
-   |
-   = note: using type defaults and const parameters in the same parameter list is currently not permitted
 
-warning: the feature `const_generics` is incomplete and may not be safe to use and/or cause compiler crashes
-  --> $DIR/wrong-order.rs:2:27
-   |
-LL | #![cfg_attr(full, feature(const_generics))]
-   |                           ^^^^^^^^^^^^^^
-   |
-   = note: `#[warn(incomplete_features)]` on by default
-   = note: see issue #44580 <https://github.com/rust-lang/rust/issues/44580> for more information
-
-error: aborting due to previous error; 1 warning emitted
+error: aborting due to previous error
 

src/test/ui/const-generics/defaults/wrong-order.min.stderr

@@ -1,10 +1,8 @@
 error: generic parameters with a default must be trailing
-  --> $DIR/wrong-order.rs:4:10
+  --> $DIR/wrong-order.rs:6:10
    |
 LL | struct A<T = u32, const N: usize> {
    |          ^
-   |
-   = note: using type defaults and const parameters in the same parameter list is currently not permitted
 
 error: aborting due to previous error
 

src/test/ui/const-generics/defaults/wrong-order.rs

@@ -1,5 +1,7 @@
 // revisions: full min
-#![cfg_attr(full, feature(const_generics))] //[full]~WARN the feature `const_generics` is incomplete
+#![cfg_attr(full, feature(const_generics))]
+#![feature(const_generics_defaults)]
+#![allow(incomplete_features)]
 
 struct A<T = u32, const N: usize> {
     //~^ ERROR generic parameters with a default must be trailing

src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.full.stderr

@@ -1,5 +1,5 @@
 error: generic parameters with a default must be trailing
-  --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:11:12
+  --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:10:12
    |
 LL | struct Bar<T = [u8; N], const N: usize>(T);
    |            ^
@@ -7,7 +7,7 @@ LL | struct Bar<T = [u8; N], const N: usize>(T);
    = note: using type defaults and const parameters in the same parameter list is currently not permitted
 
 error[E0128]: generic parameters with a default cannot use forward declared identifiers
-  --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:11:21
+  --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:10:21
    |
 LL | struct Bar<T = [u8; N], const N: usize>(T);
    |                     ^ defaulted generic parameters cannot be forward declared

src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.min.stderr

@@ -1,5 +1,5 @@
 error: generic parameters with a default must be trailing
-  --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:11:12
+  --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:10:12
    |
 LL | struct Bar<T = [u8; N], const N: usize>(T);
    |            ^
@@ -16,7 +16,7 @@ LL | struct Foo<T, U = [u8; std::mem::size_of::<T>()]>(T, U);
    = help: use `#![feature(const_generics)]` and `#![feature(const_evaluatable_checked)]` to allow generic const expressions
 
 error[E0128]: generic parameters with a default cannot use forward declared identifiers
-  --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:11:21
+  --> $DIR/params-in-ct-in-ty-param-lazy-norm.rs:10:21
    |
 LL | struct Bar<T = [u8; N], const N: usize>(T);
    |                     ^ defaulted generic parameters cannot be forward declared

src/test/ui/const-generics/params-in-ct-in-ty-param-lazy-norm.rs

@@ -7,7 +7,6 @@ struct Foo<T, U = [u8; std::mem::size_of::<T>()]>(T, U);
 //[full]~^ ERROR the size for values of type `T` cannot be known at compilation time
 //[min]~^^ ERROR generic parameters may not be used in const operations
 
-// FIXME(const_generics_defaults): We still don't know how to deal with type defaults.
 struct Bar<T = [u8; N], const N: usize>(T);
 //~^ ERROR generic parameters with a default cannot use forward declared identifiers
 //~| ERROR generic parameters with a default